Merge branch '11.7' into 'master'11.7

add upstream 11.7

See merge request opensource-tracking/FreeFileSync!31

122 files changed, 2500 insertions, 2294 deletions

diff --git a/Changelog.txt b/Changelog.txt
index dd6e9d4e..e4199c8d 100644
--- a/Changelog.txt
+++ b/Changelog.txt
@@ -1,3 +1,23 @@
+FreeFileSync 11.7 [2021-03-01]
+------------------------------
+Detect moved files on FTP (if server supports MLSD)
+Allow installation only for current or all user(s) (Linux)
+Added application uninstaller: uninstall.sh (Linux)
+Use login user config path when running as root (macOS, Linux)
+Fixed detection of moved files with unstable device IDs (macOS, Linux)
+Strict checking for duplicate file IDs
+Avoid EINVAL invalid argument error when using F_PREALLOCATE (macOS)
+Restore input focus after closing log panel
+Double-click on file to open Google Drive web interface
+Fixed alpha channel image scaling glitch
+Fixed recycle bin folders being created recursively
+Fixed thread count status message fluctuation
+Don't quit FreeFileSync when parent terminal is closed (SIGHUP)
+Fixed "Operation not supported" error when setting directory locks
+Show folder picker despite SHCreateItemFromParsingName() error
+Work around "OLE received a packet with an invalid header" error
+
+
 FreeFileSync 11.6 [2021-02-01]
 ------------------------------
 New FreeFileSync installer (Linux)
diff --git a/FreeFileSync/Build/Resources/Languages.zip b/FreeFileSync/Build/Resources/Languages.zip
index ed898768..1329f10b 100644
--- a/FreeFileSync/Build/Resources/Languages.zip
+++ b/FreeFileSync/Build/Resources/Languages.zip
diff --git a/FreeFileSync/Source/RealTimeSync/app_icon.h b/FreeFileSync/Source/RealTimeSync/app_icon.h
index 6352cc7a..55ae348b 100644
--- a/FreeFileSync/Source/RealTimeSync/app_icon.h
+++ b/FreeFileSync/Source/RealTimeSync/app_icon.h
@@ -16,7 +16,7 @@ inline
 wxIcon getRtsIcon() //see FFS/app_icon.h
 {
     assert(loadImage("RealTimeSync").GetWidth () == loadImage("RealTimeSync").GetHeight() &&
-           loadImage("RealTimeSync").GetWidth() == 128);
+           loadImage("RealTimeSync").GetWidth() == fastFromDIP(128));
     wxIcon icon;
     icon.CopyFromBitmap(loadImage("RealTimeSync", fastFromDIP(64)));
     return icon;
diff --git a/FreeFileSync/Source/RealTimeSync/application.cpp b/FreeFileSync/Source/RealTimeSync/application.cpp
index 729b0e49..87df96ba 100644
--- a/FreeFileSync/Source/RealTimeSync/application.cpp
+++ b/FreeFileSync/Source/RealTimeSync/application.cpp
@@ -87,6 +87,18 @@ bool Application::OnInit()
 #error unknown GTK version!
 #endif
 
+    try
+    {
+        /* we're a GUI app: ignore SIGHUP when the parent terminal quits! (or process is killed!)
+            => the FFS launcher will still be killed => fine
+            => macOS: apparently not needed! interestingly the FFS launcher does receive SIGHUP and *is* killed  */
+        if (sighandler_t oldHandler = ::signal(SIGHUP, SIG_IGN);
+            oldHandler == SIG_ERR)
+            THROW_LAST_SYS_ERROR("signal(SIGHUP)");
+        else assert(!oldHandler);
+    }
+    catch (const SysError& e) { std::cerr << utfTo<std::string>(e.toString()) << '\n'; }
+
 
     //Windows User Experience Interaction Guidelines: tool tips should have 5s timeout, info tips no timeout => compromise:
     wxToolTip::Enable(true); //yawn, a wxWidgets screw-up: wxToolTip::SetAutoPop is no-op if global tooltip window is not yet constructed: wxToolTip::Enable creates it
@@ -177,7 +189,7 @@ void Application::OnUnhandledException() //handles both wxApp::OnInit() + wxApp:
     }
     catch (const std::bad_alloc& e) //the only kind of exception we don't want crash dumps for
     {
-        fff::logFatalError(e.what()); //it's not always possible to display a message box, e.g. corrupted stack, however low-level file output works!
+        fff::logFatalError(utfTo<std::wstring>(e.what())); //it's not always possible to display a message box, e.g. corrupted stack, however low-level file output works!
 
         const auto titleFmt = copyStringTo<std::wstring>(wxTheApp->GetAppDisplayName()) + SPACED_DASH + _("An exception occurred");
         std::cerr << utfTo<std::string>(titleFmt + SPACED_DASH) << e.what() << '\n';
diff --git a/FreeFileSync/Source/RealTimeSync/main_dlg.cpp b/FreeFileSync/Source/RealTimeSync/main_dlg.cpp
index fc9e1acb..f308d0fa 100644
--- a/FreeFileSync/Source/RealTimeSync/main_dlg.cpp
+++ b/FreeFileSync/Source/RealTimeSync/main_dlg.cpp
@@ -376,7 +376,7 @@ void MainDialog::onAddFolder(wxCommandEvent& event)
     //clear existing top folder first
     firstFolderPanel_->setPath(Zstring());
 
-    insertAddFolder({ topFolder }, 0);
+    insertAddFolder({topFolder}, 0);
 }
 
 
diff --git a/FreeFileSync/Source/RealTimeSync/monitor.cpp b/FreeFileSync/Source/RealTimeSync/monitor.cpp
index 1866b764..e0dabf2c 100644
--- a/FreeFileSync/Source/RealTimeSync/monitor.cpp
+++ b/FreeFileSync/Source/RealTimeSync/monitor.cpp
@@ -26,7 +26,7 @@ std::set<Zstring, LessNativePath> waitForMissingDirs(const std::vector<Zstring>&
                                                      const std::function<void(const Zstring& folderPath)>& requestUiUpdate, std::chrono::milliseconds cbInterval)
 {
     //early failure! check for unsupported folder paths:
-    for (const std::string& protoName : { "ftp", "sftp", "mtp", "gdrive" })
+    for (const std::string& protoName : {"ftp", "sftp", "mtp", "gdrive"})
         for (const Zstring& phrase : folderPathPhrases)
             //hopefully clear enough now: https://freefilesync.org/forum/viewtopic.php?t=4302
             if (startsWithAsciiNoCase(trimCpy(phrase), protoName + ':'))
@@ -118,7 +118,7 @@ DirWatcher::Change waitForChanges(const std::set<Zstring, LessNativePath>& folde
         catch (FileError&)
         {
             if (!dirAvailable(folderPath)) //folder not existing or can't access
-                return { DirWatcher::ChangeType::baseFolderUnavailable, folderPath };
+                return {DirWatcher::ChangeType::baseFolderUnavailable, folderPath};
             throw;
         }
 
@@ -141,7 +141,7 @@ DirWatcher::Change waitForChanges(const std::set<Zstring, LessNativePath>& folde
             //IMPORTANT CHECK: DirWatcher has problems detecting removal of top watched directories!
             if (checkDirNow)
                 if (!dirAvailable(folderPath)) //catch errors related to directory removal, e.g. ERROR_NETNAME_DELETED
-                    return { DirWatcher::ChangeType::baseFolderUnavailable, folderPath };
+                    return {DirWatcher::ChangeType::baseFolderUnavailable, folderPath};
             try
             {
                 std::vector<DirWatcher::Change> changes = watcher->fetchChanges([&] { requestUiUpdate(false /*readyForSync*/); /*throw X*/ },
@@ -167,7 +167,7 @@ DirWatcher::Change waitForChanges(const std::set<Zstring, LessNativePath>& folde
             catch (FileError&)
             {
                 if (!dirAvailable(folderPath)) //a benign(?) race condition with FileError
-                    return { DirWatcher::ChangeType::baseFolderUnavailable, folderPath };
+                    return {DirWatcher::ChangeType::baseFolderUnavailable, folderPath};
                 throw;
             }
         }
diff --git a/FreeFileSync/Source/afs/abstract.cpp b/FreeFileSync/Source/afs/abstract.cpp
index 08d5bda0..614f1290 100644
--- a/FreeFileSync/Source/afs/abstract.cpp
+++ b/FreeFileSync/Source/afs/abstract.cpp
@@ -21,7 +21,7 @@ bool fff::isValidRelPath(const Zstring& relPath)
     if constexpr (FILE_NAME_SEPARATOR != Zstr('/' )) if (contains(relPath, Zstr('/' ))) return false;
     if constexpr (FILE_NAME_SEPARATOR != Zstr('\\')) if (contains(relPath, Zstr('\\'))) return false;
 
-    const Zchar doubleSep[] = { FILE_NAME_SEPARATOR, FILE_NAME_SEPARATOR, 0 };
+    const Zchar doubleSep[] = {FILE_NAME_SEPARATOR, FILE_NAME_SEPARATOR, 0};
     return !startsWith(relPath, FILE_NAME_SEPARATOR)&& !endsWith(relPath, FILE_NAME_SEPARATOR)&&
            !contains(relPath, doubleSep);
 }
@@ -80,7 +80,7 @@ struct FlatTraverserCallback : public AFS::TraverserCallback
 private:
     void                               onFile   (const AFS::FileInfo&    fi) override { if (onFile_)    onFile_   (fi); }
     std::shared_ptr<TraverserCallback> onFolder (const AFS::FolderInfo&  fi) override { if (onFolder_)  onFolder_ (fi); return nullptr; }
-    HandleLink                         onSymlink(const AFS::SymlinkInfo& si) override { if (onSymlink_) onSymlink_(si); return TraverserCallback::LINK_SKIP; }
+    HandleLink                         onSymlink(const AFS::SymlinkInfo& si) override { if (onSymlink_) onSymlink_(si); return TraverserCallback::HandleLink::skip; }
 
     HandleError reportDirError (const ErrorInfo& errorInfo)                          override { throw FileError(errorInfo.msg); }
     HandleError reportItemError(const ErrorInfo& errorInfo, const Zstring& itemName) override { throw FileError(errorInfo.msg); }
@@ -98,13 +98,13 @@ void AFS::traverseFolderFlat(const AfsPath& afsPath, //throw FileError
                              const std::function<void (const SymlinkInfo& si)>& onSymlink) const
 {
     auto ft = std::make_shared<FlatTraverserCallback>(onFile, onFolder, onSymlink); //throw FileError
-    traverseFolderRecursive({{ afsPath, ft }}, 1 /*parallelOps*/); //throw FileError
+    traverseFolderRecursive({{afsPath, ft}}, 1 /*parallelOps*/); //throw FileError
 }
 
 
 //already existing: undefined behavior! (e.g. fail/overwrite/auto-rename)
 AFS::FileCopyResult AFS::copyFileAsStream(const AfsPath& afsSource, const StreamAttributes& attrSource, //throw FileError, ErrorFileLocked, X
-                                          const AbstractPath& apTarget, const IOCallback& notifyUnbufferedIO /*throw X*/) const
+                                          const AbstractPath& apTarget, const IoCallback& notifyUnbufferedIO /*throw X*/) const
 {
     int64_t totalUnbufferedIO = 0;
     IOCallbackDivider cbd(notifyUnbufferedIO, totalUnbufferedIO);
@@ -148,14 +148,13 @@ AFS::FileCopyResult AFS::copyFileAsStream(const AfsPath& afsSource, const Stream
                         replaceCpy(replaceCpy(_("Unexpected size of data stream.\nExpected: %x bytes\nActual: %y bytes"),
                                               L"%x", numberTo<std::wstring>(totalBytesRead)),
                                    L"%y", numberTo<std::wstring>(totalBytesWritten)) + L" [notifyUnbufferedWrite]");
-
     FileCopyResult cpResult;
-    cpResult.fileSize     = attrSourceNew.fileSize;
-    cpResult.modTime      = attrSourceNew.modTime;
-    cpResult.sourceFileId = attrSourceNew.fileId;
-    cpResult.targetFileId = finResult.fileId;
-    cpResult.errorModTime = finResult.errorModTime;
-    /* Failing to set modification time is not a serious problem from synchronization perspective (treated like external update)
+    cpResult.fileSize        = attrSourceNew.fileSize;
+    cpResult.modTime         = attrSourceNew.modTime;
+    cpResult.sourceFilePrint = attrSourceNew.filePrint;
+    cpResult.targetFilePrint = finResult.filePrint;
+    cpResult.errorModTime    = finResult.errorModTime;
+    /* Failing to set modification time is not a serious problem from synchronization perspective (treat like external update)
             => Support additional scenarios:
             - GVFS failing to set modTime for FTP: https://freefilesync.org/forum/viewtopic.php?t=2372
             - GVFS failing to set modTime for MTP: https://freefilesync.org/forum/viewtopic.php?t=2803
@@ -171,7 +170,7 @@ AFS::FileCopyResult AFS::copyFileTransactional(const AbstractPath& apSource, con
                                                bool copyFilePermissions,
                                                bool transactionalCopy,
                                                const std::function<void()>& onDeleteTargetFile,
-                                               const IOCallback& notifyUnbufferedIO /*throw X*/)
+                                               const IoCallback& notifyUnbufferedIO /*throw X*/)
 {
 
     auto copyFilePlain = [&](const AbstractPath& apTargetTmp)
diff --git a/FreeFileSync/Source/afs/abstract.h b/FreeFileSync/Source/afs/abstract.h
index c37c5f8a..691fd464 100644
--- a/FreeFileSync/Source/afs/abstract.h
+++ b/FreeFileSync/Source/afs/abstract.h
@@ -69,8 +69,6 @@ struct AbstractFileSystem //THREAD-SAFETY: "const" member functions must model t
 
     static Zstring getInitPathPhrase(const AbstractPath& ap) { return ap.afsDevice.ref().getInitPathPhrase(ap.afsPath); }
 
-    static std::optional<Zstring> getNativeItemPath(const AbstractPath& ap) { return ap.afsDevice.ref().getNativeItemPath(ap.afsPath); }
-
     //----------------------------------------------------------------------------------------------------------------
     static void authenticateAccess(const AfsDevice& afsDevice, bool allowUserInteraction) //throw FileError
     { return afsDevice.ref().authenticateAccess(allowUserInteraction); }
@@ -82,7 +80,7 @@ struct AbstractFileSystem //THREAD-SAFETY: "const" member functions must model t
     static bool hasNativeTransactionalCopy(const AbstractPath& ap) { return ap.afsDevice.ref().hasNativeTransactionalCopy(); }
     //----------------------------------------------------------------------------------------------------------------
 
-    using FileId = std::string; //AfsDevice-dependent unique ID
+    using FingerPrint = uint64_t; //AfsDevice-dependent persistent unique ID
 
     enum class ItemType : unsigned char
     {
@@ -135,7 +133,7 @@ struct AbstractFileSystem //THREAD-SAFETY: "const" member functions must model t
     {
         time_t modTime; //number of seconds since Jan. 1st 1970 UTC
         uint64_t fileSize;
-        FileId fileId; //optional!
+        FingerPrint filePrint; //optional
     };
 
     //----------------------------------------------------------------------------------------------------------------
@@ -149,13 +147,13 @@ struct AbstractFileSystem //THREAD-SAFETY: "const" member functions must model t
         virtual std::optional<StreamAttributes> getAttributesBuffered() = 0; //throw FileError
     };
     //return value always bound:
-    static std::unique_ptr<InputStream> getInputStream(const AbstractPath& ap, const zen::IOCallback& notifyUnbufferedIO /*throw X*/) //throw FileError, ErrorFileLocked
+    static std::unique_ptr<InputStream> getInputStream(const AbstractPath& ap, const zen::IoCallback& notifyUnbufferedIO /*throw X*/) //throw FileError, ErrorFileLocked
     { return ap.afsDevice.ref().getInputStream(ap.afsPath, notifyUnbufferedIO); }
 
 
     struct FinalizeResult
     {
-        FileId fileId;
+        FingerPrint filePrint; //optional
         std::optional<zen::FileError> errorModTime;
     };
 
@@ -184,14 +182,14 @@ struct AbstractFileSystem //THREAD-SAFETY: "const" member functions must model t
     static std::unique_ptr<OutputStream> getOutputStream(const AbstractPath& ap, //throw FileError
                                                          std::optional<uint64_t> streamSize,
                                                          std::optional<time_t> modTime,
-                                                         const zen::IOCallback& notifyUnbufferedIO /*throw X*/)
+                                                         const zen::IoCallback& notifyUnbufferedIO /*throw X*/)
     { return std::make_unique<OutputStream>(ap.afsDevice.ref().getOutputStream(ap.afsPath, streamSize, modTime, notifyUnbufferedIO), ap, streamSize); }
     //----------------------------------------------------------------------------------------------------------------
 
     struct SymlinkInfo
     {
         Zstring itemName;
-        time_t modTime; //number of seconds since Jan. 1st 1970 UTC
+        time_t modTime;
     };
 
     struct FileInfo
@@ -199,7 +197,7 @@ struct AbstractFileSystem //THREAD-SAFETY: "const" member functions must model t
         Zstring itemName;
         uint64_t fileSize; //unit: bytes!
         time_t modTime; //number of seconds since Jan. 1st 1970 UTC
-        FileId fileId; //optional: empty if not supported!
+        FingerPrint filePrint; //optional; persistent + unique (relative to device) or 0!
         bool isFollowedSymlink;
     };
 
@@ -213,16 +211,16 @@ struct AbstractFileSystem //THREAD-SAFETY: "const" member functions must model t
     {
         virtual ~TraverserCallback() {}
 
-        enum HandleLink
+        enum class HandleLink
         {
-            LINK_FOLLOW, //dereferences link, then calls "onFolder()" or "onFile()"
-            LINK_SKIP
+            follow, //follows link, then calls "onFolder()" or "onFile()"
+            skip
         };
 
-        enum HandleError
+        enum class HandleError
         {
-            ON_ERROR_RETRY,
-            ON_ERROR_CONTINUE
+            retry,
+            ignore
         };
 
         virtual void                               onFile   (const FileInfo&    fi) = 0; //
@@ -264,8 +262,8 @@ struct AbstractFileSystem //THREAD-SAFETY: "const" member functions must model t
     {
         uint64_t fileSize = 0;
         time_t modTime = 0; //number of seconds since Jan. 1st 1970 UTC
-        FileId sourceFileId;
-        FileId targetFileId;
+        FingerPrint sourceFilePrint; //optional
+        FingerPrint targetFilePrint; //
         std::optional<zen::FileError> errorModTime; //failure to set modification time
     };
 
@@ -280,7 +278,7 @@ struct AbstractFileSystem //THREAD-SAFETY: "const" member functions must model t
                                                 //if transactionalCopy == true, full read access on source had been proven at this point, so it's safe to delete it.
                                                 const std::function<void()>& onDeleteTargetFile /*throw X*/,
                                                 //accummulated delta != file size! consider ADS, sparse, compressed files
-                                                const zen::IOCallback& notifyUnbufferedIO /*throw X*/);
+                                                const zen::IoCallback& notifyUnbufferedIO /*throw X*/);
 
     //already existing: fail
     //symlink handling: follow
@@ -331,7 +329,7 @@ protected:
 
     //already existing: undefined behavior! (e.g. fail/overwrite/auto-rename)
     FileCopyResult copyFileAsStream(const AfsPath& afsSource, const StreamAttributes& attrSource, //throw FileError, ErrorFileLocked, X
-                                    const AbstractPath& apTarget, const zen::IOCallback& notifyUnbufferedIO /*throw X*/) const;
+                                    const AbstractPath& apTarget, const zen::IoCallback& notifyUnbufferedIO /*throw X*/) const;
 
 private:
     virtual std::optional<Zstring> getNativeItemPath(const AfsPath& afsPath) const { return {}; };
@@ -363,13 +361,13 @@ private:
     virtual bool equalSymlinkContentForSameAfsType(const AfsPath& afsLhs, const AbstractPath& apRhs) const = 0; //throw FileError
 
     //----------------------------------------------------------------------------------------------------------------
-    virtual std::unique_ptr<InputStream> getInputStream(const AfsPath& afsPath, const zen::IOCallback& notifyUnbufferedIO /*throw X*/) const = 0; //throw FileError, ErrorFileLocked
+    virtual std::unique_ptr<InputStream> getInputStream(const AfsPath& afsPath, const zen::IoCallback& notifyUnbufferedIO /*throw X*/) const = 0; //throw FileError, ErrorFileLocked
 
     //already existing: undefined behavior! (e.g. fail/overwrite/auto-rename)
     virtual std::unique_ptr<OutputStreamImpl> getOutputStream(const AfsPath& afsPath, //throw FileError
                                                               std::optional<uint64_t> streamSize,
                                                               std::optional<time_t> modTime,
-                                                              const zen::IOCallback& notifyUnbufferedIO /*throw X*/) const = 0;
+                                                              const zen::IoCallback& notifyUnbufferedIO /*throw X*/) const = 0;
     //----------------------------------------------------------------------------------------------------------------
     virtual void traverseFolderRecursive(const TraverserWorkload& workload /*throw X*/, size_t parallelOps) const = 0;
     //----------------------------------------------------------------------------------------------------------------
@@ -383,7 +381,7 @@ private:
     virtual FileCopyResult copyFileForSameAfsType(const AfsPath& afsSource, const StreamAttributes& attrSource, //throw FileError, ErrorFileLocked, X
                                                   const AbstractPath& apTarget, bool copyFilePermissions,
                                                   //accummulated delta != file size! consider ADS, sparse, compressed files
-                                                  const zen::IOCallback& notifyUnbufferedIO /*throw X*/) const = 0;
+                                                  const zen::IoCallback& notifyUnbufferedIO /*throw X*/) const = 0;
 
 
     //symlink handling: follow
diff --git a/FreeFileSync/Source/afs/abstract_impl.h b/FreeFileSync/Source/afs/abstract_impl.h
index e7ab071e..4ecc2614 100644
--- a/FreeFileSync/Source/afs/abstract_impl.h
+++ b/FreeFileSync/Source/afs/abstract_impl.h
@@ -28,9 +28,9 @@ std::wstring tryReportingDirError(Function cmd /*throw FileError*/, AbstractFile
             assert(!e.toString().empty());
             switch (cb.reportDirError({e.toString(), std::chrono::steady_clock::now(), retryNumber})) //throw X
             {
-                case AbstractFileSystem::TraverserCallback::ON_ERROR_CONTINUE:
+                case AbstractFileSystem::TraverserCallback::HandleError::ignore:
                     return e.toString();
-                case AbstractFileSystem::TraverserCallback::ON_ERROR_RETRY:
+                case AbstractFileSystem::TraverserCallback::HandleError::retry:
                     break; //continue with loop
             }
         }
@@ -49,9 +49,9 @@ bool tryReportingItemError(Command cmd, AbstractFileSystem::TraverserCallback& c
         {
             switch (callback.reportItemError({e.toString(), std::chrono::steady_clock::now(), retryNumber}, itemName)) //throw X
             {
-                case AbstractFileSystem::TraverserCallback::ON_ERROR_RETRY:
+                case AbstractFileSystem::TraverserCallback::HandleError::retry:
                     break;
-                case AbstractFileSystem::TraverserCallback::ON_ERROR_CONTINUE:
+                case AbstractFileSystem::TraverserCallback::HandleError::ignore:
                     return false;
             }
         }
@@ -197,8 +197,8 @@ private:
     std::condition_variable conditionBytesWritten_;
     std::condition_variable conditionBytesRead_;
 
-    std::atomic<uint64_t> totalBytesWritten_{ 0 }; //std:atomic is uninitialized by default!
-    std::atomic<uint64_t> totalBytesRead_   { 0 }; //
+    std::atomic<uint64_t> totalBytesWritten_{0}; //std:atomic is uninitialized by default!
+    std::atomic<uint64_t> totalBytesRead_   {0}; //
 };
 
 //==========================================================================================
diff --git a/FreeFileSync/Source/afs/ftp.cpp b/FreeFileSync/Source/afs/ftp.cpp
index 88afa144..0685066f 100644
--- a/FreeFileSync/Source/afs/ftp.cpp
+++ b/FreeFileSync/Source/afs/ftp.cpp
@@ -93,7 +93,7 @@ Zstring ansiToUtfEncoding(const std::string& str) //throw SysError
         throw SysError(formatGlibError("g_convert(" + utfTo<std::string>(str) + ')', error));
     ZEN_ON_SCOPE_EXIT(::g_free(utfStr));
 
-    return { utfStr, bytesWritten };
+    return {utfStr, bytesWritten};
 
 
 }
@@ -117,7 +117,7 @@ std::string utfToAnsiEncoding(const Zstring& str) //throw SysError
         throw SysError(formatGlibError("g_convert(" + utfTo<std::string>(str) + ')', error));
     ZEN_ON_SCOPE_EXIT(::g_free(ansiStr));
 
-    return { ansiStr, bytesWritten };
+    return {ansiStr, bytesWritten};
 
 }
 
@@ -494,8 +494,8 @@ public:
 
         return perform(AfsPath(), true /*isDir*/, CURLFTPMETHOD_NOCWD /*avoid needless CWDs*/,
         {
-            { CURLOPT_NOBODY, 1L },
-            { CURLOPT_QUOTE, quote },
+            {CURLOPT_NOBODY, 1L},
+            {CURLOPT_QUOTE, quote},
         }, requiresUtf8, timeoutSec); //throw SysError
     }
 
@@ -510,7 +510,7 @@ public:
             => are there servers supporting neither FEAT nor HELP? only time will tell...
             ... and it tells! FUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU https://freefilesync.org/forum/viewtopic.php?t=8041             */
 
-        //=> * to the rescue: as long as we get an FTP response, *any* FTP response, including 550, the connection itself is fine!
+        //=> * to the rescue: as long as we get an FTP response - *any* FTP response (including 550) - the connection itself is fine!
         const std::string& featBuf = runSingleFtpCommand("*FEAT", false /*requiresUtf8*/, timeoutSec); //throw SysError
 
         for (const std::string& line : splitFtpResponse(featBuf))
@@ -563,7 +563,7 @@ public:
                                     ++it; //skip double quote
                                 else
                                 {
-                                    const std::string homePathRaw = replaceCpy<std::string>({ itBegin, it }, "\"\"", '"');
+                                    const std::string homePathRaw = replaceCpy(std::string{itBegin, it}, "\"\"", '"');
                                     const ServerEncoding enc = getServerEncoding(timeoutSec); //throw SysError
                                     const Zstring homePathUtf = serverToUtfEncoding(homePathRaw, enc); //throw SysError
                                     return sanitizeDeviceRelativePath(homePathUtf);
@@ -917,6 +917,7 @@ struct FtpItem
     Zstring itemName;
     uint64_t fileSize = 0;
     time_t modTime = 0;
+    AFS::FingerPrint filePrint = 0; //optional
 };
 
 
@@ -1023,8 +1024,8 @@ public:
             {
                 std::vector<CurlOption> options =
                 {
-                    { CURLOPT_WRITEDATA, &rawListing },
-                    { CURLOPT_WRITEFUNCTION, onBytesReceived },
+                    {CURLOPT_WRITEDATA, &rawListing},
+                    {CURLOPT_WRITEFUNCTION, onBytesReceived},
                 };
                 curl_ftpmethod pathMethod = CURLFTPMETHOD_SINGLECWD;
 
@@ -1142,16 +1143,22 @@ private:
                 }
                 else if (startsWithAsciiNoCase(fact, "unique="))
                 {
-                    warn_static("reevaluate: https://tools.ietf.org/html/rfc3659#section-7.5.2")
-                    //note: as far as the RFC goes, the "unique" fact is not required to act like a persistent file id!
-                    auto fileId
-                    /*item.fileId */= afterFirst(fact, '=', IfNotFoundReturn::none);
+                    /*  https://tools.ietf.org/html/rfc3659#section-7.5.2
+                        "The mapping between files, and unique fact tokens should be maintained, [...] for
+                         *at least* the lifetime of the control connection from user-PI to server-PI."
+
+                        => not necessarily *persistent* as far as the RFC goes!
+                           BUT: practially this will be the inode ID/file index, so we can assume persistence */
+                    const std::string uniqueId = afterFirst(fact, '=', IfNotFoundReturn::none);
+                    assert(!uniqueId.empty());
+                    item.filePrint = hashArray<AFS::FingerPrint>(uniqueId.begin(), uniqueId.end());
+                    //other metadata to hash e.g. create fact? => not available on Linux-hosted FTP!
                 }
 
             if (equalAsciiNoCase(typeFact, "cdir"))
-                return { AFS::ItemType::folder, Zstr("."), 0, 0 };
+                return {AFS::ItemType::folder, Zstr("."), 0, 0};
             if (equalAsciiNoCase(typeFact, "pdir"))
-                return { AFS::ItemType::folder, Zstr(".."), 0, 0 };
+                return {AFS::ItemType::folder, Zstr(".."), 0, 0};
 
             if (equalAsciiNoCase(typeFact, "dir"))
                 item.type = AFS::ItemType::folder;
@@ -1238,33 +1245,33 @@ private:
 
     static FtpItem parseUnixLine(const std::string& rawLine, time_t utcTimeNow, int utcCurrentYear, bool haveGroup, ServerEncoding enc) //throw SysError
     {
-        try
-        {
-            FtpLineParser parser(rawLine);
-            /*  total 4953                                                  <- optional first line
-                drwxr-xr-x 1 root root    4096 Jan 10 11:58 version
-                -rwxr-xr-x 1 root root    1084 Sep  2 01:17 Unit Test.vcxproj.user
-                -rwxr-xr-x 1 1000  300    2217 Feb 28  2016 win32.manifest
-                lrwxr-xr-x 1 root root      18 Apr 26 15:17 Projects -> /mnt/hgfs/Projects
+        /*  total 4953                                                  <- optional first line
+            drwxr-xr-x 1 root root    4096 Jan 10 11:58 version
+            -rwxr-xr-x 1 root root    1084 Sep  2 01:17 Unit Test.vcxproj.user
+            -rwxr-xr-x 1 1000  300    2217 Feb 28  2016 win32.manifest
+            lrwxr-xr-x 1 root root      18 Apr 26 15:17 Projects -> /mnt/hgfs/Projects
 
-            file type: -:file  l:symlink  d:directory  b:block device  p:named pipe  c:char device  s:socket
+        file type: -:file  l:symlink  d:directory  b:block device  p:named pipe  c:char device  s:socket
 
-            permissions: (r|-)(w|-)(x|s|S|-)    user
-                         (r|-)(w|-)(x|s|S|-)    group  s := S + x      S = Setgid
-                         (r|-)(w|-)(x|t|T|-)    others t := T + x      T = sticky bit
+        permissions: (r|-)(w|-)(x|s|S|-)    user
+                     (r|-)(w|-)(x|s|S|-)    group  s := S + x      S = Setgid
+                     (r|-)(w|-)(x|t|T|-)    others t := T + x      T = sticky bit
 
-            Alternative formats:
-               Unix, no group ("ls -alG") https://freefilesync.org/forum/viewtopic.php?t=4306
-                   dr-xr-xr-x   2 root                  512 Apr  8  1994 etc
+        Alternative formats:
+           Unix, no group ("ls -alG") https://freefilesync.org/forum/viewtopic.php?t=4306
+               dr-xr-xr-x   2 root                  512 Apr  8  1994 etc
 
-            Yet to be seen in the wild:
-               Netware:
-                   d [R----F--] supervisor            512       Jan 16 18:53    login
-                   - [R----F--] rhesus             214059       Oct 20 15:27    cx.exe
+        Yet to be seen in the wild:
+           Netware:
+               d [R----F--] supervisor            512       Jan 16 18:53    login
+               - [R----F--] rhesus             214059       Oct 20 15:27    cx.exe
 
-               NetPresenz for the Mac:
-               -------r--         326  1391972  1392298 Nov 22  1995 MegaPhone.sit
-               drwxrwxr-x               folder        2 May 10  1996 network                     */
+           NetPresenz for the Mac:
+           -------r--         326  1391972  1392298 Nov 22  1995 MegaPhone.sit
+           drwxrwxr-x               folder        2 May 10  1996 network                     */
+        try
+        {
+            FtpLineParser parser(rawLine);
 
             const std::string typeTag = parser.readRange(1, [](char c) //throw SysError
             {
@@ -1300,7 +1307,7 @@ private:
             const std::string monthStr = parser.readRange(std::not_fn(isWhiteSpace<char>)); //throw SysError
             parser.readRange(&isWhiteSpace<char>);                                                  //throw SysError
 
-            const char* months[] = { "Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec" };
+            const char* months[] = {"Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"};
             auto itMonth = std::find_if(std::begin(months), std::end(months), [&](const char* name) { return equalAsciiNoCase(name, monthStr); });
             if (itMonth == std::end(months))
                 throw SysError(L"Failed to parse month name.");
@@ -1344,8 +1351,8 @@ private:
             else
                 throw SysError(L"Failed to parse file time.");
 
-            warn_static("reevaluate: can't we detect the server offset via MDTM!?")
             //let's pretend the time listing is UTC (same behavior as FileZilla): hopefully MLSD will make this mess obsolete soon...
+            //  => find exact offset with some MDTM hackery? yes, could do that, but this doesn't solve the bigger problem of imprecise LIST file times, so why bother?
             time_t utcTime = utcToTimeT(timeComp); //returns -1 on error
             if (utcTime == -1)
             {
@@ -1366,7 +1373,7 @@ private:
                 throw SysError(L"Item name not available.");
 
             if (itemName == "." || itemName == "..") //sometimes returned, e.g. by freefilesync.org
-                return { AFS::ItemType::folder, utfTo<Zstring>(itemName), 0, 0 };
+                return {AFS::ItemType::folder, utfTo<Zstring>(itemName), 0, 0};
             //------------------------------------------------------------------------------------
             FtpItem item;
             if (typeTag == "d")
@@ -1391,29 +1398,28 @@ private:
     //"dir"
     static std::vector<FtpItem> parseWindows(const std::string& buf, ServerEncoding enc) //throw SysError
     {
-        /*
-        Test server: test.rebex.net username:demo pw:password  useTls = true
+        /*  Test server: test.rebex.net username:demo pw:password  useTls = true
+
+            listing supported by libcurl (US server)
+                10-27-15  03:46AM       <DIR>          pub
+                04-08-14  03:09PM               11,399 readme.txt
 
-        listing supported by libcurl (US server)
-            10-27-15  03:46AM       <DIR>          pub
-            04-08-14  03:09PM               11,399 readme.txt
+            Datalogic Windows CE 5.0
+                01-01-98  13:00       <DIR>          Storage Card
 
-        Datalogic Windows CE 5.0
-            01-01-98  13:00       <DIR>          Storage Card
+            IIS option "four-digit years"
+                06-22-2017  04:25PM       <DIR>          test
+                06-20-2017  12:50PM              1875499 zstring.obj
 
-        IIS option "four-digit years"
-            06-22-2017  04:25PM       <DIR>          test
-            06-20-2017  12:50PM              1875499 zstring.obj
+            Alternative formats (yet to be seen in the wild)
+                "dir" on Windows, US:
+                    10/27/2015  03:46 AM  <DIR>          pub
+                    04/08/2014  03:09 PM          11,399 readme.txt
 
-        Alternative formats (yet to be seen in the wild)
-            "dir" on Windows, US:
-                10/27/2015  03:46 AM  <DIR>          pub
-                04/08/2014  03:09 PM          11,399 readme.txt
+                "dir" on Windows, German:
+                    21.09.2016  18:31    <DIR>          Favorites
+                    12.01.2017  19:57            11.399 gsview64.ini        */
 
-            "dir" on Windows, German:
-                21.09.2016  18:31    <DIR>          Favorites
-                12.01.2017  19:57            11.399 gsview64.ini
-        */
         const TimeComp tc = getUtcTime();
         if (tc == TimeComp())
             throw SysError(L"Failed to determine current time: " + numberTo<std::wstring>(std::time(nullptr)));
@@ -1473,8 +1479,8 @@ private:
                 timeComp.day    = day;
                 timeComp.hour   = hour;
                 timeComp.minute = minute;
-                warn_static("reevaluate: can't we detect the server offset via MDTM!?")
                 //let's pretend the time listing is UTC (same behavior as FileZilla): hopefully MLSD will make this mess obsolete soon...
+                //  => find exact offset with some MDTM hackery? yes, could do that, but this doesn't solve the bigger problem of imprecise LIST file times, so why bother?
                 time_t utcTime = utcToTimeT(timeComp); //returns -1 on error
                 if (utcTime == -1)
                 {
@@ -1561,18 +1567,18 @@ private:
             switch (item.type)
             {
                 case AFS::ItemType::file:
-                    cb.onFile({ item.itemName, item.fileSize, item.modTime, AFS::FileId(), false /*isFollowedSymlink*/ }); //throw X
+                    cb.onFile({item.itemName, item.fileSize, item.modTime, item.filePrint, false /*isFollowedSymlink*/}); //throw X
                     break;
 
                 case AFS::ItemType::folder:
-                    if (std::shared_ptr<AFS::TraverserCallback> cbSub = cb.onFolder({ item.itemName, false /*isFollowedSymlink*/ })) //throw X
-                        workload_.push_back({ itemPath, std::move(cbSub) });
+                    if (std::shared_ptr<AFS::TraverserCallback> cbSub = cb.onFolder({item.itemName, false /*isFollowedSymlink*/})) //throw X
+                        workload_.push_back({itemPath, std::move(cbSub)});
                     break;
 
                 case AFS::ItemType::symlink:
-                    switch (cb.onSymlink({ item.itemName, item.modTime })) //throw X
+                    switch (cb.onSymlink({item.itemName, item.modTime})) //throw X
                     {
-                        case AFS::TraverserCallback::LINK_FOLLOW:
+                        case AFS::TraverserCallback::HandleLink::follow:
                         {
                             FtpItem target = {};
                             if (!tryReportingItemError([&] //throw X
@@ -1583,15 +1589,15 @@ private:
 
                             if (target.type == AFS::ItemType::folder)
                             {
-                                if (std::shared_ptr<AFS::TraverserCallback> cbSub = cb.onFolder({ item.itemName, true /*isFollowedSymlink*/ })) //throw X
-                                    workload_.push_back({ itemPath, std::move(cbSub) });
+                                if (std::shared_ptr<AFS::TraverserCallback> cbSub = cb.onFolder({item.itemName, true /*isFollowedSymlink*/})) //throw X
+                                    workload_.push_back({itemPath, std::move(cbSub)});
                             }
                             else //a file or named pipe, etc.
-                                cb.onFile({ item.itemName, target.fileSize, target.modTime, AFS::FileId(), true /*isFollowedSymlink*/ }); //throw X
+                                cb.onFile({item.itemName, target.fileSize, target.modTime, item.filePrint, true /*isFollowedSymlink*/}); //throw X
                         }
                         break;
 
-                        case AFS::TraverserCallback::LINK_SKIP:
+                        case AFS::TraverserCallback::HandleLink::skip:
                             break;
                     }
                     break;
@@ -1643,9 +1649,9 @@ void ftpFileDownload(const FtpLogin& login, const AfsPath& afsFilePath, //throw
         {
             session.perform(afsFilePath, false /*isDir*/, CURLFTPMETHOD_NOCWD, //are there any servers that require CURLFTPMETHOD_SINGLECWD? let's find out
             {
-                { CURLOPT_WRITEDATA, &onBytesReceived },
-                { CURLOPT_WRITEFUNCTION, onBytesReceivedWrapper },
-                { CURLOPT_IGNORE_CONTENT_LENGTH, 1L }, //skip FTP "SIZE" command before download (=> download until actual EOF if file size changes)
+                {CURLOPT_WRITEDATA, &onBytesReceived},
+                {CURLOPT_WRITEFUNCTION, onBytesReceivedWrapper},
+                {CURLOPT_IGNORE_CONTENT_LENGTH, 1L}, //skip FTP "SIZE" command before download (=> download until actual EOF if file size changes)
             }, true /*requiresUtf8*/, login.timeoutSec); //throw SysError
         });
     }
@@ -1706,15 +1712,15 @@ void ftpFileUpload(const FtpLogin& login, const AfsPath& afsFilePath, //throw Fi
             */
             session.perform(afsFilePath, false /*isDir*/, CURLFTPMETHOD_NOCWD, //are there any servers that require CURLFTPMETHOD_SINGLECWD? let's find out
             {
-                { CURLOPT_UPLOAD, 1L },
-                { CURLOPT_READDATA, &getBytesToSend },
-                { CURLOPT_READFUNCTION, getBytesToSendWrapper },
+                {CURLOPT_UPLOAD, 1L},
+                {CURLOPT_READDATA, &getBytesToSend},
+                {CURLOPT_READFUNCTION, getBytesToSendWrapper},
 
-                //{ CURLOPT_INFILESIZE_LARGE, static_cast<curl_off_t>(inputBuffer.size()) },
+                //{CURLOPT_INFILESIZE_LARGE, static_cast<curl_off_t>(inputBuffer.size())},
                 //=> CURLOPT_INFILESIZE_LARGE does not issue a specific FTP command, but is used by libcurl only!
 
-                //{ CURLOPT_PREQUOTE,  quote },
-                //{ CURLOPT_POSTQUOTE, quote },
+                //{CURLOPT_PREQUOTE,  quote},
+                //{CURLOPT_POSTQUOTE, quote},
             }, true /*requiresUtf8*/, login.timeoutSec); //throw SysError
         });
     }
@@ -1733,7 +1739,7 @@ struct InputStreamFtp : public AFS::InputStream
 {
     InputStreamFtp(const FtpLogin& login,
                    const AfsPath& afsPath,
-                   const IOCallback& notifyUnbufferedIO /*throw X*/) :
+                   const IoCallback& notifyUnbufferedIO /*throw X*/) :
         notifyUnbufferedIO_(notifyUnbufferedIO)
     {
         worker_ = InterruptibleThread([asyncStreamOut = this->asyncStreamIn_, login, afsPath]
@@ -1784,7 +1790,7 @@ private:
         totalBytesReported_ = totalBytesDownloaded;
     }
 
-    const IOCallback notifyUnbufferedIO_; //throw X
+    const IoCallback notifyUnbufferedIO_; //throw X
     int64_t totalBytesReported_ = 0;
     std::shared_ptr<AsyncStreamBuffer> asyncStreamIn_ = std::make_shared<AsyncStreamBuffer>(FTP_STREAM_BUFFER_SIZE);
     InterruptibleThread worker_;
@@ -1799,7 +1805,7 @@ struct OutputStreamFtp : public AFS::OutputStreamImpl
     OutputStreamFtp(const FtpLogin& login,
                     const AfsPath& afsPath,
                     std::optional<time_t> modTime,
-                    const IOCallback& notifyUnbufferedIO /*throw X*/) :
+                    const IoCallback& notifyUnbufferedIO /*throw X*/) :
         login_(login),
         afsPath_(afsPath),
         modTime_(modTime),
@@ -1861,7 +1867,7 @@ struct OutputStreamFtp : public AFS::OutputStreamImpl
         futUploadDone_.get(); //throw FileError
 
         AFS::FinalizeResult result;
-        //result.fileId = ... -> not supported by FTP
+        //result.filePrint = ... -> yet unknown at this point
         try
         {
             setModTimeIfAvailable(); //throw FileError, follows symlinks
@@ -1910,7 +1916,7 @@ private:
     const FtpLogin login_;
     const AfsPath afsPath_;
     const std::optional<time_t> modTime_;
-    const IOCallback notifyUnbufferedIO_; //throw X
+    const IoCallback notifyUnbufferedIO_; //throw X
     int64_t totalBytesReported_ = 0;
     std::shared_ptr<AsyncStreamBuffer> asyncStreamOut_ = std::make_shared<AsyncStreamBuffer>(FTP_STREAM_BUFFER_SIZE);
     InterruptibleThread worker_;
@@ -2110,7 +2116,7 @@ private:
     //----------------------------------------------------------------------------------------------------------------
 
     //return value always bound:
-    std::unique_ptr<InputStream> getInputStream(const AfsPath& afsPath, const IOCallback& notifyUnbufferedIO /*throw X*/) const override //throw FileError, (ErrorFileLocked)
+    std::unique_ptr<InputStream> getInputStream(const AfsPath& afsPath, const IoCallback& notifyUnbufferedIO /*throw X*/) const override //throw FileError, (ErrorFileLocked)
     {
         return std::make_unique<InputStreamFtp>(login_, afsPath, notifyUnbufferedIO);
     }
@@ -2120,7 +2126,7 @@ private:
     std::unique_ptr<OutputStreamImpl> getOutputStream(const AfsPath& afsPath, //throw FileError
                                                       std::optional<uint64_t> streamSize,
                                                       std::optional<time_t> modTime,
-                                                      const IOCallback& notifyUnbufferedIO /*throw X*/) const override
+                                                      const IoCallback& notifyUnbufferedIO /*throw X*/) const override
     {
         /* most FTP servers overwrite, but some (e.g. IIS) can be configured to fail, others (pureFTP) can be configured to auto-rename:
            https://download.pureftpd.org/pub/pure-ftpd/doc/README
@@ -2140,7 +2146,7 @@ private:
     //symlink handling: follow
     //already existing: undefined behavior! (e.g. fail/overwrite/auto-rename)
     FileCopyResult copyFileForSameAfsType(const AfsPath& afsSource, const StreamAttributes& attrSource, //throw FileError, (ErrorFileLocked), X
-                                          const AbstractPath& apTarget, bool copyFilePermissions, const IOCallback& notifyUnbufferedIO /*throw X*/) const override
+                                          const AbstractPath& apTarget, bool copyFilePermissions, const IoCallback& notifyUnbufferedIO /*throw X*/) const override
     {
         //no native FTP file copy => use stream-based file copy:
         if (copyFilePermissions)
@@ -2195,8 +2201,8 @@ private:
 
                 session.perform(AfsPath(), true /*isDir*/, CURLFTPMETHOD_NOCWD, //avoid needless CWDs
                 {
-                    { CURLOPT_NOBODY, 1L },
-                    { CURLOPT_QUOTE, quote },
+                    {CURLOPT_NOBODY, 1L},
+                    {CURLOPT_QUOTE, quote},
                 }, true /*requiresUtf8*/, login_.timeoutSec); //throw SysError
             });
         }
@@ -2361,7 +2367,7 @@ AbstractPath fff::createItemPathFtp(const Zstring& itemPathPhrase) //noexcept
 
     auto it = std::find_if(fullPath.begin(), fullPath.end(), [](Zchar c) { return c == '/' || c == '\\'; });
     const Zstring serverPort(fullPath.begin(), it);
-    const AfsPath serverRelPath = sanitizeDeviceRelativePath({ it, fullPath.end() });
+    const AfsPath serverRelPath = sanitizeDeviceRelativePath({it, fullPath.end()});
 
     login.server       = beforeLast(serverPort, Zstr(':'), IfNotFoundReturn::all);
     const Zstring port =  afterLast(serverPort, Zstr(':'), IfNotFoundReturn::none);
diff --git a/FreeFileSync/Source/afs/gdrive.cpp b/FreeFileSync/Source/afs/gdrive.cpp
index b731477b..863fad43 100644
--- a/FreeFileSync/Source/afs/gdrive.cpp
+++ b/FreeFileSync/Source/afs/gdrive.cpp
@@ -169,6 +169,14 @@ std::wstring formatGdriveErrorRaw(std::string serverResponse)
     return utfTo<std::wstring>(serverResponse);
 }
 
+
+AFS::FingerPrint getGdriveFilePrint(const std::string& itemId)
+{
+    assert(!itemId.empty());
+    //Google Drive item ID is persistent and globally unique! :)
+    return hashArray<AFS::FingerPrint>(itemId.begin(), itemId.end());
+}
+
 //----------------------------------------------------------------------------------------------------------------
 
 constinit2 Global<UniSessionCounter> httpSessionCount;
@@ -180,7 +188,8 @@ UniInitializer startupInitHttp(*httpSessionCount.get());
 class HttpSessionManager //reuse (healthy) HTTP sessions globally
 {
 public:
-    explicit HttpSessionManager(const Zstring& caCertFilePath) : caCertFilePath_(caCertFilePath),
+    explicit HttpSessionManager(const Zstring& caCertFilePath) :
+        caCertFilePath_(caCertFilePath),
         sessionCleaner_([this]
     {
         setCurrentThreadName(Zstr("Session Cleaner[HTTP]"));
@@ -317,7 +326,7 @@ HttpSession::Result gdriveHttpsRequest(const std::string& serverRelPath, //throw
         {
             //https://developers.google.com/drive/api/v3/performance
             //"In order to receive a gzip-encoded response you must do two things: Set an Accept-Encoding header, ["gzip" automatically set by HttpSession]
-            { CURLOPT_USERAGENT, "FreeFileSync (gzip)" }, //and modify your user agent to contain the string gzip."
+            {CURLOPT_USERAGENT, "FreeFileSync (gzip)"}, //and modify your user agent to contain the string gzip."
         };
         append(options, extraOptions);
 
@@ -338,10 +347,10 @@ GdriveUser getGdriveUser(const std::string& accessToken) //throw SysError
     //https://developers.google.com/drive/api/v3/reference/about
     const std::string& queryParams = xWwwFormUrlEncode(
     {
-        { "fields", "user/displayName,user/emailAddress" },
+        {"fields", "user/displayName,user/emailAddress"},
     });
     std::string response;
-    gdriveHttpsRequest("/drive/v3/about?" + queryParams, { "Authorization: Bearer " + accessToken }, {} /*extraOptions*/, //throw SysError
+    gdriveHttpsRequest("/drive/v3/about?" + queryParams, {"Authorization: Bearer " + accessToken}, {} /*extraOptions*/, //throw SysError
     [&](const void* buffer, size_t bytesToWrite) { response.append(static_cast<const char*>(buffer), bytesToWrite); }, nullptr /*readRequest*/);
 
     JsonValue jresponse;
@@ -353,7 +362,7 @@ GdriveUser getGdriveUser(const std::string& accessToken) //throw SysError
         const std::optional<std::string> displayName = getPrimitiveFromJsonObject(*user, "displayName");
         const std::optional<std::string> email       = getPrimitiveFromJsonObject(*user, "emailAddress");
         if (displayName && email)
-            return { utfTo<std::wstring>(*displayName), *email };
+            return {utfTo<std::wstring>(*displayName), *email};
     }
 
     throw SysError(formatGdriveErrorRaw(response));
@@ -385,15 +394,15 @@ GdriveAccessInfo gdriveExchangeAuthCode(const GdriveAuthCode& authCode) //throw
     //https://developers.google.com/identity/protocols/OAuth2InstalledApp#exchange-authorization-code
     const std::string postBuf = xWwwFormUrlEncode(
     {
-        { "code",          authCode.code },
-        { "client_id",     getGdriveClientId() },
-        { "client_secret", getGdriveClientSecret() },
-        { "redirect_uri",  authCode.redirectUrl },
-        { "grant_type",    "authorization_code" },
-        { "code_verifier", authCode.codeChallenge },
+        {"code",          authCode.code},
+        {"client_id",     getGdriveClientId()},
+        {"client_secret", getGdriveClientSecret()},
+        {"redirect_uri",  authCode.redirectUrl},
+        {"grant_type",    "authorization_code"},
+        {"code_verifier", authCode.codeChallenge},
     });
     std::string response;
-    gdriveHttpsRequest("/oauth2/v4/token", {} /*extraHeaders*/, { { CURLOPT_POSTFIELDS, postBuf.c_str() } }, //throw SysError
+    gdriveHttpsRequest("/oauth2/v4/token", {} /*extraHeaders*/, {{ CURLOPT_POSTFIELDS, postBuf.c_str()}}, //throw SysError
     [&](const void* buffer, size_t bytesToWrite) { response.append(static_cast<const char*>(buffer), bytesToWrite); }, nullptr /*readRequest*/);
 
     JsonValue jresponse;
@@ -408,7 +417,7 @@ GdriveAccessInfo gdriveExchangeAuthCode(const GdriveAuthCode& authCode) //throw
 
     const GdriveUser userInfo = getGdriveUser(*accessToken); //throw SysError
 
-    return { { *accessToken, std::time(nullptr) + stringTo<time_t>(*expiresIn) }, *refreshToken, userInfo };
+    return {{*accessToken, std::time(nullptr) + stringTo<time_t>(*expiresIn)}, *refreshToken, userInfo};
 }
 
 
@@ -426,9 +435,9 @@ GdriveAccessInfo gdriveAuthorizeAccess(const std::string& gdriveLoginHint, const
     ZEN_ON_SCOPE_EXIT(if (servinfo) ::freeaddrinfo(servinfo));
 
     //ServiceName == "0" => open the next best free port
-    const int rcGai = ::getaddrinfo(nullptr,    //_In_opt_ PCSTR            pNodeName,
-                                    "0",        //_In_opt_ PCSTR            pServiceName,
-                                    &hints,     //_In_opt_ const ADDRINFOA* pHints,
+    const int rcGai = ::getaddrinfo(nullptr,    //_In_opt_ PCSTR            pNodeName
+                                    "0",        //_In_opt_ PCSTR            pServiceName
+                                    &hints,     //_In_opt_ const ADDRINFOA* pHints
                                     &servinfo); //_Outptr_ PADDRINFOA*      ppResult
     if (rcGai != 0)
         throw SysError(formatSystemError("getaddrinfo", replaceCpy(_("Error code %x"), L"%x", numberTo<std::wstring>(rcGai)), utfTo<std::wstring>(::gai_strerror(rcGai))));
@@ -493,13 +502,13 @@ GdriveAccessInfo gdriveAuthorizeAccess(const std::string& gdriveLoginHint, const
     //authenticate Google Drive via browser: https://developers.google.com/identity/protocols/OAuth2InstalledApp#step-2-send-a-request-to-googles-oauth-20-server
     const std::string oauthUrl = "https://accounts.google.com/o/oauth2/v2/auth?" + xWwwFormUrlEncode(
     {
-        { "client_id",      getGdriveClientId() },
-        { "redirect_uri",   redirectUrl },
-        { "response_type",  "code" },
-        { "scope",          "https://www.googleapis.com/auth/drive" },
-        { "code_challenge", codeChallenge },
-        { "code_challenge_method", "plain" },
-        { "login_hint",     gdriveLoginHint },
+        {"client_id",      getGdriveClientId()},
+        {"redirect_uri",   redirectUrl},
+        {"response_type",  "code"},
+        {"scope",          "https://www.googleapis.com/auth/drive"},
+        {"code_challenge", codeChallenge},
+        {"code_challenge_method", "plain"},
+        {"login_hint",     gdriveLoginHint},
     });
     try
     {
@@ -519,7 +528,7 @@ GdriveAccessInfo gdriveAuthorizeAccess(const std::string& gdriveLoginHint, const
             FD_SET(socket, &rfd);
             fd_set* readfds = &rfd;
 
-            struct ::timeval tv = {};
+            timeval tv = {};
             tv.tv_usec = static_cast<long>(100 /*ms*/) * 1000;
 
             //WSAPoll broken, even ::poll() on OS X? https://daniel.haxx.se/blog/2012/10/10/wsapoll-is-broken/
@@ -613,7 +622,7 @@ GdriveAccessInfo gdriveAuthorizeAccess(const std::string& gdriveLoginHint, const
 
                 //do as many login-related tasks as possible while we have the browser as an error output device!
                 //see AFS::connectNetworkFolder() => errors will be lost after time out in dir_exist_async.h!
-                authResult = gdriveExchangeAuthCode({ code, redirectUrl, codeChallenge }); //throw SysError
+                authResult = gdriveExchangeAuthCode({code, redirectUrl, codeChallenge}); //throw SysError
                 replace(htmlMsg, "TITLE_PLACEHOLDER",   utfTo<std::string>(_("Authentication completed.")));
                 replace(htmlMsg, "MESSAGE_PLACEHOLDER", utfTo<std::string>(_("You may close this page now and continue with FreeFileSync.")));
             }
@@ -651,14 +660,14 @@ GdriveAccessToken gdriveRefreshAccess(const std::string& refreshToken) //throw S
     //https://developers.google.com/identity/protocols/OAuth2InstalledApp#offline
     const std::string postBuf = xWwwFormUrlEncode(
     {
-        { "refresh_token", refreshToken },
-        { "client_id",     getGdriveClientId() },
-        { "client_secret", getGdriveClientSecret() },
-        { "grant_type",    "refresh_token" },
+        {"refresh_token", refreshToken},
+        {"client_id",     getGdriveClientId()},
+        {"client_secret", getGdriveClientSecret()},
+        {"grant_type",    "refresh_token"},
     });
 
     std::string response;
-    gdriveHttpsRequest("/oauth2/v4/token", {} /*extraHeaders*/, { { CURLOPT_POSTFIELDS, postBuf.c_str() } }, //throw SysError
+    gdriveHttpsRequest("/oauth2/v4/token", {} /*extraHeaders*/, {{CURLOPT_POSTFIELDS, postBuf.c_str()}}, //throw SysError
     [&](const void* buffer, size_t bytesToWrite) { response.append(static_cast<const char*>(buffer), bytesToWrite); }, nullptr /*readRequest*/);
 
     JsonValue jresponse;
@@ -670,7 +679,7 @@ GdriveAccessToken gdriveRefreshAccess(const std::string& refreshToken) //throw S
     if (!accessToken || !expiresIn)
         throw SysError(formatGdriveErrorRaw(response));
 
-    return { *accessToken, std::time(nullptr) + stringTo<time_t>(*expiresIn) };
+    return {*accessToken, std::time(nullptr) + stringTo<time_t>(*expiresIn)};
 }
 
 
@@ -686,7 +695,7 @@ void gdriveRevokeAccess(const std::string& accessToken) //throw SysError
 
     mgr->access(HttpSessionId(Zstr("accounts.google.com")), [&](HttpSession& session) //throw SysError
     {
-        httpResult = session.perform("/o/oauth2/revoke?token=" + accessToken, { "Content-Type: application/x-www-form-urlencoded" }, {} /*extraOptions*/,
+        httpResult = session.perform("/o/oauth2/revoke?token=" + accessToken, {"Content-Type: application/x-www-form-urlencoded"}, {} /*extraOptions*/,
         [&](const void* buffer, size_t bytesToWrite) { response.append(static_cast<const char*>(buffer), bytesToWrite); }, nullptr /*readRequest*/); //throw SysError
     });
 
@@ -699,7 +708,7 @@ int64_t gdriveGetMyDriveFreeSpace(const std::string& accessToken) //throw SysErr
 {
     //https://developers.google.com/drive/api/v3/reference/about
     std::string response;
-    gdriveHttpsRequest("/drive/v3/about?fields=storageQuota", { "Authorization: Bearer " + accessToken }, {} /*extraOptions*/, //throw SysError
+    gdriveHttpsRequest("/drive/v3/about?fields=storageQuota", {"Authorization: Bearer " + accessToken}, {} /*extraOptions*/, //throw SysError
     [&](const void* buffer, size_t bytesToWrite) { response.append(static_cast<const char*>(buffer), bytesToWrite); }, nullptr /*readRequest*/);
 
     JsonValue jresponse;
@@ -741,14 +750,14 @@ std::vector<DriveDetails> getSharedDrives(const std::string& accessToken) //thro
         {
             std::string queryParams = xWwwFormUrlEncode(
             {
-                { "pageSize", "100" }, //"[1, 100] Default: 10"
-                { "fields", "nextPageToken,drives(id,name)" },
+                {"pageSize", "100"}, //"[1, 100] Default: 10"
+                {"fields", "nextPageToken,drives(id,name)"},
             });
             if (nextPageToken)
-                queryParams += '&' + xWwwFormUrlEncode({ { "pageToken", *nextPageToken } });
+                queryParams += '&' + xWwwFormUrlEncode({{"pageToken", *nextPageToken}});
 
             std::string response;
-            gdriveHttpsRequest("/drive/v3/drives?" + queryParams, { "Authorization: Bearer " + accessToken }, {} /*extraOptions*/, //throw SysError
+            gdriveHttpsRequest("/drive/v3/drives?" + queryParams, {"Authorization: Bearer " + accessToken}, {} /*extraOptions*/, //throw SysError
             [&](const void* buffer, size_t bytesToWrite) { response.append(static_cast<const char*>(buffer), bytesToWrite); }, nullptr /*readRequest*/);
 
             JsonValue jresponse;
@@ -767,7 +776,7 @@ std::vector<DriveDetails> getSharedDrives(const std::string& accessToken) //thro
                 if (!driveId || !driveName)
                     throw SysError(formatGdriveErrorRaw(serializeJson(driveVal)));
 
-                sharedDrives.push_back({ std::move(*driveId), utfTo<Zstring>(*driveName) });
+                sharedDrives.push_back({std::move(*driveId), utfTo<Zstring>(*driveName)});
             }
         }
         while (nextPageToken);
@@ -865,7 +874,7 @@ GdriveItemDetails extractItemDetails(JsonValue jvalue) //throw SysError
         //evaluate "targetMimeType" ? don't bother: "The MIME type of a shortcut can become stale"!
     }
 
-    return { utfTo<Zstring>(*itemName), fileSize, modTime, type, owner, std::move(targetId), std::move(parentIds) };
+    return {utfTo<Zstring>(*itemName), fileSize, modTime, type, owner, std::move(targetId), std::move(parentIds)};
 }
 
 
@@ -874,11 +883,11 @@ GdriveItemDetails getItemDetails(const std::string& itemId, const std::string& a
     //https://developers.google.com/drive/api/v3/reference/files/get
     const std::string& queryParams = xWwwFormUrlEncode(
     {
-        { "fields", "trashed,name,mimeType,ownedByMe,size,modifiedTime,parents,shortcutDetails(targetId)" },
-        { "supportsAllDrives", "true" },
+        {"fields", "trashed,name,mimeType,ownedByMe,size,modifiedTime,parents,shortcutDetails(targetId)"},
+        {"supportsAllDrives", "true"},
     });
     std::string response;
-    gdriveHttpsRequest("/drive/v3/files/" + itemId + '?' + queryParams, { "Authorization: Bearer " + accessToken }, {} /*extraOptions*/, //throw SysError
+    gdriveHttpsRequest("/drive/v3/files/" + itemId + '?' + queryParams, {"Authorization: Bearer " + accessToken}, {} /*extraOptions*/, //throw SysError
     [&](const void* buffer, size_t bytesToWrite) { response.append(static_cast<const char*>(buffer), bytesToWrite); }, nullptr /*readRequest*/);
     try
     {
@@ -912,19 +921,19 @@ std::vector<GdriveItem> readFolderContent(const std::string& folderId, const std
         {
             std::string queryParams = xWwwFormUrlEncode(
             {
-                { "corpora", "allDrives" }, //"The 'user' corpus includes all files in "My Drive" and "Shared with me" https://developers.google.com/drive/api/v3/reference/files/list
-                { "includeItemsFromAllDrives", "true" },
-                { "pageSize", "1000" }, //"[1, 1000] Default: 100"
-                { "q", "trashed=false and '" + folderId + "' in parents" },
-                { "spaces", "drive" },
-                { "supportsAllDrives", "true" },
-                { "fields", "nextPageToken,incompleteSearch,files(id,name,mimeType,ownedByMe,size,modifiedTime,parents,shortcutDetails(targetId))" }, //https://developers.google.com/drive/api/v3/reference/files
+                {"corpora", "allDrives"}, //"The 'user' corpus includes all files in "My Drive" and "Shared with me" https://developers.google.com/drive/api/v3/reference/files/list
+                {"includeItemsFromAllDrives", "true"},
+                {"pageSize", "1000"}, //"[1, 1000] Default: 100"
+                {"q", "trashed=false and '" + folderId + "' in parents"},
+                {"spaces", "drive"},
+                {"supportsAllDrives", "true"},
+                {"fields", "nextPageToken,incompleteSearch,files(id,name,mimeType,ownedByMe,size,modifiedTime,parents,shortcutDetails(targetId))"}, //https://developers.google.com/drive/api/v3/reference/files
             });
             if (nextPageToken)
-                queryParams += '&' + xWwwFormUrlEncode({ { "pageToken", *nextPageToken } });
+                queryParams += '&' + xWwwFormUrlEncode({{"pageToken", *nextPageToken}});
 
             std::string response;
-            gdriveHttpsRequest("/drive/v3/files?" + queryParams, { "Authorization: Bearer " + accessToken }, {} /*extraOptions*/, //throw SysError
+            gdriveHttpsRequest("/drive/v3/files?" + queryParams, {"Authorization: Bearer " + accessToken}, {} /*extraOptions*/, //throw SysError
             [&](const void* buffer, size_t bytesToWrite) { response.append(static_cast<const char*>(buffer), bytesToWrite); }, nullptr /*readRequest*/);
 
             JsonValue jresponse;
@@ -946,7 +955,7 @@ std::vector<GdriveItem> readFolderContent(const std::string& folderId, const std
                 GdriveItemDetails itemDetails(extractItemDetails(childVal)); //throw SysError
                 assert(std::find(itemDetails.parentIds.begin(), itemDetails.parentIds.end(), folderId) != itemDetails.parentIds.end());
 
-                childItems.push_back({ std::move(*itemId), std::move(itemDetails) });
+                childItems.push_back({std::move(*itemId), std::move(itemDetails)});
             }
         }
         while (nextPageToken);
@@ -980,16 +989,16 @@ ChangesDelta getChangesDelta(const std::string& startPageToken, const std::strin
     {
         const std::string& queryParams = xWwwFormUrlEncode(
         {
-            { "pageToken", *nextPageToken },
-            { "fields", "kind,nextPageToken,newStartPageToken,changes(kind,changeType,removed,fileId,file(trashed,name,mimeType,ownedByMe,size,modifiedTime,parents,shortcutDetails(targetId)),driveId,drive(name))" },
-            { "includeItemsFromAllDrives", "true" },
-            { "pageSize", "1000" }, //"[1, 1000] Default: 100"
-            { "spaces", "drive" },
-            { "supportsAllDrives", "true" },
+            {"pageToken", *nextPageToken},
+            {"fields", "kind,nextPageToken,newStartPageToken,changes(kind,changeType,removed,fileId,file(trashed,name,mimeType,ownedByMe,size,modifiedTime,parents,shortcutDetails(targetId)),driveId,drive(name))"},
+            {"includeItemsFromAllDrives", "true"},
+            {"pageSize", "1000"}, //"[1, 1000] Default: 100"
+            {"spaces", "drive"},
+            {"supportsAllDrives", "true"},
             //do NOT "restrictToMyDrive": we're also interested in "Shared with me" items, which might be referenced by a shortcut in "My Drive"
         });
         std::string response;
-        gdriveHttpsRequest("/drive/v3/changes?" + queryParams, { "Authorization: Bearer " + accessToken }, {} /*extraOptions*/, //throw SysError
+        gdriveHttpsRequest("/drive/v3/changes?" + queryParams, {"Authorization: Bearer " + accessToken}, {} /*extraOptions*/, //throw SysError
         [&](const void* buffer, size_t bytesToWrite) { response.append(static_cast<const char*>(buffer), bytesToWrite); }, nullptr /*readRequest*/);
 
         JsonValue jresponse;
@@ -1076,10 +1085,10 @@ std::string /*startPageToken*/ getChangesCurrentToken(const std::string& accessT
     //https://developers.google.com/drive/api/v3/reference/changes/getStartPageToken
     const std::string& queryParams = xWwwFormUrlEncode(
     {
-        { "supportsAllDrives", "true" },
+        {"supportsAllDrives", "true"},
     });
     std::string response;
-    gdriveHttpsRequest("/drive/v3/changes/startPageToken?" + queryParams, { "Authorization: Bearer " + accessToken }, {} /*extraOptions*/, //throw SysError
+    gdriveHttpsRequest("/drive/v3/changes/startPageToken?" + queryParams, {"Authorization: Bearer " + accessToken}, {} /*extraOptions*/, //throw SysError
     [&](const void* buffer, size_t bytesToWrite) { response.append(static_cast<const char*>(buffer), bytesToWrite); }, nullptr /*readRequest*/);
 
     JsonValue jresponse;
@@ -1101,11 +1110,11 @@ void gdriveDeleteItem(const std::string& itemId, const std::string& accessToken)
     //https://developers.google.com/drive/api/v3/reference/files/delete
     const std::string& queryParams = xWwwFormUrlEncode(
     {
-        { "supportsAllDrives", "true" },
+        {"supportsAllDrives", "true"},
     });
     std::string response;
-    const HttpSession::Result httpResult = gdriveHttpsRequest("/drive/v3/files/" + itemId + '?' + queryParams, { "Authorization: Bearer " + accessToken }, //throw SysError
-    { { CURLOPT_CUSTOMREQUEST, "DELETE" } }, [&](const void* buffer, size_t bytesToWrite) { response.append(static_cast<const char*>(buffer), bytesToWrite); }, nullptr /*readRequest*/);
+    const HttpSession::Result httpResult = gdriveHttpsRequest("/drive/v3/files/" + itemId + '?' + queryParams, {"Authorization: Bearer " + accessToken}, //throw SysError
+    {{CURLOPT_CUSTOMREQUEST, "DELETE"}}, [&](const void* buffer, size_t bytesToWrite) { response.append(static_cast<const char*>(buffer), bytesToWrite); }, nullptr /*readRequest*/);
 
     if (response.empty() && httpResult.statusCode == 204)
         return; //"If successful, this method returns an empty response body"
@@ -1120,14 +1129,14 @@ void gdriveUnlinkParent(const std::string& itemId, const std::string& parentId,
     //https://developers.google.com/drive/api/v3/reference/files/update
     const std::string& queryParams = xWwwFormUrlEncode(
     {
-        { "removeParents", parentId },
-        { "supportsAllDrives", "true" },
-        { "fields", "id,parents" }, //for test if operation was successful
+        {"removeParents", parentId},
+        {"supportsAllDrives", "true"},
+        {"fields", "id,parents"}, //for test if operation was successful
     });
     std::string response;
     const HttpSession::Result httpResult = gdriveHttpsRequest("/drive/v3/files/" + itemId + '?' + queryParams, //throw SysError
-    { "Authorization: Bearer " + accessToken, "Content-Type: application/json; charset=UTF-8" },
-    { { CURLOPT_CUSTOMREQUEST, "PATCH" }, { CURLOPT_POSTFIELDS, "{}" } },
+    {"Authorization: Bearer " + accessToken, "Content-Type: application/json; charset=UTF-8"},
+    {{ CURLOPT_CUSTOMREQUEST, "PATCH"}, { CURLOPT_POSTFIELDS, "{}"}},
     [&](const void* buffer, size_t bytesToWrite) { response.append(static_cast<const char*>(buffer), bytesToWrite); }, nullptr /*readRequest*/);
 
     if (response.empty() && httpResult.statusCode == 204)
@@ -1157,14 +1166,14 @@ void gdriveMoveToTrash(const std::string& itemId, const std::string& accessToken
     //https://developers.google.com/drive/api/v3/reference/files/update
     const std::string& queryParams = xWwwFormUrlEncode(
     {
-        { "supportsAllDrives", "true" },
-        { "fields", "trashed" },
+        {"supportsAllDrives", "true"},
+        {"fields", "trashed"},
     });
     const std::string postBuf = R"({ "trashed": true })";
 
     std::string response;
-    gdriveHttpsRequest("/drive/v3/files/" + itemId + '?' + queryParams, { "Authorization: Bearer " + accessToken, "Content-Type: application/json; charset=UTF-8" }, //throw SysError
-    { { CURLOPT_CUSTOMREQUEST, "PATCH" }, { CURLOPT_POSTFIELDS, postBuf.c_str() } },
+    gdriveHttpsRequest("/drive/v3/files/" + itemId + '?' + queryParams, {"Authorization: Bearer " + accessToken, "Content-Type: application/json; charset=UTF-8"}, //throw SysError
+    {{CURLOPT_CUSTOMREQUEST, "PATCH"}, {CURLOPT_POSTFIELDS, postBuf.c_str()}},
     [&](const void* buffer, size_t bytesToWrite) { response.append(static_cast<const char*>(buffer), bytesToWrite); }, nullptr /*readRequest*/);
 
     JsonValue jresponse;
@@ -1183,18 +1192,18 @@ std::string /*folderId*/ gdriveCreateFolderPlain(const Zstring& folderName, cons
     //https://developers.google.com/drive/api/v3/folder#creating_a_folder
     const std::string& queryParams = xWwwFormUrlEncode(
     {
-        { "supportsAllDrives", "true" },
-        { "fields", "id" },
+        {"supportsAllDrives", "true"},
+        {"fields", "id"},
     });
     JsonValue postParams(JsonValue::Type::object);
     postParams.objectVal.emplace("mimeType", gdriveFolderMimeType);
     postParams.objectVal.emplace("name", utfTo<std::string>(folderName));
-    postParams.objectVal.emplace("parents", std::vector<JsonValue> { JsonValue(parentId) });
+    postParams.objectVal.emplace("parents", std::vector<JsonValue> {JsonValue(parentId)});
     const std::string& postBuf = serializeJson(postParams, "" /*lineBreak*/, "" /*indent*/);
 
     std::string response;
-    gdriveHttpsRequest("/drive/v3/files?" + queryParams, { "Authorization: Bearer " + accessToken, "Content-Type: application/json; charset=UTF-8" },
-    { { CURLOPT_POSTFIELDS, postBuf.c_str() } },
+    gdriveHttpsRequest("/drive/v3/files?" + queryParams, {"Authorization: Bearer " + accessToken, "Content-Type: application/json; charset=UTF-8"},
+    {{CURLOPT_POSTFIELDS, postBuf.c_str()}},
     [&](const void* buffer, size_t bytesToWrite) { response.append(static_cast<const char*>(buffer), bytesToWrite); }, nullptr /*readRequest*/); //throw SysError
 
     JsonValue jresponse;
@@ -1216,8 +1225,8 @@ std::string /*shortcutId*/ gdriveCreateShortcutPlain(const Zstring& shortcutName
        - creating shortcuts to shortcuts fails with "Internal Error"              */
     const std::string& queryParams = xWwwFormUrlEncode(
     {
-        { "supportsAllDrives", "true" },
-        { "fields", "id" },
+        {"supportsAllDrives", "true"},
+        {"fields", "id"},
     });
     JsonValue shortcutDetails(JsonValue::Type::object);
     shortcutDetails.objectVal.emplace("targetId", targetId);
@@ -1225,13 +1234,13 @@ std::string /*shortcutId*/ gdriveCreateShortcutPlain(const Zstring& shortcutName
     JsonValue postParams(JsonValue::Type::object);
     postParams.objectVal.emplace("mimeType", gdriveShortcutMimeType);
     postParams.objectVal.emplace("name", utfTo<std::string>(shortcutName));
-    postParams.objectVal.emplace("parents", std::vector<JsonValue> { JsonValue(parentId) });
+    postParams.objectVal.emplace("parents", std::vector<JsonValue> {JsonValue(parentId)});
     postParams.objectVal.emplace("shortcutDetails", std::move(shortcutDetails));
     const std::string& postBuf = serializeJson(postParams, "" /*lineBreak*/, "" /*indent*/);
 
     std::string response;
-    gdriveHttpsRequest("/drive/v3/files?" + queryParams, { "Authorization: Bearer " + accessToken, "Content-Type: application/json; charset=UTF-8" },
-    { { CURLOPT_POSTFIELDS, postBuf.c_str() } },
+    gdriveHttpsRequest("/drive/v3/files?" + queryParams, {"Authorization: Bearer " + accessToken, "Content-Type: application/json; charset=UTF-8"},
+    {{CURLOPT_POSTFIELDS, postBuf.c_str()}},
     [&](const void* buffer, size_t bytesToWrite) { response.append(static_cast<const char*>(buffer), bytesToWrite); }, nullptr /*readRequest*/); //throw SysError
 
     JsonValue jresponse;
@@ -1252,8 +1261,8 @@ std::string /*fileId*/ gdriveCopyFile(const std::string& fileId, const std::stri
     //https://developers.google.com/drive/api/v3/reference/files/copy
     const std::string queryParams = xWwwFormUrlEncode(
     {
-        { "supportsAllDrives", "true" },
-        { "fields", "id" },
+        {"supportsAllDrives", "true"},
+        {"fields", "id"},
     });
 
     //more Google Drive peculiarities: changing the file name changes modifiedTime!!! => workaround:
@@ -1265,13 +1274,13 @@ std::string /*fileId*/ gdriveCopyFile(const std::string& fileId, const std::stri
 
     JsonValue postParams(JsonValue::Type::object);
     postParams.objectVal.emplace("name", utfTo<std::string>(newName));
-    postParams.objectVal.emplace("parents", std::vector<JsonValue> { JsonValue(parentIdTo) });
+    postParams.objectVal.emplace("parents", std::vector<JsonValue> {JsonValue(parentIdTo)});
     postParams.objectVal.emplace("modifiedTime", modTimeRfc);
     const std::string& postBuf = serializeJson(postParams, "" /*lineBreak*/, "" /*indent*/);
 
     std::string response;
     gdriveHttpsRequest("/drive/v3/files/" + fileId + "/copy?" + queryParams, //throw SysError
-    { "Authorization: Bearer " + accessToken, "Content-Type: application/json; charset=UTF-8" }, { { CURLOPT_POSTFIELDS, postBuf.c_str() } },
+    {"Authorization: Bearer " + accessToken, "Content-Type: application/json; charset=UTF-8"}, {{CURLOPT_POSTFIELDS, postBuf.c_str()}},
     [&](const void* buffer, size_t bytesToWrite) { response.append(static_cast<const char*>(buffer), bytesToWrite); }, nullptr /*readRequest*/);
 
     JsonValue jresponse;
@@ -1294,15 +1303,15 @@ void gdriveMoveAndRenameItem(const std::string& itemId, const std::string& paren
     //https://developers.google.com/drive/api/v3/folder#moving_files_between_folders
     std::string queryParams = xWwwFormUrlEncode(
     {
-        { "supportsAllDrives", "true" },
-        { "fields", "name,parents" }, //for test if operation was successful
+        {"supportsAllDrives", "true"},
+        {"fields", "name,parents"}, //for test if operation was successful
     });
 
     if (parentIdFrom != parentIdTo)
         queryParams += '&' + xWwwFormUrlEncode(
     {
-        { "removeParents", parentIdFrom },
-        { "addParents",    parentIdTo },
+        {"removeParents", parentIdFrom},
+        {"addParents",    parentIdTo},
     });
 
     //more Google Drive peculiarities: changing the file name changes modifiedTime!!! => workaround:
@@ -1319,8 +1328,8 @@ void gdriveMoveAndRenameItem(const std::string& itemId, const std::string& paren
 
     std::string response;
     gdriveHttpsRequest("/drive/v3/files/" + itemId + '?' + queryParams, //throw SysError
-    { "Authorization: Bearer " + accessToken, "Content-Type: application/json; charset=UTF-8" },
-    { { CURLOPT_CUSTOMREQUEST, "PATCH" }, { CURLOPT_POSTFIELDS, postBuf.c_str() } },
+    {"Authorization: Bearer " + accessToken, "Content-Type: application/json; charset=UTF-8"},
+    {{CURLOPT_CUSTOMREQUEST, "PATCH"}, {CURLOPT_POSTFIELDS, postBuf.c_str()}},
     [&](const void* buffer, size_t bytesToWrite) { response.append(static_cast<const char*>(buffer), bytesToWrite); }, nullptr /*readRequest*/);
 
     JsonValue jresponse;
@@ -1350,14 +1359,14 @@ void setModTime(const std::string& itemId, time_t modTime, const std::string& ac
 
     const std::string& queryParams = xWwwFormUrlEncode(
     {
-        { "supportsAllDrives", "true" },
-        { "fields", "modifiedTime" },
+        {"supportsAllDrives", "true"},
+        {"fields", "modifiedTime"},
     });
     const std::string postBuf = R"({ "modifiedTime": ")" + modTimeRfc + "\" }";
 
     std::string response;
-    gdriveHttpsRequest("/drive/v3/files/" + itemId + '?' + queryParams, { "Authorization: Bearer " + accessToken, "Content-Type: application/json; charset=UTF-8" }, //throw SysError
-    { { CURLOPT_CUSTOMREQUEST, "PATCH" }, { CURLOPT_POSTFIELDS, postBuf.c_str() } },
+    gdriveHttpsRequest("/drive/v3/files/" + itemId + '?' + queryParams, {"Authorization: Bearer " + accessToken, "Content-Type: application/json; charset=UTF-8"}, //throw SysError
+    {{CURLOPT_CUSTOMREQUEST, "PATCH"}, {CURLOPT_POSTFIELDS, postBuf.c_str()}},
     [&](const void* buffer, size_t bytesToWrite) { response.append(static_cast<const char*>(buffer), bytesToWrite); }, nullptr /*readRequest*/);
 
     JsonValue jresponse;
@@ -1382,17 +1391,17 @@ void gdriveDownloadFileImpl(const std::string& fileId, const std::function<void(
 
     std::string queryParams = xWwwFormUrlEncode(
     {
-        { "supportsAllDrives", "true" },
-        { "alt", "media" },
+        {"supportsAllDrives", "true"},
+        {"alt", "media"},
     });
     if (acknowledgeAbuse) //apply on demand only! https://freefilesync.org/forum/viewtopic.php?t=7520")
-        queryParams += '&' + xWwwFormUrlEncode({ { "acknowledgeAbuse", "true" } });
+        queryParams += '&' + xWwwFormUrlEncode({{"acknowledgeAbuse", "true"}});
 
     std::string responseHead; //save front part of the response in case we get an error
     bool headFlushed = false;
 
     const HttpSession::Result httpResult = gdriveHttpsRequest("/drive/v3/files/" + fileId + '?' + queryParams, //throw SysError, X
-    { "Authorization: Bearer " + accessToken }, {} /*extraOptions*/,
+    {"Authorization: Bearer " + accessToken}, {} /*extraOptions*/,
     [&](const void* buffer, size_t bytesToWrite)
     {
         if (responseHead.size() < 10000) //don't access writeBlock() in case of error! (=> support acknowledgeAbuse retry handling)
@@ -1456,7 +1465,7 @@ std::string /*itemId*/ gdriveUploadSmallFile(const Zstring& fileName, const std:
 
     JsonValue postParams(JsonValue::Type::object);
     postParams.objectVal.emplace("name", utfTo<std::string>(fileName));
-    postParams.objectVal.emplace("parents", std::vector<JsonValue> { JsonValue(parentId) });
+    postParams.objectVal.emplace("parents", std::vector<JsonValue> {JsonValue(parentId)});
     if (modTime) //convert to RFC 3339 date-time: e.g. "2018-09-29T08:39:12.053Z"
     {
         const std::string& modTimeRfc = utfTo<std::string>(formatTime(Zstr("%Y-%m-%dT%H:%M:%S.000Z"), getUtcTime(*modTime))); //returns empty string on failure
@@ -1521,8 +1530,8 @@ TODO:
 
     const std::string& queryParams = xWwwFormUrlEncode(
     {
-        { "supportsAllDrives", "true" },
-        { "uploadType", "multipart" },
+        {"supportsAllDrives", "true"},
+        {"uploadType", "multipart"},
     });
     std::string response;
     const HttpSession::Result httpResult = gdriveHttpsRequest("/upload/drive/v3/files?" + queryParams, //throw SysError, X
@@ -1531,7 +1540,7 @@ TODO:
         "Content-Type: multipart/related; boundary=" + boundaryString,
         "Content-Length: " + numberTo<std::string>(postBufHead.size() + streamSize + postBufTail.size())
     },
-    { { CURLOPT_POST, 1 } }, //otherwise HttpSession::perform() will PUT
+    {{CURLOPT_POST, 1}}, //otherwise HttpSession::perform() will PUT
     [&](const void* buffer, size_t bytesToWrite) { response.append(static_cast<const char*>(buffer), bytesToWrite); }, readMultipartBlock );
 
     JsonValue jresponse;
@@ -1561,12 +1570,12 @@ std::string /*itemId*/ gdriveUploadFile(const Zstring& fileName, const std::stri
     {
         const std::string& queryParams = xWwwFormUrlEncode(
         {
-            { "supportsAllDrives", "true" },
-            { "uploadType", "resumable" },
+            {"supportsAllDrives", "true"},
+            {"uploadType", "resumable"},
         });
         JsonValue postParams(JsonValue::Type::object);
         postParams.objectVal.emplace("name", utfTo<std::string>(fileName));
-        postParams.objectVal.emplace("parents", std::vector<JsonValue> { JsonValue(parentId) });
+        postParams.objectVal.emplace("parents", std::vector<JsonValue> {JsonValue(parentId)});
         if (modTime) //convert to RFC 3339 date-time: e.g. "2018-09-29T08:39:12.053Z"
         {
             const std::string& modTimeRfc = utfTo<std::string>(formatTime(Zstr("%Y-%m-%dT%H:%M:%S.000Z"), getUtcTime(*modTime))); //returns empty string on failure
@@ -1601,8 +1610,8 @@ std::string /*itemId*/ gdriveUploadFile(const Zstring& fileName, const std::stri
 
         std::string response;
         const HttpSession::Result httpResult = gdriveHttpsRequest("/upload/drive/v3/files?" + queryParams, //throw SysError
-        { "Authorization: Bearer " + accessToken, "Content-Type: application/json; charset=UTF-8" },
-        { { CURLOPT_POSTFIELDS, postBuf.c_str() }, { CURLOPT_HEADERDATA, &onBytesReceived }, { CURLOPT_HEADERFUNCTION, onBytesReceivedWrapper } },
+        {"Authorization: Bearer " + accessToken, "Content-Type: application/json; charset=UTF-8"},
+        {{CURLOPT_POSTFIELDS, postBuf.c_str()}, {CURLOPT_HEADERDATA, &onBytesReceived}, {CURLOPT_HEADERFUNCTION, onBytesReceivedWrapper}},
         [&](const void* buffer, size_t bytesToWrite) { response.append(static_cast<const char*>(buffer), bytesToWrite); }, nullptr /*readRequest*/);
 
         if (httpResult.statusCode != 200)
@@ -1644,11 +1653,11 @@ std::string /*itemId*/ getMyDriveId(const std::string& accessToken) //throw SysE
     //https://developers.google.com/drive/api/v3/reference/files/get
     const std::string& queryParams = xWwwFormUrlEncode(
     {
-        { "supportsAllDrives", "true" },
-        { "fields", "id" },
+        {"supportsAllDrives", "true"},
+        {"fields", "id"},
     });
     std::string response;
-    gdriveHttpsRequest("/drive/v3/files/root?" + queryParams, { "Authorization: Bearer " + accessToken }, {} /*extraOptions*/, //throw SysError
+    gdriveHttpsRequest("/drive/v3/files/root?" + queryParams, {"Authorization: Bearer " + accessToken}, {} /*extraOptions*/, //throw SysError
     [&](const void* buffer, size_t bytesToWrite) { response.append(static_cast<const char*>(buffer), bytesToWrite); }, nullptr /*readRequest*/);
 
     JsonValue jresponse;
@@ -1721,7 +1730,7 @@ class GdriveFileState //per-user-session! => serialize access (perf: amortized f
 {
 public:
     GdriveFileState(GdriveAccessBuffer& accessBuf) : //throw SysError
-        /* issue getChangesCurrentToken() as the very first Google Drive query!*/
+        /* issue getChangesCurrentToken() as the very first Google Drive query! */
         lastSyncToken_(getChangesCurrentToken(accessBuf.getAccessToken())), //throw SysError
         myDriveId_    (getMyDriveId          (accessBuf.getAccessToken())), //
         accessBuf_(accessBuf)
@@ -1863,20 +1872,20 @@ public:
                 {
                     if (itFound != sharedDrives_.end())
                         throw SysError(replaceCpy(_("Cannot find %x."), L"%x",
-                        fmtPath(getGdriveDisplayPath({{ accessBuf_.getUserEmail(), sharedDriveName}, AfsPath() }))) + L' ' +
+                        fmtPath(getGdriveDisplayPath({{accessBuf_.getUserEmail(), sharedDriveName}, AfsPath()}))) + L' ' +
                     replaceCpy(_("The name %x is used by more than one item in the folder."), L"%x", fmtPath(sharedDriveName)));
                     itFound = it;
                 }
             if (itFound == sharedDrives_.end())
                 throw SysError(replaceCpy(_("Cannot find %x."), L"%x",
-                fmtPath(getGdriveDisplayPath({{ accessBuf_.getUserEmail(), sharedDriveName}, AfsPath() }))));
+                fmtPath(getGdriveDisplayPath({{accessBuf_.getUserEmail(), sharedDriveName}, AfsPath()}))));
 
             return itFound->first;
         }();
 
         const std::vector<Zstring> relPath = split(afsPath.value, FILE_NAME_SEPARATOR, SplitOnEmpty::skip);
         if (relPath.empty())
-            return { driveId, GdriveItemType::folder, AfsPath(), {} };
+            return {driveId, GdriveItemType::folder, AfsPath(), {}};
         else
             return getPathStatusSub(driveId, sharedDriveName, AfsPath(), relPath, followLeafShortcut); //throw SysError
     }
@@ -1888,7 +1897,7 @@ public:
             return ps.existingItemId;
 
         const AfsPath afsPathMissingChild(nativeAppendPaths(ps.existingPath.value, ps.relPath.front()));
-        throw SysError(replaceCpy(_("Cannot find %x."), L"%x", fmtPath(getGdriveDisplayPath({ { accessBuf_.getUserEmail(), sharedDriveName }, afsPathMissingChild }))));
+        throw SysError(replaceCpy(_("Cannot find %x."), L"%x", fmtPath(getGdriveDisplayPath({{accessBuf_.getUserEmail(), sharedDriveName}, afsPathMissingChild}))));
     }
 
     std::pair<std::string /*itemId*/, GdriveItemDetails> getFileAttributes(const Zstring& sharedDriveName, const AfsPath& afsPath, bool followLeafShortcut) //throw SysError
@@ -1903,7 +1912,7 @@ public:
             {
                 rootDetails.itemName = Zstr("My Drive");
                 rootDetails.owner = FileOwner::me;
-                return { itemId, std::move(rootDetails) };
+                return {itemId, std::move(rootDetails)};
             }
 
             if (auto it = sharedDrives_.find(itemId);
@@ -1911,7 +1920,7 @@ public:
             {
                 rootDetails.itemName = it->second;
                 rootDetails.owner = FileOwner::none;
-                return { itemId, std::move(rootDetails) };
+                return {itemId, std::move(rootDetails)};
             }
         }
         else if (auto it = itemDetails_.find(itemId);
@@ -1940,7 +1949,7 @@ public:
         for (auto itChild : it->second.childItems)
         {
             const auto& [childId, childDetails] = *itChild;
-            childItems.push_back({ childId, childDetails });
+            childItems.push_back({childId, childDetails});
         }
         return std::move(childItems); //[!] need std::move!
     }
@@ -2116,14 +2125,14 @@ private:
             {
                 if (itFound != itemDetails_.end())
                     throw SysError(replaceCpy(_("Cannot find %x."), L"%x",
-                    fmtPath(getGdriveDisplayPath({{ accessBuf_.getUserEmail(), sharedDriveName}, AfsPath(nativeAppendPaths(folderPath.value, relPath.front())) }))) + L' ' +
+                    fmtPath(getGdriveDisplayPath({{accessBuf_.getUserEmail(), sharedDriveName}, AfsPath(nativeAppendPaths(folderPath.value, relPath.front()))}))) + L' ' +
                 replaceCpy(_("The name %x is used by more than one item in the folder."), L"%x", fmtPath(relPath.front())));
 
                 itFound = itChild;
             }
 
         if (itFound == itemDetails_.end())
-            return { folderId, GdriveItemType::folder, folderPath, relPath }; //always a folder, see check before recursion above
+            return {folderId, GdriveItemType::folder, folderPath, relPath}; //always a folder, see check before recursion above
         else
         {
             auto getItemDetailsBuffered = [&](const std::string& itemId) -> const GdriveItemDetails&
@@ -2131,7 +2140,7 @@ private:
                 auto it = itemDetails_.find(itemId);
                 if (it == itemDetails_.end())
                 {
-                    notifyItemUpdated(registerFileStateDelta(), { itemId, getItemDetails(itemId, accessBuf_.getAccessToken()) }); //throw SysError
+                    notifyItemUpdated(registerFileStateDelta(), {itemId, getItemDetails(itemId, accessBuf_.getAccessToken())}); //throw SysError
                     //perf: always buffered, except for direct, first-time folder access!
                     it = itemDetails_.find(itemId);
                     assert(it != itemDetails_.end());
@@ -2146,15 +2155,15 @@ private:
             if (childRelPath.empty())
             {
                 if (childDetails.type == GdriveItemType::shortcut && followLeafShortcut)
-                    return { childDetails.targetId, getItemDetailsBuffered(childDetails.targetId).type, childItemPath, childRelPath };
+                    return {childDetails.targetId, getItemDetailsBuffered(childDetails.targetId).type, childItemPath, childRelPath};
                 else
-                    return { childId, childDetails.type, childItemPath, childRelPath };
+                    return {childId, childDetails.type, childItemPath, childRelPath};
             }
 
             switch (childDetails.type)
             {
                 case GdriveItemType::file: //parent/file/child-rel-path... => obscure, but possible (and not an error)
-                    return { childId, childDetails.type, childItemPath, childRelPath };
+                    return {childId, childDetails.type, childItemPath, childRelPath};
 
                 case GdriveItemType::folder:
                     return getPathStatusSub(childId, sharedDriveName, childItemPath, childRelPath, followLeafShortcut); //throw SysError
@@ -2163,14 +2172,14 @@ private:
                     switch (getItemDetailsBuffered(childDetails.targetId).type)
                     {
                         case GdriveItemType::file: //parent/file-symlink/child-rel-path... => obscure, but possible (and not an error)
-                            return { childDetails.targetId, GdriveItemType::file, childItemPath, childRelPath }; //resolve symlinks if in the *middle* of a path!
+                            return {childDetails.targetId, GdriveItemType::file, childItemPath, childRelPath}; //resolve symlinks if in the *middle* of a path!
 
                         case GdriveItemType::folder: //parent/folder-symlink/child-rel-path... => always follow
                             return getPathStatusSub(childDetails.targetId, sharedDriveName, childItemPath, childRelPath, followLeafShortcut); //throw SysError
 
                         case GdriveItemType::shortcut: //should never happen: creating shortcuts to shortcuts fails with "Internal Error"
                             throw SysError(replaceCpy(_("Cannot resolve symbolic link %x."), L"%x",
-                            fmtPath(getGdriveDisplayPath({{ accessBuf_.getUserEmail(), sharedDriveName}, AfsPath(nativeAppendPaths(folderPath.value, relPath.front())) }))) + L' ' +
+                            fmtPath(getGdriveDisplayPath({{accessBuf_.getUserEmail(), sharedDriveName}, AfsPath(nativeAppendPaths(folderPath.value, relPath.front()))}))) + L' ' +
                             L"Google Drive Shortcut points to another Shortcut.");
                     }
                     break;
@@ -2343,7 +2352,7 @@ public:
             {
                 auto accessBuf = makeSharedRef<GdriveAccessBuffer>(accessInfo);
                 auto fileState = makeSharedRef<GdriveFileState   >(accessBuf.ref()); //throw SysError
-                userSession = { accessBuf, fileState };
+                userSession = {accessBuf, fileState};
             }
         });
 
@@ -2449,7 +2458,7 @@ public:
 
             useFileState(userSession->fileState.ref()); //throw X
         });
-        return { accessToken, stateDelta };
+        return {accessToken, stateDelta};
     }
 
 private:
@@ -2550,7 +2559,7 @@ private:
                     makeSharedRef<GdriveFileState>(           accessBuf.ref()) : //throw SysError
                     makeSharedRef<GdriveFileState>(streamIn2, accessBuf.ref());  //
 
-                return UserSession{ accessBuf, fileState };
+                return UserSession{accessBuf, fileState};
             }
             else
             {
@@ -2566,7 +2575,7 @@ private:
                 auto accessBuf = makeSharedRef<GdriveAccessBuffer>(streamInBody); //throw SysError
                 auto fileState = makeSharedRef<GdriveFileState   >(streamInBody, accessBuf.ref()); //throw SysError
 
-                return UserSession{ accessBuf, fileState };
+                return UserSession{accessBuf, fileState};
             }
         }
         catch (const SysError& e)
@@ -2647,7 +2656,7 @@ struct GetDirDetails
                 if (item.details.itemName.empty())
                     throw SysError(L"Folder contains an item without name."); //mostly an issue for FFS's folder traversal, but NOT for globalGdriveSessions!
 
-            return { std::move(*childItemsBuf), folderPath_ };
+            return {std::move(*childItemsBuf), folderPath_};
         }
         catch (const SysError& e) { throw FileError(replaceCpy(_("Cannot read directory %x."), L"%x", fmtPath(getGdriveDisplayPath(folderPath_))), e.toString()); }
     }
@@ -2683,14 +2692,15 @@ struct GetShortcutTargetDetails
                 //buffer new file state ASAP
                 accessGlobalFileState(shortcutPath_.gdriveLogin.email, [&](GdriveFileState& fileState) //throw SysError
                 {
-                    fileState.notifyItemUpdated(aai.stateDelta, { shortcutDetails_.targetId, *targetDetailsBuf });
+                    fileState.notifyItemUpdated(aai.stateDelta, {shortcutDetails_.targetId, *targetDetailsBuf});
                 });
             }
 
+            assert(targetDetailsBuf->targetId.empty());
             if (targetDetailsBuf->type == GdriveItemType::shortcut) //should never happen: creating shortcuts to shortcuts fails with "Internal Error"
                 throw SysError(L"Google Drive Shortcut points to another Shortcut.");
 
-            return { std::move(*targetDetailsBuf), shortcutDetails_, shortcutPath_ };
+            return {std::move(*targetDetailsBuf), shortcutDetails_, shortcutPath_};
         }
         catch (const SysError& e) { throw FileError(replaceCpy(_("Cannot resolve symbolic link %x."), L"%x", fmtPath(getGdriveDisplayPath(shortcutPath_))), e.toString()); }
     }
@@ -2726,7 +2736,7 @@ private:
 
     void traverseWithException(const AfsPath& folderPath, AFS::TraverserCallback& cb) //throw FileError, X
     {
-        const std::vector<GdriveItem>& childItems = GetDirDetails({ gdriveLogin_, folderPath })().childItems; //throw FileError
+        const std::vector<GdriveItem>& childItems = GetDirDetails({gdriveLogin_, folderPath})().childItems; //throw FileError
 
         for (const GdriveItem& item : childItems)
         {
@@ -2735,42 +2745,42 @@ private:
             switch (item.details.type)
             {
                 case GdriveItemType::file:
-                    cb.onFile({ itemName, item.details.fileSize, item.details.modTime, item.itemId, false /*isFollowedSymlink*/ }); //throw X
+                    cb.onFile({itemName, item.details.fileSize, item.details.modTime, getGdriveFilePrint(item.itemId), false /*isFollowedSymlink*/}); //throw X
                     break;
 
                 case GdriveItemType::folder:
-                    if (std::shared_ptr<AFS::TraverserCallback> cbSub = cb.onFolder({ itemName, false /*isFollowedSymlink*/ })) //throw X
+                    if (std::shared_ptr<AFS::TraverserCallback> cbSub = cb.onFolder({itemName, false /*isFollowedSymlink*/})) //throw X
                     {
                         const AfsPath afsItemPath(nativeAppendPaths(folderPath.value, itemName));
-                        workload_.push_back({ afsItemPath, std::move(cbSub) });
+                        workload_.push_back({afsItemPath, std::move(cbSub)});
                     }
                     break;
 
                 case GdriveItemType::shortcut:
-                    switch (cb.onSymlink({ itemName, item.details.modTime })) //throw X
+                    switch (cb.onSymlink({itemName, item.details.modTime})) //throw X
                     {
-                        case AFS::TraverserCallback::LINK_FOLLOW:
+                        case AFS::TraverserCallback::HandleLink::follow:
                         {
                             const AfsPath afsItemPath(nativeAppendPaths(folderPath.value, itemName));
 
                             GdriveItemDetails targetDetails = {};
                             if (!tryReportingItemError([&] //throw X
                         {
-                            targetDetails = GetShortcutTargetDetails({ gdriveLogin_, afsItemPath }, item.details)().target; //throw FileError
+                            targetDetails = GetShortcutTargetDetails({gdriveLogin_, afsItemPath}, item.details)().target; //throw FileError
                             }, cb, itemName))
                             continue;
 
                             if (targetDetails.type == GdriveItemType::folder)
                             {
-                                if (std::shared_ptr<AFS::TraverserCallback> cbSub = cb.onFolder({ itemName, true /*isFollowedSymlink*/ })) //throw X
-                                    workload_.push_back({ afsItemPath, std::move(cbSub) });
+                                if (std::shared_ptr<AFS::TraverserCallback> cbSub = cb.onFolder({itemName, true /*isFollowedSymlink*/})) //throw X
+                                    workload_.push_back({afsItemPath, std::move(cbSub)});
                             }
                             else //a file or named pipe, etc.
-                                cb.onFile({ itemName, targetDetails.fileSize, targetDetails.modTime, item.details.targetId, true /*isFollowedSymlink*/ }); //throw X
+                                cb.onFile({itemName, targetDetails.fileSize, targetDetails.modTime, getGdriveFilePrint(item.details.targetId), true /*isFollowedSymlink*/}); //throw X
                         }
                         break;
 
-                        case AFS::TraverserCallback::LINK_SKIP:
+                        case AFS::TraverserCallback::HandleLink::skip:
                             break;
                     }
                     break;
@@ -2792,7 +2802,7 @@ void gdriveTraverseFolderRecursive(const GdriveLogin& gdriveLogin, const std::ve
 
 struct InputStreamGdrive : public AFS::InputStream
 {
-    InputStreamGdrive(const GdrivePath& gdrivePath, const IOCallback& notifyUnbufferedIO /*throw X*/) :
+    InputStreamGdrive(const GdrivePath& gdrivePath, const IoCallback& notifyUnbufferedIO /*throw X*/) :
         gdrivePath_(gdrivePath),
         notifyUnbufferedIO_(notifyUnbufferedIO)
     {
@@ -2854,7 +2864,7 @@ struct InputStreamGdrive : public AFS::InputStream
                 const auto& [itemId, itemDetails] = fileState.getFileAttributes(gdrivePath_.gdriveLogin.sharedDriveName, gdrivePath_.itemPath, true /*followLeafShortcut*/); //throw SysError
                 attr.modTime  = itemDetails.modTime;
                 attr.fileSize = itemDetails.fileSize;
-                attr.fileId   = itemId;
+                attr.filePrint = getGdriveFilePrint(itemId);
             });
         }
         catch (const SysError& e) { throw FileError(replaceCpy(_("Cannot read file attributes of %x."), L"%x", fmtPath(getGdriveDisplayPath(gdrivePath_))), e.toString()); }
@@ -2870,7 +2880,7 @@ private:
     }
 
     const GdrivePath gdrivePath_;
-    const IOCallback notifyUnbufferedIO_; //throw X
+    const IoCallback notifyUnbufferedIO_; //throw X
     int64_t totalBytesReported_ = 0;
     std::shared_ptr<AsyncStreamBuffer> asyncStreamIn_ = std::make_shared<AsyncStreamBuffer>(GDRIVE_STREAM_BUFFER_SIZE);
     InterruptibleThread worker_;
@@ -2884,12 +2894,12 @@ struct OutputStreamGdrive : public AFS::OutputStreamImpl
     OutputStreamGdrive(const GdrivePath& gdrivePath, //throw SysError
                        std::optional<uint64_t> /*streamSize*/,
                        std::optional<time_t> modTime,
-                       const IOCallback& notifyUnbufferedIO /*throw X*/,
+                       const IoCallback& notifyUnbufferedIO /*throw X*/,
                        std::unique_ptr<PathAccessLock>&& pal) :
         notifyUnbufferedIO_(notifyUnbufferedIO)
     {
-        std::promise<AFS::FileId> pFileId;
-        futFileId_ = pFileId.get_future();
+        std::promise<AFS::FingerPrint> pFilePrint;
+        futFilePrint_ = pFilePrint.get_future();
 
         //CAVEAT: if file is already existing, OutputStreamGdrive *constructor* must fail, not OutputStreamGdrive::write(),
         //        otherwise ~OutputStreamImpl() will delete the already existing file! => don't check asynchronously!
@@ -2908,10 +2918,10 @@ struct OutputStreamGdrive : public AFS::OutputStreamImpl
         });
 
         worker_ = InterruptibleThread([gdrivePath, modTime, fileName, asyncStreamIn = this->asyncStreamOut_,
-                                                   pFileId  = std::move(pFileId),
-                                                   parentId = std::move(parentId),
-                                                   aai      = std::move(aai),
-                                                   pal      = std::move(pal)]() mutable
+                                                   pFilePrint = std::move(pFilePrint),
+                                                   parentId   = std::move(parentId),
+                                                   aai        = std::move(aai),
+                                                   pal        = std::move(pal)]() mutable
         {
             assert(pal); //bind life time to worker thread!
             setCurrentThreadName(Zstr("Ostream[Gdrive] ") + utfTo<Zstring>(getGdriveDisplayPath(gdrivePath)));
@@ -2946,14 +2956,14 @@ struct OutputStreamGdrive : public AFS::OutputStreamImpl
                     fileState.notifyItemCreated(aai.stateDelta, newFileItem);
                 });
 
-                pFileId.set_value(fileIdNew);
+                pFilePrint.set_value(getGdriveFilePrint(fileIdNew));
             }
             catch (const SysError& e)
             {
                 FileError fe(replaceCpy(_("Cannot write file %x."), L"%x", fmtPath(getGdriveDisplayPath(gdrivePath))), e.toString());
                 const std::exception_ptr exptr = std::make_exception_ptr(std::move(fe));
                 asyncStreamIn->setReadError(exptr); //set both!
-                pFileId.set_exception(exptr);       //
+                pFilePrint.set_exception(exptr);    //
             }
             //let ThreadStopRequest pass through!
         });
@@ -2974,7 +2984,7 @@ struct OutputStreamGdrive : public AFS::OutputStreamImpl
     {
         asyncStreamOut_->closeStream();
 
-        while (futFileId_.wait_for(std::chrono::milliseconds(50)) == std::future_status::timeout)
+        while (futFilePrint_.wait_for(std::chrono::milliseconds(50)) == std::future_status::timeout)
             reportBytesProcessed(); //throw X
         reportBytesProcessed(); //[!] once more, now that *all* bytes were written
 
@@ -2982,8 +2992,8 @@ struct OutputStreamGdrive : public AFS::OutputStreamImpl
         //--------------------------------------------------------------------
 
         AFS::FinalizeResult result;
-        assert(isReady(futFileId_));
-        result.fileId = futFileId_.get(); //throw FileError
+        assert(isReady(futFilePrint_));
+        result.filePrint = futFilePrint_.get(); //throw FileError
         //result.errorModTime -> already (successfully) set during file creation
         return result;
     }
@@ -2996,11 +3006,11 @@ private:
         totalBytesReported_ = totalBytesUploaded;
     }
 
-    const IOCallback notifyUnbufferedIO_; //throw X
+    const IoCallback notifyUnbufferedIO_; //throw X
     int64_t totalBytesReported_ = 0;
     std::shared_ptr<AsyncStreamBuffer> asyncStreamOut_ = std::make_shared<AsyncStreamBuffer>(GDRIVE_STREAM_BUFFER_SIZE);
     InterruptibleThread worker_;
-    std::future<AFS::FileId> futFileId_;
+    std::future<AFS::FingerPrint> futFilePrint_;
 };
 
 //==========================================================================================
@@ -3012,8 +3022,29 @@ public:
 
     const GdriveLogin& getGdriveLogin() const { return gdriveLogin_; }
 
+    Zstring getFolderUrl(const AfsPath& folderPath) const //throw FileError
+    {
+        try
+        {
+            GdriveFileState::PathStatus ps;
+            accessGlobalFileState(gdriveLogin_.email, [&](GdriveFileState& fileState) //throw SysError
+            {
+                ps = fileState.getPathStatus(gdriveLogin_.sharedDriveName, folderPath, true /*followLeafShortcut*/); //throw SysError
+            });
+
+            if (!ps.relPath.empty())
+                throw FileError(replaceCpy(_("Cannot find %x."), L"%x", fmtPath(getDisplayPath(folderPath))));
+
+            if (ps.existingType != GdriveItemType::folder)
+                throw SysError(replaceCpy<std::wstring>(L"%x is not a folder.", L"%x", fmtPath(getItemName(folderPath))));
+
+            return Zstr("https://drive.google.com/drive/folders/") + utfTo<Zstring>(ps.existingItemId);
+        }
+        catch (const SysError& e) { throw FileError(replaceCpy(_("Cannot read file attributes of %x."), L"%x", fmtPath(getDisplayPath(folderPath))), e.toString()); }
+    }
+
 private:
-    GdrivePath getGdrivePath(const AfsPath& afsPath) const { return { gdriveLogin_, afsPath }; }
+    GdrivePath getGdrivePath(const AfsPath& afsPath) const { return {gdriveLogin_, afsPath}; }
 
     GdriveRawPath getGdriveRawPath(const AfsPath& afsPath) const //throw SysError
     {
@@ -3224,7 +3255,7 @@ private:
     //----------------------------------------------------------------------------------------------------------------
 
     //return value always bound:
-    std::unique_ptr<InputStream> getInputStream(const AfsPath& afsPath, const IOCallback& notifyUnbufferedIO /*throw X*/) const override //throw FileError, (ErrorFileLocked)
+    std::unique_ptr<InputStream> getInputStream(const AfsPath& afsPath, const IoCallback& notifyUnbufferedIO /*throw X*/) const override //throw FileError, (ErrorFileLocked)
     {
         return std::make_unique<InputStreamGdrive>(getGdrivePath(afsPath), notifyUnbufferedIO);
     }
@@ -3234,7 +3265,7 @@ private:
     std::unique_ptr<OutputStreamImpl> getOutputStream(const AfsPath& afsPath, //throw FileError
                                                       std::optional<uint64_t> streamSize,
                                                       std::optional<time_t> modTime,
-                                                      const IOCallback& notifyUnbufferedIO /*throw X*/) const override
+                                                      const IoCallback& notifyUnbufferedIO /*throw X*/) const override
     {
         try
         {
@@ -3262,7 +3293,7 @@ private:
     //already existing: undefined behavior! (e.g. fail/overwrite/auto-rename)
     //=> actual behavior: 1. fails or 2. creates duplicate (unlikely)
     FileCopyResult copyFileForSameAfsType(const AfsPath& afsSource, const StreamAttributes& attrSource, //throw FileError, (ErrorFileLocked), (X)
-                                          const AbstractPath& apTarget, bool copyFilePermissions, const IOCallback& notifyUnbufferedIO /*throw X*/) const override
+                                          const AbstractPath& apTarget, bool copyFilePermissions, const IoCallback& notifyUnbufferedIO /*throw X*/) const override
     {
         //no native Google Drive file copy => use stream-based file copy:
         if (copyFilePermissions)
@@ -3325,10 +3356,10 @@ private:
             });
 
             FileCopyResult result;
-            result.fileSize     = fileSize;
-            result.modTime      = modTime;
-            result.sourceFileId = itemIdSrc;
-            result.targetFileId = fileIdTrg;
+            result.fileSize = fileSize;
+            result.modTime  = modTime;
+            result.sourceFilePrint = getGdriveFilePrint(itemIdSrc);
+            result.targetFilePrint = getGdriveFilePrint(fileIdTrg);
             /*result.errorModTime = */
             return result;
         }
@@ -3597,7 +3628,7 @@ void fff::gdriveRemoveUser(const std::string& accountEmail) //throw FileError
 
         throw SysError(formatSystemError("gdriveRemoveUser", L"", L"Function call not allowed during init/shutdown."));
     }
-    catch (const SysError& e) { throw FileError(replaceCpy(_("Unable to disconnect from %x."), L"%x", fmtPath(getGdriveDisplayPath({{ accountEmail, Zstr("")}, AfsPath() }))), e.toString()); }
+    catch (const SysError& e) { throw FileError(replaceCpy(_("Unable to disconnect from %x."), L"%x", fmtPath(getGdriveDisplayPath({{accountEmail, Zstr("")}, AfsPath()}))), e.toString()); }
 }
 
 
@@ -3625,7 +3656,7 @@ std::vector<Zstring /*sharedDriveName*/> fff::gdriveListSharedDrives(const std::
         });
         return sharedDriveNames;
     }
-    catch (const SysError& e) { throw FileError(replaceCpy(_("Unable to access %x."), L"%x", fmtPath(getGdriveDisplayPath({{ accountEmail, Zstr("")}, AfsPath() }))), e.toString()); }
+    catch (const SysError& e) { throw FileError(replaceCpy(_("Unable to access %x."), L"%x", fmtPath(getGdriveDisplayPath({{accountEmail, Zstr("")}, AfsPath()}))), e.toString()); }
 }
 
 
@@ -3649,6 +3680,15 @@ GdriveLogin fff::extractGdriveLogin(const AfsDevice& afsDevice) //noexcept
 }
 
 
+Zstring fff::getGoogleDriveFolderUrl(const AbstractPath& folderPath) //throw FileError
+{
+    if (const auto gdriveDevice = dynamic_cast<const GdriveFileSystem*>(&folderPath.afsDevice.ref()))
+        return gdriveDevice->getFolderUrl(folderPath.afsPath); //throw FileError
+
+    return {};
+}
+
+
 bool fff::acceptsItemPathPhraseGdrive(const Zstring& itemPathPhrase) //noexcept
 {
     Zstring path = expandMacros(itemPathPhrase); //expand before trimming!
diff --git a/FreeFileSync/Source/afs/gdrive.h b/FreeFileSync/Source/afs/gdrive.h
index abca18ad..75bb4a80 100644
--- a/FreeFileSync/Source/afs/gdrive.h
+++ b/FreeFileSync/Source/afs/gdrive.h
@@ -33,6 +33,9 @@ struct GdriveLogin
 };
 AfsDevice   condenseToGdriveDevice(const GdriveLogin& login); //noexcept; potentially messy user input
 GdriveLogin extractGdriveLogin(const AfsDevice& afsDevice);   //noexcept
+
+//return empty, if not a Google Drive path
+Zstring getGoogleDriveFolderUrl(const AbstractPath& folderPath); //throw FileError
 }
 
 #endif //FS_GDRIVE_9238425018342701356
diff --git a/FreeFileSync/Source/afs/native.cpp b/FreeFileSync/Source/afs/native.cpp
index 2e078378..9f677d36 100644
--- a/FreeFileSync/Source/afs/native.cpp
+++ b/FreeFileSync/Source/afs/native.cpp
@@ -8,7 +8,6 @@
 #include <zen/file_access.h>
 #include <zen/symlink_target.h>
 #include <zen/file_io.h>
-#include <zen/file_id_def.h>
 #include <zen/stl_tools.h>
 #include <zen/resolve_path.h>
 #include <zen/recycler.h>
@@ -18,6 +17,7 @@
 #include "abstract_impl.h"
 #include "../base/icon_loader.h"
 
+    #include <sys/vfs.h> //statfs
 
     #include <sys/stat.h>
     #include <dirent.h>
@@ -30,6 +30,7 @@ using AFS = AbstractFileSystem;
 
 namespace
 {
+
 void initComForThread() //throw FileError
 {
 }
@@ -37,34 +38,59 @@ void initComForThread() //throw FileError
 //====================================================================================================
 //====================================================================================================
 
+//persistent + unique (relative to volume) or 0!
 inline
-AFS::FileId convertToAbstractFileId(const zen::FileId& fid)
+AFS::FingerPrint getFileFingerprint(FileIndex fileIndex)
 {
-    if (fid == zen::FileId())
-        return AFS::FileId();
-
-    AFS::FileId   out(reinterpret_cast<const char*>(&fid.volumeId),  sizeof(fid.volumeId));
-    return out.append(reinterpret_cast<const char*>(&fid.fileIndex), sizeof(fid.fileIndex));
+    static_assert(sizeof(fileIndex) == sizeof(AFS::FingerPrint));
+    return fileIndex; //== 0 if not supported
+    /*  File details
+        ------------
+            st_mtim      (Linux)
+            st_mtimespec (macOS): nanosecond-precision for improved uniqueness?
+                          => essentially unknown after file copy (e.g. to FAT) without extra directory traversal :(
+
+            macOS st_birthtimespec: "if not supported by file system, holds the ctime instead"
+                                    ctime: inode modification time => changed on* rename*! => FU...
+
+        Volume details
+        --------------
+            st_dev: "st_dev value is not necessarily consistent across reboots or system crashes" https://freefilesync.org/forum/viewtopic.php?t=8054
+                    only locally unique and depends on device mount point! => FU...
+
+            f_fsid: "Some operating systems use the device number..." => fuck!
+                    "Several OSes restrict giving out the f_fsid field to the superuser only"
+
+            f_bsize  macOS: "fundamental file system block size"
+                     Linux: "optimal transfer block size" -> no! for all intents and purposes this *is* the "fundamental file system block size": https://stackoverflow.com/a/54835515
+            f_blocks => meh...
+
+            f_type Linux: documented values, nice! https://linux.die.net/man/2/statfs
+                    macOS: - not stable between macOS releases: https://developer.apple.com/forums/thread/87745
+                            - Apple docs say: "generally not a useful value"
+                            - f_fstypename can be used as alternative
+
+            DADiskGetBSDName(): macOS only           */
 }
 
 
 struct NativeFileInfo
 {
-    time_t   modTime;
+    FileTimeNative modTime;
     uint64_t fileSize;
-    FileId   fileId; //optional
+    FileIndex fileIndex;
 };
 NativeFileInfo getFileAttributes(FileBase::FileHandle fh) //throw SysError
 {
-    struct ::stat fileAttr = {};
-    if (::fstat(fh, &fileAttr) != 0)
+    struct stat fileInfo = {};
+    if (::fstat(fh, &fileInfo) != 0)
         THROW_LAST_SYS_ERROR("fstat");
 
     return
     {
-        fileAttr.st_mtime,
-        makeUnsigned(fileAttr.st_size),
-        generateFileId(fileAttr)
+        fileInfo.st_mtim,
+        fileInfo.st_ino,
+        makeUnsigned(fileInfo.st_size)
     };
 }
 
@@ -94,7 +120,7 @@ std::vector<FsItem> getDirContentFlat(const Zstring& dirPath) //throw FileError
            macOS: - libc: readdir thread-safe already in code from 2000: https://opensource.apple.com/source/Libc/Libc-166/gen.subproj/readdir.c.auto.html
                   - and in the latest version from 2017:                 https://opensource.apple.com/source/Libc/Libc-1244.30.3/gen/FreeBSD/readdir.c.auto.html                   */
         errno = 0;
-        const struct ::dirent* dirEntry = ::readdir(folder);
+        const dirent* dirEntry = ::readdir(folder);
         if (!dirEntry)
         {
             if (errno == 0) //errno left unchanged => no more items
@@ -114,7 +140,7 @@ std::vector<FsItem> getDirContentFlat(const Zstring& dirPath) //throw FileError
         if (itemNameRaw[0] == 0) //show error instead of endless recursion!!!
             throw FileError(replaceCpy(_("Cannot read directory %x."), L"%x", fmtPath(dirPath)), formatSystemError("readdir", L"", L"Folder contains an item without name."));
 
-        output.push_back({ itemNameRaw });
+        output.push_back({itemNameRaw});
 
         /* Unicode normalization is file-system-dependent:
 
@@ -150,32 +176,42 @@ struct FsItemDetails
     ItemType type;
     time_t   modTime; //number of seconds since Jan. 1st 1970 UTC
     uint64_t fileSize; //unit: bytes!
-    FileId   fileId;
+    AFS::FingerPrint filePrint;
 };
 FsItemDetails getItemDetails(const Zstring& itemPath) //throw FileError
 {
-    struct ::stat statData = {};
-    if (::lstat(itemPath.c_str(), &statData) != 0) //lstat() does not resolve symlinks
+    struct stat itemInfo = {};
+    if (::lstat(itemPath.c_str(), &itemInfo) != 0) //lstat() does not resolve symlinks
         THROW_LAST_FILE_ERROR(replaceCpy(_("Cannot read file attributes of %x."), L"%x", fmtPath(itemPath)), "lstat");
 
-    return { S_ISLNK(statData.st_mode) ? ItemType::symlink : //on Linux there is no distinction between file and directory symlinks!
-             /**/ (S_ISDIR(statData.st_mode) ? ItemType::folder : ItemType::file), //a file or named pipe, etc. => dont't check using S_ISREG(): see comment in file_traverser.cpp
-             statData.st_mtime,
-             makeUnsigned(statData.st_size),
-             generateFileId(statData) };
+    return {S_ISLNK(itemInfo.st_mode) ? ItemType::symlink : //on Linux there is no distinction between file and directory symlinks!
+            /**/ (S_ISDIR(itemInfo.st_mode) ? ItemType::folder : ItemType::file), //a file or named pipe, etc. => dont't check using S_ISREG(): see comment in file_traverser.cpp
+            itemInfo.st_mtime,
+            makeUnsigned(itemInfo.st_size),
+            getFileFingerprint(itemInfo.st_ino)};
 }
 
 
 FsItemDetails getSymlinkTargetDetails(const Zstring& linkPath) //throw FileError
 {
-    struct ::stat statData = {};
-    if (::stat(linkPath.c_str(), &statData) != 0)
-        THROW_LAST_FILE_ERROR(replaceCpy(_("Cannot resolve symbolic link %x."), L"%x", fmtPath(linkPath)), "stat");
-
-    return { S_ISDIR(statData.st_mode) ? ItemType::folder : ItemType::file,
-             statData.st_mtime,
-             makeUnsigned(statData.st_size),
-             generateFileId(statData) };
+    try
+    {
+        struct stat itemInfo = {};
+        if (::stat(linkPath.c_str(), &itemInfo) != 0)
+            THROW_LAST_SYS_ERROR("stat");
+
+        const ItemType targetType = S_ISDIR(itemInfo.st_mode) ? ItemType::folder : ItemType::file;
+
+        const AFS::FingerPrint filePrint = targetType == ItemType::folder ? 0 : getFileFingerprint(itemInfo.st_ino);
+        return {targetType,
+                itemInfo.st_mtime,
+                makeUnsigned(itemInfo.st_size),
+                filePrint};
+    }
+    catch (const SysError& e)
+    {
+        throw FileError(replaceCpy(_("Cannot resolve symbolic link %x."), L"%x", fmtPath(linkPath)), e.toString());
+    }
 }
 
 
@@ -185,7 +221,7 @@ public:
     SingleFolderTraverser(const std::vector<std::pair<Zstring, std::shared_ptr<AFS::TraverserCallback>>>& workload /*throw X*/)
     {
         for (const auto& [folderPath, cb] : workload)
-            workload_.push_back({ folderPath, cb });
+            workload_.push_back({folderPath, cb});
 
         while (!workload_.empty())
         {
@@ -219,18 +255,18 @@ private:
             switch (itemDetails.type)
             {
                 case ItemType::file:
-                    cb.onFile({ itemName, itemDetails.fileSize, itemDetails.modTime, convertToAbstractFileId(itemDetails.fileId), false /*isFollowedSymlink*/ }); //throw X
+                    cb.onFile({itemName, itemDetails.fileSize, itemDetails.modTime, itemDetails.filePrint, false /*isFollowedSymlink*/}); //throw X
                     break;
 
                 case ItemType::folder:
-                    if (std::shared_ptr<AFS::TraverserCallback> cbSub = cb.onFolder({ itemName, false /*isFollowedSymlink*/ })) //throw X
-                        workload_.push_back({ itemPath, std::move(cbSub) });
+                    if (std::shared_ptr<AFS::TraverserCallback> cbSub = cb.onFolder({itemName, false /*isFollowedSymlink*/})) //throw X
+                        workload_.push_back({itemPath, std::move(cbSub)});
                     break;
 
                 case ItemType::symlink:
-                    switch (cb.onSymlink({ itemName, itemDetails.modTime })) //throw X
+                    switch (cb.onSymlink({itemName, itemDetails.modTime})) //throw X
                     {
-                        case AFS::TraverserCallback::LINK_FOLLOW:
+                        case AFS::TraverserCallback::HandleLink::follow:
                         {
                             FsItemDetails targetDetails = {};
                             if (!tryReportingItemError([&] //throw X
@@ -241,15 +277,15 @@ private:
 
                             if (targetDetails.type == ItemType::folder)
                             {
-                                if (std::shared_ptr<AFS::TraverserCallback> cbSub = cb.onFolder({ itemName, true /*isFollowedSymlink*/ })) //throw X
-                                    workload_.push_back({ itemPath, std::move(cbSub) });
+                                if (std::shared_ptr<AFS::TraverserCallback> cbSub = cb.onFolder({itemName, true /*isFollowedSymlink*/})) //throw X
+                                    workload_.push_back({itemPath, std::move(cbSub)}); //symlink may link to different volume!
                             }
                             else //a file or named pipe, etc.
-                                cb.onFile({ itemName, targetDetails.fileSize, targetDetails.modTime, convertToAbstractFileId(targetDetails.fileId), true /*isFollowedSymlink*/ }); //throw X
+                                cb.onFile({itemName, targetDetails.fileSize, targetDetails.modTime, targetDetails.filePrint, true /*isFollowedSymlink*/}); //throw X
                         }
                         break;
 
-                        case AFS::TraverserCallback::LINK_SKIP:
+                        case AFS::TraverserCallback::HandleLink::skip:
                             break;
                     }
                     break;
@@ -289,7 +325,7 @@ private:
 
 struct InputStreamNative : public AFS::InputStream
 {
-    InputStreamNative(const Zstring& filePath, const IOCallback& notifyUnbufferedIO /*throw X*/) : fi_(filePath, notifyUnbufferedIO) {} //throw FileError, ErrorFileLocked
+    InputStreamNative(const Zstring& filePath, const IoCallback& notifyUnbufferedIO /*throw X*/) : fi_(filePath, notifyUnbufferedIO) {} //throw FileError, ErrorFileLocked
 
     size_t read(void* buffer, size_t bytesToRead) override { return fi_.read(buffer, bytesToRead); } //throw FileError, ErrorFileLocked, X; return "bytesToRead" bytes unless end of stream!
     size_t getBlockSize() const override { return fi_.getBlockSize(); } //non-zero block size is AFS contract!
@@ -297,13 +333,11 @@ struct InputStreamNative : public AFS::InputStream
     {
         try
         {
-            const NativeFileInfo fileInfo = getFileAttributes(fi_.getHandle()); //throw SysError
-            return AFS::StreamAttributes(
-            {
-                fileInfo.modTime,
-                fileInfo.fileSize,
-                convertToAbstractFileId(fileInfo.fileId)
-            });
+            const NativeFileInfo& fileInfo = getFileAttributes(fi_.getHandle()); //throw SysError
+
+            return AFS::StreamAttributes({nativeFileTimeToTimeT(fileInfo.modTime),
+                                          fileInfo.fileSize,
+                                          getFileFingerprint(fileInfo.fileIndex)});
         }
         catch (const SysError& e) { throw FileError(replaceCpy(_("Cannot read file attributes of %x."), L"%x", fmtPath(fi_.getFilePath())), e.toString()); }
     }
@@ -319,7 +353,7 @@ struct OutputStreamNative : public AFS::OutputStreamImpl
     OutputStreamNative(const Zstring& filePath,
                        std::optional<uint64_t> streamSize,
                        std::optional<time_t> modTime,
-                       const IOCallback& notifyUnbufferedIO /*throw X*/) :
+                       const IoCallback& notifyUnbufferedIO /*throw X*/) :
         fo_(filePath, notifyUnbufferedIO), //throw FileError, ErrorTargetExisting
         modTime_(modTime)
     {
@@ -332,20 +366,22 @@ struct OutputStreamNative : public AFS::OutputStreamImpl
     AFS::FinalizeResult finalize() override //throw FileError, X
     {
         AFS::FinalizeResult result;
-        try
-        {
-            result.fileId = convertToAbstractFileId(getFileAttributes(fo_.getHandle()).fileId); //throw SysError
-        }
-        catch (const SysError& e) { throw FileError(replaceCpy(_("Cannot read file attributes of %x."), L"%x", fmtPath(fo_.getFilePath())), e.toString()); }
+        if (modTime_)
+            try
+            {
+                const FileIndex fileIndex = getFileAttributes(fo_.getHandle()).fileIndex; //throw SysError
+                result.filePrint = getFileFingerprint(fileIndex);
+            }
+            catch (const SysError& e) { throw FileError(replaceCpy(_("Cannot read file attributes of %x."), L"%x", fmtPath(fo_.getFilePath())), e.toString()); }
 
         fo_.finalize(); //throw FileError, X
 
         try
         {
             if (modTime_)
-                setFileTime(fo_.getFilePath(), *modTime_, ProcSymlink::FOLLOW); //throw FileError
+                setFileTime(fo_.getFilePath(), *modTime_, ProcSymlink::follow); //throw FileError
             /* is setting modtime after closing the file handle a pessimization?
-                Native: no, needed for functional correctness, see file_access.cpp */
+               no, needed for functional correctness, see file_access.cpp */
         }
         catch (const FileError& e) { result.errorModTime = FileError(e.toString()); /*avoid slicing*/ }
 
@@ -364,11 +400,9 @@ class NativeFileSystem : public AbstractFileSystem
 public:
     NativeFileSystem(const Zstring& rootPath) : rootPath_(rootPath) {}
 
-private:
-    Zstring getNativePath(const AfsPath& afsPath) const { return nativeAppendPaths(rootPath_, afsPath.value); }
-
-    std::optional<Zstring> getNativeItemPath(const AfsPath& afsPath) const override { return getNativePath(afsPath); }
+    Zstring getNativePath(const AfsPath& afsPath) const { return isNullFileSystem() ? Zstring() : nativeAppendPaths(rootPath_, afsPath.value); }
 
+private:
     Zstring getInitPathPhrase(const AfsPath& afsPath) const override
     {
         Zstring initPathPhrase = getNativePath(afsPath);
@@ -475,7 +509,7 @@ private:
     //----------------------------------------------------------------------------------------------------------------
 
     //return value always bound:
-    std::unique_ptr<InputStream> getInputStream(const AfsPath& afsPath, const IOCallback& notifyUnbufferedIO /*throw X*/) const override //throw FileError, ErrorFileLocked
+    std::unique_ptr<InputStream> getInputStream(const AfsPath& afsPath, const IoCallback& notifyUnbufferedIO /*throw X*/) const override //throw FileError, ErrorFileLocked
     {
         initComForThread(); //throw FileError
         return std::make_unique<InputStreamNative>(getNativePath(afsPath), notifyUnbufferedIO); //throw FileError, ErrorFileLocked
@@ -486,7 +520,7 @@ private:
     std::unique_ptr<OutputStreamImpl> getOutputStream(const AfsPath& afsPath, //throw FileError
                                                       std::optional<uint64_t> streamSize,
                                                       std::optional<time_t> modTime,
-                                                      const IOCallback& notifyUnbufferedIO /*throw X*/) const override
+                                                      const IoCallback& notifyUnbufferedIO /*throw X*/) const override
     {
         initComForThread(); //throw FileError
         return std::make_unique<OutputStreamNative>(getNativePath(afsPath), streamSize, modTime, notifyUnbufferedIO); //throw FileError
@@ -509,7 +543,7 @@ private:
     //already existing: undefined behavior! (e.g. fail/overwrite/auto-rename)
     //=> actual behavior: fail with clear error message
     FileCopyResult copyFileForSameAfsType(const AfsPath& afsSource, const StreamAttributes& attrSource, //throw FileError, ErrorFileLocked, X
-                                          const AbstractPath& apTarget, bool copyFilePermissions, const IOCallback& notifyUnbufferedIO /*throw X*/) const override
+                                          const AbstractPath& apTarget, bool copyFilePermissions, const IoCallback& notifyUnbufferedIO /*throw X*/) const override
     {
         const Zstring nativePathTarget = static_cast<const NativeFileSystem&>(apTarget.afsDevice.ref()).getNativePath(apTarget.afsPath);
 
@@ -522,13 +556,14 @@ private:
         catch (FileError&) {});
 
         if (copyFilePermissions)
-            copyItemPermissions(getNativePath(afsSource), nativePathTarget, ProcSymlink::FOLLOW); //throw FileError
+            copyItemPermissions(getNativePath(afsSource), nativePathTarget, ProcSymlink::follow); //throw FileError
 
         FileCopyResult result;
-        result.fileSize     = nativeResult.fileSize;
-        result.modTime      = nativeResult.modTime;
-        result.sourceFileId = convertToAbstractFileId(nativeResult.sourceFileId);
-        result.targetFileId = convertToAbstractFileId(nativeResult.targetFileId);
+        result.fileSize = nativeResult.fileSize;
+        //caveat: modTime will be incorrect for file systems with imprecise file times, e.g. see FAT_FILE_TIME_PRECISION_SEC
+        result.modTime = nativeFileTimeToTimeT(nativeResult.sourceModTime);
+        result.sourceFilePrint = getFileFingerprint(nativeResult.sourceFileIdx);
+        result.targetFilePrint = getFileFingerprint(nativeResult.targetFileIdx);
         result.errorModTime = nativeResult.errorModTime;
         return result;
     }
@@ -553,7 +588,7 @@ private:
             tryCopyDirectoryAttributes(sourcePath, targetPath); //throw FileError
 
         if (copyFilePermissions)
-            copyItemPermissions(sourcePath, targetPath, ProcSymlink::FOLLOW); //throw FileError
+            copyItemPermissions(sourcePath, targetPath, ProcSymlink::follow); //throw FileError
     }
 
     //already existing: fail
@@ -568,7 +603,7 @@ private:
         catch (FileError&) {});
 
         if (copyFilePermissions)
-            copyItemPermissions(getNativePath(afsSource), nativePathTarget, ProcSymlink::DIRECT); //throw FileError
+            copyItemPermissions(getNativePath(afsSource), nativePathTarget, ProcSymlink::direct); //throw FileError
     }
 
     //already existing: undefined behavior! (e.g. fail/overwrite)
@@ -662,11 +697,11 @@ void RecycleSessionNative::recycleItemIfExists(const AbstractPath& itemPath, con
 {
     assert(!startsWith(logicalRelPath, FILE_NAME_SEPARATOR));
 
-    std::optional<Zstring> itemPathNative = AFS::getNativeItemPath(itemPath);
-    if (!itemPathNative)
+    const Zstring& itemPathNative = getNativeItemPath(itemPath);
+    if (itemPathNative.empty())
         throw std::logic_error("Contract violation! " + std::string(__FILE__) + ':' + numberTo<std::string>(__LINE__));
 
-    recycleOrDeleteIfExists(*itemPathNative); //throw FileError
+    recycleOrDeleteIfExists(itemPathNative); //throw FileError
 }
 
 
@@ -710,3 +745,11 @@ AbstractPath fff::createItemPathNativeNoFormatting(const Zstring& nativePath) //
     else //broken path syntax
         return AbstractPath(makeSharedRef<NativeFileSystem>(nativePath), AfsPath());
 }
+
+
+Zstring fff::getNativeItemPath(const AbstractPath& ap)
+{
+    if (const auto nativeDevice = dynamic_cast<const NativeFileSystem*>(&ap.afsDevice.ref()))
+        return nativeDevice->getNativePath(ap.afsPath);
+    return {};
+}
diff --git a/FreeFileSync/Source/afs/native.h b/FreeFileSync/Source/afs/native.h
index 77896e91..24270e9f 100644
--- a/FreeFileSync/Source/afs/native.h
+++ b/FreeFileSync/Source/afs/native.h
@@ -14,7 +14,12 @@ namespace fff
 bool  acceptsItemPathPhraseNative(const Zstring& itemPathPhrase); //noexcept
 AbstractPath createItemPathNative(const Zstring& itemPathPhrase); //noexcept
 
+//-------------------------------------------------------
+
 AbstractPath createItemPathNativeNoFormatting(const Zstring& nativePath); //noexcept
+
+//return empty, if not a native path
+Zstring getNativeItemPath(const AbstractPath& ap);
 }
 
 #endif //FS_NATIVE_183247018532434563465
diff --git a/FreeFileSync/Source/afs/sftp.cpp b/FreeFileSync/Source/afs/sftp.cpp
index 325aa412..74dc1657 100644
--- a/FreeFileSync/Source/afs/sftp.cpp
+++ b/FreeFileSync/Source/afs/sftp.cpp
@@ -478,7 +478,7 @@ public:
         int rc = LIBSSH2_ERROR_NONE;
         try
         {
-            rc = sftpCommand({ sshSession_, sftpChannel }); //noexcept
+            rc = sftpCommand({sshSession_, sftpChannel}); //noexcept
         }
         catch (...) { assert(false); rc = LIBSSH2_ERROR_BAD_USE; }
 
@@ -563,16 +563,16 @@ public:
                 return; //time-out! => let next tryNonBlocking() call fail with detailed error!
             const auto waitTimeMs = std::chrono::duration_cast<std::chrono::milliseconds>(endTime - now).count();
 
-            struct ::timeval tv = {};
+            timeval tv = {};
             tv.tv_sec  = static_cast<long>(waitTimeMs / 1000);
             tv.tv_usec = static_cast<long>(waitTimeMs - tv.tv_sec * 1000) * 1000;
 
             //WSAPoll is broken, ::poll() on macOS even worse: https://daniel.haxx.se/blog/2012/10/10/wsapoll-is-broken/
             //perf: no significant difference compared to ::WSAPoll()
-            const int rc = ::select(nfds + 1, //int nfds,
-                                    readCount  > 0 ? &readfds  : nullptr, //fd_set* readfds,
-                                    writeCount > 0 ? &writefds : nullptr, //fd_set* writefds,
-                                    nullptr,  //fd_set* exceptfds,
+            const int rc = ::select(nfds + 1, //int nfds
+                                    readCount  > 0 ? &readfds  : nullptr, //fd_set* readfds
+                                    writeCount > 0 ? &writefds : nullptr, //fd_set* writefds
+                                    nullptr,  //fd_set* exceptfds
                                     &tv);     //struct timeval* timeout
             if (rc == 0)
                 return; //time-out! => let next tryNonBlocking() call fail with detailed error!
@@ -738,7 +738,7 @@ public:
         void init() //throw SysError, FatalSshError
         {
             if (session_->getSftpChannelCount() == 0) //make sure the SSH session contains at least one SFTP channel
-                SshSession::addSftpChannel({ session_.get() }, timeoutSec_); //throw SysError, FatalSshError
+                SshSession::addSftpChannel({session_.get()}, timeoutSec_); //throw SysError, FatalSshError
         }
 
         //bool isHealthy() const { return session_->isHealthy(); }
@@ -753,7 +753,7 @@ public:
                 if (session_->tryNonBlocking(0, sftpCommandStartTime, functionName, sftpCommand, timeoutSec_)) //throw SysError, FatalSshError
                     return;
                 else //pending
-                    SshSession::waitForTraffic({ session_.get() }, timeoutSec_); //throw FatalSshError
+                    SshSession::waitForTraffic({session_.get()}, timeoutSec_); //throw FatalSshError
         }
 
     private:
@@ -783,7 +783,7 @@ public:
                     if (session_->tryNonBlocking(channelNo, commandStartTime, functionName, sftpCommand, timeoutSec_)) //throw SysError, FatalSshError
                         return;
                     else //pending
-                        SshSession::waitForTraffic({ session_.get() }, timeoutSec_); //throw FatalSshError
+                        SshSession::waitForTraffic({session_.get()}, timeoutSec_); //throw FatalSshError
                 }
                 catch (const SysError&     ) { return; }
                 catch (const FatalSshError&) { return; }
@@ -1087,17 +1087,17 @@ std::vector<SftpItem> getDirContentFlat(const SftpLogin& login, const AfsPath& d
         {
             if ((attribs.flags & LIBSSH2_SFTP_ATTR_ACMODTIME) == 0) //server probably does not support these attributes => fail at folder level
                 throw FileError(replaceCpy(_("Cannot read file attributes of %x."), L"%x", fmtPath(getSftpDisplayPath(login.server, itemPath))), L"Modification time not supported.");
-            output.push_back({ itemName, { AFS::ItemType::symlink, 0, static_cast<time_t>(attribs.mtime) }});
+            output.push_back({itemName, {AFS::ItemType::symlink, 0, static_cast<time_t>(attribs.mtime)}});
         }
         else if (LIBSSH2_SFTP_S_ISDIR(attribs.permissions))
-            output.push_back({ itemName, { AFS::ItemType::folder, 0, static_cast<time_t>(attribs.mtime) }});
+            output.push_back({itemName, {AFS::ItemType::folder, 0, static_cast<time_t>(attribs.mtime)}});
         else //a file or named pipe, ect: LIBSSH2_SFTP_S_ISREG, LIBSSH2_SFTP_S_ISCHR, LIBSSH2_SFTP_S_ISBLK, LIBSSH2_SFTP_S_ISFIFO, LIBSSH2_SFTP_S_ISSOCK
         {
             if ((attribs.flags & LIBSSH2_SFTP_ATTR_ACMODTIME) == 0) //server probably does not support these attributes => fail at folder level
                 throw FileError(replaceCpy(_("Cannot read file attributes of %x."), L"%x", fmtPath(getSftpDisplayPath(login.server, itemPath))), L"Modification time not supported.");
             if ((attribs.flags & LIBSSH2_SFTP_ATTR_SIZE) == 0)
                 throw FileError(replaceCpy(_("Cannot read file attributes of %x."), L"%x", fmtPath(getSftpDisplayPath(login.server, itemPath))), L"File size not supported.");
-            output.push_back({ itemName, { AFS::ItemType::file, attribs.filesize, static_cast<time_t>(attribs.mtime) }});
+            output.push_back({itemName, {AFS::ItemType::file, attribs.filesize, static_cast<time_t>(attribs.mtime)}});
         }
     }
 }
@@ -1117,7 +1117,7 @@ SftpItemDetails getSymlinkTargetDetails(const SftpLogin& login, const AfsPath& l
         throw FileError(replaceCpy(_("Cannot read file attributes of %x."), L"%x", fmtPath(getSftpDisplayPath(login.server, linkPath))), L"File attributes not available.");
 
     if (LIBSSH2_SFTP_S_ISDIR(attribsTrg.permissions))
-        return { AFS::ItemType::folder, 0, static_cast<time_t>(attribsTrg.mtime) };
+        return {AFS::ItemType::folder, 0, static_cast<time_t>(attribsTrg.mtime)};
     else
     {
         if ((attribsTrg.flags & LIBSSH2_SFTP_ATTR_ACMODTIME) == 0) //server probably does not support these attributes => should fail at folder level!
@@ -1125,7 +1125,7 @@ SftpItemDetails getSymlinkTargetDetails(const SftpLogin& login, const AfsPath& l
         if ((attribsTrg.flags & LIBSSH2_SFTP_ATTR_SIZE) == 0)
             throw FileError(replaceCpy(_("Cannot read file attributes of %x."), L"%x", fmtPath(getSftpDisplayPath(login.server, linkPath))), L"File size not supported.");
 
-        return { AFS::ItemType::file, attribsTrg.filesize, static_cast<time_t>(attribsTrg.mtime) };
+        return {AFS::ItemType::file, attribsTrg.filesize, static_cast<time_t>(attribsTrg.mtime)};
     }
 }
 
@@ -1167,18 +1167,18 @@ private:
             switch (item.details.type)
             {
                 case AFS::ItemType::file:
-                    cb.onFile({ item.itemName, item.details.fileSize, item.details.modTime, AFS::FileId(), false /*isFollowedSymlink*/ }); //throw X
+                    cb.onFile({item.itemName, item.details.fileSize, item.details.modTime, AFS::FingerPrint() /*not supported by SFTP*/, false /*isFollowedSymlink*/}); //throw X
                     break;
 
                 case AFS::ItemType::folder:
-                    if (std::shared_ptr<AFS::TraverserCallback> cbSub = cb.onFolder({ item.itemName, false /*isFollowedSymlink*/ })) //throw X
-                        workload_.push_back(WorkItem{ itemPath, std::move(cbSub) });
+                    if (std::shared_ptr<AFS::TraverserCallback> cbSub = cb.onFolder({item.itemName, false /*isFollowedSymlink*/})) //throw X
+                        workload_.push_back(WorkItem{itemPath, std::move(cbSub)});
                     break;
 
                 case AFS::ItemType::symlink:
-                    switch (cb.onSymlink({ item.itemName, item.details.modTime })) //throw X
+                    switch (cb.onSymlink({item.itemName, item.details.modTime})) //throw X
                     {
-                        case AFS::TraverserCallback::LINK_FOLLOW:
+                        case AFS::TraverserCallback::HandleLink::follow:
                         {
                             SftpItemDetails targetDetails = {};
                             if (!tryReportingItemError([&] //throw X
@@ -1189,15 +1189,15 @@ private:
 
                             if (targetDetails.type == AFS::ItemType::folder)
                             {
-                                if (std::shared_ptr<AFS::TraverserCallback> cbSub = cb.onFolder({ item.itemName, true /*isFollowedSymlink*/ })) //throw X
-                                    workload_.push_back(WorkItem{ itemPath, std::move(cbSub) });
+                                if (std::shared_ptr<AFS::TraverserCallback> cbSub = cb.onFolder({item.itemName, true /*isFollowedSymlink*/})) //throw X
+                                    workload_.push_back(WorkItem{itemPath, std::move(cbSub)});
                             }
                             else //a file or named pipe, etc.
-                                cb.onFile({ item.itemName, targetDetails.fileSize, targetDetails.modTime, AFS::FileId(), true /*isFollowedSymlink*/ }); //throw X
+                                cb.onFile({item.itemName, targetDetails.fileSize, targetDetails.modTime, AFS::FingerPrint() /*not supported by SFTP*/, true /*isFollowedSymlink*/}); //throw X
                         }
                         break;
 
-                        case AFS::TraverserCallback::LINK_SKIP:
+                        case AFS::TraverserCallback::HandleLink::skip:
                             break;
                     }
                     break;
@@ -1219,7 +1219,7 @@ void traverseFolderRecursiveSftp(const SftpLogin& login, const std::vector<std::
 
 struct InputStreamSftp : public AFS::InputStream
 {
-    InputStreamSftp(const SftpLogin& login, const AfsPath& filePath, const IOCallback& notifyUnbufferedIO /*throw X*/) : //throw FileError
+    InputStreamSftp(const SftpLogin& login, const AfsPath& filePath, const IoCallback& notifyUnbufferedIO /*throw X*/) : //throw FileError
         displayPath_(getSftpDisplayPath(login.server, filePath)),
         notifyUnbufferedIO_(notifyUnbufferedIO)
     {
@@ -1318,7 +1318,7 @@ private:
 
     const std::wstring displayPath_;
     LIBSSH2_SFTP_HANDLE* fileHandle_ = nullptr;
-    const IOCallback notifyUnbufferedIO_; //throw X
+    const IoCallback notifyUnbufferedIO_; //throw X
     std::shared_ptr<SftpSessionManager::SshSessionShared> session_;
 
     std::vector<std::byte> memBuf_ = std::vector<std::byte>(getBlockSize());
@@ -1334,7 +1334,7 @@ struct OutputStreamSftp : public AFS::OutputStreamImpl
     OutputStreamSftp(const SftpLogin& login, //throw FileError
                      const AfsPath& filePath,
                      std::optional<time_t> modTime,
-                     const IOCallback& notifyUnbufferedIO /*throw X*/) :
+                     const IoCallback& notifyUnbufferedIO /*throw X*/) :
         filePath_(filePath),
         displayPath_(getSftpDisplayPath(login.server, filePath)),
         modTime_(modTime),
@@ -1422,12 +1422,12 @@ struct OutputStreamSftp : public AFS::OutputStreamImpl
         //it seems libssh2_sftp_fsetstat() triggers bugs on synology server => set mtime by path! https://freefilesync.org/forum/viewtopic.php?t=1281
 
         AFS::FinalizeResult result;
-        //result.fileId = ... -> not supported by SFTP
+        //result.filePrint = ... -> not supported by SFTP
         try
         {
             setModTimeIfAvailable(); //throw FileError, follows symlinks
             /* is setting modtime after closing the file handle a pessimization?
-                SFTP:   no, needed for functional correctness (synology server), just as for Native */
+                SFTP: no, needed for functional correctness (synology server), same as for Native */
         }
         catch (const FileError& e) { result.errorModTime = e; /*slicing?*/ }
 
@@ -1502,7 +1502,7 @@ private:
     const std::wstring displayPath_;
     LIBSSH2_SFTP_HANDLE* fileHandle_ = nullptr;
     const std::optional<time_t> modTime_;
-    const IOCallback notifyUnbufferedIO_; //throw X
+    const IoCallback notifyUnbufferedIO_; //throw X
     std::shared_ptr<SftpSessionManager::SshSessionShared> session_;
 
     std::vector<std::byte> memBuf_ = std::vector<std::byte>(getBlockSize());
@@ -1702,7 +1702,7 @@ private:
     //----------------------------------------------------------------------------------------------------------------
 
     //return value always bound:
-    std::unique_ptr<InputStream> getInputStream(const AfsPath& afsPath, const IOCallback& notifyUnbufferedIO /*throw X*/) const override //throw FileError, (ErrorFileLocked)
+    std::unique_ptr<InputStream> getInputStream(const AfsPath& afsPath, const IoCallback& notifyUnbufferedIO /*throw X*/) const override //throw FileError, (ErrorFileLocked)
     {
         return std::make_unique<InputStreamSftp>(login_, afsPath, notifyUnbufferedIO); //throw FileError
     }
@@ -1712,7 +1712,7 @@ private:
     std::unique_ptr<OutputStreamImpl> getOutputStream(const AfsPath& afsPath, //throw FileError
                                                       std::optional<uint64_t> streamSize,
                                                       std::optional<time_t> modTime,
-                                                      const IOCallback& notifyUnbufferedIO /*throw X*/) const override
+                                                      const IoCallback& notifyUnbufferedIO /*throw X*/) const override
     {
         return std::make_unique<OutputStreamSftp>(login_, afsPath, modTime, notifyUnbufferedIO); //throw FileError
     }
@@ -1727,7 +1727,7 @@ private:
     //symlink handling: follow
     //already existing: undefined behavior! (e.g. fail/overwrite/auto-rename)
     FileCopyResult copyFileForSameAfsType(const AfsPath& afsSource, const StreamAttributes& attrSource, //throw FileError, (ErrorFileLocked), X
-                                          const AbstractPath& apTarget, bool copyFilePermissions, const IOCallback& notifyUnbufferedIO /*throw X*/) const override
+                                          const AbstractPath& apTarget, bool copyFilePermissions, const IoCallback& notifyUnbufferedIO /*throw X*/) const override
     {
         //no native SFTP file copy => use stream-based file copy:
         if (copyFilePermissions)
@@ -1961,7 +1961,7 @@ int fff::getServerMaxChannelsPerConnection(const SftpLogin& login) //throw FileE
         {
             try
             {
-                SftpSessionManager::SshSessionExclusive::addSftpChannel({ exSession.get() }); //throw SysError, FatalSshError
+                SftpSessionManager::SshSessionExclusive::addSftpChannel({exSession.get()}); //throw SysError, FatalSshError
             }
             catch (const SysError&       ) { if (exSession->getSftpChannelCount() == 0) throw;                        return static_cast<int>(exSession->getSftpChannelCount()); }
             catch (const FatalSshError& e) { if (exSession->getSftpChannelCount() == 0) throw SysError(e.toString()); return static_cast<int>(exSession->getSftpChannelCount()); }
@@ -2012,7 +2012,7 @@ AbstractPath fff::createItemPathSftp(const Zstring& itemPathPhrase) //noexcept
 
     auto it = std::find_if(fullPath.begin(), fullPath.end(), [](Zchar c) { return c == '/' || c == '\\'; });
     const Zstring serverPort(fullPath.begin(), it);
-    const AfsPath serverRelPath = sanitizeDeviceRelativePath({ it, fullPath.end() });
+    const AfsPath serverRelPath = sanitizeDeviceRelativePath({it, fullPath.end()});
 
     login.server       = beforeLast(serverPort, Zstr(':'), IfNotFoundReturn::all);
     const Zstring port =  afterLast(serverPort, Zstr(':'), IfNotFoundReturn::none);
diff --git a/FreeFileSync/Source/application.cpp b/FreeFileSync/Source/application.cpp
index c1ccd1d2..dc24ad19 100644
--- a/FreeFileSync/Source/application.cpp
+++ b/FreeFileSync/Source/application.cpp
@@ -92,8 +92,8 @@ bool Application::OnInit()
         if (error)
             throw SysError(formatGlibError("gtk_css_provider_load_from_path", error));
 
-        ::gtk_style_context_add_provider_for_screen(::gdk_screen_get_default(),               //GdkScreen* screen,
-                                                    GTK_STYLE_PROVIDER(provider),             //GtkStyleProvider* provider,
+        ::gtk_style_context_add_provider_for_screen(::gdk_screen_get_default(),               //GdkScreen* screen
+                                                    GTK_STYLE_PROVIDER(provider),             //GtkStyleProvider* provider
                                                     GTK_STYLE_PROVIDER_PRIORITY_APPLICATION); //guint priority
     };
     try
@@ -113,6 +113,18 @@ bool Application::OnInit()
 #error unknown GTK version!
 #endif
 
+    try
+    {
+        /* we're a GUI app: ignore SIGHUP when the parent terminal quits! (or process is killed!)
+            => the FFS launcher will still be killed => fine
+            => macOS: apparently not needed! interestingly the FFS launcher does receive SIGHUP and *is* killed  */
+        if (sighandler_t oldHandler = ::signal(SIGHUP, SIG_IGN);
+            oldHandler == SIG_ERR)
+            THROW_LAST_SYS_ERROR("signal(SIGHUP)");
+        else assert(!oldHandler);
+    }
+    catch (const SysError& e) { std::cerr << utfTo<std::string>(e.toString()) << '\n'; }
+
 
     //Windows User Experience Interaction Guidelines: tool tips should have 5s timeout, info tips no timeout => compromise:
     wxToolTip::Enable(true); //yawn, a wxWidgets screw-up: wxToolTip::SetAutoPop is no-op if global tooltip window is not yet constructed: wxToolTip::Enable creates it
@@ -127,7 +139,7 @@ bool Application::OnInit()
     }
     catch (FileError&) { assert(false); }
 
-    initAfs({ getResourceDirPf(), getConfigDirPathPf() }); //bonus: using FTP Gdrive implicitly inits OpenSSL (used in runSanityChecks() on Linux) alredy during globals init
+    initAfs({getResourceDirPf(), getConfigDirPathPf()}); //bonus: using FTP Gdrive implicitly inits OpenSSL (used in runSanityChecks() on Linux) alredy during globals init
 
 
     Bind(wxEVT_QUERY_END_SESSION, [this](wxCloseEvent& event) { onQueryEndSession(event); }); //can veto
@@ -178,7 +190,7 @@ void Application::OnUnhandledException() //handles both wxApp::OnInit() + wxApp:
     }
     catch (const std::bad_alloc& e) //the only kind of exception we don't want crash dumps for
     {
-        logFatalError(e.what()); //it's not always possible to display a message box, e.g. corrupted stack, however low-level file output works!
+        logFatalError(utfTo<std::wstring>(e.what())); //it's not always possible to display a message box, e.g. corrupted stack, however low-level file output works!
 
         const auto& titleFmt = copyStringTo<std::wstring>(wxTheApp->GetAppDisplayName()) + SPACED_DASH + _("An exception occurred");
         std::cerr << utfTo<std::string>(titleFmt + SPACED_DASH) << e.what() << '\n';
@@ -212,7 +224,7 @@ void Application::launch(const std::vector<Zstring>& commandArgs)
 
     auto notifyFatalError = [&](const std::wstring& msg, const std::wstring& title)
     {
-        logFatalError(utfTo<std::string>(msg));
+        logFatalError(msg);
 
         //error handling strategy unknown and no sync log output available at this point!
         auto titleFmt = copyStringTo<std::wstring>(wxTheApp->GetAppDisplayName()) + SPACED_DASH + title;
@@ -347,9 +359,9 @@ void Application::launch(const std::vector<Zstring>& commandArgs)
 
     auto hasNonDefaultConfig = [](const LocalPairConfig& lpc)
     {
-        return lpc != LocalPairConfig{ lpc.folderPathPhraseLeft,
-                                       lpc.folderPathPhraseRight,
-                                       std::nullopt, std::nullopt, FilterConfig() };
+        return lpc != LocalPairConfig{lpc.folderPathPhraseLeft,
+                                      lpc.folderPathPhraseRight,
+                                      std::nullopt, std::nullopt, FilterConfig()};
     };
 
     auto replaceDirectories = [&](MainConfiguration& mainCfg)
@@ -371,8 +383,8 @@ void Application::launch(const std::vector<Zstring>& commandArgs)
                     mainCfg.firstPair.folderPathPhraseRight = dirPathPhrasePairs[0].second;
                 }
                 else
-                    mainCfg.additionalPairs.push_back({ dirPathPhrasePairs[i].first, dirPathPhrasePairs[i].second,
-                                                        std::nullopt, std::nullopt, FilterConfig() });
+                    mainCfg.additionalPairs.push_back({dirPathPhrasePairs[i].first, dirPathPhrasePairs[i].second,
+                                                       std::nullopt, std::nullopt, FilterConfig()});
         }
         return true;
     };
@@ -516,8 +528,11 @@ void runBatchMode(const Zstring& globalConfigFilePath, const XmlBatchConfig& bat
     {
         if (showPopupAllowed)
             showNotificationDialog(nullptr, DialogInfoType::error, PopupDialogCfg().setDetailInstructions(msg));
-        else //"exit" or "ignore"
-            logFatalError(utfTo<std::string>(msg));
+        else //"ignoreErrors" or BatchErrorHandling::cancel
+        {
+            logFatalError(msg);
+            std::cerr << utfTo<std::string>(wxTheApp->GetAppDisplayName() + SPACED_DASH + msg) << '\n'; //Linux, macOS
+        }
 
         raiseExitCode(exitCode, rc);
     };
@@ -669,7 +684,7 @@ void runBatchMode(const Zstring& globalConfigFilePath, const XmlBatchConfig& bat
         case FinalRequest::none:
             break;
         case FinalRequest::switchGui: //open new top-level window *after* progress dialog is gone => run on main event loop
-            MainDialog::create(globalConfigFilePath, &globalCfg, convertBatchToGui(batchCfg), { cfgFilePath }, true /*startComparison*/);
+            MainDialog::create(globalConfigFilePath, &globalCfg, convertBatchToGui(batchCfg), {cfgFilePath}, true /*startComparison*/);
             break;
         case FinalRequest::shutdown: //run *after* last sync stats were updated and saved! https://freefilesync.org/forum/viewtopic.php?t=5761
             try
diff --git a/FreeFileSync/Source/base/algorithm.cpp b/FreeFileSync/Source/base/algorithm.cpp
index bcbba259..cf4a0ce9 100644
--- a/FreeFileSync/Source/base/algorithm.cpp
+++ b/FreeFileSync/Source/base/algorithm.cpp
@@ -120,9 +120,9 @@ private:
         const CompareFileResult cat = file.getCategory();
 
         //##################### schedule old temporary files for deletion ####################
-        if (cat == FILE_LEFT_SIDE_ONLY && endsWith(file.getItemName<LEFT_SIDE>(), AFS::TEMP_FILE_ENDING))
+        if (cat == FILE_LEFT_SIDE_ONLY && endsWith(file.getItemName<SelectSide::left>(), AFS::TEMP_FILE_ENDING))
             return file.setSyncDir(SyncDirection::left);
-        else if (cat == FILE_RIGHT_SIDE_ONLY && endsWith(file.getItemName<RIGHT_SIDE>(), AFS::TEMP_FILE_ENDING))
+        else if (cat == FILE_RIGHT_SIDE_ONLY && endsWith(file.getItemName<SelectSide::right>(), AFS::TEMP_FILE_ENDING))
             return file.setSyncDir(SyncDirection::right);
         //####################################################################################
 
@@ -193,9 +193,9 @@ private:
         const CompareDirResult cat = folder.getDirCategory();
 
         //########### schedule abandoned temporary recycle bin directory for deletion  ##########
-        if (cat == DIR_LEFT_SIDE_ONLY && endsWith(folder.getItemName<LEFT_SIDE>(), AFS::TEMP_FILE_ENDING))
+        if (cat == DIR_LEFT_SIDE_ONLY && endsWith(folder.getItemName<SelectSide::left>(), AFS::TEMP_FILE_ENDING))
             return setSyncDirectionRec(SyncDirection::left, folder); //
-        else if (cat == DIR_RIGHT_SIDE_ONLY && endsWith(folder.getItemName<RIGHT_SIDE>(), AFS::TEMP_FILE_ENDING))
+        else if (cat == DIR_RIGHT_SIDE_ONLY && endsWith(folder.getItemName<SelectSide::right>(), AFS::TEMP_FILE_ENDING))
             return setSyncDirectionRec(SyncDirection::right, folder); //don't recurse below!
         //#######################################################################################
 
@@ -252,7 +252,7 @@ bool fff::allElementsEqual(const FolderComparison& folderCmp)
 
 namespace
 {
-template <SelectedSide side> inline
+template <SelectSide side> inline
 bool matchesDbEntry(const FilePair& file, const InSyncFile* dbFile, const std::vector<unsigned int>& ignoreTimeShiftMinutes)
 {
     if (file.isEmpty<side>())
@@ -262,11 +262,10 @@ bool matchesDbEntry(const FilePair& file, const InSyncFile* dbFile, const std::v
 
     const InSyncDescrFile& descrDb = SelectParam<side>::ref(dbFile->left, dbFile->right);
 
-    //respect 2 second FAT/FAT32 precision! copying a file to a FAT32 drive changes it's modification date by up to 2 seconds
     return //we're not interested in "fileTimeTolerance" here!
-        sameFileTime(file.getLastWriteTime<side>(), descrDb.modTime, 2, ignoreTimeShiftMinutes) &&
+        sameFileTime(file.getLastWriteTime<side>(), descrDb.modTime, FAT_FILE_TIME_PRECISION_SEC, ignoreTimeShiftMinutes) &&
         file.getFileSize<side>() == dbFile->fileSize;
-    //note: we do *not* consider FileId here, but are only interested in *visual* changes. Consider user moving data to some other medium, this is not a change!
+    //note: we do *not* consider file ID here, but are only interested in *visual* changes. Consider user moving data to some other medium, this is not a change!
 }
 
 
@@ -297,7 +296,7 @@ bool stillInSync(const InSyncFile& dbFile, CompareVariant compareVar, int fileTi
 //--------------------------------------------------------------------
 
 //check whether database entry and current item match: *irrespective* of current comparison settings
-template <SelectedSide side> inline
+template <SelectSide side> inline
 bool matchesDbEntry(const SymlinkPair& symlink, const InSyncSymlink* dbSymlink, const std::vector<unsigned int>& ignoreTimeShiftMinutes)
 {
     if (symlink.isEmpty<side>())
@@ -307,8 +306,7 @@ bool matchesDbEntry(const SymlinkPair& symlink, const InSyncSymlink* dbSymlink,
 
     const InSyncDescrLink& descrDb = SelectParam<side>::ref(dbSymlink->left, dbSymlink->right);
 
-    //respect 2 second FAT/FAT32 precision! copying a file to a FAT32 drive changes its modification date by up to 2 seconds
-    return sameFileTime(symlink.getLastWriteTime<side>(), descrDb.modTime, 2, ignoreTimeShiftMinutes);
+    return sameFileTime(symlink.getLastWriteTime<side>(), descrDb.modTime, FAT_FILE_TIME_PRECISION_SEC, ignoreTimeShiftMinutes);
 }
 
 
@@ -337,7 +335,7 @@ bool stillInSync(const InSyncSymlink& dbLink, CompareVariant compareVar, int fil
 //--------------------------------------------------------------------
 
 //check whether database entry and current item match: *irrespective* of current comparison settings
-template <SelectedSide side> inline
+template <SelectSide side> inline
 bool matchesDbEntry(const FolderPair& folder, const InSyncFolder* dbFolder)
 {
     const bool haveDbEntry = dbFolder && dbFolder->status != InSyncFolder::DIR_STATUS_STRAW_MAN;
@@ -368,6 +366,9 @@ private:
     {
         recurse(baseFolder, &dbFolder, &dbFolder);
 
+        purgeDuplicates< SelectSide::left>(filesL_,  exLeftOnlyById_);
+        purgeDuplicates<SelectSide::right>(filesR_, exRightOnlyById_);
+
         if ((!exLeftOnlyById_ .empty() || !exLeftOnlyByPath_ .empty()) &&
             (!exRightOnlyById_.empty() || !exRightOnlyByPath_.empty()))
             detectMovePairs(dbFolder);
@@ -377,40 +378,31 @@ private:
     {
         for (FilePair& file : hierObj.refSubFiles())
         {
+            const AFS::FingerPrint filePrintL = file.getFilePrint< SelectSide::left>();
+            const AFS::FingerPrint filePrintR = file.getFilePrint<SelectSide::right>();
+
+            if (filePrintL != 0) filesL_.push_back(&file); //collect *all* prints for uniqueness check!
+            if (filePrintR != 0) filesR_.push_back(&file); //
+
             auto getDbEntry = [](const InSyncFolder* dbFolder, const Zstring& fileName) -> const InSyncFile*
             {
                 if (dbFolder)
-                {
-                    auto it = dbFolder->files.find(fileName);
-                    if (it != dbFolder->files.end())
+                    if (const auto it = dbFolder->files.find(fileName);
+                        it != dbFolder->files.end())
                         return &it->second;
-                }
                 return nullptr;
             };
 
-            const CompareFileResult cat = file.getCategory();
-
-            if (cat == FILE_LEFT_SIDE_ONLY)
+            if (const CompareFileResult cat = file.getCategory();
+                cat == FILE_LEFT_SIDE_ONLY)
             {
-                if (const InSyncFile* dbEntry = getDbEntry(dbFolderL, file.getItemName<LEFT_SIDE>()))
+                if (const InSyncFile* dbEntry = getDbEntry(dbFolderL, file.getItemName<SelectSide::left>()))
                     exLeftOnlyByPath_.emplace(dbEntry, &file);
-                else if (!file.getFileId<LEFT_SIDE>().empty())
-                {
-                    const auto [it, inserted] = exLeftOnlyById_.emplace(file.getFileId<LEFT_SIDE>(), &file);
-                    if (!inserted) //duplicate file ID! NTFS hard link/symlink?
-                        it->second = nullptr;
-                }
             }
             else if (cat == FILE_RIGHT_SIDE_ONLY)
             {
-                if (const InSyncFile* dbEntry = getDbEntry(dbFolderR, file.getItemName<RIGHT_SIDE>()))
+                if (const InSyncFile* dbEntry = getDbEntry(dbFolderR, file.getItemName<SelectSide::right>()))
                     exRightOnlyByPath_.emplace(dbEntry, &file);
-                else if (!file.getFileId<RIGHT_SIDE>().empty())
-                {
-                    const auto [it, inserted] = exRightOnlyById_.emplace(file.getFileId<RIGHT_SIDE>(), &file);
-                    if (!inserted) //duplicate file ID! NTFS hard link/symlink?
-                        it->second = nullptr;
-                }
             }
         }
 
@@ -419,22 +411,59 @@ private:
             auto getDbEntry = [](const InSyncFolder* dbFolder, const Zstring& folderName) -> const InSyncFolder*
             {
                 if (dbFolder)
-                {
-                    auto it = dbFolder->folders.find(folderName);
-                    if (it != dbFolder->folders.end())
+                    if (const auto it = dbFolder->folders.find(folderName);
+                        it != dbFolder->folders.end())
                         return &it->second;
-                }
                 return nullptr;
             };
-            const InSyncFolder* dbEntryL = getDbEntry(dbFolderL, folder.getItemName<LEFT_SIDE>());
+            const InSyncFolder* dbEntryL = getDbEntry(dbFolderL, folder.getItemName<SelectSide::left>());
             const InSyncFolder* dbEntryR = dbEntryL;
-            if (dbFolderL != dbFolderR || getUnicodeNormalForm(folder.getItemName<LEFT_SIDE>()) != getUnicodeNormalForm(folder.getItemName<RIGHT_SIDE>()))
-                dbEntryR = getDbEntry(dbFolderR, folder.getItemName<RIGHT_SIDE>());
+            if (dbFolderL != dbFolderR ||
+                getUnicodeNormalForm(folder.getItemName< SelectSide::left>()) !=
+                getUnicodeNormalForm(folder.getItemName<SelectSide::right>()))
+                dbEntryR = getDbEntry(dbFolderR, folder.getItemName<SelectSide::right>());
 
             recurse(folder, dbEntryL, dbEntryR);
         }
     }
 
+    template <SelectSide side>
+    static void purgeDuplicates(std::vector<FilePair*>& files,
+                                std::unordered_map<AFS::FingerPrint, FilePair*>& exOneSideById)
+    {
+        if (!files.empty())
+        {
+            std::sort(files.begin(), files.end(), [](const FilePair* lhs, const FilePair* rhs)
+            { return lhs->getFilePrint<side>() < rhs->getFilePrint<side>(); });
+
+            AFS::FingerPrint prevPrint = files[0]->getFilePrint<side>();
+
+            for (auto it = files.begin() + 1; it != files.end(); ++it)
+                if (const AFS::FingerPrint filePrint = (*it)->getFilePrint<side>();
+                    prevPrint != filePrint)
+                    prevPrint = filePrint;
+                else //duplicate file ID! NTFS hard link/symlink?
+                {
+                    const auto dupFirst = it - 1;
+                    const auto dupLast = std::find_if(it + 1, files.end(), [prevPrint](const FilePair* file)
+                    { return file->getFilePrint<side>() != prevPrint; });
+
+                    //remove from model: do *not* store invalid file prints in sync.ffs_db!
+                    std::for_each(dupFirst, dupLast, [](FilePair* file) { file->clearFilePrint<side>(); });
+                    it = dupLast - 1;
+                }
+
+            //collect unique file prints for files existing on one side only:
+            constexpr CompareFileResult oneSideOnlyTag = side == SelectSide::left ? FILE_LEFT_SIDE_ONLY : FILE_RIGHT_SIDE_ONLY;
+
+            for (FilePair* file : files)
+                if (file->getCategory() == oneSideOnlyTag)
+                    if (const AFS::FingerPrint filePrint = file->getFilePrint<side>();
+                        filePrint != 0) //skip duplicates marked by clearFilePrint()
+                        exOneSideById.emplace(filePrint, file);
+        }
+    }
+
     void detectMovePairs(const InSyncFolder& container) const
     {
         for (const auto& [fileName, dbAttrib] : container.files)
@@ -444,93 +473,99 @@ private:
             detectMovePairs(subFolder);
     }
 
-    template <SelectedSide side>
+    template <SelectSide side>
     static bool sameSizeAndDate(const FilePair& file, const InSyncFile& dbFile)
     {
         return file.getFileSize<side>() == dbFile.fileSize &&
-               sameFileTime(file.getLastWriteTime<side>(), SelectParam<side>::ref(dbFile.left, dbFile.right).modTime, 2, {});
-        //- respect 2 second FAT/FAT32 precision! not user-configurable!
-        //- "ignoreTimeShiftMinutes" may lead to false positive move detections => let's be conservative and not allow it
-        //  (time shift is only ever required during FAT DST switches)
-
-        //PS: *never* allow 2 sec tolerance as container predicate!!
-        // => no strict weak ordering relation! reason: no transitivity of equivalence!
+               file.getLastWriteTime<side>() == SelectParam<side>::ref(dbFile.left, dbFile.right).modTime;
+        /* do NOT consider FAT_FILE_TIME_PRECISION_SEC:
+            1. if DB contains file metadata collected during folder comparison we can be as precise as we want here
+            2. if DB contains file metadata *estimated* directly after file copy:
+                - most file systems store file times with sub-second precision...
+                - ...except for FAT, but FAT does not have stable file IDs after file copy anyway (see comment below)
+            => file time comparison with seconds precision is fine!
+
+        PS: *never* allow a tolerance as container predicate!!
+            => no strict weak ordering relation! reason: no transitivity of equivalence!          */
     }
 
-    template <SelectedSide side>
+    template <SelectSide side>
     FilePair* getAssocFilePair(const InSyncFile& dbFile) const
     {
-        const std::unordered_map<AFS::FileId,       FilePair*>& exOneSideById   = SelectParam<side>::ref(exLeftOnlyById_,   exRightOnlyById_);
         const std::unordered_map<const InSyncFile*, FilePair*>& exOneSideByPath = SelectParam<side>::ref(exLeftOnlyByPath_, exRightOnlyByPath_);
-        {
-            auto it = exOneSideByPath.find(&dbFile);
-            if (it != exOneSideByPath.end())
-                return it->second; //if there is an association by path, don't care if there is also an association by id,
-            //even if the association by path doesn't match time and size while the association by id does!
-            //- there doesn't seem to be (any?) value in allowing this!
-            //- note: exOneSideById isn't filled in this case, see recurse()
-        }
+        const std::unordered_map<AFS::FingerPrint,  FilePair*>& exOneSideById   = SelectParam<side>::ref(exLeftOnlyById_,   exRightOnlyById_);
+
+        if (const auto it = exOneSideByPath.find(&dbFile);
+            it != exOneSideByPath.end())
+            return it->second; //if there is an association by path, don't care if there is also an association by ID,
+        //even if the association by path doesn't match time and size while the association by ID does!
+        //there doesn't seem to be (any?) value in allowing this!
+
+        if (const AFS::FingerPrint filePrint = SelectParam<side>::ref(dbFile.left, dbFile.right).filePrint;
+            filePrint != 0)
+            if (const auto it = exOneSideById.find(filePrint);
+                it != exOneSideById.end())
+                return it->second;
 
-        const AFS::FileId fileId = SelectParam<side>::ref(dbFile.left, dbFile.right).fileId;
-        if (!fileId.empty())
-        {
-            auto it = exOneSideById.find(fileId);
-            if (it != exOneSideById.end())
-                return it->second; //= nullptr, if duplicate ID!
-        }
         return nullptr;
     }
 
     void findAndSetMovePair(const InSyncFile& dbFile) const
     {
         if (stillInSync(dbFile, cmpVar_, fileTimeTolerance_, ignoreTimeShiftMinutes_))
-            if (FilePair* fileLeftOnly = getAssocFilePair<LEFT_SIDE>(dbFile))
-                if (sameSizeAndDate<LEFT_SIDE>(*fileLeftOnly, dbFile))
-                    if (FilePair* fileRightOnly = getAssocFilePair<RIGHT_SIDE>(dbFile))
-                        if (sameSizeAndDate<RIGHT_SIDE>(*fileRightOnly, dbFile))
-                            if (fileLeftOnly ->getMoveRef() == nullptr && //don't let a row participate in two move pairs!
+            if (FilePair* fileLeftOnly = getAssocFilePair<SelectSide::left>(dbFile))
+                if (sameSizeAndDate<SelectSide::left>(*fileLeftOnly, dbFile))
+                    if (FilePair* fileRightOnly = getAssocFilePair<SelectSide::right>(dbFile))
+                        if (sameSizeAndDate<SelectSide::right>(*fileRightOnly, dbFile))
+                        {
+                            assert((!fileLeftOnly ->getMoveRef() &&
+                                    !fileRightOnly->getMoveRef()) ||
+                                   (fileLeftOnly ->getMoveRef() == fileRightOnly->getId() &&
+                                    fileRightOnly->getMoveRef() == fileLeftOnly ->getId()));
+
+                            if (fileLeftOnly ->getMoveRef() == nullptr && //needless check!? file prints are unique in this context!
                                 fileRightOnly->getMoveRef() == nullptr)   //
                             {
                                 fileLeftOnly ->setMoveRef(fileRightOnly->getId()); //found a pair, mark it!
                                 fileRightOnly->setMoveRef(fileLeftOnly ->getId()); //
                             }
+                        }
     }
 
     const CompareVariant cmpVar_;
     const int fileTimeTolerance_;
     const std::vector<unsigned int> ignoreTimeShiftMinutes_;
 
-    std::unordered_map<AFS::FileId, FilePair*> exLeftOnlyById_;  //FilePair* == nullptr for duplicate ids! => consider aliasing through symlinks!
-    std::unordered_map<AFS::FileId, FilePair*> exRightOnlyById_; //=> avoid ambiguity for mixtures of files/symlinks on one side and allow 1-1 mapping only!
-    //MSVC: std::unordered_map: about twice as fast as std::map for 1 million items!
+    std::vector<FilePair*> filesL_; //collection of *all* file items (with non-null filePrint)
+    std::vector<FilePair*> filesR_; // => detect duplicate file IDs
+
+    std::unordered_map<AFS::FingerPrint, FilePair*>  exLeftOnlyById_; //MSVC: twice as fast as std::map for 1 million items!
+    std::unordered_map<AFS::FingerPrint, FilePair*> exRightOnlyById_;
 
-    std::unordered_map<const InSyncFile*, FilePair*> exLeftOnlyByPath_; //MSVC: only 4% faster than std::map for 1 million items!
+    std::unordered_map<const InSyncFile*, FilePair*>  exLeftOnlyByPath_; //MSVC: only 4% faster than std::map for 1 million items!
     std::unordered_map<const InSyncFile*, FilePair*> exRightOnlyByPath_;
-    /*
-    detect renamed files:
-
-     X  ->  |_|      Create right
-    |_| ->   Y       Delete right
-
-    is detected as:
-
-    Rename Y to X on right
-
-    Algorithm:
-    ----------
-    DB-file left  <--- (name, size, date) --->  DB-file right
-          |                                          |
-          |  (file ID, size, date)                   |  (file ID, size, date)
-          |            or                            |            or
-          |  (file path, size, date)                 |  (file path, size, date)
-         \|/                                        \|/
-    file left only                             file right only
-
-       FAT caveat: File Ids are generally not stable when file is either moved or renamed!
-       => 1. Move/rename operations on FAT cannot be detected reliably.
-       => 2. database generally contains wrong file ID on FAT after renaming from .ffs_tmp files => correct file IDs in database only after next sync
-       => 3. even exFAT screws up (but less than FAT) and changes IDs after file move. Did they learn nothing from the past?
-    */
+
+    /*  Detect Renamed Files:
+
+         X  ->  |_|      Create right
+        |_| ->   Y       Delete right
+
+        resolve as: Rename Y to X on right
+
+        Algorithm:
+        ----------
+        DB-file left  <--- (name, size, date) --->  DB-file right
+              |                                          |
+              |  (file ID, size, date)                   |  (file ID, size, date)
+              |            or                            |            or
+              |  (file path, size, date)                 |  (file path, size, date)
+             \|/                                        \|/
+        file left only                             file right only
+
+       FAT caveat: file IDs are generally not stable when file is either moved or renamed!
+         1. Move/rename operations on FAT cannot be detected reliably.
+         2. database generally contains wrong file ID on FAT after renaming from .ffs_tmp files => correct file IDs in database only after next sync
+         3. even exFAT screws up (but less than FAT) and changes IDs after file move. Did they learn nothing from the past?           */
 };
 
 //----------------------------------------------------------------------------------------------
@@ -569,9 +604,9 @@ private:
             return;
 
         //##################### schedule old temporary files for deletion ####################
-        if (cat == FILE_LEFT_SIDE_ONLY && endsWith(file.getItemName<LEFT_SIDE>(), AFS::TEMP_FILE_ENDING))
+        if (cat == FILE_LEFT_SIDE_ONLY && endsWith(file.getItemName<SelectSide::left>(), AFS::TEMP_FILE_ENDING))
             return file.setSyncDir(SyncDirection::left);
-        else if (cat == FILE_RIGHT_SIDE_ONLY && endsWith(file.getItemName<RIGHT_SIDE>(), AFS::TEMP_FILE_ENDING))
+        else if (cat == FILE_RIGHT_SIDE_ONLY && endsWith(file.getItemName<SelectSide::right>(), AFS::TEMP_FILE_ENDING))
             return file.setSyncDir(SyncDirection::right);
         //####################################################################################
 
@@ -586,14 +621,14 @@ private:
             }
             return nullptr;
         };
-        const InSyncFile* dbEntryL = getDbEntry(dbFolderL, file.getItemName<LEFT_SIDE>());
+        const InSyncFile* dbEntryL = getDbEntry(dbFolderL, file.getItemName<SelectSide::left>());
         const InSyncFile* dbEntryR = dbEntryL;
-        if (dbFolderL != dbFolderR || getUnicodeNormalForm(file.getItemName<LEFT_SIDE>()) != getUnicodeNormalForm(file.getItemName<RIGHT_SIDE>()))
-            dbEntryR = getDbEntry(dbFolderR, file.getItemName<RIGHT_SIDE>());
+        if (dbFolderL != dbFolderR || getUnicodeNormalForm(file.getItemName<SelectSide::left>()) != getUnicodeNormalForm(file.getItemName<SelectSide::right>()))
+            dbEntryR = getDbEntry(dbFolderR, file.getItemName<SelectSide::right>());
 
         //evaluation
-        const bool changeOnLeft  = !matchesDbEntry< LEFT_SIDE>(file, dbEntryL, ignoreTimeShiftMinutes_);
-        const bool changeOnRight = !matchesDbEntry<RIGHT_SIDE>(file, dbEntryR, ignoreTimeShiftMinutes_);
+        const bool changeOnLeft  = !matchesDbEntry< SelectSide::left>(file, dbEntryL, ignoreTimeShiftMinutes_);
+        const bool changeOnRight = !matchesDbEntry<SelectSide::right>(file, dbEntryR, ignoreTimeShiftMinutes_);
 
         if (changeOnLeft != changeOnRight)
         {
@@ -630,14 +665,14 @@ private:
             }
             return nullptr;
         };
-        const InSyncSymlink* dbEntryL = getDbEntry(dbFolderL, symlink.getItemName<LEFT_SIDE>());
+        const InSyncSymlink* dbEntryL = getDbEntry(dbFolderL, symlink.getItemName<SelectSide::left>());
         const InSyncSymlink* dbEntryR = dbEntryL;
-        if (dbFolderL != dbFolderR || getUnicodeNormalForm(symlink.getItemName<LEFT_SIDE>()) != getUnicodeNormalForm(symlink.getItemName<RIGHT_SIDE>()))
-            dbEntryR = getDbEntry(dbFolderR, symlink.getItemName<RIGHT_SIDE>());
+        if (dbFolderL != dbFolderR || getUnicodeNormalForm(symlink.getItemName<SelectSide::left>()) != getUnicodeNormalForm(symlink.getItemName<SelectSide::right>()))
+            dbEntryR = getDbEntry(dbFolderR, symlink.getItemName<SelectSide::right>());
 
         //evaluation
-        const bool changeOnLeft  = !matchesDbEntry< LEFT_SIDE>(symlink, dbEntryL, ignoreTimeShiftMinutes_);
-        const bool changeOnRight = !matchesDbEntry<RIGHT_SIDE>(symlink, dbEntryR, ignoreTimeShiftMinutes_);
+        const bool changeOnLeft  = !matchesDbEntry< SelectSide::left>(symlink, dbEntryL, ignoreTimeShiftMinutes_);
+        const bool changeOnRight = !matchesDbEntry<SelectSide::right>(symlink, dbEntryR, ignoreTimeShiftMinutes_);
 
         if (changeOnLeft != changeOnRight)
         {
@@ -662,9 +697,9 @@ private:
         const CompareDirResult cat = folder.getDirCategory();
 
         //########### schedule abandoned temporary recycle bin directory for deletion  ##########
-        if (cat == DIR_LEFT_SIDE_ONLY && endsWith(folder.getItemName<LEFT_SIDE>(), AFS::TEMP_FILE_ENDING))
+        if (cat == DIR_LEFT_SIDE_ONLY && endsWith(folder.getItemName<SelectSide::left>(), AFS::TEMP_FILE_ENDING))
             return setSyncDirectionRec(SyncDirection::left, folder); //
-        else if (cat == DIR_RIGHT_SIDE_ONLY && endsWith(folder.getItemName<RIGHT_SIDE>(), AFS::TEMP_FILE_ENDING))
+        else if (cat == DIR_RIGHT_SIDE_ONLY && endsWith(folder.getItemName<SelectSide::right>(), AFS::TEMP_FILE_ENDING))
             return setSyncDirectionRec(SyncDirection::right, folder); //don't recurse below!
         //#######################################################################################
 
@@ -679,16 +714,16 @@ private:
             }
             return nullptr;
         };
-        const InSyncFolder* dbEntryL = getDbEntry(dbFolderL, folder.getItemName<LEFT_SIDE>());
+        const InSyncFolder* dbEntryL = getDbEntry(dbFolderL, folder.getItemName<SelectSide::left>());
         const InSyncFolder* dbEntryR = dbEntryL;
-        if (dbFolderL != dbFolderR || getUnicodeNormalForm(folder.getItemName<LEFT_SIDE>()) != getUnicodeNormalForm(folder.getItemName<RIGHT_SIDE>()))
-            dbEntryR = getDbEntry(dbFolderR, folder.getItemName<RIGHT_SIDE>());
+        if (dbFolderL != dbFolderR || getUnicodeNormalForm(folder.getItemName<SelectSide::left>()) != getUnicodeNormalForm(folder.getItemName<SelectSide::right>()))
+            dbEntryR = getDbEntry(dbFolderR, folder.getItemName<SelectSide::right>());
 
         if (cat != DIR_EQUAL)
         {
             //evaluation
-            const bool changeOnLeft  = !matchesDbEntry< LEFT_SIDE>(folder, dbEntryL);
-            const bool changeOnRight = !matchesDbEntry<RIGHT_SIDE>(folder, dbEntryR);
+            const bool changeOnLeft  = !matchesDbEntry< SelectSide::left>(folder, dbEntryL);
+            const bool changeOnRight = !matchesDbEntry<SelectSide::right>(folder, dbEntryR);
 
             if (changeOnLeft != changeOnRight)
             {
@@ -778,10 +813,10 @@ void fff::redetermineSyncDirection(const std::vector<std::pair<BaseFolderPair*,
                     {
                         std::wstring msg = _("Setting directions for first synchronization: Old files will be overwritten with newer files.");
                         if (directCfgs.size() > 1)
-                            msg += L'\n' + AFS::getDisplayPath(baseFolder->getAbstractPath< LEFT_SIDE>()) + L' ' + getVariantNameWithSymbol(dirCfg.var) + L' ' +
-                                          AFS::getDisplayPath(baseFolder->getAbstractPath<RIGHT_SIDE>());
+                            msg += L'\n' + AFS::getDisplayPath(baseFolder->getAbstractPath< SelectSide::left>()) + L' ' + getVariantNameWithSymbol(dirCfg.var) + L' ' +
+                                          AFS::getDisplayPath(baseFolder->getAbstractPath<SelectSide::right>());
 
-                        try { callback.reportInfo(msg); /*throw X*/} catch (...) {};
+                        try { callback.logInfo(msg); /*throw X*/} catch (...) {};
 
                         Redetermine::execute(getTwoWayUpdateSet(), *baseFolder);
                     }
@@ -1000,12 +1035,12 @@ private:
     {
         if (Eval<strategy>::process(file))
         {
-            if (file.isEmpty<LEFT_SIDE>())
-                file.setActive(matchSize<RIGHT_SIDE>(file) &&
-                               matchTime<RIGHT_SIDE>(file));
-            else if (file.isEmpty<RIGHT_SIDE>())
-                file.setActive(matchSize<LEFT_SIDE>(file) &&
-                               matchTime<LEFT_SIDE>(file));
+            if (file.isEmpty<SelectSide::left>())
+                file.setActive(matchSize<SelectSide::right>(file) &&
+                               matchTime<SelectSide::right>(file));
+            else if (file.isEmpty<SelectSide::right>())
+                file.setActive(matchSize<SelectSide::left>(file) &&
+                               matchTime<SelectSide::left>(file));
             else
             {
                 //the only case with partially unclear semantics:
@@ -1023,10 +1058,10 @@ private:
                             ------------
                 */
                 //let's set ? := E
-                file.setActive((matchSize<RIGHT_SIDE>(file) &&
-                                matchTime<RIGHT_SIDE>(file)) ||
-                               (matchSize<LEFT_SIDE>(file) &&
-                                matchTime<LEFT_SIDE>(file)));
+                file.setActive((matchSize<SelectSide::right>(file) &&
+                                matchTime<SelectSide::right>(file)) ||
+                               (matchSize<SelectSide::left>(file) &&
+                                matchTime<SelectSide::left>(file)));
             }
         }
     }
@@ -1035,13 +1070,13 @@ private:
     {
         if (Eval<strategy>::process(symlink))
         {
-            if (symlink.isEmpty<LEFT_SIDE>())
-                symlink.setActive(matchTime<RIGHT_SIDE>(symlink));
-            else if (symlink.isEmpty<RIGHT_SIDE>())
-                symlink.setActive(matchTime<LEFT_SIDE>(symlink));
+            if (symlink.isEmpty<SelectSide::left>())
+                symlink.setActive(matchTime<SelectSide::right>(symlink));
+            else if (symlink.isEmpty<SelectSide::right>())
+                symlink.setActive(matchTime<SelectSide::left>(symlink));
             else
-                symlink.setActive(matchTime<RIGHT_SIDE>(symlink) ||
-                                  matchTime<LEFT_SIDE> (symlink));
+                symlink.setActive(matchTime<SelectSide::right>(symlink) ||
+                                  matchTime<SelectSide::left> (symlink));
         }
     }
 
@@ -1053,13 +1088,13 @@ private:
         recurse(folder);
     }
 
-    template <SelectedSide side, class T>
+    template <SelectSide side, class T>
     bool matchTime(const T& obj) const
     {
         return timeSizeFilter_.matchTime(obj.template getLastWriteTime<side>());
     }
 
-    template <SelectedSide side, class T>
+    template <SelectSide side, class T>
     bool matchSize(const T& obj) const
     {
         return timeSizeFilter_.matchSize(obj.template getFileSize<side>());
@@ -1136,24 +1171,24 @@ private:
 
     void processFile(FilePair& file) const
     {
-        if (file.isEmpty<LEFT_SIDE>())
-            file.setActive(matchTime<RIGHT_SIDE>(file));
-        else if (file.isEmpty<RIGHT_SIDE>())
-            file.setActive(matchTime<LEFT_SIDE>(file));
+        if (file.isEmpty<SelectSide::left>())
+            file.setActive(matchTime<SelectSide::right>(file));
+        else if (file.isEmpty<SelectSide::right>())
+            file.setActive(matchTime<SelectSide::left>(file));
         else
-            file.setActive(matchTime<RIGHT_SIDE>(file) ||
-                           matchTime<LEFT_SIDE>(file));
+            file.setActive(matchTime<SelectSide::right>(file) ||
+                           matchTime<SelectSide::left>(file));
     }
 
     void processLink(SymlinkPair& link) const
     {
-        if (link.isEmpty<LEFT_SIDE>())
-            link.setActive(matchTime<RIGHT_SIDE>(link));
-        else if (link.isEmpty<RIGHT_SIDE>())
-            link.setActive(matchTime<LEFT_SIDE>(link));
+        if (link.isEmpty<SelectSide::left>())
+            link.setActive(matchTime<SelectSide::right>(link));
+        else if (link.isEmpty<SelectSide::right>())
+            link.setActive(matchTime<SelectSide::left>(link));
         else
-            link.setActive(matchTime<RIGHT_SIDE>(link) ||
-                           matchTime<LEFT_SIDE> (link));
+            link.setActive(matchTime<SelectSide::right>(link) ||
+                           matchTime<SelectSide::left> (link));
     }
 
     void processDir(FolderPair& folder) const
@@ -1162,7 +1197,7 @@ private:
         recurse(folder);
     }
 
-    template <SelectedSide side, class T>
+    template <SelectSide side, class T>
     bool matchTime(const T& obj) const
     {
         return timeFrom_ <= obj.template getLastWriteTime<side>() &&
@@ -1212,7 +1247,7 @@ std::optional<PathDependency> fff::getPathDependency(const AbstractPath& basePat
                 // - user may have manually excluded the conflicting items or changed the filter settings without running a re-compare
                 bool childItemMightMatch = true;
                 if (relDirPath.empty() || filterP.passDirFilter(relDirPath, &childItemMightMatch) || childItemMightMatch)
-                    return PathDependency({ basePathP, basePathC, relDirPath });
+                    return PathDependency({basePathP, basePathC, relDirPath});
             }
         }
     }
@@ -1229,26 +1264,26 @@ std::pair<std::wstring, int> fff::getSelectedItemsAsString(std::span<const FileS
     int totalDelCount = 0;
 
     for (const FileSystemObject* fsObj : selectionLeft)
-        if (!fsObj->isEmpty<LEFT_SIDE>())
+        if (!fsObj->isEmpty<SelectSide::left>())
         {
-            fileList += AFS::getDisplayPath(fsObj->getAbstractPath<LEFT_SIDE>()) + L'\n';
+            fileList += AFS::getDisplayPath(fsObj->getAbstractPath<SelectSide::left>()) + L'\n';
             ++totalDelCount;
         }
 
     for (const FileSystemObject* fsObj : selectionRight)
-        if (!fsObj->isEmpty<RIGHT_SIDE>())
+        if (!fsObj->isEmpty<SelectSide::right>())
         {
-            fileList += AFS::getDisplayPath(fsObj->getAbstractPath<RIGHT_SIDE>()) + L'\n';
+            fileList += AFS::getDisplayPath(fsObj->getAbstractPath<SelectSide::right>()) + L'\n';
             ++totalDelCount;
         }
 
-    return { fileList, totalDelCount };
+    return {fileList, totalDelCount};
 }
 
 
 namespace
 {
-template <SelectedSide side>
+template <SelectSide side>
 void copyToAlternateFolderFrom(const std::vector<const FileSystemObject*>& rowsToCopy,
                                const AbstractPath& targetFolderPath,
                                bool keepRelPaths,
@@ -1257,7 +1292,9 @@ void copyToAlternateFolderFrom(const std::vector<const FileSystemObject*>& rowsT
 {
     auto notifyItemCopy = [&](const std::wstring& statusText, const std::wstring& displayPath)
     {
-        callback.reportInfo(replaceCpy(statusText, L"%x", fmtPath(displayPath))); //throw X
+        std::wstring msg = replaceCpy(statusText, L"%x", fmtPath(displayPath));
+        callback.logInfo(msg);                 //throw X
+        callback.updateStatus(std::move(msg)); //
     };
     const std::wstring txtCreatingFile  (_("Creating file %x"         ));
     const std::wstring txtCreatingFolder(_("Creating folder %x"       ));
@@ -1319,7 +1356,7 @@ void copyToAlternateFolderFrom(const std::vector<const FileSystemObject*>& rowsT
 
         visitFSObject(*fsObj, [&](const FolderPair& folder)
         {
-            ItemStatReporter<> statReporter(1, 0, callback);
+            ItemStatReporter statReporter(1, 0, callback);
             notifyItemCopy(txtCreatingFolder, AFS::getDisplayPath(targetPath));
 
             AFS::createFolderIfMissingRecursion(targetPath); //throw FileError
@@ -1333,7 +1370,7 @@ void copyToAlternateFolderFrom(const std::vector<const FileSystemObject*>& rowsT
             notifyItemCopy(txtCreatingFile, AFS::getDisplayPath(targetPath));
 
             const FileAttributes attr = file.getAttributes<side>();
-            const AFS::StreamAttributes sourceAttr{ attr.modTime, attr.fileSize, attr.fileId };
+            const AFS::StreamAttributes sourceAttr{attr.modTime, attr.fileSize, attr.filePrint};
 
             copyItem(targetPath, statReporter, [&](const std::function<void()>& deleteTargetItem) //throw FileError
             {
@@ -1380,19 +1417,19 @@ void fff::copyToAlternateFolder(std::span<const FileSystemObject* const> rowsToC
 {
     std::vector<const FileSystemObject*> itemSelectionLeft (rowsToCopyOnLeft .begin(), rowsToCopyOnLeft .end());
     std::vector<const FileSystemObject*> itemSelectionRight(rowsToCopyOnRight.begin(), rowsToCopyOnRight.end());
-    std::erase_if(itemSelectionLeft,  [](const FileSystemObject* fsObj) { return fsObj->isEmpty< LEFT_SIDE>(); }); //needed for correct stats!
-    std::erase_if(itemSelectionRight, [](const FileSystemObject* fsObj) { return fsObj->isEmpty<RIGHT_SIDE>(); }); //
+    std::erase_if(itemSelectionLeft,  [](const FileSystemObject* fsObj) { return fsObj->isEmpty< SelectSide::left>(); }); //needed for correct stats!
+    std::erase_if(itemSelectionRight, [](const FileSystemObject* fsObj) { return fsObj->isEmpty<SelectSide::right>(); }); //
 
     const int itemTotal = static_cast<int>(itemSelectionLeft.size() + itemSelectionRight.size());
     int64_t bytesTotal = 0;
 
     for (const FileSystemObject* fsObj : itemSelectionLeft)
         visitFSObject(*fsObj, [](const FolderPair& folder) {},
-    [&](const FilePair& file) { bytesTotal += static_cast<int64_t>(file.getFileSize<LEFT_SIDE>()); }, [](const SymlinkPair& symlink) {});
+    [&](const FilePair& file) { bytesTotal += static_cast<int64_t>(file.getFileSize<SelectSide::left>()); }, [](const SymlinkPair& symlink) {});
 
     for (const FileSystemObject* fsObj : itemSelectionRight)
         visitFSObject(*fsObj, [](const FolderPair& folder) {},
-    [&](const FilePair& file) { bytesTotal += static_cast<int64_t>(file.getFileSize<RIGHT_SIDE>()); }, [](const SymlinkPair& symlink) {});
+    [&](const FilePair& file) { bytesTotal += static_cast<int64_t>(file.getFileSize<SelectSide::right>()); }, [](const SymlinkPair& symlink) {});
 
     callback.initNewPhase(itemTotal, bytesTotal, ProcessPhase::none); //throw X
 
@@ -1400,22 +1437,24 @@ void fff::copyToAlternateFolder(std::span<const FileSystemObject* const> rowsToC
 
     const AbstractPath targetFolderPath = createAbstractPath(targetFolderPathPhrase);
 
-    copyToAlternateFolderFrom< LEFT_SIDE>(itemSelectionLeft,  targetFolderPath, keepRelPaths, overwriteIfExists, callback);
-    copyToAlternateFolderFrom<RIGHT_SIDE>(itemSelectionRight, targetFolderPath, keepRelPaths, overwriteIfExists, callback);
+    copyToAlternateFolderFrom< SelectSide::left>(itemSelectionLeft,  targetFolderPath, keepRelPaths, overwriteIfExists, callback);
+    copyToAlternateFolderFrom<SelectSide::right>(itemSelectionRight, targetFolderPath, keepRelPaths, overwriteIfExists, callback);
 }
 
 //############################################################################################################
 
 namespace
 {
-template <SelectedSide side>
+template <SelectSide side>
 void deleteFromGridAndHDOneSide(std::vector<FileSystemObject*>& rowsToDelete,
                                 bool useRecycleBin,
                                 PhaseCallback& callback)
 {
     auto notifyItemDeletion = [&](const std::wstring& statusText, const std::wstring& displayPath)
     {
-        callback.reportInfo(replaceCpy(statusText, L"%x", fmtPath(displayPath))); //throw X
+        std::wstring msg = replaceCpy(statusText, L"%x", fmtPath(displayPath));
+        callback.logInfo(msg);                 //throw X
+        callback.updateStatus(std::move(msg)); //
     };
 
     std::wstring txtRemovingFile;
@@ -1501,7 +1540,7 @@ void deleteFromGridAndHDOneSide(std::vector<FileSystemObject*>& rowsToDelete,
 }
 
 
-template <SelectedSide side>
+template <SelectSide side>
 void categorize(const std::vector<FileSystemObject*>& rows,
                 std::vector<FileSystemObject*>& deletePermanent,
                 std::vector<FileSystemObject*>& deleteRecyler,
@@ -1556,8 +1595,8 @@ void fff::deleteFromGridAndHD(const std::vector<FileSystemObject*>& rowsToDelete
     std::vector<FileSystemObject*> deleteLeft  = rowsToDeleteOnLeft;
     std::vector<FileSystemObject*> deleteRight = rowsToDeleteOnRight;
 
-    std::erase_if(deleteLeft,  [](const FileSystemObject* fsObj) { return fsObj->isEmpty< LEFT_SIDE>(); }); //needed?
-    std::erase_if(deleteRight, [](const FileSystemObject* fsObj) { return fsObj->isEmpty<RIGHT_SIDE>(); }); //yes, for correct stats:
+    std::erase_if(deleteLeft,  [](const FileSystemObject* fsObj) { return fsObj->isEmpty< SelectSide::left>(); }); //needed?
+    std::erase_if(deleteRight, [](const FileSystemObject* fsObj) { return fsObj->isEmpty<SelectSide::right>(); }); //yes, for correct stats:
 
     const int itemCount = static_cast<int>(deleteLeft.size() + deleteRight.size());
     callback.initNewPhase(itemCount, 0, ProcessPhase::none); //throw X
@@ -1577,7 +1616,7 @@ void fff::deleteFromGridAndHD(const std::vector<FileSystemObject*>& rowsToDelete
         {
             FileSystemObject& fsObj = **it; //all pointers are required(!) to be bound
 
-            if (fsObj.isEmpty<LEFT_SIDE>() != fsObj.isEmpty<RIGHT_SIDE>()) //make sure objects exists on one side only
+            if (fsObj.isEmpty<SelectSide::left>() != fsObj.isEmpty<SelectSide::right>()) //make sure objects exists on one side only
             {
                 auto cfgIter = baseFolderCfgs.find(&fsObj.base());
                 assert(cfgIter != baseFolderCfgs.end());
@@ -1586,11 +1625,11 @@ void fff::deleteFromGridAndHD(const std::vector<FileSystemObject*>& rowsToDelete
                     SyncDirection newDir = SyncDirection::none;
 
                     if (cfgIter->second.var == SyncVariant::twoWay)
-                        newDir = fsObj.isEmpty<LEFT_SIDE>() ? SyncDirection::right : SyncDirection::left;
+                        newDir = fsObj.isEmpty<SelectSide::left>() ? SyncDirection::right : SyncDirection::left;
                     else
                     {
                         const DirectionSet& dirCfg = extractDirections(cfgIter->second);
-                        newDir = fsObj.isEmpty<LEFT_SIDE>() ? dirCfg.exRightSideOnly : dirCfg.exLeftSideOnly;
+                        newDir = fsObj.isEmpty<SelectSide::left>() ? dirCfg.exRightSideOnly : dirCfg.exLeftSideOnly;
                     }
 
                     setSyncDirectionRec(newDir, fsObj); //set new direction (recursively)
@@ -1611,8 +1650,8 @@ void fff::deleteFromGridAndHD(const std::vector<FileSystemObject*>& rowsToDelete
     std::vector<FileSystemObject*> deleteRecylerRight;
 
     std::map<AbstractPath, bool> recyclerSupported;
-    categorize< LEFT_SIDE>(deleteLeft,  deletePermanentLeft,  deleteRecylerLeft,  useRecycleBin, recyclerSupported, callback); //throw X
-    categorize<RIGHT_SIDE>(deleteRight, deletePermanentRight, deleteRecylerRight, useRecycleBin, recyclerSupported, callback); //
+    categorize< SelectSide::left>(deleteLeft,  deletePermanentLeft,  deleteRecylerLeft,  useRecycleBin, recyclerSupported, callback); //throw X
+    categorize<SelectSide::right>(deleteRight, deletePermanentRight, deleteRecylerRight, useRecycleBin, recyclerSupported, callback); //
 
     //windows: check if recycle bin really exists; if not, Windows will silently delete, which is wrong
     if (useRecycleBin &&
@@ -1627,11 +1666,11 @@ void fff::deleteFromGridAndHD(const std::vector<FileSystemObject*>& rowsToDelete
         callback.reportWarning(msg, warnRecyclerMissing); //throw?
     }
 
-    deleteFromGridAndHDOneSide<LEFT_SIDE>(deleteRecylerLeft,   true,  callback);
-    deleteFromGridAndHDOneSide<LEFT_SIDE>(deletePermanentLeft, false, callback);
+    deleteFromGridAndHDOneSide<SelectSide::left>(deleteRecylerLeft,   true,  callback);
+    deleteFromGridAndHDOneSide<SelectSide::left>(deletePermanentLeft, false, callback);
 
-    deleteFromGridAndHDOneSide<RIGHT_SIDE>(deleteRecylerRight,   true,  callback);
-    deleteFromGridAndHDOneSide<RIGHT_SIDE>(deletePermanentRight, false, callback);
+    deleteFromGridAndHDOneSide<SelectSide::right>(deleteRecylerRight,   true,  callback);
+    deleteFromGridAndHDOneSide<SelectSide::right>(deletePermanentRight, false, callback);
 }
 
 //############################################################################################################
@@ -1693,7 +1732,7 @@ void TempFileBuffer::createTempFiles(const std::set<FileDescriptor>& workLoad, P
         MemoryStreamOut<std::string> cookie; //create hash to distinguish different versions and file locations
         writeNumber   (cookie, descr.attr.modTime);
         writeNumber   (cookie, descr.attr.fileSize);
-        writeContainer(cookie, descr.attr.fileId);
+        writeNumber   (cookie, descr.attr.filePrint);
         writeNumber   (cookie, descr.attr.isFollowedSymlink);
         writeContainer(cookie, AFS::getInitPathPhrase(descr.path));
 
@@ -1706,13 +1745,15 @@ void TempFileBuffer::createTempFiles(const std::set<FileDescriptor>& workLoad, P
         const Zstring tempFileName = Zstring(fileName.begin(), it) + Zstr('~') + descrHash + Zstring(it, fileName.end());
 
         const Zstring tempFilePath = appendSeparator(tempFolderPath_) + tempFileName;
-        const AFS::StreamAttributes sourceAttr{ descr.attr.modTime, descr.attr.fileSize, descr.attr.fileId };
+        const AFS::StreamAttributes sourceAttr{descr.attr.modTime, descr.attr.fileSize, descr.attr.filePrint};
 
         tryReportingError([&]
         {
-            ItemStatReporter<> statReporter(1, descr.attr.fileSize, callback);
+            ItemStatReporter statReporter(1, descr.attr.fileSize, callback);
 
-            callback.reportInfo(replaceCpy(_("Creating file %x"), L"%x", fmtPath(tempFilePath))); //throw X
+            std::wstring msg = replaceCpy(_("Creating file %x"), L"%x", fmtPath(tempFilePath)); //throw X
+            callback.logInfo(msg);                 //throw X
+            callback.updateStatus(std::move(msg)); //
 
             auto notifyUnbufferedIO = [&](int64_t bytesDelta)
             {
diff --git a/FreeFileSync/Source/base/binary.cpp b/FreeFileSync/Source/base/binary.cpp
index f3199f67..49bdd6eb 100644
--- a/FreeFileSync/Source/base/binary.cpp
+++ b/FreeFileSync/Source/base/binary.cpp
@@ -39,7 +39,7 @@ const size_t BLOCK_SIZE_MAX =  16 * 1024 * 1024;
 
 struct StreamReader
 {
-    StreamReader(const AbstractPath& filePath, const IOCallback& notifyUnbufferedIO) : //throw FileError
+    StreamReader(const AbstractPath& filePath, const IoCallback& notifyUnbufferedIO) : //throw FileError
         stream_(AFS::getInputStream(filePath, notifyUnbufferedIO)), //throw FileError, ErrorFileLocked
         defaultBlockSize_(stream_->getBlockSize()),
         dynamicBlockSize_(defaultBlockSize_) { assert(defaultBlockSize_ > 0); }
@@ -94,7 +94,7 @@ private:
 }
 
 
-bool fff::filesHaveSameContent(const AbstractPath& filePath1, const AbstractPath& filePath2, const IOCallback& notifyUnbufferedIO /*throw X*/) //throw FileError, X
+bool fff::filesHaveSameContent(const AbstractPath& filePath1, const AbstractPath& filePath2, const IoCallback& notifyUnbufferedIO /*throw X*/) //throw FileError, X
 {
     int64_t totalUnbufferedIO = 0;
 
diff --git a/FreeFileSync/Source/base/binary.h b/FreeFileSync/Source/base/binary.h
index 3c2db11a..1223cb05 100644
--- a/FreeFileSync/Source/base/binary.h
+++ b/FreeFileSync/Source/base/binary.h
@@ -14,7 +14,7 @@ namespace fff
 {
 bool filesHaveSameContent(const AbstractPath& filePath1, //throw FileError, X
                           const AbstractPath& filePath2,
-                          const zen::IOCallback& notifyUnbufferedIO  /*throw X*/);
+                          const zen::IoCallback& notifyUnbufferedIO  /*throw X*/);
 }
 
 #endif //BINARY_H_3941281398513241134
diff --git a/FreeFileSync/Source/base/comparison.cpp b/FreeFileSync/Source/base/comparison.cpp
index 87055154..bf1afafa 100644
--- a/FreeFileSync/Source/base/comparison.cpp
+++ b/FreeFileSync/Source/base/comparison.cpp
@@ -17,6 +17,7 @@
 #include "cmp_filetime.h"
 #include "status_handler_impl.h"
 #include "../afs/concrete.h"
+#include "../afs/native.h"
 
 using namespace zen;
 using namespace fff;
@@ -25,7 +26,7 @@ using namespace fff;
 std::vector<FolderPairCfg> fff::extractCompareCfg(const MainConfiguration& mainCfg)
 {
     //merge first and additional pairs
-    std::vector<LocalPairConfig> localCfgs = { mainCfg.firstPair };
+    std::vector<LocalPairConfig> localCfgs = {mainCfg.firstPair};
     append(localCfgs, mainCfg.additionalPairs);
 
     std::vector<FolderPairCfg> output;
@@ -206,9 +207,9 @@ ComparisonBuffer::ComparisonBuffer(const std::set<DirectoryKey>& foldersToRead,
 
     const int64_t totalTimeSec = std::chrono::duration_cast<std::chrono::seconds>(std::chrono::steady_clock::now() - compareStartTime).count();
 
-    callback.reportInfo(_("Comparison finished:") + L' ' +
-                        _P("1 item found", "%x items found", itemsReported) + L" | " +
-                        _("Time elapsed:") + L' ' + copyStringTo<std::wstring>(wxTimeSpan::Seconds(totalTimeSec).Format())); //throw X
+    callback.logInfo(_("Comparison finished:") + L' ' +
+                     _P("1 item found", "%x items found", itemsReported) + L" | " +
+                     _("Time elapsed:") + L' ' + copyStringTo<std::wstring>(wxTimeSpan::Seconds(totalTimeSec).Format())); //throw X
 }
 
 
@@ -222,7 +223,7 @@ const wchar_t arrowRight[] = L"->";
 //NOTE: conflict texts are NOT expected to contain additional path info (already implicit through associated item!)
 //      => only add path info if information is relevant, e.g. conflict is specific to left/right side only
 
-template <SelectedSide side, class FileOrLinkPair> inline
+template <SelectSide side, class FileOrLinkPair> inline
 Zstringc getConflictInvalidDate(const FileOrLinkPair& file)
 {
     return utfTo<Zstringc>(replaceCpy(_("File %x has an invalid date."), L"%x", fmtPath(AFS::getDisplayPath(file.template getAbstractPath<side>()))) + L'\n' +
@@ -233,8 +234,8 @@ Zstringc getConflictInvalidDate(const FileOrLinkPair& file)
 Zstringc getConflictSameDateDiffSize(const FilePair& file)
 {
     return utfTo<Zstringc>(_("Files have the same date but a different size.") + L'\n' +
-                           arrowLeft  + L' ' + _("Date:") + L' ' + formatUtcToLocalTime(file.getLastWriteTime< LEFT_SIDE>()) + L"    " + _("Size:") + L' ' + formatNumber(file.getFileSize<LEFT_SIDE>()) + L'\n' +
-                           arrowRight + L' ' + _("Date:") + L' ' + formatUtcToLocalTime(file.getLastWriteTime<RIGHT_SIDE>()) + L"    " + _("Size:") + L' ' + formatNumber(file.getFileSize<RIGHT_SIDE>()));
+                           arrowLeft  + L' ' + _("Date:") + L' ' + formatUtcToLocalTime(file.getLastWriteTime< SelectSide::left>()) + L"    " + _("Size:") + L' ' + formatNumber(file.getFileSize<SelectSide::left>()) + L'\n' +
+                           arrowRight + L' ' + _("Date:") + L' ' + formatUtcToLocalTime(file.getLastWriteTime<SelectSide::right>()) + L"    " + _("Size:") + L' ' + formatNumber(file.getFileSize<SelectSide::right>()));
 }
 
 
@@ -247,8 +248,8 @@ Zstringc getConflictSkippedBinaryComparison()
 Zstringc getDescrDiffMetaShortnameCase(const FileSystemObject& fsObj)
 {
     return utfTo<Zstringc>(_("Items differ in attributes only") + L'\n' +
-                           arrowLeft  + L' ' + fmtPath(fsObj.getItemName< LEFT_SIDE>()) + L'\n' +
-                           arrowRight + L' ' + fmtPath(fsObj.getItemName<RIGHT_SIDE>()));
+                           arrowLeft  + L' ' + fmtPath(fsObj.getItemName< SelectSide::left>()) + L'\n' +
+                           arrowRight + L' ' + fmtPath(fsObj.getItemName<SelectSide::right>()));
 }
 
 
@@ -257,8 +258,8 @@ template <class FileOrLinkPair>
 Zstringc getDescrDiffMetaData(const FileOrLinkPair& file)
 {
     return utfTo<Zstringc>(_("Items differ in attributes only") + L'\n' +
-                           arrowLeft  + L' ' + _("Date:") + L' ' + formatUtcToLocalTime(file.template getLastWriteTime< LEFT_SIDE>()) + L'\n' +
-                           arrowRight + L' ' + _("Date:") + L' ' + formatUtcToLocalTime(file.template getLastWriteTime<RIGHT_SIDE>()));
+                           arrowLeft  + L' ' + _("Date:") + L' ' + formatUtcToLocalTime(file.template getLastWriteTime< SelectSide::left>()) + L'\n' +
+                           arrowRight + L' ' + _("Date:") + L' ' + formatUtcToLocalTime(file.template getLastWriteTime<SelectSide::right>()));
 }
 #endif
 
@@ -273,16 +274,16 @@ Zstringc getConflictAmbiguousItemName(const Zstring& itemName)
 void categorizeSymlinkByTime(SymlinkPair& symlink)
 {
     //categorize symlinks that exist on both sides
-    switch (compareFileTime(symlink.getLastWriteTime<LEFT_SIDE>(),
-                            symlink.getLastWriteTime<RIGHT_SIDE>(), symlink.base().getFileTimeTolerance(), symlink.base().getIgnoredTimeShift()))
+    switch (compareFileTime(symlink.getLastWriteTime<SelectSide::left>(),
+                            symlink.getLastWriteTime<SelectSide::right>(), symlink.base().getFileTimeTolerance(), symlink.base().getIgnoredTimeShift()))
     {
         case TimeResult::equal:
             //Caveat:
             //1. SYMLINK_EQUAL may only be set if short names match in case: InSyncFolder's mapping tables use short name as a key! see db_file.cpp
             //2. harmonize with "bool stillInSync()" in algorithm.cpp
 
-            if (getUnicodeNormalForm(symlink.getItemName< LEFT_SIDE>()) ==
-                getUnicodeNormalForm(symlink.getItemName<RIGHT_SIDE>()))
+            if (getUnicodeNormalForm(symlink.getItemName< SelectSide::left>()) ==
+                getUnicodeNormalForm(symlink.getItemName<SelectSide::right>()))
                 symlink.setCategory<FILE_EQUAL>();
             else
                 symlink.setCategoryDiffMetadata(getDescrDiffMetaShortnameCase(symlink));
@@ -297,11 +298,11 @@ void categorizeSymlinkByTime(SymlinkPair& symlink)
             break;
 
         case TimeResult::leftInvalid:
-            symlink.setCategoryConflict(getConflictInvalidDate<LEFT_SIDE>(symlink));
+            symlink.setCategoryConflict(getConflictInvalidDate<SelectSide::left>(symlink));
             break;
 
         case TimeResult::rightInvalid:
-            symlink.setCategoryConflict(getConflictInvalidDate<RIGHT_SIDE>(symlink));
+            symlink.setCategoryConflict(getConflictInvalidDate<SelectSide::right>(symlink));
             break;
     }
 }
@@ -321,18 +322,18 @@ std::shared_ptr<BaseFolderPair> ComparisonBuffer::compareByTimeSize(const Resolv
     //categorize files that exist on both sides
     for (FilePair* file : uncategorizedFiles)
     {
-        switch (compareFileTime(file->getLastWriteTime<LEFT_SIDE>(),
-                                file->getLastWriteTime<RIGHT_SIDE>(), fileTimeTolerance_, fpConfig.ignoreTimeShiftMinutes))
+        switch (compareFileTime(file->getLastWriteTime<SelectSide::left>(),
+                                file->getLastWriteTime<SelectSide::right>(), fileTimeTolerance_, fpConfig.ignoreTimeShiftMinutes))
         {
             case TimeResult::equal:
                 //Caveat:
                 //1. FILE_EQUAL may only be set if short names match in case: InSyncFolder's mapping tables use short name as a key! see db_file.cpp
                 //2. FILE_EQUAL is expected to mean identical file sizes! See InSyncFile
                 //3. harmonize with "bool stillInSync()" in algorithm.cpp, FilePair::setSyncedTo() in file_hierarchy.h
-                if (file->getFileSize<LEFT_SIDE>() == file->getFileSize<RIGHT_SIDE>())
+                if (file->getFileSize<SelectSide::left>() == file->getFileSize<SelectSide::right>())
                 {
-                    if (getUnicodeNormalForm(file->getItemName< LEFT_SIDE>()) ==
-                        getUnicodeNormalForm(file->getItemName<RIGHT_SIDE>()))
+                    if (getUnicodeNormalForm(file->getItemName< SelectSide::left>()) ==
+                        getUnicodeNormalForm(file->getItemName<SelectSide::right>()))
                         file->setCategory<FILE_EQUAL>();
                     else
                         file->setCategoryDiffMetadata(getDescrDiffMetaShortnameCase(*file));
@@ -350,11 +351,11 @@ std::shared_ptr<BaseFolderPair> ComparisonBuffer::compareByTimeSize(const Resolv
                 break;
 
             case TimeResult::leftInvalid:
-                file->setCategoryConflict(getConflictInvalidDate<LEFT_SIDE>(*file));
+                file->setCategoryConflict(getConflictInvalidDate<SelectSide::left>(*file));
                 break;
 
             case TimeResult::rightInvalid:
-                file->setCategoryConflict(getConflictInvalidDate<RIGHT_SIDE>(*file));
+                file->setCategoryConflict(getConflictInvalidDate<SelectSide::right>(*file));
                 break;
         }
     }
@@ -367,14 +368,14 @@ namespace
 void categorizeSymlinkByContent(SymlinkPair& symlink, PhaseCallback& callback)
 {
     //categorize symlinks that exist on both sides
-    callback.updateStatus(replaceCpy(_("Resolving symbolic link %x"), L"%x", fmtPath(AFS::getDisplayPath(symlink.getAbstractPath< LEFT_SIDE>())))); //throw X
-    callback.updateStatus(replaceCpy(_("Resolving symbolic link %x"), L"%x", fmtPath(AFS::getDisplayPath(symlink.getAbstractPath<RIGHT_SIDE>())))); //throw X
+    callback.updateStatus(replaceCpy(_("Resolving symbolic link %x"), L"%x", fmtPath(AFS::getDisplayPath(symlink.getAbstractPath< SelectSide::left>())))); //throw X
+    callback.updateStatus(replaceCpy(_("Resolving symbolic link %x"), L"%x", fmtPath(AFS::getDisplayPath(symlink.getAbstractPath<SelectSide::right>())))); //throw X
 
     bool equalContent = false;
     const std::wstring errMsg = tryReportingError([&]
     {
-        equalContent = AFS::equalSymlinkContent(symlink.getAbstractPath< LEFT_SIDE>(),
-                                                symlink.getAbstractPath<RIGHT_SIDE>()); //throw FileError
+        equalContent = AFS::equalSymlinkContent(symlink.getAbstractPath< SelectSide::left>(),
+                                                symlink.getAbstractPath<SelectSide::right>()); //throw FileError
     }, callback); //throw X
 
     if (!errMsg.empty())
@@ -387,11 +388,11 @@ void categorizeSymlinkByContent(SymlinkPair& symlink, PhaseCallback& callback)
             //1. SYMLINK_EQUAL may only be set if short names match in case: InSyncFolder's mapping tables use short name as a key! see db_file.cpp
             //2. harmonize with "bool stillInSync()" in algorithm.cpp, FilePair::setSyncedTo() in file_hierarchy.h
 
-            if (getUnicodeNormalForm(symlink.getItemName< LEFT_SIDE>()) !=
-                getUnicodeNormalForm(symlink.getItemName<RIGHT_SIDE>()))
+            if (getUnicodeNormalForm(symlink.getItemName< SelectSide::left>()) !=
+                getUnicodeNormalForm(symlink.getItemName<SelectSide::right>()))
                 symlink.setCategoryDiffMetadata(getDescrDiffMetaShortnameCase(symlink));
-            //else if (!sameFileTime(symlink.getLastWriteTime<LEFT_SIDE>(),
-            //                       symlink.getLastWriteTime<RIGHT_SIDE>(), symlink.base().getFileTimeTolerance(), symlink.base().getIgnoredTimeShift()))
+            //else if (!sameFileTime(symlink.getLastWriteTime<SelectSide::left>(),
+            //                       symlink.getLastWriteTime<SelectSide::right>(), symlink.base().getFileTimeTolerance(), symlink.base().getIgnoredTimeShift()))
             //    symlink.setCategoryDiffMetadata(getDescrDiffMetaData(symlink));
             else
                 symlink.setCategory<FILE_EQUAL>();
@@ -422,10 +423,10 @@ std::shared_ptr<BaseFolderPair> ComparisonBuffer::compareBySize(const ResolvedFo
         //1. FILE_EQUAL may only be set if short names match in case: InSyncFolder's mapping tables use short name as a key! see db_file.cpp
         //2. FILE_EQUAL is expected to mean identical file sizes! See InSyncFile
         //3. harmonize with "bool stillInSync()" in algorithm.cpp, FilePair::setSyncedTo() in file_hierarchy.h
-        if (file->getFileSize<LEFT_SIDE>() == file->getFileSize<RIGHT_SIDE>())
+        if (file->getFileSize<SelectSide::left>() == file->getFileSize<SelectSide::right>())
         {
-            if (getUnicodeNormalForm(file->getItemName< LEFT_SIDE>()) ==
-                getUnicodeNormalForm(file->getItemName<RIGHT_SIDE>()))
+            if (getUnicodeNormalForm(file->getItemName< SelectSide::left>()) ==
+                getUnicodeNormalForm(file->getItemName<SelectSide::right>()))
                 file->setCategory<FILE_EQUAL>();
             else
                 file->setCategoryDiffMetadata(getDescrDiffMetaShortnameCase(*file));
@@ -444,7 +445,7 @@ namespace parallel
 //--------------------------------------------------------------
 inline
 bool filesHaveSameContent(const AbstractPath& filePath1, const AbstractPath& filePath2, //throw FileError, X
-                          const IOCallback& notifyUnbufferedIO /*throw X*/,
+                          const IoCallback& notifyUnbufferedIO /*throw X*/,
                           std::mutex& singleThread)
 { return parallelScope([=] { return filesHaveSameContent(filePath1, filePath2, notifyUnbufferedIO); /*throw FileError, X*/ }, singleThread); }
 }
@@ -459,7 +460,7 @@ void categorizeFileByContent(FilePair& file, const std::wstring& txtComparingCon
     bool haveSameContent = false;
     const std::wstring errMsg = tryReportingError([&]
     {
-        AsyncItemStatReporter statReporter(1, file.getFileSize<LEFT_SIDE>(), acb);
+        AsyncItemStatReporter statReporter(1, file.getFileSize<SelectSide::left>(), acb);
 
         //callbacks run *outside* singleThread_ lock! => fine
         auto notifyUnbufferedIO = [&statReporter](int64_t bytesDelta)
@@ -468,8 +469,8 @@ void categorizeFileByContent(FilePair& file, const std::wstring& txtComparingCon
             interruptionPoint(); //throw ThreadStopRequest
         };
 
-        haveSameContent = parallel::filesHaveSameContent(file.getAbstractPath< LEFT_SIDE>(),
-                                                         file.getAbstractPath<RIGHT_SIDE>(), notifyUnbufferedIO, singleThread); //throw FileError, ThreadStopRequest
+        haveSameContent = parallel::filesHaveSameContent(file.getAbstractPath< SelectSide::left>(),
+                                                         file.getAbstractPath<SelectSide::right>(), notifyUnbufferedIO, singleThread); //throw FileError, ThreadStopRequest
         statReporter.reportDelta(1, 0);
     }, acb); //throw ThreadStopRequest
 
@@ -483,12 +484,12 @@ void categorizeFileByContent(FilePair& file, const std::wstring& txtComparingCon
             //1. FILE_EQUAL may only be set if short names match in case: InSyncFolder's mapping tables use short name as a key! see db_file.cpp
             //2. FILE_EQUAL is expected to mean identical file sizes! See InSyncFile
             //3. harmonize with "bool stillInSync()" in algorithm.cpp, FilePair::setSyncedTo() in file_hierarchy.h
-            if (getUnicodeNormalForm(file.getItemName< LEFT_SIDE>()) !=
-                getUnicodeNormalForm(file.getItemName<RIGHT_SIDE>()))
+            if (getUnicodeNormalForm(file.getItemName< SelectSide::left>()) !=
+                getUnicodeNormalForm(file.getItemName<SelectSide::right>()))
                 file.setCategoryDiffMetadata(getDescrDiffMetaShortnameCase(file));
 #if 0 //don't synchronize modtime only see FolderPairSyncer::synchronizeFileInt(), SO_COPY_METADATA_TO_*
-            else if (!sameFileTime(file.getLastWriteTime<LEFT_SIDE>(),
-                                   file.getLastWriteTime<RIGHT_SIDE>(), file.base().getFileTimeTolerance(), file.base().getIgnoredTimeShift()))
+            else if (!sameFileTime(file.getLastWriteTime<SelectSide::left>(),
+                                   file.getLastWriteTime<SelectSide::right>(), file.base().getFileTimeTolerance(), file.base().getIgnoredTimeShift()))
                 file.setCategoryDiffMetadata(getDescrDiffMetaData(file));
 #endif
             else
@@ -521,7 +522,7 @@ std::list<std::shared_ptr<BaseFolderPair>> ComparisonBuffer::compareByContent(co
     {
         ParallelOps& posL = parallelOpsStatus[basePathL.afsDevice];
         ParallelOps& posR = parallelOpsStatus[basePathR.afsDevice];
-        fpWorkload.push_back({ posL, posR, std::move(filesToCompareBytewise) });
+        fpWorkload.push_back({posL, posR, std::move(filesToCompareBytewise)});
     };
 
     //PERF_START;
@@ -541,7 +542,7 @@ std::list<std::shared_ptr<BaseFolderPair>> ComparisonBuffer::compareByContent(co
         //in order to separate into two processes (scanning and comparing)
         for (FilePair* file : undefinedFiles)
             //pre-check: files have different content if they have a different file size (must not be FILE_EQUAL: see InSyncFile)
-            if (file->getFileSize<LEFT_SIDE>() != file->getFileSize<RIGHT_SIDE>())
+            if (file->getFileSize<SelectSide::left>() != file->getFileSize<SelectSide::right>())
                 file->setCategory<FILE_DIFFERENT_CONTENT>();
             else
             {
@@ -553,8 +554,8 @@ std::list<std::shared_ptr<BaseFolderPair>> ComparisonBuffer::compareByContent(co
                     filesToCompareBytewise.push_back(file);
             }
         if (!filesToCompareBytewise.empty())
-            addToBinaryWorkload(output.back()->getAbstractPath< LEFT_SIDE>(),
-                                output.back()->getAbstractPath<RIGHT_SIDE>(), std::move(filesToCompareBytewise));
+            addToBinaryWorkload(output.back()->getAbstractPath< SelectSide::left>(),
+                                output.back()->getAbstractPath<SelectSide::right>(), std::move(filesToCompareBytewise));
 
         //finish symlink categorization
         for (SymlinkPair* symlink : uncategorizedLinks)
@@ -571,7 +572,7 @@ std::list<std::shared_ptr<BaseFolderPair>> ComparisonBuffer::compareByContent(co
             itemsTotal += bwl.filesToCompareBytewise.size();
 
             for (const FilePair* file : bwl.filesToCompareBytewise)
-                bytesTotal += file->getFileSize<LEFT_SIDE>(); //left and right file sizes are equal
+                bytesTotal += file->getFileSize<SelectSide::left>(); //left and right file sizes are equal
         }
         cb_.initNewPhase(itemsTotal, bytesTotal, ProcessPhase::comparingContent); //throw X
 
@@ -594,7 +595,7 @@ std::list<std::shared_ptr<BaseFolderPair>> ComparisonBuffer::compareByContent(co
                 BinaryWorkload& bwl = fpWorkload[j];
                 ParallelOps& posL = bwl.parallelOpsL;
                 ParallelOps& posR = bwl.parallelOpsR;
-                const size_t newTaskCount = std::min<size_t>({ 1                 - posL.current, 1                 - posR.current, bwl.filesToCompareBytewise.size() });
+                const size_t newTaskCount = std::min<size_t>({1                 - posL.current, 1                 - posR.current, bwl.filesToCompareBytewise.size()});
                 if (&posL != &posR)
                     posL.current += newTaskCount; //
                 posR.current += newTaskCount;     //consider aliasing!
@@ -659,7 +660,7 @@ public:
 private:
     void mergeTwoSides(const FolderContainer& lhs, const FolderContainer& rhs, const Zstringc* errorMsg, ContainerObject& output);
 
-    template <SelectedSide side>
+    template <SelectSide side>
     void fillOneSide(const FolderContainer& folderCont, const Zstringc* errorMsg, ContainerObject& output);
 
     const Zstringc* checkFailedRead(FileSystemObject& fsObj, const Zstringc* errorMsg);
@@ -690,7 +691,7 @@ const Zstringc* MergeSides::checkFailedRead(FileSystemObject& fsObj, const Zstri
 }
 
 
-template <SelectedSide side>
+template <SelectSide side>
 void MergeSides::fillOneSide(const FolderContainer& folderCont, const Zstringc* errorMsg, ContainerObject& output)
 {
     for (const auto& [fileName, attrib] : folderCont.files)
@@ -726,8 +727,8 @@ void matchFolders(const MapType& mapLeft, const MapType& mapRight, ProcessLeftOn
     std::vector<FileRef> fileList;
     fileList.reserve(mapLeft.size() + mapRight.size()); //perf: ~5% shorter runtime
 
-    for (const auto& item : mapLeft ) fileList.push_back({ getUpperCase(item.first), &item, true });
-    for (const auto& item : mapRight) fileList.push_back({ getUpperCase(item.first), &item, false });
+    for (const auto& item : mapLeft ) fileList.push_back({getUpperCase(item.first), &item, true});
+    for (const auto& item : mapRight) fileList.push_back({getUpperCase(item.first), &item, false});
 
     //primary sort: ignore unicode normal form and case
     //bonus: natural default sequence on file guid UI
@@ -792,12 +793,12 @@ void MergeSides::mergeTwoSides(const FolderContainer& lhs, const FolderContainer
 
     matchFolders(lhs.files, rhs.files, [&](const FileData& fileLeft, const Zstringc* conflictMsg)
     {
-        FilePair& newItem = output.addSubFile< LEFT_SIDE>(fileLeft .first, fileLeft .second);
+        FilePair& newItem = output.addSubFile< SelectSide::left>(fileLeft .first, fileLeft .second);
         checkFailedRead(newItem, conflictMsg ? conflictMsg : errorMsg);
     },
     [&](const FileData& fileRight, const Zstringc* conflictMsg)
     {
-        FilePair& newItem = output.addSubFile<RIGHT_SIDE>(fileRight.first, fileRight.second);
+        FilePair& newItem = output.addSubFile<SelectSide::right>(fileRight.first, fileRight.second);
         checkFailedRead(newItem, conflictMsg ? conflictMsg : errorMsg);
     },
     [&](const FileData& fileLeft, const FileData& fileRight)
@@ -817,12 +818,12 @@ void MergeSides::mergeTwoSides(const FolderContainer& lhs, const FolderContainer
 
     matchFolders(lhs.symlinks, rhs.symlinks, [&](const SymlinkData& symlinkLeft, const Zstringc* conflictMsg)
     {
-        SymlinkPair& newItem = output.addSubLink< LEFT_SIDE>(symlinkLeft .first, symlinkLeft .second);
+        SymlinkPair& newItem = output.addSubLink< SelectSide::left>(symlinkLeft .first, symlinkLeft .second);
         checkFailedRead(newItem, conflictMsg ? conflictMsg : errorMsg);
     },
     [&](const SymlinkData& symlinkRight, const Zstringc* conflictMsg)
     {
-        SymlinkPair& newItem = output.addSubLink<RIGHT_SIDE>(symlinkRight.first, symlinkRight.second);
+        SymlinkPair& newItem = output.addSubLink<SelectSide::right>(symlinkRight.first, symlinkRight.second);
         checkFailedRead(newItem, conflictMsg ? conflictMsg : errorMsg);
     },
     [&](const SymlinkData& symlinkLeft, const SymlinkData& symlinkRight) //both sides
@@ -841,15 +842,15 @@ void MergeSides::mergeTwoSides(const FolderContainer& lhs, const FolderContainer
 
     matchFolders(lhs.folders, rhs.folders, [&](const FolderData& dirLeft, const Zstringc* conflictMsg)
     {
-        FolderPair& newFolder = output.addSubFolder<LEFT_SIDE>(dirLeft.first, dirLeft.second.first);
+        FolderPair& newFolder = output.addSubFolder<SelectSide::left>(dirLeft.first, dirLeft.second.first);
         const Zstringc* errorMsgNew = checkFailedRead(newFolder, conflictMsg ? conflictMsg : errorMsg);
-        this->fillOneSide<LEFT_SIDE>(dirLeft.second.second, errorMsgNew, newFolder); //recurse
+        this->fillOneSide<SelectSide::left>(dirLeft.second.second, errorMsgNew, newFolder); //recurse
     },
     [&](const FolderData& dirRight, const Zstringc* conflictMsg)
     {
-        FolderPair& newFolder = output.addSubFolder<RIGHT_SIDE>(dirRight.first, dirRight.second.first);
+        FolderPair& newFolder = output.addSubFolder<SelectSide::right>(dirRight.first, dirRight.second.first);
         const Zstringc* errorMsgNew = checkFailedRead(newFolder, conflictMsg ? conflictMsg : errorMsg);
-        this->fillOneSide<RIGHT_SIDE>(dirRight.second.second, errorMsgNew, newFolder); //recurse
+        this->fillOneSide<SelectSide::right>(dirRight.second.second, errorMsgNew, newFolder); //recurse
     },
     [&](const FolderData& dirLeft, const FolderData& dirRight)
     {
@@ -904,7 +905,7 @@ std::shared_ptr<BaseFolderPair> ComparisonBuffer::performComparison(const Resolv
 
     auto getDirValue = [&](const AbstractPath& folderPath) -> const DirectoryValue*
     {
-        auto it = directoryBuffer_.find({ folderPath, fpCfg.filter.nameFilter, fpCfg.handleSymlinks });
+        auto it = directoryBuffer_.find({folderPath, fpCfg.filter.nameFilter, fpCfg.handleSymlinks});
         return it != directoryBuffer_.end() ? &it->second : nullptr;
     };
 
@@ -986,7 +987,7 @@ FolderComparison fff::compare(WarningDialogs& warnings,
     //indicator at the very beginning of the log to make sense of "total time"
     //init process: keep at beginning so that all gui elements are initialized properly
     callback.initNewPhase(-1, -1, ProcessPhase::scanning); //throw X; it's unknown how many files will be scanned => -1 objects
-    //callback.reportInfo(Comparison started")); -> still useful?
+    //callback.logInfo(Comparison started")); -> still useful?
 
     //-------------------------------------------------------------------------------
 
@@ -1006,7 +1007,7 @@ FolderComparison fff::compare(WarningDialogs& warnings,
     }
     catch (const FileError& e) //failure is not critical => log only
     {
-        callback.reportInfo(e.toString()); //throw X
+        callback.logInfo(e.toString()); //throw X
     }
 
     const ResolvedBaseFolders& resInfo = initializeBaseFolders(fpCfgList,
@@ -1067,8 +1068,10 @@ FolderComparison fff::compare(WarningDialogs& warnings,
     {
         std::set<Zstring> folderPathsToLock;
         for (const AbstractPath& folderPath : resInfo.existingBaseFolders)
-            if (std::optional<Zstring> nativePath = AFS::getNativeItemPath(folderPath)) //restrict directory locking to native paths until further
-                folderPathsToLock.insert(*nativePath);
+
+            if (const Zstring& nativePath = getNativeItemPath(folderPath); //restrict directory locking to native paths until further
+                !nativePath.empty())
+                folderPathsToLock.insert(nativePath);
 
         dirLocks = std::make_unique<LockHolder>(folderPathsToLock, warnings.warnDirectoryLockFailed, callback);
     }
@@ -1081,9 +1084,9 @@ FolderComparison fff::compare(WarningDialogs& warnings,
         for (const auto& [folderPair, fpCfg] : workLoad)
         {
             if (basefolderExisting(folderPair.folderPathLeft)) //only traverse *currently existing* folders: at this point user is aware that non-ex + empty string are seen as empty folder!
-                foldersToRead.emplace(DirectoryKey({ folderPair.folderPathLeft, fpCfg.filter.nameFilter, fpCfg.handleSymlinks }));
+                foldersToRead.emplace(DirectoryKey({folderPair.folderPathLeft, fpCfg.filter.nameFilter, fpCfg.handleSymlinks}));
             if (basefolderExisting(folderPair.folderPathRight))
-                foldersToRead.emplace(DirectoryKey({ folderPair.folderPathRight, fpCfg.filter.nameFilter, fpCfg.handleSymlinks }));
+                foldersToRead.emplace(DirectoryKey({folderPair.folderPathRight, fpCfg.filter.nameFilter, fpCfg.handleSymlinks}));
         }
 
         FolderComparison output;
@@ -1100,7 +1103,7 @@ FolderComparison fff::compare(WarningDialogs& warnings,
             std::vector<std::pair<ResolvedFolderPair, FolderPairCfg>> workLoadByContent;
             for (const auto& [folderPair, fpCfg] : workLoad)
                 if (fpCfg.compareVar == CompareVariant::content)
-                    workLoadByContent.push_back({ folderPair, fpCfg });
+                    workLoadByContent.push_back({folderPair, fpCfg});
 
             std::list<std::shared_ptr<BaseFolderPair>> outputByContent = cmpBuff.compareByContent(workLoadByContent);
 
diff --git a/FreeFileSync/Source/base/db_file.cpp b/FreeFileSync/Source/base/db_file.cpp
index ed32e884..27f47565 100644
--- a/FreeFileSync/Source/base/db_file.cpp
+++ b/FreeFileSync/Source/base/db_file.cpp
@@ -11,6 +11,7 @@
 #include <zen/build_info.h>
 #include <zen/zlib_wrap.h>
 #include "../afs/concrete.h"
+#include "../afs/native.h"
 #include "status_handler_impl.h"
 
 
@@ -23,7 +24,7 @@ namespace
 //-------------------------------------------------------------------------------------------------------------------------------
 const char DB_FILE_DESCR[] = "FreeFileSync";
 const int DB_FILE_VERSION   = 11; //2020-02-07
-const int DB_STREAM_VERSION =  3; //2017-02-01
+const int DB_STREAM_VERSION =  4; //2021-02-14
 //-------------------------------------------------------------------------------------------------------------------------------
 
 DEFINE_NEW_FILE_ERROR(FileErrorDatabaseNotExisting)
@@ -44,7 +45,7 @@ using DbStreams = std::unordered_map<UniqueId, SessionData>; //list of streams b
   | ensure 32/64 bit portability: use fixed size data types only e.g. uint32_t |
   ------------------------------------------------------------------------------*/
 
-template <SelectedSide side> inline
+template <SelectSide side> inline
 AbstractPath getDatabaseFilePath(const BaseFolderPair& baseFolder)
 {
     static_assert(std::endian::native == std::endian::little);
@@ -57,13 +58,13 @@ AbstractPath getDatabaseFilePath(const BaseFolderPair& baseFolder)
         - 32 vs 64-bit: already handled
 
         => give db files different names:                   */
-    const Zstring dbName = Zstr(".sync"); //files beginning with dots are hidden e.g. in Nautilus
+    const Zstring dbName = Zstr(".sync"); //files beginning with dots are usually hidden
     return AFS::appendRelPath(baseFolder.getAbstractPath<side>(), dbName + SYNC_DB_FILE_ENDING);
 }
 
 //#######################################################################################################################################
 
-void saveStreams(const DbStreams& streamList, const AbstractPath& dbPath, const IOCallback& notifyUnbufferedIO /*throw X*/) //throw FileError, X
+void saveStreams(const DbStreams& streamList, const AbstractPath& dbPath, const IoCallback& notifyUnbufferedIO /*throw X*/) //throw FileError, X
 {
     MemoryStreamOut<std::string> memStreamOut;
 
@@ -98,7 +99,7 @@ void saveStreams(const DbStreams& streamList, const AbstractPath& dbPath, const
 }
 
 
-DbStreams loadStreams(const AbstractPath& dbPath, const IOCallback& notifyUnbufferedIO /*throw X*/) //throw FileError, FileErrorDatabaseNotExisting, X
+DbStreams loadStreams(const AbstractPath& dbPath, const IoCallback& notifyUnbufferedIO /*throw X*/) //throw FileError, FileErrorDatabaseNotExisting, X
 {
     std::string byteStream;
     try
@@ -133,7 +134,7 @@ DbStreams loadStreams(const AbstractPath& dbPath, const IOCallback& notifyUnbuff
         if (version ==  9 || //TODO: remove migration code at some time!  v9 used until 2017-02-01
             version == 10)   //TODO: remove migration code at some time! v10 used until 2020-02-07
             ;
-        else if (version == DB_FILE_VERSION)//catch data corruption ASAP + don't rely on std::bad_alloc for consistency checking
+        else if (version == DB_FILE_VERSION) //catch data corruption ASAP + don't rely on std::bad_alloc for consistency checking
             // => only "partially" useful for container/stream metadata since the streams data is zlib-compressed
         {
             assert(byteStream.size() >= sizeof(uint32_t)); //obviously in this context!
@@ -273,8 +274,8 @@ private:
             writeItemName(itemName);
             writeNumber(streamOutSmallNum_, static_cast<int32_t>(inSyncData.cmpVar));
 
-            writeLinkDescr(inSyncData.left);
-            writeLinkDescr(inSyncData.right);
+            writeNumber<int64_t>(streamOutBigNum_, inSyncData.left .modTime);
+            writeNumber<int64_t>(streamOutBigNum_, inSyncData.right.modTime);
         }
 
         writeNumber<uint32_t>(streamOutSmallNum_, static_cast<uint32_t>(container.folders.size()));
@@ -291,13 +292,11 @@ private:
 
     void writeFileDescr(const InSyncDescrFile& descr)
     {
-        writeNumber<int64_t>(streamOutBigNum_, descr.modTime);
-        writeContainer<std::string>(streamOutBigNum_, descr.fileId);
+        writeNumber<int64_t         >(streamOutBigNum_, descr.modTime);
+        writeNumber<AFS::FingerPrint>(streamOutBigNum_, descr.filePrint);
         static_assert(sizeof(descr.modTime) <= sizeof(int64_t)); //ensure cross-platform compatibility!
     }
 
-    void writeLinkDescr(const InSyncDescrLink& descr) { writeNumber<int64_t>(streamOutBigNum_, descr.modTime); }
-
     /* maximize zlib compression by grouping similar data (=> 20% size reduction!)
          -> further ~5% reduction possible by having one container per data type
 
@@ -364,7 +363,8 @@ public:
                 parser.recurse(output.ref()); //throw SysError
                 return output;
             }
-            else if (streamVersion == DB_STREAM_VERSION)
+            else if (streamVersion == 3 || //TODO: remove migration code at some time! 2021-02-14
+                     streamVersion == DB_STREAM_VERSION)
             {
                 MemoryStreamIn<std::string>& streamInPart1 = leadStreamLeft ? streamInL : streamInR;
                 MemoryStreamIn<std::string>& streamInPart2 = leadStreamLeft ? streamInR : streamInL;
@@ -387,9 +387,9 @@ public:
                                     decompress(bufSmallNum), //throw SysError
                                     decompress(bufBigNum));  //
                 if (leadStreamLeft)
-                    parser.recurse<LEFT_SIDE>(output.ref()); //throw SysError
+                    parser.recurse<SelectSide::left>(output.ref()); //throw SysError
                 else
-                    parser.recurse<RIGHT_SIDE>(output.ref()); //throw SysError
+                    parser.recurse<SelectSide::right>(output.ref()); //throw SysError
                 return output;
             }
             else
@@ -406,23 +406,20 @@ private:
         streamVersion_(streamVersion),
         streamInText_(bufText),
         streamInSmallNum_(bufSmallNumbers),
-        streamInBigNum_(bufBigNumbers)
-    {
-        (void)streamVersion_; //clang: -Wunused-private-field
-    }
+        streamInBigNum_(bufBigNumbers) {}
 
-    template <SelectedSide leadSide>
+    template <SelectSide leadSide>
     void recurse(InSyncFolder& container) //throw SysError
     {
-        size_t fileCount = readNumber<uint32_t>(streamInSmallNum_);
+        size_t fileCount = readNumber<uint32_t>(streamInSmallNum_); //throw SysErrorUnexpectedEos
         while (fileCount-- != 0)
         {
-            const Zstring itemName = readItemName();
-            const auto cmpVar = static_cast<CompareVariant>(readNumber<int32_t>(streamInSmallNum_));
-            const uint64_t fileSize = readNumber<uint64_t>(streamInSmallNum_);
+            const Zstring itemName = readItemName(); //
+            const auto cmpVar = static_cast<CompareVariant>(readNumber<int32_t>(streamInSmallNum_)); //
+            const uint64_t fileSize = readNumber<uint64_t>(streamInSmallNum_); //
 
-            const InSyncDescrFile dataL = readFileDescr();
-            const InSyncDescrFile dataT = readFileDescr();
+            const InSyncDescrFile dataL = readFileDescr(); //throw SysErrorUnexpectedEos
+            const InSyncDescrFile dataT = readFileDescr(); //
 
             container.addFile(itemName,
                               SelectParam<leadSide>::ref(dataL, dataT),
@@ -432,22 +429,22 @@ private:
         size_t linkCount = readNumber<uint32_t>(streamInSmallNum_);
         while (linkCount-- != 0)
         {
-            const Zstring itemName = readItemName();
-            const auto cmpVar = static_cast<CompareVariant>(readNumber<int32_t>(streamInSmallNum_));
+            const Zstring itemName = readItemName(); //
+            const auto cmpVar = static_cast<CompareVariant>(readNumber<int32_t>(streamInSmallNum_)); //
 
-            const InSyncDescrLink dataL = readLinkDescr();
-            const InSyncDescrLink dataT = readLinkDescr();
+            const InSyncDescrLink dataL(readNumber<int64_t>(streamInBigNum_)); //throw SysErrorUnexpectedEos
+            const InSyncDescrLink dataT(readNumber<int64_t>(streamInBigNum_)); //
 
             container.addSymlink(itemName,
                                  SelectParam<leadSide>::ref(dataL, dataT),
                                  SelectParam<leadSide>::ref(dataT, dataL), cmpVar);
         }
 
-        size_t dirCount = readNumber<uint32_t>(streamInSmallNum_);
+        size_t dirCount = readNumber<uint32_t>(streamInSmallNum_); //
         while (dirCount-- != 0)
         {
-            const Zstring itemName = readItemName();
-            const auto status = static_cast<InSyncFolder::InSyncStatus>(readNumber<int32_t>(streamInSmallNum_));
+            const Zstring itemName = readItemName(); //
+            const auto status = static_cast<InSyncFolder::InSyncStatus>(readNumber<int32_t>(streamInSmallNum_)); //
 
             InSyncFolder& dbFolder = container.addFolder(itemName, status);
             recurse<leadSide>(dbFolder);
@@ -458,17 +455,24 @@ private:
 
     InSyncDescrFile readFileDescr() //throw SysErrorUnexpectedEos
     {
-        //attention: order of function argument evaluation is undefined! So do it one after the other...
-        const auto modTime = readNumber<int64_t>(streamInBigNum_);       //throw SysErrorUnexpectedEos
-        const auto fileId = readContainer<std::string>(streamInBigNum_); //
+        const auto modTime = readNumber<int64_t>(streamInBigNum_); //throw SysErrorUnexpectedEos
 
-        return InSyncDescrFile(modTime, fileId);
-    }
+        AFS::FingerPrint filePrint = 0;
+        if (streamVersion_ == 3) //TODO: remove migration code at some time! 2021-02-14
+        {
+            const auto& devFileId = readContainer<std::string>(streamInBigNum_); //throw SysErrorUnexpectedEos
+            ino_t fileIndex = 0;
+            if (devFileId.size() == sizeof(dev_t) + sizeof(fileIndex))
+            {
+                std::memcpy(&fileIndex, &devFileId[devFileId.size() - sizeof(fileIndex)], sizeof(fileIndex));
+                filePrint = fileIndex;
+            }
+            else assert(devFileId.empty());
+        }
+        else
+            filePrint = readNumber<AFS::FingerPrint>(streamInBigNum_); //throw SysErrorUnexpectedEos
 
-    InSyncDescrLink readLinkDescr() //throw SysErrorUnexpectedEos
-    {
-        const auto modTime = readNumber<int64_t>(streamInBigNum_); //throw SysErrorUnexpectedEos
-        return InSyncDescrLink(modTime);
+        return InSyncDescrFile(modTime, filePrint);
     }
 
     //TODO: remove migration code at some time! 2017-02-01
@@ -491,10 +495,10 @@ private:
                 const auto cmpVar = static_cast<CompareVariant>(readNumber<int32_t>(inputBoth_));
                 const uint64_t fileSize = readNumber<uint64_t>(inputBoth_);
                 const auto modTimeL = readNumber<int64_t>(inputLeft_);
-                const auto fileIdL = readContainer<std::string>(inputLeft_);
+                /*const auto fileIdL =*/ readContainer<std::string>(inputLeft_);
                 const auto modTimeR = readNumber<int64_t>(inputRight_);
-                const auto fileIdR = readContainer<std::string>(inputRight_);
-                container.addFile(itemName, InSyncDescrFile(modTimeL, fileIdL), InSyncDescrFile(modTimeR, fileIdR), cmpVar, fileSize);
+                /*const auto fileIdR =*/ readContainer<std::string>(inputRight_);
+                container.addFile(itemName, InSyncDescrFile(modTimeL, AFS::FingerPrint()), InSyncDescrFile(modTimeR, AFS::FingerPrint()), cmpVar, fileSize);
             }
 
             size_t linkCount = readNumber<uint32_t>(inputBoth_);
@@ -568,23 +572,23 @@ private:
                 {
                     //Caveat: If FILE_EQUAL, we *implicitly* assume equal left and right short names matching case: InSyncFolder's mapping tables use short name as a key!
                     //This makes us silently dependent from code in algorithm.h!!!
-                    assert(getUnicodeNormalForm(file.getItemName<LEFT_SIDE>()) == getUnicodeNormalForm(file.getItemName<RIGHT_SIDE>()));
-                    assert(file.getFileSize<LEFT_SIDE>() == file.getFileSize<RIGHT_SIDE>());
+                    assert(getUnicodeNormalForm(file.getItemName<SelectSide::left>()) == getUnicodeNormalForm(file.getItemName<SelectSide::right>()));
+                    assert(file.getFileSize<SelectSide::left>() == file.getFileSize<SelectSide::right>());
 
                     //create or update new "in-sync" state
                     dbFiles.insert_or_assign(file.getItemNameAny(),
-                                             InSyncFile(InSyncDescrFile(file.getLastWriteTime< LEFT_SIDE>(),
-                                                                        file.getFileId       < LEFT_SIDE>()),
-                                                        InSyncDescrFile(file.getLastWriteTime<RIGHT_SIDE>(),
-                                                                        file.getFileId       <RIGHT_SIDE>()),
+                                             InSyncFile(InSyncDescrFile(file.getLastWriteTime< SelectSide::left>(),
+                                                                        file.getFilePrint    < SelectSide::left>()),
+                                                        InSyncDescrFile(file.getLastWriteTime<SelectSide::right>(),
+                                                                        file.getFilePrint    <SelectSide::right>()),
                                                         activeCmpVar_,
-                                                        file.getFileSize<LEFT_SIDE>()));
+                                                        file.getFileSize<SelectSide::left>()));
                     toPreserve.insert(file.getItemNameAny());
                 }
                 else //not in sync: preserve last synchronous state
                 {
-                    toPreserve.insert(file.getItemName< LEFT_SIDE>()); //left/right may differ in case!
-                    toPreserve.insert(file.getItemName<RIGHT_SIDE>()); //
+                    toPreserve.insert(file.getItemName< SelectSide::left>()); //left/right may differ in case!
+                    toPreserve.insert(file.getItemName<SelectSide::right>()); //
                 }
             }
 
@@ -609,19 +613,19 @@ private:
             {
                 if (symlink.getLinkCategory() == SYMLINK_EQUAL) //data in sync: write current state
                 {
-                    assert(getUnicodeNormalForm(symlink.getItemName<LEFT_SIDE>()) == getUnicodeNormalForm(symlink.getItemName<RIGHT_SIDE>()));
+                    assert(getUnicodeNormalForm(symlink.getItemName<SelectSide::left>()) == getUnicodeNormalForm(symlink.getItemName<SelectSide::right>()));
 
                     //create or update new "in-sync" state
                     dbSymlinks.insert_or_assign(symlink.getItemNameAny(),
-                                                InSyncSymlink(InSyncDescrLink(symlink.getLastWriteTime< LEFT_SIDE>()),
-                                                              InSyncDescrLink(symlink.getLastWriteTime<RIGHT_SIDE>()),
+                                                InSyncSymlink(InSyncDescrLink(symlink.getLastWriteTime< SelectSide::left>()),
+                                                              InSyncDescrLink(symlink.getLastWriteTime<SelectSide::right>()),
                                                               activeCmpVar_));
                     toPreserve.insert(symlink.getItemNameAny());
                 }
                 else //not in sync: preserve last synchronous state
                 {
-                    toPreserve.insert(symlink.getItemName< LEFT_SIDE>()); //left/right may differ in case!
-                    toPreserve.insert(symlink.getItemName<RIGHT_SIDE>()); //
+                    toPreserve.insert(symlink.getItemName< SelectSide::left>()); //left/right may differ in case!
+                    toPreserve.insert(symlink.getItemName<SelectSide::right>()); //
                 }
             }
 
@@ -645,7 +649,7 @@ private:
             {
                 if (folder.getDirCategory() == DIR_EQUAL)
                 {
-                    assert(getUnicodeNormalForm(folder.getItemName<LEFT_SIDE>()) == getUnicodeNormalForm(folder.getItemName<RIGHT_SIDE>()));
+                    assert(getUnicodeNormalForm(folder.getItemName<SelectSide::left>()) == getUnicodeNormalForm(folder.getItemName<SelectSide::right>()));
 
                     //update directory entry only (shallow), but do *not touch* existing child elements!!!
                     InSyncFolder& dbFolder = dbFolders.emplace(folder.getItemNameAny(), InSyncFolder(InSyncFolder::DIR_STATUS_IN_SYNC)).first->second; //get or create
@@ -655,8 +659,8 @@ private:
                 }
                 else //not in sync: preserve last synchronous state
                 {
-                    toPreserve.emplace(folder.getItemName< LEFT_SIDE>(), &folder); //names differing in case? => treat like any other folder rename
-                    toPreserve.emplace(folder.getItemName<RIGHT_SIDE>(), &folder); //=> no *new* database entries even if child items are in sync
+                    toPreserve.emplace(folder.getItemName< SelectSide::left>(), &folder); //names differing in case? => treat like any other folder rename
+                    toPreserve.emplace(folder.getItemName<SelectSide::right>(), &folder); //=> no *new* database entries even if child items are in sync
                 }
             }
 
@@ -749,7 +753,7 @@ std::pair<DbStreams::const_iterator,
             }
     }
 
-    return { itCommonL, itCommonR };
+    return {itCommonL, itCommonR};
 }
 }
 
@@ -762,11 +766,11 @@ std::unordered_map<const BaseFolderPair*, SharedRef<const InSyncFolder>> fff::lo
 
     for (const BaseFolderPair* baseFolder : baseFolders)
         //avoid race condition with directory existence check: reading sync.ffs_db may succeed although first dir check had failed => conflicts!
-        if (baseFolder->isAvailable< LEFT_SIDE>() &&
-            baseFolder->isAvailable<RIGHT_SIDE>())
+        if (baseFolder->isAvailable< SelectSide::left>() &&
+            baseFolder->isAvailable<SelectSide::right>())
         {
-            dbFilePaths.insert(getDatabaseFilePath< LEFT_SIDE>(*baseFolder));
-            dbFilePaths.insert(getDatabaseFilePath<RIGHT_SIDE>(*baseFolder));
+            dbFilePaths.insert(getDatabaseFilePath< SelectSide::left>(*baseFolder));
+            dbFilePaths.insert(getDatabaseFilePath<SelectSide::right>(*baseFolder));
         }
     //else: ignore; there's no value in reporting it other than to confuse users
 
@@ -801,11 +805,11 @@ std::unordered_map<const BaseFolderPair*, SharedRef<const InSyncFolder>> fff::lo
     std::unordered_map<const BaseFolderPair*, SharedRef<const InSyncFolder>> output;
 
     for (const BaseFolderPair* baseFolder : baseFolders)
-        if (baseFolder->isAvailable< LEFT_SIDE>() &&
-            baseFolder->isAvailable<RIGHT_SIDE>())
+        if (baseFolder->isAvailable< SelectSide::left>() &&
+            baseFolder->isAvailable<SelectSide::right>())
         {
-            const AbstractPath dbPathL = getDatabaseFilePath< LEFT_SIDE>(*baseFolder);
-            const AbstractPath dbPathR = getDatabaseFilePath<RIGHT_SIDE>(*baseFolder);
+            const AbstractPath dbPathL = getDatabaseFilePath< SelectSide::left>(*baseFolder);
+            const AbstractPath dbPathR = getDatabaseFilePath<SelectSide::right>(*baseFolder);
 
             auto itL = dbStreamsByPath.find(dbPathL);
             auto itR = dbStreamsByPath.find(dbPathR);
@@ -842,8 +846,8 @@ std::unordered_map<const BaseFolderPair*, SharedRef<const InSyncFolder>> fff::lo
 void fff::saveLastSynchronousState(const BaseFolderPair& baseFolder, bool transactionalCopy,
                                    PhaseCallback& callback /*throw X*/) //throw X
 {
-    const AbstractPath dbPathL = getDatabaseFilePath< LEFT_SIDE>(baseFolder);
-    const AbstractPath dbPathR = getDatabaseFilePath<RIGHT_SIDE>(baseFolder);
+    const AbstractPath dbPathL = getDatabaseFilePath< SelectSide::left>(baseFolder);
+    const AbstractPath dbPathR = getDatabaseFilePath<SelectSide::right>(baseFolder);
 
     //------------ (try to) load DB files in parallel -------------------------
     DbStreams streamsL; //list of session ID + DirInfo-stream
diff --git a/FreeFileSync/Source/base/db_file.h b/FreeFileSync/Source/base/db_file.h
index f9e0dabb..49d14813 100644
--- a/FreeFileSync/Source/base/db_file.h
+++ b/FreeFileSync/Source/base/db_file.h
@@ -19,12 +19,12 @@ const Zchar SYNC_DB_FILE_ENDING[] = Zstr(".ffs_db"); //don't use Zstring as glob
 
 struct InSyncDescrFile //subset of FileAttributes
 {
-    InSyncDescrFile(time_t modTimeIn, const AFS::FileId& idIn) :
+    InSyncDescrFile(time_t modTimeIn, AFS::FingerPrint filePrintIn) :
         modTime(modTimeIn),
-        fileId(idIn) {}
+        filePrint(filePrintIn) {}
 
     time_t modTime = 0;
-    AFS::FileId fileId; // == file id: optional! (however, always set on Linux, and *generally* available on Windows)
+    AFS::FingerPrint filePrint = 0; //optional!
 };
 
 struct InSyncDescrLink
diff --git a/FreeFileSync/Source/base/dir_exist_async.h b/FreeFileSync/Source/base/dir_exist_async.h
index 98430b2e..593dc3b9 100644
--- a/FreeFileSync/Source/base/dir_exist_async.h
+++ b/FreeFileSync/Source/base/dir_exist_async.h
@@ -53,7 +53,8 @@ FolderStatus getFolderStatusNonBlocking(const std::set<AbstractPath>& folderPath
         threadGroup.detach(); //don't wait on threads hanging longer than "folderAccessTimeout"
 
         //1. login to network share, connect with Google Drive, etc.
-        std::shared_future<void> ftAuth = runAsync([afsDevice /*clang bug*/= afsDevice, allowUserInteraction] { AFS::authenticateAccess(afsDevice, allowUserInteraction); /*throw FileError*/ });
+        std::shared_future<void> ftAuth = runAsync([afsDevice /*clang bug*/= afsDevice, allowUserInteraction]
+        { AFS::authenticateAccess(afsDevice, allowUserInteraction); /*throw FileError*/ });
 
         for (const AbstractPath& folderPath : deviceFolderPaths)
         {
diff --git a/FreeFileSync/Source/base/dir_lock.cpp b/FreeFileSync/Source/base/dir_lock.cpp
index de392fe9..f70cf513 100644
--- a/FreeFileSync/Source/base/dir_lock.cpp
+++ b/FreeFileSync/Source/base/dir_lock.cpp
@@ -96,12 +96,13 @@ private:
     {
         try
         {
+#if 1
             const int fdLockFile = ::open(lockFilePath_.c_str(), O_WRONLY | O_APPEND | O_CLOEXEC);
             if (fdLockFile == -1)
                 THROW_LAST_SYS_ERROR("open");
             ZEN_ON_SCOPE_EXIT(::close(fdLockFile));
 
-#if 0//alternative using lseek => no apparent benefit https://freefilesync.org/forum/viewtopic.php?t=7553#p25505
+#else //alternative using lseek => no apparent benefit https://freefilesync.org/forum/viewtopic.php?t=7553#p25505
             const int fdLockFile = ::open(lockFilePath_.c_str(), O_WRONLY | O_CLOEXEC);
             if (fdLockFile == -1)
                 THROW_LAST_SYS_ERROR("open");
@@ -302,7 +303,7 @@ ProcessStatus getProcessStatus(const LockInformation& lockInfo) //throw FileErro
 DEFINE_NEW_FILE_ERROR(ErrorFileNotExisting)
 uint64_t getLockFileSize(const Zstring& filePath) //throw FileError, ErrorFileNotExisting
 {
-    struct ::stat fileInfo = {};
+    struct stat fileInfo = {};
     if (::stat(filePath.c_str(), &fileInfo) == 0)
         return fileInfo.st_size;
 
@@ -316,7 +317,7 @@ void waitOnDirLock(const Zstring& lockFilePath, const DirLockCallback& notifySta
 {
     std::wstring infoMsg = _("Waiting while directory is in use:") + L' ' + fmtPath(lockFilePath);
 
-    if (notifyStatus) notifyStatus(infoMsg); //throw X
+    if (notifyStatus) notifyStatus(std::wstring(infoMsg)); //throw X
 
     //convenience optimization only: if we know the owning process crashed, we needn't wait DETECT_ABANDONED_INTERVAL sec
     bool lockOwnderDead = false;
@@ -399,7 +400,7 @@ void waitOnDirLock(const Zstring& lockFilePath, const DirLockCallback& notifySta
                     notifyStatus(infoMsg + L" | " + _("Detecting abandoned lock...") + L' ' + _P("1 sec", "%x sec", remainingSeconds)); //throw X
                 }
                 else
-                    notifyStatus(infoMsg); //throw X; emit a message in any case (might clear other one)
+                    notifyStatus(std::wstring(infoMsg)); //throw X; emit a message in any case (might clear other one)
             }
             std::this_thread::sleep_for(cbInterval);
         }
@@ -419,10 +420,17 @@ void releaseLock(const Zstring& lockFilePath) //noexcept
 
 bool tryLock(const Zstring& lockFilePath) //throw FileError
 {
+    //important: we want the lock file to have exactly the permissions specified
+    //=> yes, disabling umask() is messy (per-process!), but fchmod() may not be supported: https://freefilesync.org/forum/viewtopic.php?t=8096
+    const mode_t oldMask = ::umask(0); //always succeeds
+    ZEN_ON_SCOPE_EXIT(::umask(oldMask));
+
     const mode_t lockFileMode = S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH; //0666
 
     //O_EXCL contains a race condition on NFS file systems: https://linux.die.net/man/2/open
-    const int hFile = ::open(lockFilePath.c_str(), O_CREAT | O_EXCL | O_WRONLY | O_CLOEXEC, lockFileMode);
+    const int hFile = ::open(lockFilePath.c_str(),                    //const char* pathname
+                             O_CREAT | O_EXCL | O_WRONLY | O_CLOEXEC, //int flags
+                             lockFileMode);                           //mode_t mode
     if (hFile == -1)
     {
         if (errno == EEXIST)
@@ -432,10 +440,6 @@ bool tryLock(const Zstring& lockFilePath) //throw FileError
     }
     FileOutput fileOut(hFile, lockFilePath, nullptr /*notifyUnbufferedIO*/); //pass handle ownership
 
-    //consider umask! we want the lock file to have exactly the permissions specified
-    if (::fchmod(hFile, lockFileMode) != 0)
-        THROW_LAST_FILE_ERROR(replaceCpy(_("Cannot write permissions of %x."), L"%x", fmtPath(lockFilePath)), "fchmod");
-
     //write housekeeping info: user, process info, lock GUID
     const std::string byteStream = serialize(getLockInfoFromCurrentProcess()); //throw FileError
 
diff --git a/FreeFileSync/Source/base/dir_lock.h b/FreeFileSync/Source/base/dir_lock.h
index 269dc7d1..87b3a7e6 100644
--- a/FreeFileSync/Source/base/dir_lock.h
+++ b/FreeFileSync/Source/base/dir_lock.h
@@ -25,7 +25,7 @@ namespace fff
     - NOT thread-safe! (1. global LockAdmin 2. locks for directory aliases should be created sequentially to detect duplicate locks!)         */
 
 //while waiting for the lock
-using DirLockCallback = std::function<void(const std::wstring& msg)>; //throw X
+using DirLockCallback = std::function<void(std::wstring&& msg)>; //throw X
 
 class DirLock
 {
diff --git a/FreeFileSync/Source/base/file_hierarchy.cpp b/FreeFileSync/Source/base/file_hierarchy.cpp
index 6e184b97..0aa176cb 100644
--- a/FreeFileSync/Source/base/file_hierarchy.cpp
+++ b/FreeFileSync/Source/base/file_hierarchy.cpp
@@ -186,13 +186,13 @@ bool hasDirectChild(const ContainerObject& hierObj, Predicate p)
 
 SyncOperation FileSystemObject::testSyncOperation(SyncDirection testSyncDir) const //semantics: "what if"! assumes "active, no conflict, no recursion (directory)!
 {
-    return getIsolatedSyncOperation(!isEmpty<LEFT_SIDE>(), !isEmpty<RIGHT_SIDE>(), getCategory(), true, testSyncDir, false);
+    return getIsolatedSyncOperation(!isEmpty<SelectSide::left>(), !isEmpty<SelectSide::right>(), getCategory(), true, testSyncDir, false);
 }
 
 
 SyncOperation FileSystemObject::getSyncOperation() const
 {
-    return getIsolatedSyncOperation(!isEmpty<LEFT_SIDE>(), !isEmpty<RIGHT_SIDE>(), getCategory(), selectedForSync_, getSyncDir(), !syncDirectionConflict_.empty());
+    return getIsolatedSyncOperation(!isEmpty<SelectSide::left>(), !isEmpty<SelectSide::right>(), getCategory(), selectedForSync_, getSyncDir(), !syncDirectionConflict_.empty());
     //do *not* make a virtual call to testSyncOperation()! See FilePair::testSyncOperation()! <- better not implement one in terms of the other!!!
 }
 
@@ -228,7 +228,7 @@ SyncOperation FolderPair::getSyncOperation() const
             case SO_DELETE_RIGHT:
             case SO_DO_NOTHING:
             case SO_UNRESOLVED_CONFLICT:
-                if (isEmpty<LEFT_SIDE>())
+                if (isEmpty<SelectSide::left>())
                 {
                     //1. if at least one child-element is to be created, make sure parent folder is created also
                     //note: this automatically fulfills "create parent folders even if excluded"
@@ -253,7 +253,7 @@ SyncOperation FolderPair::getSyncOperation() const
                     }))
                     syncOpBuffered_ = SO_DO_NOTHING;
                 }
-                else if (isEmpty<RIGHT_SIDE>())
+                else if (isEmpty<SelectSide::right>())
                 {
                     if (hasDirectChild(*this,
                                        [](const FileSystemObject& fsObj)
@@ -285,10 +285,8 @@ SyncOperation FolderPair::getSyncOperation() const
 inline //called by private only!
 SyncOperation FilePair::applyMoveOptimization(SyncOperation op) const
 {
-    /*
-        check whether we can optimize "create + delete" via "move":
-        note: as long as we consider "create + delete" cases only, detection of renamed files, should be fine even for "binary" comparison variant!
-    */
+    /* check whether we can optimize "create + delete" via "move":
+       note: as long as we consider "create + delete" cases only, detection of renamed files, should be fine even for "binary" comparison variant!       */
     if (moveFileRef_)
         if (auto refFile = dynamic_cast<const FilePair*>(FileSystemObject::retrieve(moveFileRef_))) //we expect a "FilePair", but only need a "FileSystemObject" here
             if (refFile->moveFileRef_ == getId()) //both ends should agree...
@@ -379,14 +377,14 @@ std::wstring fff::getCategoryDescription(const FileSystemObject& fsObj)
             [&](const FilePair& file)
             {
                 descr += std::wstring(L"\n") +
-                         arrowLeft  + L' ' + formatUtcToLocalTime(file.getLastWriteTime< LEFT_SIDE>()) + L'\n' +
-                         arrowRight + L' ' + formatUtcToLocalTime(file.getLastWriteTime<RIGHT_SIDE>());
+                         arrowLeft  + L' ' + formatUtcToLocalTime(file.getLastWriteTime< SelectSide::left>()) + L'\n' +
+                         arrowRight + L' ' + formatUtcToLocalTime(file.getLastWriteTime<SelectSide::right>());
             },
             [&](const SymlinkPair& symlink)
             {
                 descr += std::wstring(L"\n") +
-                         arrowLeft  + L' ' + formatUtcToLocalTime(symlink.getLastWriteTime< LEFT_SIDE>()) + L'\n' +
-                         arrowRight + L' ' + formatUtcToLocalTime(symlink.getLastWriteTime<RIGHT_SIDE>());
+                         arrowLeft  + L' ' + formatUtcToLocalTime(symlink.getLastWriteTime< SelectSide::left>()) + L'\n' +
+                         arrowRight + L' ' + formatUtcToLocalTime(symlink.getLastWriteTime<SelectSide::right>());
             });
             return descr + footer;
         }
@@ -459,8 +457,8 @@ std::wstring fff::getSyncOpDescription(const FileSystemObject& fsObj)
         case SO_COPY_METADATA_TO_RIGHT:
             //harmonize with synchronization.cpp::FolderPairSyncer::synchronizeFileInt, ect!!
         {
-            Zstring itemNameOld = fsObj.getItemName<RIGHT_SIDE>();
-            Zstring itemNameNew = fsObj.getItemName< LEFT_SIDE>();
+            Zstring itemNameOld = fsObj.getItemName<SelectSide::right>();
+            Zstring itemNameNew = fsObj.getItemName< SelectSide::left>();
             if (op == SO_COPY_METADATA_TO_LEFT)
                 std::swap(itemNameOld, itemNameNew);
 
@@ -486,7 +484,7 @@ std::wstring fff::getSyncOpDescription(const FileSystemObject& fsObj)
                     if (!isMoveSource)
                         std::swap(fileFrom, fileTo);
 
-                    auto getRelName = [&](const FileSystemObject& fso, bool leftSide) { return leftSide ? fso.getRelativePath<LEFT_SIDE>() : fso.getRelativePath<RIGHT_SIDE>(); };
+                    auto getRelName = [&](const FileSystemObject& fso, bool leftSide) { return leftSide ? fso.getRelativePath<SelectSide::left>() : fso.getRelativePath<SelectSide::right>(); };
 
                     const Zstring relPathFrom = getRelName(*fileFrom, onLeft);
                     const Zstring relPathTo   = getRelName(*fileTo,   onLeft);
@@ -511,6 +509,3 @@ std::wstring fff::getSyncOpDescription(const FileSystemObject& fsObj)
     assert(false);
     return std::wstring();
 }
-
-
-warn_static(" FileSystemObject::isEmpty => rename: exists()!?")
diff --git a/FreeFileSync/Source/base/file_hierarchy.h b/FreeFileSync/Source/base/file_hierarchy.h
index 52000203..45c672f6 100644
--- a/FreeFileSync/Source/base/file_hierarchy.h
+++ b/FreeFileSync/Source/base/file_hierarchy.h
@@ -15,7 +15,6 @@
 #include <unordered_set>
 #include <zen/zstring.h>
 #include <zen/stl_tools.h>
-#include <zen/file_id_def.h>
 #include "structures.h"
 #include "path_filter.h"
 #include "../afs/abstract.h"
@@ -28,19 +27,19 @@ struct FileAttributes
     FileAttributes() {}
     FileAttributes(time_t modTimeIn,
                    uint64_t fileSizeIn,
-                   const AFS::FileId& idIn,
-                   bool isSymlink) :
+                   AFS::FingerPrint filePrintIn,
+                   bool followedSymlink) :
         modTime(modTimeIn),
         fileSize(fileSizeIn),
-        fileId(idIn),
-        isFollowedSymlink(isSymlink)
+        filePrint(filePrintIn),
+        isFollowedSymlink(followedSymlink)
     {
         static_assert(std::is_signed_v<time_t>, "... and signed!");
     }
 
     time_t modTime = 0; //number of seconds since Jan. 1st 1970 UTC
     uint64_t fileSize = 0;
-    AFS::FileId fileId; //optional!
+    AFS::FingerPrint filePrint = 0; //optional
     bool isFollowedSymlink = false;
 
     std::strong_ordering operator<=>(const FileAttributes&) const = default;
@@ -66,34 +65,34 @@ struct FolderAttributes
 };
 
 
-enum SelectedSide
+enum class SelectSide
 {
-    LEFT_SIDE,
-    RIGHT_SIDE
+    left,
+    right
 };
 
-template <SelectedSide side>
+template <SelectSide side>
 struct OtherSide;
 
 template <>
-struct OtherSide<LEFT_SIDE> { static const SelectedSide value = RIGHT_SIDE; };
+struct OtherSide<SelectSide::left> { static const SelectSide value = SelectSide::right; };
 
 template <>
-struct OtherSide<RIGHT_SIDE> { static const SelectedSide value = LEFT_SIDE; };
+struct OtherSide<SelectSide::right> { static const SelectSide value = SelectSide::left; };
 
 
-template <SelectedSide side>
+template <SelectSide side>
 struct SelectParam;
 
 template <>
-struct SelectParam<LEFT_SIDE>
+struct SelectParam<SelectSide::left>
 {
     template <class T>
     static T& ref(T& left, T& right) { return left; }
 };
 
 template <>
-struct SelectParam<RIGHT_SIDE>
+struct SelectParam<SelectSide::right>
 {
     template <class T>
     static T& ref(T& left, T& right) { return right; }
@@ -173,8 +172,8 @@ struct PathInformation //diamond-shaped inheritence!
 {
     virtual ~PathInformation() {}
 
-    template <SelectedSide side> AbstractPath getAbstractPath() const;
-    template <SelectedSide side> Zstring      getRelativePath() const; //get path relative to base sync dir (without leading/trailing FILE_NAME_SEPARATOR)
+    template <SelectSide side> AbstractPath getAbstractPath() const;
+    template <SelectSide side> Zstring      getRelativePath() const; //get path relative to base sync dir (without leading/trailing FILE_NAME_SEPARATOR)
     Zstring getRelativePathAny() const { return getRelativePathL(); } //side doesn't matter
 
 private:
@@ -185,11 +184,11 @@ private:
     virtual Zstring getRelativePathR() const = 0; //
 };
 
-template <> inline AbstractPath PathInformation::getAbstractPath< LEFT_SIDE>() const { return getAbstractPathL(); }
-template <> inline AbstractPath PathInformation::getAbstractPath<RIGHT_SIDE>() const { return getAbstractPathR(); }
+template <> inline AbstractPath PathInformation::getAbstractPath< SelectSide::left>() const { return getAbstractPathL(); }
+template <> inline AbstractPath PathInformation::getAbstractPath<SelectSide::right>() const { return getAbstractPathR(); }
 
-template <> inline Zstring PathInformation::getRelativePath< LEFT_SIDE>() const { return getRelativePathL(); }
-template <> inline Zstring PathInformation::getRelativePath<RIGHT_SIDE>() const { return getRelativePathR(); }
+template <> inline Zstring PathInformation::getRelativePath< SelectSide::left>() const { return getRelativePathL(); }
+template <> inline Zstring PathInformation::getRelativePath<SelectSide::right>() const { return getRelativePathR(); }
 
 //------------------------------------------------------------------
 
@@ -209,7 +208,7 @@ public:
                              const Zstring&          itemNameR,
                              const FolderAttributes& right);
 
-    template <SelectedSide side>
+    template <SelectSide side>
     FolderPair& addSubFolder(const Zstring& itemName, //dir exists on one side only
                              const FolderAttributes& attr);
 
@@ -219,7 +218,7 @@ public:
                          const Zstring&        itemNameR,
                          const FileAttributes& right);
 
-    template <SelectedSide side>
+    template <SelectSide side>
     FilePair& addSubFile(const Zstring&        itemName, //file exists on one side only
                          const FileAttributes& attr);
 
@@ -229,7 +228,7 @@ public:
                             const Zstring&        itemNameR,
                             const LinkAttributes& right);
 
-    template <SelectedSide side>
+    template <SelectSide side>
     SymlinkPair& addSubLink(const Zstring&        itemName, //link exists on one side only
                             const LinkAttributes& attr);
 
@@ -256,7 +255,7 @@ protected:
 
     void removeEmptyRec();
 
-    template <SelectedSide side>
+    template <SelectSide side>
     void updateRelPathsRecursion(const FileSystemObject& fsAlias);
 
 private:
@@ -300,8 +299,8 @@ public:
 
     static void removeEmpty(BaseFolderPair& baseFolder) { baseFolder.removeEmptyRec(); } //physically remove all invalid entries (where both sides are empty) recursively
 
-    template <SelectedSide side> bool isAvailable() const; //base folder status at the time of comparison!
-    template <SelectedSide side> void setAvailable(bool value); //update after creating the directory in FFS
+    template <SelectSide side> bool isAvailable() const; //base folder status at the time of comparison!
+    template <SelectSide side> void setAvailable(bool value); //update after creating the directory in FFS
 
     //get settings which were used while creating BaseFolderPair
     const PathFilter&   getFilter() const { return filter_.ref(); }
@@ -400,7 +399,6 @@ private:
     ObjectMgr           (const ObjectMgr& rhs) = delete;
     ObjectMgr& operator=(const ObjectMgr& rhs) = delete; //it's not well-defined what copying an objects means regarding object-identity in this context
 
-
     //our global ObjectMgr is not thread-safe (and currently does not need to be!)
     //assert(runningOnMainThread()); -> still, may be accessed by synchronization worker threads, one thread at a time
     static inline std::unordered_set<const ObjectMgr*> activeObjects_; //external linkage!
@@ -414,11 +412,11 @@ public:
     virtual void accept(FSObjectVisitor& visitor) const = 0;
 
     bool isPairEmpty() const; //true, if both sides are empty
-    template <SelectedSide side> bool isEmpty() const;
+    template <SelectSide side> bool isEmpty() const;
 
     //path getters always return valid values, even if isEmpty<side>()!
     Zstring getItemNameAny() const; //like getItemName() but without bias to which side is returned
-    template <SelectedSide side> Zstring getItemName() const; //case sensitive!
+    template <SelectSide side> Zstring getItemName() const; //case sensitive!
 
     //comparison result
     CompareFileResult getCategory() const { return cmpResult_; }
@@ -437,7 +435,7 @@ public:
     virtual SyncOperation getSyncOperation() const;
     std::wstring getSyncOpConflict() const; //return conflict when determining sync direction or (still unresolved) conflict during categorization
 
-    template <SelectedSide side> void removeObject(); //removes file or directory (recursively!) without physically removing the element: used by manual deletion
+    template <SelectSide side> void removeObject(); //removes file or directory (recursively!) without physically removing the element: used by manual deletion
 
     const ContainerObject& parent() const { return parent_; }
     /**/  ContainerObject& parent()       { return parent_; }
@@ -475,13 +473,13 @@ private:
     FileSystemObject           (const FileSystemObject&) = delete;
     FileSystemObject& operator=(const FileSystemObject&) = delete;
 
-    AbstractPath getAbstractPathL() const override { return AFS::appendRelPath(base().getAbstractPath< LEFT_SIDE>(), getRelativePath< LEFT_SIDE>()); }
-    AbstractPath getAbstractPathR() const override { return AFS::appendRelPath(base().getAbstractPath<RIGHT_SIDE>(), getRelativePath<RIGHT_SIDE>()); }
+    AbstractPath getAbstractPathL() const override { return AFS::appendRelPath(base().getAbstractPath< SelectSide::left>(), getRelativePath< SelectSide::left>()); }
+    AbstractPath getAbstractPathR() const override { return AFS::appendRelPath(base().getAbstractPath<SelectSide::right>(), getRelativePath<SelectSide::right>()); }
 
     virtual void removeObjectL() = 0;
     virtual void removeObjectR() = 0;
 
-    template <SelectedSide side>
+    template <SelectSide side>
     void propagateChangedItemName(const Zstring& itemNameOld); //required after any itemName changes
 
     //categorization
@@ -525,11 +523,11 @@ public:
         attrL_(attrL),
         attrR_(attrR) {}
 
-    template <SelectedSide side> bool isFollowedSymlink() const;
+    template <SelectSide side> bool isFollowedSymlink() const;
 
     SyncOperation getSyncOperation() const override;
 
-    template <SelectedSide sideTrg>
+    template <SelectSide sideTrg>
     void setSyncedTo(const Zstring& itemName, bool isSymlinkTrg, bool isSymlinkSrc); //call after sync, sets DIR_EQUAL
 
 private:
@@ -564,11 +562,12 @@ public:
         attrL_(attrL),
         attrR_(attrR) {}
 
-    template <SelectedSide side> time_t      getLastWriteTime() const;
-    template <SelectedSide side> uint64_t         getFileSize() const;
-    template <SelectedSide side> AFS::FileId        getFileId() const;
-    template <SelectedSide side> bool       isFollowedSymlink() const;
-    template <SelectedSide side> FileAttributes getAttributes() const;
+    template <SelectSide side> time_t       getLastWriteTime() const;
+    template <SelectSide side> uint64_t          getFileSize() const;
+    template <SelectSide side> bool        isFollowedSymlink() const;
+    template <SelectSide side> FileAttributes  getAttributes() const;
+    template <SelectSide side> AFS::FingerPrint getFilePrint() const;
+    template <SelectSide side> void clearFilePrint();
 
     void setMoveRef(ObjectId refId) { moveFileRef_ = refId; } //reference to corresponding renamed file
     ObjectId getMoveRef() const { return moveFileRef_; } //may be nullptr
@@ -578,19 +577,19 @@ public:
     SyncOperation testSyncOperation(SyncDirection testSyncDir) const override; //semantics: "what if"! assumes "active, no conflict, no recursion (directory)!
     SyncOperation getSyncOperation() const override;
 
-    template <SelectedSide sideTrg>
+    template <SelectSide sideTrg>
     void setSyncedTo(const Zstring& itemName, //call after sync, sets FILE_EQUAL
                      uint64_t fileSize,
                      int64_t lastWriteTimeTrg,
                      int64_t lastWriteTimeSrc,
-                     const AFS::FileId& fileIdTrg,
-                     const AFS::FileId& fileIdSrc,
+                     AFS::FingerPrint filePrintTrg,
+                     AFS::FingerPrint filePrintSrc,
                      bool isSymlinkTrg,
                      bool isSymlinkSrc);
 
 private:
-    Zstring getRelativePathL() const override { return nativeAppendPaths(parent().getRelativePath< LEFT_SIDE>(), getItemName< LEFT_SIDE>()); }
-    Zstring getRelativePathR() const override { return nativeAppendPaths(parent().getRelativePath<RIGHT_SIDE>(), getItemName<RIGHT_SIDE>()); }
+    Zstring getRelativePathL() const override { return nativeAppendPaths(parent().getRelativePath< SelectSide::left>(), getItemName< SelectSide::left>()); }
+    Zstring getRelativePathR() const override { return nativeAppendPaths(parent().getRelativePath<SelectSide::right>(), getItemName<SelectSide::right>()); }
 
     SyncOperation applyMoveOptimization(SyncOperation op) const;
 
@@ -613,7 +612,7 @@ class SymlinkPair : public FileSystemObject //this class models a TRUE symbolic
 public:
     void accept(FSObjectVisitor& visitor) const override;
 
-    template <SelectedSide side> time_t getLastWriteTime() const; //write time of the link, NOT target!
+    template <SelectSide side> time_t getLastWriteTime() const; //write time of the link, NOT target!
 
     CompareSymlinkResult getLinkCategory()   const; //returns actually used subset of CompareFileResult
 
@@ -627,14 +626,14 @@ public:
         attrL_(attrL),
         attrR_(attrR) {}
 
-    template <SelectedSide sideTrg>
+    template <SelectSide sideTrg>
     void setSyncedTo(const Zstring& itemName, //call after sync, sets SYMLINK_EQUAL
                      int64_t lastWriteTimeTrg,
                      int64_t lastWriteTimeSrc);
 
 private:
-    Zstring getRelativePathL() const override { return nativeAppendPaths(parent().getRelativePath< LEFT_SIDE>(), getItemName< LEFT_SIDE>()); }
-    Zstring getRelativePathR() const override { return nativeAppendPaths(parent().getRelativePath<RIGHT_SIDE>(), getItemName<RIGHT_SIDE>()); }
+    Zstring getRelativePathL() const override { return nativeAppendPaths(parent().getRelativePath< SelectSide::left>(), getItemName< SelectSide::left>()); }
+    Zstring getRelativePathR() const override { return nativeAppendPaths(parent().getRelativePath<SelectSide::right>(), getItemName<SelectSide::right>()); }
 
     void flip()          override;
     void removeObjectL() override { attrL_ = LinkAttributes(); }
@@ -765,7 +764,7 @@ void FileSystemObject::setActive(bool active)
 }
 
 
-template <SelectedSide side> inline
+template <SelectSide side> inline
 bool FileSystemObject::isEmpty() const
 {
     return SelectParam<side>::ref(itemNameL_, itemNameR_).empty();
@@ -775,11 +774,11 @@ bool FileSystemObject::isEmpty() const
 inline
 bool FileSystemObject::isPairEmpty() const
 {
-    return isEmpty<LEFT_SIDE>() && isEmpty<RIGHT_SIDE>();
+    return isEmpty<SelectSide::left>() && isEmpty<SelectSide::right>();
 }
 
 
-template <SelectedSide side> inline
+template <SelectSide side> inline
 Zstring FileSystemObject::getItemName() const
 {
     //assert(!itemNameL_.empty() || !itemNameR_.empty()); -> file pair might be empty (until removed after sync)
@@ -794,51 +793,51 @@ Zstring FileSystemObject::getItemName() const
 inline
 Zstring FileSystemObject::getItemNameAny() const
 {
-    return getItemName<LEFT_SIDE>(); //side doesn't matter
+    return getItemName<SelectSide::left>(); //side doesn't matter
 }
 
 
 template <> inline
-void FileSystemObject::removeObject<LEFT_SIDE>()
+void FileSystemObject::removeObject<SelectSide::left>()
 {
-    const Zstring itemNameOld = getItemName<LEFT_SIDE>();
+    const Zstring itemNameOld = getItemName<SelectSide::left>();
 
-    cmpResult_ = isEmpty<RIGHT_SIDE>() ? FILE_EQUAL : FILE_RIGHT_SIDE_ONLY;
+    cmpResult_ = isEmpty<SelectSide::right>() ? FILE_EQUAL : FILE_RIGHT_SIDE_ONLY;
     itemNameL_.clear();
     removeObjectL();
 
     setSyncDir(SyncDirection::none); //calls notifySyncCfgChanged()
-    propagateChangedItemName<LEFT_SIDE>(itemNameOld);
+    propagateChangedItemName<SelectSide::left>(itemNameOld);
 }
 
 
 template <> inline
-void FileSystemObject::removeObject<RIGHT_SIDE>()
+void FileSystemObject::removeObject<SelectSide::right>()
 {
-    const Zstring itemNameOld = getItemName<RIGHT_SIDE>();
+    const Zstring itemNameOld = getItemName<SelectSide::right>();
 
-    cmpResult_ = isEmpty<LEFT_SIDE>() ? FILE_EQUAL : FILE_LEFT_SIDE_ONLY;
+    cmpResult_ = isEmpty<SelectSide::left>() ? FILE_EQUAL : FILE_LEFT_SIDE_ONLY;
     itemNameR_.clear();
     removeObjectR();
 
     setSyncDir(SyncDirection::none); //calls notifySyncCfgChanged()
-    propagateChangedItemName<RIGHT_SIDE>(itemNameOld);
+    propagateChangedItemName<SelectSide::right>(itemNameOld);
 }
 
 
 inline
 void FileSystemObject::setSynced(const Zstring& itemName)
 {
-    const Zstring itemNameOldL = getItemName<LEFT_SIDE>();
-    const Zstring itemNameOldR = getItemName<RIGHT_SIDE>();
+    const Zstring itemNameOldL = getItemName<SelectSide::left>();
+    const Zstring itemNameOldR = getItemName<SelectSide::right>();
 
     assert(!isPairEmpty());
     itemNameR_ = itemNameL_ = itemName;
     cmpResult_ = FILE_EQUAL;
     setSyncDir(SyncDirection::none);
 
-    propagateChangedItemName< LEFT_SIDE>(itemNameOldL);
-    propagateChangedItemName<RIGHT_SIDE>(itemNameOldR);
+    propagateChangedItemName< SelectSide::left>(itemNameOldL);
+    propagateChangedItemName<SelectSide::right>(itemNameOldR);
 }
 
 
@@ -898,7 +897,7 @@ void FileSystemObject::flip()
 }
 
 
-template <SelectedSide side> inline
+template <SelectSide side> inline
 void FileSystemObject::propagateChangedItemName(const Zstring& itemNameOld)
 {
     if (itemNameL_.empty() && itemNameR_.empty()) return; //both sides might just have been deleted by removeObject<>
@@ -909,7 +908,7 @@ void FileSystemObject::propagateChangedItemName(const Zstring& itemNameOld)
 }
 
 
-template <SelectedSide side> inline
+template <SelectSide side> inline
 void ContainerObject::updateRelPathsRecursion(const FileSystemObject& fsAlias)
 {
     assert(SelectParam<side>::ref(relPathL_, relPathR_) != //perf: only call if actual item name changed!
@@ -924,14 +923,14 @@ void ContainerObject::updateRelPathsRecursion(const FileSystemObject& fsAlias)
 
 inline
 ContainerObject::ContainerObject(const FileSystemObject& fsAlias) :
-    relPathL_(nativeAppendPaths(fsAlias.parent().relPathL_, fsAlias.getItemName<LEFT_SIDE>())),
+    relPathL_(nativeAppendPaths(fsAlias.parent().relPathL_, fsAlias.getItemName<SelectSide::left>())),
     relPathR_(
         fsAlias.parent().relPathL_.c_str() ==        //
         fsAlias.parent().relPathR_.c_str() &&        //take advantage of FileSystemObject's Zstring reuse:
-        fsAlias.getItemName< LEFT_SIDE>().c_str() == //=> perf: 12% faster merge phase; -4% peak memory
-        fsAlias.getItemName<RIGHT_SIDE>().c_str() ?  //
+        fsAlias.getItemName< SelectSide::left>().c_str() == //=> perf: 12% faster merge phase; -4% peak memory
+        fsAlias.getItemName<SelectSide::right>().c_str() ?  //
         relPathL_ : //ternary-WTF! (implicit copy-constructor call!!) => no big deal for a Zstring
-        nativeAppendPaths(fsAlias.parent().relPathR_, fsAlias.getItemName<RIGHT_SIDE>())),
+        nativeAppendPaths(fsAlias.parent().relPathR_, fsAlias.getItemName<SelectSide::right>())),
     base_(fsAlias.parent().base_)
 {
     assert(relPathL_.c_str() == relPathR_.c_str() || relPathL_ != relPathR_);
@@ -965,7 +964,7 @@ FolderPair& ContainerObject::addSubFolder(const Zstring& itemNameL,
 
 
 template <> inline
-FolderPair& ContainerObject::addSubFolder<LEFT_SIDE>(const Zstring& itemName, const FolderAttributes& attr)
+FolderPair& ContainerObject::addSubFolder<SelectSide::left>(const Zstring& itemName, const FolderAttributes& attr)
 {
     subFolders_.emplace_back(itemName, attr, DIR_LEFT_SIDE_ONLY, Zstring(), FolderAttributes(), *this);
     return subFolders_.back();
@@ -973,7 +972,7 @@ FolderPair& ContainerObject::addSubFolder<LEFT_SIDE>(const Zstring& itemName, co
 
 
 template <> inline
-FolderPair& ContainerObject::addSubFolder<RIGHT_SIDE>(const Zstring& itemName, const FolderAttributes& attr)
+FolderPair& ContainerObject::addSubFolder<SelectSide::right>(const Zstring& itemName, const FolderAttributes& attr)
 {
     subFolders_.emplace_back(Zstring(), FolderAttributes(), DIR_RIGHT_SIDE_ONLY, itemName, attr, *this);
     return subFolders_.back();
@@ -993,7 +992,7 @@ FilePair& ContainerObject::addSubFile(const Zstring&        itemNameL,
 
 
 template <> inline
-FilePair& ContainerObject::addSubFile<LEFT_SIDE>(const Zstring& itemName, const FileAttributes& attr)
+FilePair& ContainerObject::addSubFile<SelectSide::left>(const Zstring& itemName, const FileAttributes& attr)
 {
     subFiles_.emplace_back(itemName, attr, FILE_LEFT_SIDE_ONLY, Zstring(), FileAttributes(), *this);
     return subFiles_.back();
@@ -1001,7 +1000,7 @@ FilePair& ContainerObject::addSubFile<LEFT_SIDE>(const Zstring& itemName, const
 
 
 template <> inline
-FilePair& ContainerObject::addSubFile<RIGHT_SIDE>(const Zstring& itemName, const FileAttributes& attr)
+FilePair& ContainerObject::addSubFile<SelectSide::right>(const Zstring& itemName, const FileAttributes& attr)
 {
     subFiles_.emplace_back(Zstring(), FileAttributes(), FILE_RIGHT_SIDE_ONLY, itemName, attr, *this);
     return subFiles_.back();
@@ -1021,7 +1020,7 @@ SymlinkPair& ContainerObject::addSubLink(const Zstring&        itemNameL,
 
 
 template <> inline
-SymlinkPair& ContainerObject::addSubLink<LEFT_SIDE>(const Zstring& itemName, const LinkAttributes& attr)
+SymlinkPair& ContainerObject::addSubLink<SelectSide::left>(const Zstring& itemName, const LinkAttributes& attr)
 {
     subLinks_.emplace_back(itemName, attr, SYMLINK_LEFT_SIDE_ONLY, Zstring(), LinkAttributes(), *this);
     return subLinks_.back();
@@ -1029,7 +1028,7 @@ SymlinkPair& ContainerObject::addSubLink<LEFT_SIDE>(const Zstring& itemName, con
 
 
 template <> inline
-SymlinkPair& ContainerObject::addSubLink<RIGHT_SIDE>(const Zstring& itemName, const LinkAttributes& attr)
+SymlinkPair& ContainerObject::addSubLink<SelectSide::right>(const Zstring& itemName, const LinkAttributes& attr)
 {
     subLinks_.emplace_back(Zstring(), LinkAttributes(), SYMLINK_RIGHT_SIDE_ONLY, itemName, attr, *this);
     return subLinks_.back();
@@ -1058,11 +1057,11 @@ inline
 void FolderPair::removeObjectL()
 {
     for (FilePair& file : refSubFiles())
-        file.removeObject<LEFT_SIDE>();
+        file.removeObject<SelectSide::left>();
     for (SymlinkPair& link : refSubLinks())
-        link.removeObject<LEFT_SIDE>();
+        link.removeObject<SelectSide::left>();
     for (FolderPair& folder : refSubFolders())
-        folder.removeObject<LEFT_SIDE>();
+        folder.removeObject<SelectSide::left>();
 
     attrL_ = FolderAttributes();
 }
@@ -1072,24 +1071,24 @@ inline
 void FolderPair::removeObjectR()
 {
     for (FilePair& file : refSubFiles())
-        file.removeObject<RIGHT_SIDE>();
+        file.removeObject<SelectSide::right>();
     for (SymlinkPair& link : refSubLinks())
-        link.removeObject<RIGHT_SIDE>();
+        link.removeObject<SelectSide::right>();
     for (FolderPair& folder : refSubFolders())
-        folder.removeObject<RIGHT_SIDE>();
+        folder.removeObject<SelectSide::right>();
 
     attrR_ = FolderAttributes();
 }
 
 
-template <SelectedSide side> inline
+template <SelectSide side> inline
 bool BaseFolderPair::isAvailable() const
 {
     return SelectParam<side>::ref(folderAvailableLeft_, folderAvailableRight_);
 }
 
 
-template <SelectedSide side> inline
+template <SelectSide side> inline
 void BaseFolderPair::setAvailable(bool value)
 {
     SelectParam<side>::ref(folderAvailableLeft_, folderAvailableRight_) = value;
@@ -1104,75 +1103,82 @@ void FilePair::flip()
 }
 
 
-template <SelectedSide side> inline
+template <SelectSide side> inline
 FileAttributes FilePair::getAttributes() const
 {
     return SelectParam<side>::ref(attrL_, attrR_);
 }
 
 
-template <SelectedSide side> inline
+template <SelectSide side> inline
 time_t FilePair::getLastWriteTime() const
 {
     return SelectParam<side>::ref(attrL_, attrR_).modTime;
 }
 
 
-template <SelectedSide side> inline
+template <SelectSide side> inline
 uint64_t FilePair::getFileSize() const
 {
     return SelectParam<side>::ref(attrL_, attrR_).fileSize;
 }
 
 
-template <SelectedSide side> inline
-AFS::FileId FilePair::getFileId() const
+template <SelectSide side> inline
+bool FilePair::isFollowedSymlink() const
 {
-    return SelectParam<side>::ref(attrL_, attrR_).fileId;
+    return SelectParam<side>::ref(attrL_, attrR_).isFollowedSymlink;
 }
 
 
-template <SelectedSide side> inline
-bool FilePair::isFollowedSymlink() const
+template <SelectSide side> inline
+bool FolderPair::isFollowedSymlink() const
 {
     return SelectParam<side>::ref(attrL_, attrR_).isFollowedSymlink;
 }
 
 
-template <SelectedSide side> inline
-bool FolderPair::isFollowedSymlink() const
+template <SelectSide side> inline
+AFS::FingerPrint FilePair::getFilePrint() const
 {
-    return SelectParam<side>::ref(attrL_, attrR_).isFollowedSymlink;
+    return SelectParam<side>::ref(attrL_, attrR_).filePrint;
+}
+
+
+template <SelectSide side> inline
+void FilePair::clearFilePrint()
+{
+    SelectParam<side>::ref(attrL_, attrR_).filePrint = 0;
 }
 
 
-template <SelectedSide sideTrg> inline
+template <SelectSide sideTrg> inline
 void FilePair::setSyncedTo(const Zstring& itemName,
                            uint64_t fileSize,
                            int64_t lastWriteTimeTrg,
                            int64_t lastWriteTimeSrc,
-                           const AFS::FileId& fileIdTrg,
-                           const AFS::FileId& fileIdSrc,
+                           AFS::FingerPrint filePrintTrg,
+                           AFS::FingerPrint filePrintSrc,
                            bool isSymlinkTrg,
                            bool isSymlinkSrc)
 {
     //FILE_EQUAL is only allowed for same short name and file size: enforced by this method!
-    constexpr SelectedSide sideSrc = OtherSide<sideTrg>::value;
+    constexpr SelectSide sideSrc = OtherSide<sideTrg>::value;
 
-    SelectParam<sideTrg>::ref(attrL_, attrR_) = FileAttributes(lastWriteTimeTrg, fileSize, fileIdTrg, isSymlinkTrg);
-    SelectParam<sideSrc>::ref(attrL_, attrR_) = FileAttributes(lastWriteTimeSrc, fileSize, fileIdSrc, isSymlinkSrc);
+    SelectParam<sideTrg>::ref(attrL_, attrR_) = FileAttributes(lastWriteTimeTrg, fileSize, filePrintTrg, isSymlinkTrg);
+    SelectParam<sideSrc>::ref(attrL_, attrR_) = FileAttributes(lastWriteTimeSrc, fileSize, filePrintSrc, isSymlinkSrc);
 
     moveFileRef_ = nullptr;
     FileSystemObject::setSynced(itemName); //set FileSystemObject specific part
 }
 
 
-template <SelectedSide sideTrg> inline
+template <SelectSide sideTrg> inline
 void SymlinkPair::setSyncedTo(const Zstring& itemName,
                               int64_t lastWriteTimeTrg,
                               int64_t lastWriteTimeSrc)
 {
-    constexpr SelectedSide sideSrc = OtherSide<sideTrg>::value;
+    constexpr SelectSide sideSrc = OtherSide<sideTrg>::value;
 
     SelectParam<sideTrg>::ref(attrL_, attrR_) = LinkAttributes(lastWriteTimeTrg);
     SelectParam<sideSrc>::ref(attrL_, attrR_) = LinkAttributes(lastWriteTimeSrc);
@@ -1181,12 +1187,12 @@ void SymlinkPair::setSyncedTo(const Zstring& itemName,
 }
 
 
-template <SelectedSide sideTrg> inline
+template <SelectSide sideTrg> inline
 void FolderPair::setSyncedTo(const Zstring& itemName,
                              bool isSymlinkTrg,
                              bool isSymlinkSrc)
 {
-    constexpr SelectedSide sideSrc = OtherSide<sideTrg>::value;
+    constexpr SelectSide sideSrc = OtherSide<sideTrg>::value;
 
     SelectParam<sideTrg>::ref(attrL_, attrR_) = FolderAttributes(isSymlinkTrg);
     SelectParam<sideSrc>::ref(attrL_, attrR_) = FolderAttributes(isSymlinkSrc);
@@ -1195,7 +1201,7 @@ void FolderPair::setSyncedTo(const Zstring& itemName,
 }
 
 
-template <SelectedSide side> inline
+template <SelectSide side> inline
 time_t SymlinkPair::getLastWriteTime() const
 {
     return SelectParam<side>::ref(attrL_, attrR_).modTime;
diff --git a/FreeFileSync/Source/base/icon_loader.cpp b/FreeFileSync/Source/base/icon_loader.cpp
index 684569ed..495793be 100644
--- a/FreeFileSync/Source/base/icon_loader.cpp
+++ b/FreeFileSync/Source/base/icon_loader.cpp
@@ -36,8 +36,7 @@ ImageHolder copyToImageHolder(const GdkPixbuf& pixBuf, int maxSize) //throw SysE
     if (channels != 3 && channels != 4)
         throw SysError(formatSystemError("gdk_pixbuf_get_n_channels", L"", L"Unexpected number of channels: " + numberTo<std::wstring>(channels)));
 
-    const bool withAlpha = channels == 4;
-    assert(::gdk_pixbuf_get_has_alpha(&pixBuf) == withAlpha);
+    assert(::gdk_pixbuf_get_has_alpha(&pixBuf) == (channels == 4));
 
     const unsigned char* srcBytes = ::gdk_pixbuf_read_pixels(&pixBuf);
     const int srcWidth  = ::gdk_pixbuf_get_width (&pixBuf);
@@ -54,10 +53,10 @@ ImageHolder copyToImageHolder(const GdkPixbuf& pixBuf, int maxSize) //throw SysE
         targetWidth  = numeric::intDivRound(targetWidth  * maxSize, maxExtent);
         targetHeight = numeric::intDivRound(targetHeight * maxSize, maxExtent);
 
-#if 0 //alternative to xbrz::bilinearScale()
-        GdkPixbuf* pixBufShrinked = ::gdk_pixbuf_scale_simple(pixBuf,               //const GdkPixbuf* src,
-                                                              targetWidth,          //int dest_width,
-                                                              targetHeight,         //int dest_height,
+#if 0 //alternative to xbrz::bilinearScaleSimple()? does it support alpha-channel?
+        GdkPixbuf* pixBufShrinked = ::gdk_pixbuf_scale_simple(pixBuf,               //const GdkPixbuf* src
+                                                              targetWidth,          //int dest_width
+                                                              targetHeight,         //int dest_height
                                                               GDK_INTERP_BILINEAR); //GdkInterpType interp_type
         if (!pixBufShrinked)
             throw SysError(formatSystemError("gdk_pixbuf_scale_simple", L"", L"Not enough memory."));
@@ -67,32 +66,38 @@ ImageHolder copyToImageHolder(const GdkPixbuf& pixBuf, int maxSize) //throw SysE
 
     const auto imgReader = [srcBytes, srcStride, channels](int x, int y, xbrz::BytePixel& pix)
     {
-        std::memcpy(pix, srcBytes + y * srcStride + channels * x, channels);
+        const unsigned char* const ptr = srcBytes + y * srcStride + channels * x;
+
+        const unsigned char a = channels == 4 ? ptr[3] : 255;
+        pix[0] = a;
+        pix[1] = xbrz::premultiply(ptr[0], a); //r
+        pix[2] = xbrz::premultiply(ptr[1], a); //g
+        pix[3] = xbrz::premultiply(ptr[2], a); //b
     };
 
-    ImageHolder imgOut(targetWidth, targetHeight, withAlpha);
+    ImageHolder imgOut(targetWidth, targetHeight, true /*withAlpha*/);
 
-    const auto imgWriter = [rgbPtr = imgOut.getRgb(), alphaPtr = imgOut.getAlpha()](const xbrz::BytePixel& pix) mutable
+    const auto imgWriter = [rgb = imgOut.getRgb(), alpha = imgOut.getAlpha()](const xbrz::BytePixel& pix) mutable
     {
-        *rgbPtr++ = pix[0]; //r
-        *rgbPtr++ = pix[1]; //g
-        *rgbPtr++ = pix[2]; //b
-        if (alphaPtr)
-            * alphaPtr++ = pix[3]; //a
+        const unsigned char a = pix[0];
+        *alpha++ = a;
+        *rgb++   = xbrz::demultiply(pix[1], a); //r
+        *rgb++   = xbrz::demultiply(pix[2], a); //g
+        *rgb++   = xbrz::demultiply(pix[3], a); //b
     };
 
     if (srcWidth  == targetWidth &&
         srcHeight == targetHeight)
         xbrz::unscaledCopy(imgReader, imgWriter, srcWidth, srcHeight); //perf: going overboard?
     else
-        xbrz::bilinearScale(imgReader,     //PixReader srcReader,
-                            srcWidth,      //int srcWidth,
-                            srcHeight,     //int srcHeight,
-                            imgWriter,     //PixWriter trgWriter
-                            targetWidth,   //int trgWidth,
-                            targetHeight,  //int trgHeight,
-                            0,             //int yFirst,
-                            targetHeight); //int yLast,
+        xbrz::bilinearScaleSimple(imgReader,     //PixReader srcReader
+                                  srcWidth,      //int srcWidth
+                                  srcHeight,     //int srcHeight
+                                  imgWriter,     //PixWriter trgWriter
+                                  targetWidth,   //int trgWidth
+                                  targetHeight,  //int trgHeight
+                                  0,             //int yFirst
+                                  targetHeight); //int yLast
     return imgOut;
 }
 
@@ -105,9 +110,9 @@ ImageHolder imageHolderFromGicon(GIcon& gicon, int maxSize) //throw SysError
     GtkIconTheme* const defaultTheme = ::gtk_icon_theme_get_default(); //not owned!
     ASSERT_SYSERROR(defaultTheme); //no more error details
 
-    GtkIconInfo* const iconInfo = ::gtk_icon_theme_lookup_by_gicon(defaultTheme,                 //GtkIconTheme* icon_theme,
-                                                                   &gicon,                       //GIcon* icon,
-                                                                   maxSize,                      //gint size,
+    GtkIconInfo* const iconInfo = ::gtk_icon_theme_lookup_by_gicon(defaultTheme,                 //GtkIconTheme* icon_theme
+                                                                   &gicon,                       //GIcon* icon
+                                                                   maxSize,                      //gint size
                                                                    GTK_ICON_LOOKUP_USE_BUILTIN); //GtkIconLookupFlags flags
     if (!iconInfo)
         throw SysError(formatSystemError("gtk_icon_theme_lookup_by_gicon", L"", L"Icon not available."));
@@ -135,9 +140,9 @@ ImageHolder imageHolderFromGicon(GIcon& gicon, int maxSize) //throw SysError
 FileIconHolder fff::getIconByTemplatePath(const Zstring& templatePath, int maxSize) //throw SysError
 {
     //uses full file name, e.g. "AUTHORS" has own mime type on Linux:
-    gchar* const contentType = ::g_content_type_guess(templatePath.c_str(), //const gchar* filename,
-                                                      nullptr,              //const guchar* data,
-                                                      0,                    //gsize data_size,
+    gchar* const contentType = ::g_content_type_guess(templatePath.c_str(), //const gchar* filename
+                                                      nullptr,              //const guchar* data
+                                                      0,                    //gsize data_size
                                                       nullptr);             //gboolean* result_uncertain
     if (!contentType)
         throw SysError(formatSystemError("g_content_type_guess(" + copyStringTo<std::string>(templatePath) + ')', L"", L"Unknown content type."));
@@ -218,7 +223,7 @@ FileIconHolder fff::getFileIcon(const Zstring& filePath, int maxSize) //throw Sy
 
 ImageHolder fff::getThumbnailImage(const Zstring& filePath, int maxSize) //throw SysError
 {
-    struct ::stat fileInfo = {};
+    struct stat fileInfo = {};
     if (::stat(filePath.c_str(), &fileInfo) != 0)
         THROW_LAST_SYS_ERROR("stat");
 
@@ -241,13 +246,18 @@ ImageHolder fff::getThumbnailImage(const Zstring& filePath, int maxSize) //throw
 wxImage fff::extractWxImage(ImageHolder&& ih)
 {
     assert(runningOnMainThread());
-
     if (!ih.getRgb())
         return wxNullImage;
 
     wxImage img(ih.getWidth(), ih.getHeight(), ih.releaseRgb(), false /*static_data*/); //pass ownership
     if (ih.getAlpha())
         img.SetAlpha(ih.releaseAlpha(), false /*static_data*/);
+    else
+    {
+        assert(false);
+        img.SetAlpha();
+        ::memset(img.GetAlpha(), wxIMAGE_ALPHA_OPAQUE, ih.getWidth() * ih.getHeight());
+    }
     return img;
 }
 
diff --git a/FreeFileSync/Source/base/icon_loader.h b/FreeFileSync/Source/base/icon_loader.h
index ae4b7b43..754cffbc 100644
--- a/FreeFileSync/Source/base/icon_loader.h
+++ b/FreeFileSync/Source/base/icon_loader.h
@@ -16,7 +16,7 @@ namespace fff
 {
 //=> all functions are safe to call from multiple threads!
 //COM needs to be initialized before calling any of these functions! CoInitializeEx/CoUninitialize
-//=> don't call from WM_PAINT handler! https://blogs.msdn.microsoft.com/yvesdolc/2009/08/06/do-you-receive-wm_paint-when-waiting-for-a-com-call-to-return/
+//=> don't call from WM_PAINT handler! https://docs.microsoft.com/en-us/archive/blogs/yvesdolc/do-you-receive-wm_paint-when-waiting-for-a-com-call-to-return
 
 zen::FileIconHolder getIconByTemplatePath(const Zstring& templatePath, int maxSize); //throw SysError
 zen::FileIconHolder genericFileIcon(int maxSize); //throw SysError
diff --git a/FreeFileSync/Source/base/lock_holder.h b/FreeFileSync/Source/base/lock_holder.h
index 87c075f9..68d8215e 100644
--- a/FreeFileSync/Source/base/lock_holder.h
+++ b/FreeFileSync/Source/base/lock_holder.h
@@ -31,7 +31,7 @@ public:
             {
                 //lock file creation is synchronous and may block noticeably for very slow devices (USB sticks, mapped cloud storage)
                 lockHolder_.emplace_back(appendSeparator(folderPath) + Zstr("sync") + LOCK_FILE_ENDING,
-                [&](const std::wstring& msg) { pcb.updateStatus(msg); /*throw X*/ },
+                [&](std::wstring&& msg) { pcb.updateStatus(std::move(msg)); /*throw X*/ },
                 UI_UPDATE_INTERVAL / 2); //throw FileError
             }
             catch (const FileError& e) { failedLocks.emplace_back(folderPath, e); }
diff --git a/FreeFileSync/Source/base/parallel_scan.cpp b/FreeFileSync/Source/base/parallel_scan.cpp
index 340bf0d8..d61ec28b 100644
--- a/FreeFileSync/Source/base/parallel_scan.cpp
+++ b/FreeFileSync/Source/base/parallel_scan.cpp
@@ -64,7 +64,7 @@ public:
         errorResponse_ = std::nullopt;
 
         dummy.unlock(); //optimization for condition_variable::notify_all()
-        conditionReadyForNewRequest_.notify_all(); //instead of notify_one(); workaround bug: https://svn.boost.org/trac/boost/ticket/7796
+        conditionReadyForNewRequest_.notify_all(); //instead of notify_one(); work around bug: https://svn.boost.org/trac/boost/ticket/7796
 
         return rv;
     }
@@ -89,14 +89,14 @@ public:
                     switch (onError({errorRequest_->msg, errorRequest_->failTime, errorRequest_->retryNumber})) //throw X
                     {
                         case PhaseCallback::ignore:
-                            errorResponse_ = AFS::TraverserCallback::ON_ERROR_CONTINUE;
+                            errorResponse_ = AFS::TraverserCallback::HandleError::ignore;
                             break;
 
                         case PhaseCallback::retry:
-                            errorResponse_ = AFS::TraverserCallback::ON_ERROR_RETRY;
+                            errorResponse_ = AFS::TraverserCallback::HandleError::retry;
                             break;
                     }
-                    conditionHaveResponse_.notify_all(); //instead of notify_one(); workaround bug: https://svn.boost.org/trac/boost/ticket/7796
+                    conditionHaveResponse_.notify_all(); //instead of notify_one(); work around bug: https://svn.boost.org/trac/boost/ticket/7796
                 }
                 if (threadsToFinish_ == 0)
                 {
@@ -303,7 +303,7 @@ void DirCallback::onFile(const AFS::FileInfo& fi) //throw ThreadStopRequest
 
         Linux: retrieveFileID takes about 50% longer in VM! (avoidable because of redundant stat() call!)       */
 
-    output_.addSubFile(fi.itemName, FileAttributes(fi.modTime, fi.fileSize, fi.fileId, fi.isFollowedSymlink ));
+    output_.addSubFile(fi.itemName, FileAttributes(fi.modTime, fi.fileSize, fi.filePrint, fi.isFollowedSymlink));
 
     cfg_.acb.incItemsScanned(); //add 1 element to the progress indicator
 }
@@ -332,16 +332,15 @@ std::shared_ptr<AFS::TraverserCallback> DirCallback::onFolder(const AFS::FolderI
         cfg_.acb.incItemsScanned(); //add 1 element to the progress indicator
 
     //------------------------------------------------------------------------------------
-    warn_static("FIX: this error cannot be retried!")
     if (level_ > FOLDER_TRAVERSAL_LEVEL_MAX) //Win32 traverser: stack overflow approximately at level 1000
         //check after FolderContainer::addSubFolder()
         for (size_t retryNumber = 0;; ++retryNumber)
             switch (reportItemError({replaceCpy(_("Cannot read directory %x."), L"%x", AFS::getDisplayPath(AFS::appendRelPath(cfg_.baseFolderPath, relPath))) +
                                      L"\n\n" L"Endless recursion.", std::chrono::steady_clock::now(), retryNumber}, fi.itemName)) //throw ThreadStopRequest
             {
-                case AFS::TraverserCallback::ON_ERROR_RETRY:
+                case AFS::TraverserCallback::HandleError::retry:
                     break;
-                case AFS::TraverserCallback::ON_ERROR_CONTINUE:
+                case AFS::TraverserCallback::HandleError::ignore:
                     return nullptr;
             }
 
@@ -362,7 +361,7 @@ DirCallback::HandleLink DirCallback::onSymlink(const AFS::SymlinkInfo& si) //thr
     switch (cfg_.handleSymlinks)
     {
         case SymLinkHandling::exclude:
-            return LINK_SKIP;
+            return HandleLink::skip;
 
         case SymLinkHandling::direct:
             if (cfg_.filter.ref().passFileFilter(relPath)) //always use file filter: Link type may not be "stable" on Linux!
@@ -370,7 +369,7 @@ DirCallback::HandleLink DirCallback::onSymlink(const AFS::SymlinkInfo& si) //thr
                 output_.addSubLink(si.itemName, LinkAttributes(si.modTime));
                 cfg_.acb.incItemsScanned(); //add 1 element to the progress indicator
             }
-            return LINK_SKIP;
+            return HandleLink::skip;
 
         case SymLinkHandling::follow:
             //filter symlinks before trying to follow them: handle user-excluded broken symlinks!
@@ -380,32 +379,32 @@ DirCallback::HandleLink DirCallback::onSymlink(const AFS::SymlinkInfo& si) //thr
                 bool childItemMightMatch = true;
                 if (!cfg_.filter.ref().passDirFilter(relPath, &childItemMightMatch))
                     if (!childItemMightMatch)
-                        return LINK_SKIP;
+                        return HandleLink::skip;
             }
-            return LINK_FOLLOW;
+            return HandleLink::follow;
     }
 
     assert(false);
-    return LINK_SKIP;
+    return HandleLink::skip;
 }
 
 
 DirCallback::HandleError DirCallback::reportError(const ErrorInfo& errorInfo, const Zstring& itemName /*optional*/) //throw ThreadStopRequest
 {
-    switch (cfg_.acb.reportError(errorInfo)) //throw ThreadStopRequest
+    const HandleError handleErr = cfg_.acb.reportError(errorInfo); //throw ThreadStopRequest
+    switch (handleErr)
     {
-        case ON_ERROR_CONTINUE:
+        case HandleError::ignore:
             if (itemName.empty())
                 cfg_.failedDirReads.emplace(beforeLast(parentRelPathPf_, FILE_NAME_SEPARATOR, IfNotFoundReturn::none), utfTo<Zstringc>(errorInfo.msg));
             else
                 cfg_.failedItemReads.emplace(parentRelPathPf_ + itemName, utfTo<Zstringc>(errorInfo.msg));
-            return ON_ERROR_CONTINUE;
+            break;
 
-        case ON_ERROR_RETRY:
-            return ON_ERROR_RETRY;
+        case HandleError::retry:
+            break;
     }
-    assert(false);
-    return ON_ERROR_CONTINUE;
+    return handleErr;
 }
 }
 
diff --git a/FreeFileSync/Source/base/parallel_scan.h b/FreeFileSync/Source/base/parallel_scan.h
index 4675bbc4..4fe46643 100644
--- a/FreeFileSync/Source/base/parallel_scan.h
+++ b/FreeFileSync/Source/base/parallel_scan.h
@@ -33,10 +33,10 @@ struct DirectoryValue
     FolderContainer folderCont;
 
     //relative paths (or empty string for root) for directories that could not be read (completely), e.g. access denied, or temporary network drop
-    std::map<Zstring, Zstringc> failedFolderReads; //with corresponding error message
+    std::map<Zstring, Zstringc /*error message*/> failedFolderReads;
 
-    //relative paths (never empty) for failure to read single file/dir/symlink with corresponding error message
-    std::map<Zstring, Zstringc> failedItemReads;
+    //relative paths (never empty) for failure to read single file/dir/symlink
+    std::map<Zstring, Zstringc /*error message*/> failedItemReads;
 };
 
 
diff --git a/FreeFileSync/Source/base/process_callback.h b/FreeFileSync/Source/base/process_callback.h
index b5b015d6..8540f872 100644
--- a/FreeFileSync/Source/base/process_callback.h
+++ b/FreeFileSync/Source/base/process_callback.h
@@ -37,11 +37,11 @@ struct PhaseCallback
     //opportunity to abort must be implemented in a frequently-executed method like requestUiUpdate()
     virtual void requestUiUpdate(bool force = false) = 0; //throw X
 
-    //UI info only, should not be logged: called periodically after data was processed: expected(!) to request GUI update
-    virtual void updateStatus(const std::wstring& msg) = 0; //throw X
+    //UI info only, should *not* be logged: called periodically after data was processed: expected(!) to request GUI update
+    virtual void updateStatus(std::wstring&& msg) = 0; //throw X
 
-    //like updateStatus() but should be logged:
-    virtual void reportInfo(const std::wstring& msg) = 0; //throw X
+    //log only; must *not* call updateStatus()!
+    virtual void logInfo(const std::wstring& msg) = 0; //throw X
 
     virtual void reportWarning(const std::wstring& msg, bool& warningActive) = 0; //throw X
 
@@ -51,7 +51,6 @@ struct PhaseCallback
         std::chrono::steady_clock::time_point failTime;
         size_t retryNumber = 0;
     };
-
     enum Response
     {
         ignore,
diff --git a/FreeFileSync/Source/base/status_handler_impl.h b/FreeFileSync/Source/base/status_handler_impl.h
index 0841a752..611c45ee 100644
--- a/FreeFileSync/Source/base/status_handler_impl.h
+++ b/FreeFileSync/Source/base/status_handler_impl.h
@@ -32,35 +32,39 @@ public:
     }
 
     //context of worker thread
-    void updateStatus(const std::wstring& msg) //throw ThreadStopRequest
+    void updateStatus(std::wstring&& msg) //throw ThreadStopRequest
     {
         assert(!zen::runningOnMainThread());
         {
             std::lock_guard dummy(lockCurrentStatus_);
             if (ThreadStatus* ts = getThreadStatus()) //call while holding "lockCurrentStatus_" lock!!
-                ts->statusMsg = msg;
+                ts->statusMsg = std::move(msg);
             else assert(false);
         }
         zen::interruptionPoint(); //throw ThreadStopRequest
     }
 
     //blocking call: context of worker thread
-    //=> indirect support for "pause": reportInfo() is called under singleThread lock,
+    //=> indirect support for "pause": logInfo() is called under singleThread lock,
     //   so all other worker threads will wait when coming out of parallel I/O (trying to lock singleThread)
-    void reportInfo(const std::wstring& msg) //throw ThreadStopRequest
+    void logInfo(const std::wstring& msg) //throw ThreadStopRequest
     {
-        updateStatus(msg); //throw ThreadStopRequest
-
         assert(!zen::runningOnMainThread());
         std::unique_lock dummy(lockRequest_);
-        zen::interruptibleWait(conditionReadyForNewRequest_, dummy, [this] { return !reportInfoRequest_; }); //throw ThreadStopRequest
+        zen::interruptibleWait(conditionReadyForNewRequest_, dummy, [this] { return !logInfoRequest_; }); //throw ThreadStopRequest
 
-        reportInfoRequest_ = /*std::move(taskPrefix) + */ msg;
+        logInfoRequest_ = /*std::move(taskPrefix) + */ msg;
 
         dummy.unlock(); //optimization for condition_variable::notify_all()
         conditionNewRequest.notify_all();
     }
 
+    void reportInfo(std::wstring&& msg) //throw ThreadStopRequest
+    {
+        logInfo(msg);                 //throw ThreadStopRequest
+        updateStatus(std::move(msg)); //
+    }
+
     //blocking call: context of worker thread
     PhaseCallback::Response reportError(const PhaseCallback::ErrorInfo& errorInfo) //throw ThreadStopRequest
     {
@@ -79,21 +83,21 @@ public:
         errorResponse_ = std::nullopt;
 
         dummy.unlock(); //optimization for condition_variable::notify_all()
-        conditionReadyForNewRequest_.notify_all(); //=> spurious wake-up for AsyncCallback::reportInfo()
+        conditionReadyForNewRequest_.notify_all(); //=> spurious wake-up for AsyncCallback::logInfo()
         return rv;
     }
 
     //context of main thread
-    void waitUntilDone(std::chrono::milliseconds duration, PhaseCallback& cb) //throw X
+    void waitUntilDone(std::chrono::milliseconds cbInterval, PhaseCallback& cb) //throw X
     {
         assert(zen::runningOnMainThread());
         for (;;)
         {
-            const std::chrono::steady_clock::time_point callbackTime = std::chrono::steady_clock::now() + duration;
+            const std::chrono::steady_clock::time_point callbackTime = std::chrono::steady_clock::now() + cbInterval;
 
             for (std::unique_lock dummy(lockRequest_);;) //process all errors without delay
             {
-                const bool rv = conditionNewRequest.wait_until(dummy, callbackTime, [this] { return (errorRequest_ && !errorResponse_) || reportInfoRequest_ || finishNowRequest_; });
+                const bool rv = conditionNewRequest.wait_until(dummy, callbackTime, [this] { return (errorRequest_ && !errorResponse_) || logInfoRequest_ || finishNowRequest_; });
                 if (!rv) //time-out + condition not met
                     break;
 
@@ -101,12 +105,12 @@ public:
                 {
                     assert(!finishNowRequest_);
                     errorResponse_ = cb.reportError(*errorRequest_); //throw X
-                    conditionHaveResponse_.notify_all(); //instead of notify_one(); workaround bug: https://svn.boost.org/trac/boost/ticket/7796
+                    conditionHaveResponse_.notify_all(); //instead of notify_one(); work around bug: https://svn.boost.org/trac/boost/ticket/7796
                 }
-                if (reportInfoRequest_)
+                if (logInfoRequest_)
                 {
-                    cb.reportInfo(*reportInfoRequest_); //throw X
-                    reportInfoRequest_ = {};
+                    cb.logInfo(*logInfoRequest_); //throw X
+                    logInfoRequest_ = {};
                     conditionReadyForNewRequest_.notify_all(); //=> spurious wake-up for AsyncCallback::reportError()
                 }
                 if (finishNowRequest_)
@@ -117,7 +121,7 @@ public:
                 }
             }
 
-            //call member functions outside of mutex scope:
+            //call back outside of mutex scope:
             cb.updateStatus(getCurrentStatus()); //throw X
             reportStats(cb);
         }
@@ -146,7 +150,7 @@ public:
         if (statusByPriority_.size() < prio + 1)
             statusByPriority_.resize(prio + 1);
 
-        statusByPriority_[prio].push_back({ threadId, /*taskIdx,*/ std::wstring() });
+        statusByPriority_[prio].push_back({threadId, /*taskIdx,*/ std::wstring()});
     }
 
     void notifyTaskEnd() //noexcept
@@ -264,7 +268,7 @@ private:
     std::condition_variable conditionHaveResponse_;
     std::optional<PhaseCallback::ErrorInfo> errorRequest_;
     std::optional<PhaseCallback::Response > errorResponse_;
-    std::optional<std::wstring>            reportInfoRequest_;
+    std::optional<std::wstring>             logInfoRequest_;
     bool finishNowRequest_ = false;
 
     //---- status updates ----
@@ -275,10 +279,10 @@ private:
     //std::vector<char/*bool*/> usedIndexNums_; //keep info for human-readable task index numbers
 
     //---- status updates II (lock-free) ----
-    std::atomic<int>     itemsDeltaProcessed_{ 0 }; //
-    std::atomic<int64_t> bytesDeltaProcessed_{ 0 }; //std:atomic is uninitialized by default!
-    std::atomic<int>     itemsDeltaTotal_    { 0 }; //
-    std::atomic<int64_t> bytesDeltaTotal_    { 0 }; //
+    std::atomic<int>     itemsDeltaProcessed_{0}; //
+    std::atomic<int64_t> bytesDeltaProcessed_{0}; //std:atomic is uninitialized by default!
+    std::atomic<int>     itemsDeltaTotal_    {0}; //
+    std::atomic<int64_t> bytesDeltaTotal_    {0}; //
 };
 
 
@@ -303,7 +307,7 @@ public:
             cb_.updateDataTotal(itemsReported_ - itemsExpected_, bytesReported_ - bytesExpected_); //noexcept!
     }
 
-    void updateStatus(const std::wstring& msg) { cb_.updateStatus(msg); } //throw ThreadStopRequest
+    void updateStatus(std::wstring&& msg) { cb_.updateStatus(std::move(msg)); } //throw ThreadStopRequest
 
     void reportDelta(int itemsDelta, int64_t bytesDelta) //noexcept!
     {
@@ -404,7 +408,7 @@ void massParallelExecute(const std::vector<std::pair<AbstractPath, ParallelWorkI
             acb.notifyTaskBegin(statusPrio);
             ZEN_ON_SCOPE_EXIT(acb.notifyTaskEnd());
 
-            ParallelContext pctx{ itemPath, acb };
+            ParallelContext pctx{itemPath, acb};
             task(pctx); //throw ThreadStopRequest
         });
 
diff --git a/FreeFileSync/Source/base/synchronization.cpp b/FreeFileSync/Source/base/synchronization.cpp
index 5350aee5..f0464ca1 100644
--- a/FreeFileSync/Source/base/synchronization.cpp
+++ b/FreeFileSync/Source/base/synchronization.cpp
@@ -84,12 +84,12 @@ void SyncStatistics::processFile(const FilePair& file)
     {
         case SO_CREATE_NEW_LEFT:
             ++createLeft_;
-            bytesToProcess_ += static_cast<int64_t>(file.getFileSize<RIGHT_SIDE>());
+            bytesToProcess_ += static_cast<int64_t>(file.getFileSize<SelectSide::right>());
             break;
 
         case SO_CREATE_NEW_RIGHT:
             ++createRight_;
-            bytesToProcess_ += static_cast<int64_t>(file.getFileSize<LEFT_SIDE>());
+            bytesToProcess_ += static_cast<int64_t>(file.getFileSize<SelectSide::left>());
             break;
 
         case SO_DELETE_LEFT:
@@ -117,20 +117,20 @@ void SyncStatistics::processFile(const FilePair& file)
 
         case SO_OVERWRITE_LEFT:
             ++updateLeft_;
-            bytesToProcess_ += static_cast<int64_t>(file.getFileSize<RIGHT_SIDE>());
+            bytesToProcess_ += static_cast<int64_t>(file.getFileSize<SelectSide::right>());
             physicalDeleteLeft_ = true;
             break;
 
         case SO_OVERWRITE_RIGHT:
             ++updateRight_;
-            bytesToProcess_ += static_cast<int64_t>(file.getFileSize<LEFT_SIDE>());
+            bytesToProcess_ += static_cast<int64_t>(file.getFileSize<SelectSide::left>());
             physicalDeleteRight_ = true;
             break;
 
         case SO_UNRESOLVED_CONFLICT:
             ++conflictCount_;
             if (conflictsPreview_.size() < CONFLICTS_PREVIEW_MAX)
-                conflictsPreview_.push_back({ file.getRelativePathAny(), file.getSyncOpConflict() });
+                conflictsPreview_.push_back({file.getRelativePathAny(), file.getSyncOpConflict()});
             break;
 
         case SO_COPY_METADATA_TO_LEFT:
@@ -186,7 +186,7 @@ void SyncStatistics::processLink(const SymlinkPair& link)
         case SO_UNRESOLVED_CONFLICT:
             ++conflictCount_;
             if (conflictsPreview_.size() < CONFLICTS_PREVIEW_MAX)
-                conflictsPreview_.push_back({ link.getRelativePathAny(), link.getSyncOpConflict() });
+                conflictsPreview_.push_back({link.getRelativePathAny(), link.getSyncOpConflict()});
             break;
 
         case SO_MOVE_LEFT_FROM:
@@ -228,7 +228,7 @@ void SyncStatistics::processFolder(const FolderPair& folder)
         case SO_UNRESOLVED_CONFLICT:
             ++conflictCount_;
             if (conflictsPreview_.size() < CONFLICTS_PREVIEW_MAX)
-                conflictsPreview_.push_back({ folder.getRelativePathAny(), folder.getSyncOpConflict() });
+                conflictsPreview_.push_back({folder.getRelativePathAny(), folder.getSyncOpConflict()});
             break;
 
         case SO_OVERWRITE_LEFT:
@@ -272,7 +272,7 @@ public:
     {
         MinimumDiskSpaceNeeded inst;
         inst.recurse(baseFolder);
-        return { inst.spaceNeededLeft_, inst.spaceNeededRight_ };
+        return {inst.spaceNeededLeft_, inst.spaceNeededRight_};
     }
 
 private:
@@ -283,33 +283,33 @@ private:
             switch (file.getSyncOperation()) //evaluate comparison result and sync direction
             {
                 case SO_CREATE_NEW_LEFT:
-                    spaceNeededLeft_ += static_cast<int64_t>(file.getFileSize<RIGHT_SIDE>());
+                    spaceNeededLeft_ += static_cast<int64_t>(file.getFileSize<SelectSide::right>());
                     break;
 
                 case SO_CREATE_NEW_RIGHT:
-                    spaceNeededRight_ += static_cast<int64_t>(file.getFileSize<LEFT_SIDE>());
+                    spaceNeededRight_ += static_cast<int64_t>(file.getFileSize<SelectSide::left>());
                     break;
 
                 case SO_DELETE_LEFT:
-                    if (!file.isFollowedSymlink<LEFT_SIDE>())
-                        spaceNeededLeft_ -= static_cast<int64_t>(file.getFileSize<LEFT_SIDE>());
+                    if (!file.isFollowedSymlink<SelectSide::left>())
+                        spaceNeededLeft_ -= static_cast<int64_t>(file.getFileSize<SelectSide::left>());
                     break;
 
                 case SO_DELETE_RIGHT:
-                    if (!file.isFollowedSymlink<RIGHT_SIDE>())
-                        spaceNeededRight_ -= static_cast<int64_t>(file.getFileSize<RIGHT_SIDE>());
+                    if (!file.isFollowedSymlink<SelectSide::right>())
+                        spaceNeededRight_ -= static_cast<int64_t>(file.getFileSize<SelectSide::right>());
                     break;
 
                 case SO_OVERWRITE_LEFT:
-                    if (!file.isFollowedSymlink<LEFT_SIDE>())
-                        spaceNeededLeft_ -= static_cast<int64_t>(file.getFileSize<LEFT_SIDE>());
-                    spaceNeededLeft_ += static_cast<int64_t>(file.getFileSize<RIGHT_SIDE>());
+                    if (!file.isFollowedSymlink<SelectSide::left>())
+                        spaceNeededLeft_ -= static_cast<int64_t>(file.getFileSize<SelectSide::left>());
+                    spaceNeededLeft_ += static_cast<int64_t>(file.getFileSize<SelectSide::right>());
                     break;
 
                 case SO_OVERWRITE_RIGHT:
-                    if (!file.isFollowedSymlink<RIGHT_SIDE>())
-                        spaceNeededRight_ -= static_cast<int64_t>(file.getFileSize<RIGHT_SIDE>());
-                    spaceNeededRight_ += static_cast<int64_t>(file.getFileSize<LEFT_SIDE>());
+                    if (!file.isFollowedSymlink<SelectSide::right>())
+                        spaceNeededRight_ -= static_cast<int64_t>(file.getFileSize<SelectSide::right>());
+                    spaceNeededRight_ += static_cast<int64_t>(file.getFileSize<SelectSide::left>());
                     break;
 
                 case SO_DO_NOTHING:
@@ -332,11 +332,11 @@ private:
             switch (folder.getSyncOperation())
             {
                 case SO_DELETE_LEFT:
-                    if (!folder.isFollowedSymlink<LEFT_SIDE>())
+                    if (!folder.isFollowedSymlink<SelectSide::left>())
                         recurse(folder); //not 100% correct: in fact more that what our model contains may be deleted (consider file filter!)
                     break;
                 case SO_DELETE_RIGHT:
-                    if (!folder.isFollowedSymlink<RIGHT_SIDE>())
+                    if (!folder.isFollowedSymlink<SelectSide::right>())
                         recurse(folder);
                     break;
 
@@ -369,7 +369,7 @@ private:
 std::vector<FolderPairSyncCfg> fff::extractSyncCfg(const MainConfiguration& mainCfg)
 {
     //merge first and additional pairs
-    std::vector<LocalPairConfig> localCfgs = { mainCfg.firstPair };
+    std::vector<LocalPairConfig> localCfgs = {mainCfg.firstPair};
     append(localCfgs, mainCfg.additionalPairs);
 
     std::vector<FolderPairSyncCfg> output;
@@ -400,7 +400,7 @@ std::vector<FolderPairSyncCfg> fff::extractSyncCfg(const MainConfiguration& main
 namespace
 {
 inline
-std::optional<SelectedSide> getTargetDirection(SyncOperation syncOp)
+std::optional<SelectSide> getTargetDirection(SyncOperation syncOp)
 {
     switch (syncOp)
     {
@@ -410,7 +410,7 @@ std::optional<SelectedSide> getTargetDirection(SyncOperation syncOp)
         case SO_COPY_METADATA_TO_LEFT:
         case SO_MOVE_LEFT_FROM:
         case SO_MOVE_LEFT_TO:
-            return LEFT_SIDE;
+            return SelectSide::left;
 
         case SO_CREATE_NEW_RIGHT:
         case SO_DELETE_RIGHT:
@@ -418,7 +418,7 @@ std::optional<SelectedSide> getTargetDirection(SyncOperation syncOp)
         case SO_COPY_METADATA_TO_RIGHT:
         case SO_MOVE_RIGHT_FROM:
         case SO_MOVE_RIGHT_TO:
-            return RIGHT_SIDE;
+            return SelectSide::right;
 
         case SO_DO_NOTHING:
         case SO_EQUAL:
@@ -433,8 +433,8 @@ std::optional<SelectedSide> getTargetDirection(SyncOperation syncOp)
 bool significantDifferenceDetected(const SyncStatistics& folderPairStat)
 {
     //initial file copying shall not be detected as major difference
-    if ((folderPairStat.createCount< LEFT_SIDE>() == 0 ||
-         folderPairStat.createCount<RIGHT_SIDE>() == 0) &&
+    if ((folderPairStat.createCount< SelectSide::left>() == 0 ||
+         folderPairStat.createCount<SelectSide::right>() == 0) &&
         folderPairStat.updateCount  () == 0 &&
         folderPairStat.deleteCount  () == 0 &&
         folderPairStat.conflictCount() == 0)
@@ -463,14 +463,15 @@ void flushFileBuffers(const Zstring& nativeFilePath) //throw FileError
 }
 
 
-void verifyFiles(const AbstractPath& sourcePath, const AbstractPath& targetPath, const IOCallback& notifyUnbufferedIO /*throw X*/) //throw FileError, X
+void verifyFiles(const AbstractPath& sourcePath, const AbstractPath& targetPath, const IoCallback& notifyUnbufferedIO /*throw X*/) //throw FileError, X
 {
     try
     {
         //do like "copy /v": 1. flush target file buffers, 2. read again as usual (using OS buffers)
         // => it seems OS buffers are not invalidated by this: snake oil???
-        if (std::optional<Zstring> nativeTargetPath = AFS::getNativeItemPath(targetPath))
-            flushFileBuffers(*nativeTargetPath); //throw FileError
+        if (const Zstring& targetPathNative = getNativeItemPath(targetPath);
+            !targetPathNative.empty())
+            flushFileBuffers(targetPathNative); //throw FileError
 
         if (!filesHaveSameContent(sourcePath, targetPath, notifyUnbufferedIO)) //throw FileError, X
             throw FileError(replaceCpy(replaceCpy(_("%x and %y have different content."),
@@ -546,7 +547,7 @@ AFS::FileCopyResult copyFileTransactional(const AbstractPath& apSource, const AF
                                           bool copyFilePermissions,
                                           bool transactionalCopy,
                                           const std::function<void()>& onDeleteTargetFile /*throw X*/,
-                                          const IOCallback& notifyUnbufferedIO /*throw X*/,
+                                          const IoCallback& notifyUnbufferedIO /*throw X*/,
                                           std::mutex& singleThread)
 {
     return parallelScope([=]
@@ -560,7 +561,7 @@ void recycleItemIfExists(AFS::RecycleSession& recyclerSession, const AbstractPat
 { parallelScope([=, &recyclerSession] { return recyclerSession.recycleItemIfExists(ap, logicalRelPath); /*throw FileError*/ }, singleThread); }
 
 inline //FileVersioner::revisionFile() is internally synchronized!
-void revisionFile(FileVersioner& versioner, const FileDescriptor& fileDescr, const Zstring& relativePath, const IOCallback& notifyUnbufferedIO /*throw X*/, std::mutex& singleThread) //throw FileError, X
+void revisionFile(FileVersioner& versioner, const FileDescriptor& fileDescr, const Zstring& relativePath, const IoCallback& notifyUnbufferedIO /*throw X*/, std::mutex& singleThread) //throw FileError, X
 { parallelScope([=, &versioner] { return versioner.revisionFile(fileDescr, relativePath, notifyUnbufferedIO); /*throw FileError, X*/ }, singleThread); }
 
 inline //FileVersioner::revisionSymlink() is internally synchronized!
@@ -572,12 +573,12 @@ void revisionFolder(FileVersioner& versioner,
                     const AbstractPath& folderPath, const Zstring& relativePath,
                     const std::function<void(const std::wstring& displayPathFrom, const std::wstring& displayPathTo)>& onBeforeFileMove    /*throw X*/,
                     const std::function<void(const std::wstring& displayPathFrom, const std::wstring& displayPathTo)>& onBeforeFolderMove  /*throw X*/,
-                    const IOCallback& notifyUnbufferedIO  /*throw X*/,
+                    const IoCallback& notifyUnbufferedIO  /*throw X*/,
                     std::mutex& singleThread) //throw FileError, X
 { parallelScope([=, &versioner] { versioner.revisionFolder(folderPath, relativePath, onBeforeFileMove, onBeforeFolderMove, notifyUnbufferedIO); /*throw FileError, X*/ }, singleThread); }
 
 inline
-void verifyFiles(const AbstractPath& apSource, const AbstractPath& apTarget, const IOCallback& notifyUnbufferedIO /*throw X*/, std::mutex& singleThread) //throw FileError, X
+void verifyFiles(const AbstractPath& apSource, const AbstractPath& apTarget, const IoCallback& notifyUnbufferedIO /*throw X*/, std::mutex& singleThread) //throw FileError, X
 { parallelScope([=] { ::verifyFiles(apSource, apTarget, notifyUnbufferedIO); /*throw FileError, X*/ }, singleThread); }
 
 }
@@ -970,18 +971,24 @@ private:
 
     static bool containsMoveTarget(const FolderPair& parent);
     void executeFileMove(FilePair& file); //throw ThreadStopRequest
-    template <SelectedSide side> void executeFileMoveImpl(FilePair& fileFrom, FilePair& fileTo); //throw ThreadStopRequest
+    template <SelectSide side> void executeFileMoveImpl(FilePair& fileFrom, FilePair& fileTo); //throw ThreadStopRequest
 
-    void synchronizeFile(FilePair& file);                                                       //
-    template <SelectedSide side> void synchronizeFileInt(FilePair& file, SyncOperation syncOp); //throw FileError, ErrorMoveUnsupported, ThreadStopRequest
+    void synchronizeFile(FilePair& file);                                                     //
+    template <SelectSide side> void synchronizeFileInt(FilePair& file, SyncOperation syncOp); //throw FileError, ErrorMoveUnsupported, ThreadStopRequest
 
-    void synchronizeLink(SymlinkPair& link);                                                          //
-    template <SelectedSide sideTrg> void synchronizeLinkInt(SymlinkPair& link, SyncOperation syncOp); //throw FileError, ThreadStopRequest
+    void synchronizeLink(SymlinkPair& link);                                                        //
+    template <SelectSide sideTrg> void synchronizeLinkInt(SymlinkPair& link, SyncOperation syncOp); //throw FileError, ThreadStopRequest
 
-    void synchronizeFolder(FolderPair& folder);                                                          //
-    template <SelectedSide sideTrg> void synchronizeFolderInt(FolderPair& folder, SyncOperation syncOp); //throw FileError, ThreadStopRequest
+    void synchronizeFolder(FolderPair& folder);                                                        //
+    template <SelectSide sideTrg> void synchronizeFolderInt(FolderPair& folder, SyncOperation syncOp); //throw FileError, ThreadStopRequest
 
+    void    logInfo(const std::wstring& rawText, const std::wstring& displayPath) { acb_.logInfo   (replaceCpy(rawText, L"%x", fmtPath(displayPath))); }
     void reportInfo(const std::wstring& rawText, const std::wstring& displayPath) { acb_.reportInfo(replaceCpy(rawText, L"%x", fmtPath(displayPath))); }
+
+    void logInfo(const std::wstring& rawText, const std::wstring& displayPath1, const std::wstring& displayPath2) //throw ThreadStopRequest
+    {
+        acb_.logInfo(replaceCpy(replaceCpy(rawText, L"%x", L'\n' + fmtPath(displayPath1)), L"%y", L'\n' + fmtPath(displayPath2))); //throw ThreadStopRequest
+    }
     void reportInfo(const std::wstring& rawText, const std::wstring& displayPath1, const std::wstring& displayPath2) //throw ThreadStopRequest
     {
         acb_.reportInfo(replaceCpy(replaceCpy(rawText, L"%x", L'\n' + fmtPath(displayPath1)), L"%y", L'\n' + fmtPath(displayPath2))); //throw ThreadStopRequest
@@ -1146,10 +1153,9 @@ RingBuffer<Workload::WorkItems> FolderPairSyncer::getFolderLevelWorkItems(PassNo
 }
 
 
-/*
-  __________________________
-  |Move algorithm, 0th pass|
-  --------------------------
+/* __________________________
+   |Move algorithm, 0th pass|
+   --------------------------
     1. loop over hierarchy and find "move targets" => remember required parent folders
 
     2. create required folders hierarchically:
@@ -1174,7 +1180,7 @@ RingBuffer<Workload::WorkItems> FolderPairSyncer::getFolderLevelWorkItems(PassNo
          b -> c/b
          a -> b/a                                                                               */
 
-template <SelectedSide side>
+template <SelectSide side>
 void FolderPairSyncer::executeFileMoveImpl(FilePair& fileFrom, FilePair& fileTo) //throw ThreadStopRequest
 {
     const bool fallBackCopyDelete = [&]
@@ -1186,10 +1192,10 @@ void FolderPairSyncer::executeFileMoveImpl(FilePair& fileFrom, FilePair& fileTo)
 
         if (parentMissing)
         {
-            reportInfo(_("Cannot move file %x to %y.") + L"\n\n" +
-                       replaceCpy(_("Parent folder %x is not existing."), L"%x", fmtPath(AFS::getDisplayPath(parentMissing->getAbstractPath<side>()))),
-                       AFS::getDisplayPath(fileFrom.getAbstractPath<side>()),
-                       AFS::getDisplayPath(fileTo  .getAbstractPath<side>())); //throw ThreadStopRequest
+            logInfo(_("Cannot move file %x to %y.") + L"\n\n" +
+                    replaceCpy(_("Parent folder %x is not existing."), L"%x", fmtPath(AFS::getDisplayPath(parentMissing->getAbstractPath<side>()))),
+                    AFS::getDisplayPath(fileFrom.getAbstractPath<side>()),
+                    AFS::getDisplayPath(fileTo  .getAbstractPath<side>())); //throw ThreadStopRequest
             return true;
         }
 
@@ -1197,9 +1203,9 @@ void FolderPairSyncer::executeFileMoveImpl(FilePair& fileFrom, FilePair& fileTo)
         if (haveNameClash(fileTo.getItemNameAny(), fileTo.parent().refSubFolders()) ||
             haveNameClash(fileTo.getItemNameAny(), fileTo.parent().refSubLinks  ()))
         {
-            reportInfo(_("Cannot move file %x to %y.") + L"\n\n" + replaceCpy(_("The name %x is already used by another item."), L"%x", fmtPath(fileTo.getItemNameAny())),
-                       AFS::getDisplayPath(fileFrom.getAbstractPath<side>()),
-                       AFS::getDisplayPath(fileTo  .getAbstractPath<side>())); //throw ThreadStopRequest
+            logInfo(_("Cannot move file %x to %y.") + L"\n\n" + replaceCpy(_("The name %x is already used by another item."), L"%x", fmtPath(fileTo.getItemNameAny())),
+                    AFS::getDisplayPath(fileFrom.getAbstractPath<side>()),
+                    AFS::getDisplayPath(fileTo  .getAbstractPath<side>())); //throw ThreadStopRequest
             return true;
         }
 
@@ -1212,7 +1218,7 @@ void FolderPairSyncer::executeFileMoveImpl(FilePair& fileFrom, FilePair& fileTo)
             }
             catch (const ErrorMoveUnsupported& e)
             {
-                acb_.reportInfo(e.toString()); //let user know that move operation is not supported, then fall back:
+                acb_.logInfo(e.toString()); //let user know that move operation is not supported, then fall back:
                 moveSupported = false;
             }
         }, acb_);
@@ -1226,7 +1232,7 @@ void FolderPairSyncer::executeFileMoveImpl(FilePair& fileFrom, FilePair& fileTo)
         {
             SyncStatistics statSrc(fileFrom);
             SyncStatistics statTrg(fileTo);
-            return { getCUD(statSrc) + getCUD(statTrg), statSrc.getBytesToProcess() + statTrg.getBytesToProcess() };
+            return {getCUD(statSrc) + getCUD(statTrg), statSrc.getBytesToProcess() + statTrg.getBytesToProcess()};
         };
         const auto [itemsBefore, bytesBefore] = getStats();
         fileFrom.setMoveRef(nullptr);
@@ -1251,9 +1257,9 @@ void FolderPairSyncer::executeFileMove(FilePair& file) //throw ThreadStopRequest
                 assert(fileFrom->getMoveRef() == file.getId());
 
                 if (syncOp == SO_MOVE_LEFT_TO)
-                    executeFileMoveImpl<LEFT_SIDE>(*fileFrom, file); //throw ThreadStopRequest
+                    executeFileMoveImpl<SelectSide::left>(*fileFrom, file); //throw ThreadStopRequest
                 else
-                    executeFileMoveImpl<RIGHT_SIDE>(*fileFrom, file); //throw ThreadStopRequest
+                    executeFileMoveImpl<SelectSide::right>(*fileFrom, file); //throw ThreadStopRequest
             }
             else assert(false);
             break;
@@ -1307,7 +1313,7 @@ bool FolderPairSyncer::needZeroPass(const FolderPair& folder)
         case SO_OVERWRITE_RIGHT: //
         case SO_COPY_METADATA_TO_LEFT:
         case SO_COPY_METADATA_TO_RIGHT:
-            assert((!folder.isEmpty<LEFT_SIDE>() && !folder.isEmpty<RIGHT_SIDE>()) || !containsMoveTarget(folder));
+            assert((!folder.isEmpty<SelectSide::left>() && !folder.isEmpty<SelectSide::right>()) || !containsMoveTarget(folder));
             //we're good to move contained items
             break;
         case SO_DELETE_LEFT:  //not possible in the context of planning to move a child item, see FolderPair::getSyncOperation()
@@ -1367,10 +1373,10 @@ FolderPairSyncer::PassNo FolderPairSyncer::getPass(const FilePair& file)
             return PassNo::one;
 
         case SO_OVERWRITE_LEFT:
-            return file.getFileSize<LEFT_SIDE>() > file.getFileSize<RIGHT_SIDE>() ? PassNo::one : PassNo::two;
+            return file.getFileSize<SelectSide::left>() > file.getFileSize<SelectSide::right>() ? PassNo::one : PassNo::two;
 
         case SO_OVERWRITE_RIGHT:
-            return file.getFileSize<LEFT_SIDE>() < file.getFileSize<RIGHT_SIDE>() ? PassNo::one : PassNo::two;
+            return file.getFileSize<SelectSide::left>() < file.getFileSize<SelectSide::right>() ? PassNo::one : PassNo::two;
 
         case SO_MOVE_LEFT_FROM:  //
         case SO_MOVE_RIGHT_FROM: // [!]
@@ -1467,20 +1473,20 @@ void FolderPairSyncer::synchronizeFile(FilePair& file) //throw FileError, ErrorM
 {
     const SyncOperation syncOp = file.getSyncOperation();
 
-    if (std::optional<SelectedSide> sideTrg = getTargetDirection(syncOp))
+    if (std::optional<SelectSide> sideTrg = getTargetDirection(syncOp))
     {
-        if (*sideTrg == LEFT_SIDE)
-            synchronizeFileInt<LEFT_SIDE>(file, syncOp);
+        if (*sideTrg == SelectSide::left)
+            synchronizeFileInt<SelectSide::left>(file, syncOp);
         else
-            synchronizeFileInt<RIGHT_SIDE>(file, syncOp);
+            synchronizeFileInt<SelectSide::right>(file, syncOp);
     }
 }
 
 
-template <SelectedSide sideTrg>
+template <SelectSide sideTrg>
 void FolderPairSyncer::synchronizeFileInt(FilePair& file, SyncOperation syncOp) //throw FileError, ErrorMoveUnsupported, ThreadStopRequest
 {
-    constexpr SelectedSide sideSrc = OtherSide<sideTrg>::value;
+    constexpr SelectSide sideSrc = OtherSide<sideTrg>::value;
     DeletionHandler& delHandlerTrg = SelectParam<sideTrg>::ref(delHandlerLeft_, delHandlerRight_);
 
     switch (syncOp)
@@ -1498,7 +1504,7 @@ void FolderPairSyncer::synchronizeFileInt(FilePair& file, SyncOperation syncOp)
             AsyncItemStatReporter statReporter(1, file.getFileSize<sideSrc>(), acb_);
             try
             {
-                const AFS::FileCopyResult result = copyFileWithCallback({ file.getAbstractPath<sideSrc>(), file.getAttributes<sideSrc>() },
+                const AFS::FileCopyResult result = copyFileWithCallback({file.getAbstractPath<sideSrc>(), file.getAttributes<sideSrc>()},
                                                                         targetPath,
                                                                         nullptr, //onDeleteTargetFile: nothing to delete
                                                                         //if existing: undefined behavior! (e.g. fail/overwrite/auto-rename)
@@ -1509,8 +1515,8 @@ void FolderPairSyncer::synchronizeFileInt(FilePair& file, SyncOperation syncOp)
                 file.setSyncedTo<sideTrg>(file.getItemName<sideSrc>(), result.fileSize,
                                           result.modTime, //target time set from source
                                           result.modTime,
-                                          result.targetFileId,
-                                          result.sourceFileId,
+                                          result.targetFilePrint,
+                                          result.sourceFilePrint,
                                           false, file.isFollowedSymlink<sideSrc>());
 
                 if (result.errorModTime)
@@ -1521,7 +1527,7 @@ void FolderPairSyncer::synchronizeFileInt(FilePair& file, SyncOperation syncOp)
                             break;
                         case CompareVariant::content: //just log, no warning:
                         case CompareVariant::size:    //e.g. FTP server not supporting MFMT command
-                            acb_.reportInfo(result.errorModTime->toString());
+                            acb_.logInfo(result.errorModTime->toString());
                             break;
                     }
             }
@@ -1539,7 +1545,7 @@ void FolderPairSyncer::synchronizeFileInt(FilePair& file, SyncOperation syncOp)
                     statReporter.reportDelta(1, 0); //even if the source item does not exist anymore, significant I/O work was done => report
                     file.removeObject<sideSrc>(); //source deleted meanwhile...nothing was done (logical point of view!)
 
-                    reportInfo(txtSourceItemNotFound_, AFS::getDisplayPath(file.getAbstractPath<sideSrc>())); //throw ThreadStopRequest
+                    logInfo(txtSourceItemNotFound_, AFS::getDisplayPath(file.getAbstractPath<sideSrc>())); //throw ThreadStopRequest
                 }
                 else
                     throw;
@@ -1553,7 +1559,7 @@ void FolderPairSyncer::synchronizeFileInt(FilePair& file, SyncOperation syncOp)
             {
                 AsyncItemStatReporter statReporter(1, 0, acb_);
 
-                delHandlerTrg.removeFileWithCallback({ file.getAbstractPath<sideTrg>(), file.getAttributes<sideTrg>() },
+                delHandlerTrg.removeFileWithCallback({file.getAbstractPath<sideTrg>(), file.getAttributes<sideTrg>()},
                                                      file.getRelativePath<sideTrg>(), statReporter, singleThread_); //throw FileError, X
                 file.removeObject<sideTrg>(); //update FilePair
             }
@@ -1566,8 +1572,8 @@ void FolderPairSyncer::synchronizeFileInt(FilePair& file, SyncOperation syncOp)
                 FilePair* fileTo = &file;
                 assert(fileFrom->getMoveRef() == fileTo->getId());
 
-                assert((fileFrom->getSyncOperation() == SO_MOVE_LEFT_FROM  && fileTo->getSyncOperation() == SO_MOVE_LEFT_TO  && sideTrg == LEFT_SIDE) ||
-                       (fileFrom->getSyncOperation() == SO_MOVE_RIGHT_FROM && fileTo->getSyncOperation() == SO_MOVE_RIGHT_TO && sideTrg == RIGHT_SIDE));
+                assert((fileFrom->getSyncOperation() == SO_MOVE_LEFT_FROM  && fileTo->getSyncOperation() == SO_MOVE_LEFT_TO  && sideTrg == SelectSide::left) ||
+                       (fileFrom->getSyncOperation() == SO_MOVE_RIGHT_FROM && fileTo->getSyncOperation() == SO_MOVE_RIGHT_TO && sideTrg == SelectSide::right));
 
                 const AbstractPath pathFrom = fileFrom->getAbstractPath<sideTrg>();
                 const AbstractPath pathTo   = fileTo  ->getAbstractPath<sideTrg>();
@@ -1587,8 +1593,8 @@ void FolderPairSyncer::synchronizeFileInt(FilePair& file, SyncOperation syncOp)
                                              fileTo  ->getFileSize<sideSrc>(),
                                              fileFrom->getLastWriteTime<sideTrg>(),
                                              fileTo  ->getLastWriteTime<sideSrc>(),
-                                             fileFrom->getFileId<sideTrg>(),
-                                             fileTo  ->getFileId<sideSrc>(),
+                                             fileFrom->getFilePrint<sideTrg>(),
+                                             fileTo  ->getFilePrint<sideSrc>(),
                                              fileFrom->isFollowedSymlink<sideTrg>(),
                                              fileTo  ->isFollowedSymlink<sideSrc>());
                 fileFrom->removeObject<sideTrg>(); //remove only *after* evaluating "fileFrom, sideTrg"!
@@ -1624,7 +1630,7 @@ void FolderPairSyncer::synchronizeFileInt(FilePair& file, SyncOperation syncOp)
                 FileAttributes followedTargetAttr = file.getAttributes<sideTrg>();
                 followedTargetAttr.isFollowedSymlink = false;
 
-                delHandlerTrg.removeFileWithCallback({ targetPathResolvedOld, followedTargetAttr }, file.getRelativePath<sideTrg>(), statReporter, singleThread_); //throw FileError, X
+                delHandlerTrg.removeFileWithCallback({targetPathResolvedOld, followedTargetAttr}, file.getRelativePath<sideTrg>(), statReporter, singleThread_); //throw FileError, X
                 //no (logical) item count update desired - but total byte count may change, e.g. move(copy) old file to versioning dir
                 statReporter.reportDelta(-1, 0); //undo item stats reporting within DeletionHandler::removeFileWithCallback()
 
@@ -1635,7 +1641,7 @@ void FolderPairSyncer::synchronizeFileInt(FilePair& file, SyncOperation syncOp)
                 //=> if failSafeFileCopy_ : don't run callbacks that could throw
             };
 
-            const AFS::FileCopyResult result = copyFileWithCallback({ file.getAbstractPath<sideSrc>(), file.getAttributes<sideSrc>() },
+            const AFS::FileCopyResult result = copyFileWithCallback({file.getAbstractPath<sideSrc>(), file.getAttributes<sideSrc>()},
                                                                     targetPathResolvedNew,
                                                                     onDeleteTargetFile,
                                                                     statReporter); //throw FileError, ThreadStopRequest, X
@@ -1645,8 +1651,8 @@ void FolderPairSyncer::synchronizeFileInt(FilePair& file, SyncOperation syncOp)
             file.setSyncedTo<sideTrg>(file.getItemName<sideSrc>(), result.fileSize,
                                       result.modTime, //target time set from source
                                       result.modTime,
-                                      result.targetFileId,
-                                      result.sourceFileId,
+                                      result.targetFilePrint,
+                                      result.sourceFilePrint,
                                       file.isFollowedSymlink<sideTrg>(),
                                       file.isFollowedSymlink<sideSrc>());
 
@@ -1658,7 +1664,7 @@ void FolderPairSyncer::synchronizeFileInt(FilePair& file, SyncOperation syncOp)
                         break;
                     case CompareVariant::content: //just log, no warning:
                     case CompareVariant::size:    //e.g. FTP server not supporting MFMT command
-                        acb_.reportInfo(result.errorModTime->toString());
+                        acb_.logInfo(result.errorModTime->toString());
                         break;
                 }
         }
@@ -1691,10 +1697,10 @@ void FolderPairSyncer::synchronizeFileInt(FilePair& file, SyncOperation syncOp)
                 //-> both sides *should* be completely equal now...
                 assert(file.getFileSize<sideTrg>() == file.getFileSize<sideSrc>());
                 file.setSyncedTo<sideTrg>(file.getItemName<sideSrc>(), file.getFileSize<sideSrc>(),
-                                          file.getLastWriteTime<sideTrg>(),
-                                          file.getLastWriteTime<sideSrc>(),
-                                          file.getFileId       <sideTrg>(),
-                                          file.getFileId       <sideSrc>(),
+                                          file.getLastWriteTime <sideTrg>(),
+                                          file.getLastWriteTime <sideSrc>(),
+                                          file.getFilePrint     <sideTrg>(),
+                                          file.getFilePrint     <sideSrc>(),
                                           file.isFollowedSymlink<sideTrg>(),
                                           file.isFollowedSymlink<sideSrc>());
             }
@@ -1716,20 +1722,20 @@ void FolderPairSyncer::synchronizeLink(SymlinkPair& link) //throw FileError, Thr
 {
     const SyncOperation syncOp = link.getSyncOperation();
 
-    if (std::optional<SelectedSide> sideTrg = getTargetDirection(syncOp))
+    if (std::optional<SelectSide> sideTrg = getTargetDirection(syncOp))
     {
-        if (*sideTrg == LEFT_SIDE)
-            synchronizeLinkInt<LEFT_SIDE>(link, syncOp);
+        if (*sideTrg == SelectSide::left)
+            synchronizeLinkInt<SelectSide::left>(link, syncOp);
         else
-            synchronizeLinkInt<RIGHT_SIDE>(link, syncOp);
+            synchronizeLinkInt<SelectSide::right>(link, syncOp);
     }
 }
 
 
-template <SelectedSide sideTrg>
+template <SelectSide sideTrg>
 void FolderPairSyncer::synchronizeLinkInt(SymlinkPair& symlink, SyncOperation syncOp) //throw FileError, ThreadStopRequest
 {
-    constexpr SelectedSide sideSrc = OtherSide<sideTrg>::value;
+    constexpr SelectSide sideSrc = OtherSide<sideTrg>::value;
     DeletionHandler& delHandlerTrg = SelectParam<sideTrg>::ref(delHandlerLeft_, delHandlerRight_);
 
     switch (syncOp)
@@ -1771,7 +1777,7 @@ void FolderPairSyncer::synchronizeLinkInt(SymlinkPair& symlink, SyncOperation sy
                     statReporter.reportDelta(1, 0);
                     symlink.removeObject<sideSrc>(); //source deleted meanwhile...nothing was done (logical point of view!)
 
-                    reportInfo(txtSourceItemNotFound_, AFS::getDisplayPath(symlink.getAbstractPath<sideSrc>())); //throw ThreadStopRequest
+                    logInfo(txtSourceItemNotFound_, AFS::getDisplayPath(symlink.getAbstractPath<sideSrc>())); //throw ThreadStopRequest
                 }
                 else
                     throw;
@@ -1865,20 +1871,20 @@ void FolderPairSyncer::synchronizeFolder(FolderPair& folder) //throw FileError,
 {
     const SyncOperation syncOp = folder.getSyncOperation();
 
-    if (std::optional<SelectedSide> sideTrg = getTargetDirection(syncOp))
+    if (std::optional<SelectSide> sideTrg = getTargetDirection(syncOp))
     {
-        if (*sideTrg == LEFT_SIDE)
-            synchronizeFolderInt<LEFT_SIDE>(folder, syncOp);
+        if (*sideTrg == SelectSide::left)
+            synchronizeFolderInt<SelectSide::left>(folder, syncOp);
         else
-            synchronizeFolderInt<RIGHT_SIDE>(folder, syncOp);
+            synchronizeFolderInt<SelectSide::right>(folder, syncOp);
     }
 }
 
 
-template <SelectedSide sideTrg>
+template <SelectSide sideTrg>
 void FolderPairSyncer::synchronizeFolderInt(FolderPair& folder, SyncOperation syncOp) //throw FileError, ThreadStopRequest
 {
-    constexpr SelectedSide sideSrc = OtherSide<sideTrg>::value;
+    constexpr SelectSide sideSrc = OtherSide<sideTrg>::value;
     DeletionHandler& delHandlerTrg = SelectParam<sideTrg>::ref(delHandlerLeft_, delHandlerRight_);
 
     switch (syncOp)
@@ -1932,7 +1938,7 @@ void FolderPairSyncer::synchronizeFolderInt(FolderPair& folder, SyncOperation sy
                 acb_.updateDataProcessed(1, 0); //even if the source item does not exist anymore, significant I/O work was done => report
                 acb_.updateDataTotal(getCUD(statsAfter) - getCUD(statsBefore) + 1, statsAfter.getBytesToProcess() - statsBefore.getBytesToProcess()); //noexcept
 
-                reportInfo(txtSourceItemNotFound_, AFS::getDisplayPath(folder.getAbstractPath<sideSrc>())); //throw ThreadStopRequest
+                logInfo(txtSourceItemNotFound_, AFS::getDisplayPath(folder.getAbstractPath<sideSrc>())); //throw ThreadStopRequest
             }
         }
         break;
@@ -2002,7 +2008,7 @@ AFS::FileCopyResult FolderPairSyncer::copyFileWithCallback(const FileDescriptor&
                                                            AsyncItemStatReporter& statReporter)
 {
     const AbstractPath& sourcePath = sourceDescr.path;
-    const AFS::StreamAttributes sourceAttr{ sourceDescr.attr.modTime, sourceDescr.attr.fileSize, sourceDescr.attr.fileId };
+    const AFS::StreamAttributes sourceAttr{sourceDescr.attr.modTime, sourceDescr.attr.fileSize, sourceDescr.attr.filePrint};
 
     auto copyOperation = [this, &sourceAttr, &targetPath, &onDeleteTargetFile, &statReporter](const AbstractPath& sourcePathTmp)
     {
@@ -2048,7 +2054,7 @@ AFS::FileCopyResult FolderPairSyncer::copyFileWithCallback(const FileDescriptor&
 
 //###########################################################################################
 
-template <SelectedSide side>
+template <SelectSide side>
 bool baseFolderDrop(BaseFolderPair& baseFolder, PhaseCallback& callback)
 {
     const AbstractPath folderPath = baseFolder.getAbstractPath<side>();
@@ -2057,7 +2063,7 @@ bool baseFolderDrop(BaseFolderPair& baseFolder, PhaseCallback& callback)
     {
         const std::wstring errMsg = tryReportingError([&]
         {
-            const FolderStatus status = getFolderStatusNonBlocking({ folderPath },
+            const FolderStatus status = getFolderStatusNonBlocking({folderPath},
             false /*allowUserInteraction*/, callback);
 
             static_assert(std::is_same_v<decltype(status.failedChecks.begin()->second), FileError>);
@@ -2076,10 +2082,10 @@ bool baseFolderDrop(BaseFolderPair& baseFolder, PhaseCallback& callback)
 }
 
 
-template <SelectedSide side> //create base directories first (if not yet existing) -> no symlink or attribute copying!
+template <SelectSide side> //create base directories first (if not yet existing) -> no symlink or attribute copying!
 bool createBaseFolder(BaseFolderPair& baseFolder, bool copyFilePermissions, PhaseCallback& callback) //return false if fatal error occurred
 {
-    static const SelectedSide sideSrc = OtherSide<side>::value;
+    static const SelectSide sideSrc = OtherSide<side>::value;
     const AbstractPath baseFolderPath = baseFolder.getAbstractPath<side>();
 
     if (AFS::isNullPath(baseFolderPath))
@@ -2090,7 +2096,7 @@ bool createBaseFolder(BaseFolderPair& baseFolder, bool copyFilePermissions, Phas
         bool temporaryNetworkDrop = false;
         const std::wstring errMsg = tryReportingError([&]
         {
-            const FolderStatus status = getFolderStatusNonBlocking({ baseFolderPath },
+            const FolderStatus status = getFolderStatusNonBlocking({baseFolderPath},
             false /*allowUserInteraction*/, callback);
 
             static_assert(std::is_same_v<decltype(status.failedChecks.begin()->second), FileError>);
@@ -2196,7 +2202,7 @@ void fff::synchronize(const std::chrono::system_clock::time_point& syncStartTime
     }
     catch (const FileError& e) //failure is not critical => log only
     {
-        callback.reportInfo(e.toString()); //throw X
+        callback.logInfo(e.toString()); //throw X
     }
 
     //-------------------execute basic checks all at once BEFORE starting sync--------------------------------------
@@ -2243,8 +2249,8 @@ void fff::synchronize(const std::chrono::system_clock::time_point& syncStartTime
         //===============================================================================
 
         //exclude a few pathological cases (including empty left, right folders)
-        if (baseFolder.getAbstractPath< LEFT_SIDE>() ==
-            baseFolder.getAbstractPath<RIGHT_SIDE>())
+        if (baseFolder.getAbstractPath< SelectSide::left>() ==
+            baseFolder.getAbstractPath<SelectSide::right>())
         {
             jobType[folderIndex] = FolderPairJobType::SKIP;
             continue;
@@ -2258,17 +2264,17 @@ void fff::synchronize(const std::chrono::system_clock::time_point& syncStartTime
             continue;
         }
 
-        const bool writeLeft = folderPairStat.createCount<LEFT_SIDE>() +
-                               folderPairStat.updateCount<LEFT_SIDE>() +
-                               folderPairStat.deleteCount<LEFT_SIDE>() > 0;
+        const bool writeLeft = folderPairStat.createCount<SelectSide::left>() +
+                               folderPairStat.updateCount<SelectSide::left>() +
+                               folderPairStat.deleteCount<SelectSide::left>() > 0;
 
-        const bool writeRight = folderPairStat.createCount<RIGHT_SIDE>() +
-                                folderPairStat.updateCount<RIGHT_SIDE>() +
-                                folderPairStat.deleteCount<RIGHT_SIDE>() > 0;
+        const bool writeRight = folderPairStat.createCount<SelectSide::right>() +
+                                folderPairStat.updateCount<SelectSide::right>() +
+                                folderPairStat.deleteCount<SelectSide::right>() > 0;
 
         //check for empty target folder paths: this only makes sense if empty field is source (and no DB files need to be created)
-        if ((AFS::isNullPath(baseFolder.getAbstractPath< LEFT_SIDE>()) && (writeLeft  || folderPairCfg.saveSyncDB)) ||
-            (AFS::isNullPath(baseFolder.getAbstractPath<RIGHT_SIDE>()) && (writeRight || folderPairCfg.saveSyncDB)))
+        if ((AFS::isNullPath(baseFolder.getAbstractPath< SelectSide::left>()) && (writeLeft  || folderPairCfg.saveSyncDB)) ||
+            (AFS::isNullPath(baseFolder.getAbstractPath<SelectSide::right>()) && (writeRight || folderPairCfg.saveSyncDB)))
         {
             callback.reportFatalError(_("Target folder input field must not be empty."));
             jobType[folderIndex] = FolderPairJobType::SKIP;
@@ -2278,8 +2284,8 @@ void fff::synchronize(const std::chrono::system_clock::time_point& syncStartTime
         //check for network drops after comparison
         // - convenience: exit sync right here instead of showing tons of errors during file copy
         // - early failure! there's no point in evaluating subsequent warnings
-        if (baseFolderDrop< LEFT_SIDE>(baseFolder, callback) ||
-            baseFolderDrop<RIGHT_SIDE>(baseFolder, callback))
+        if (baseFolderDrop< SelectSide::left>(baseFolder, callback) ||
+            baseFolderDrop<SelectSide::right>(baseFolder, callback))
         {
             jobType[folderIndex] = FolderPairJobType::SKIP;
             continue;
@@ -2300,8 +2306,8 @@ void fff::synchronize(const std::chrono::system_clock::time_point& syncStartTime
                     }
             return false;
         };
-        if (sourceFolderMissing(baseFolder.getAbstractPath< LEFT_SIDE>(), baseFolder.isAvailable< LEFT_SIDE>()) ||
-            sourceFolderMissing(baseFolder.getAbstractPath<RIGHT_SIDE>(), baseFolder.isAvailable<RIGHT_SIDE>()))
+        if (sourceFolderMissing(baseFolder.getAbstractPath< SelectSide::left>(), baseFolder.isAvailable< SelectSide::left>()) ||
+            sourceFolderMissing(baseFolder.getAbstractPath<SelectSide::right>(), baseFolder.isAvailable<SelectSide::right>()))
         {
             jobType[folderIndex] = FolderPairJobType::SKIP;
             continue;
@@ -2323,20 +2329,20 @@ void fff::synchronize(const std::chrono::system_clock::time_point& syncStartTime
 
             //prepare: check if versioning path itself will be synchronized (and was not excluded via filter)
             checkVersioningPaths.insert(versioningFolderPath);
-            checkVersioningBasePaths.emplace_back(baseFolder.getAbstractPath< LEFT_SIDE>(), &baseFolder.getFilter());
-            checkVersioningBasePaths.emplace_back(baseFolder.getAbstractPath<RIGHT_SIDE>(), &baseFolder.getFilter());
+            checkVersioningBasePaths.emplace_back(baseFolder.getAbstractPath< SelectSide::left>(), &baseFolder.getFilter());
+            checkVersioningBasePaths.emplace_back(baseFolder.getAbstractPath<SelectSide::right>(), &baseFolder.getFilter());
         }
 
         //prepare: check if folders are used by multiple pairs in read/write access
-        checkReadWriteBaseFolders.emplace_back(baseFolder.getAbstractPath< LEFT_SIDE>(), &baseFolder.getFilter(), writeLeft);
-        checkReadWriteBaseFolders.emplace_back(baseFolder.getAbstractPath<RIGHT_SIDE>(), &baseFolder.getFilter(), writeRight);
+        checkReadWriteBaseFolders.emplace_back(baseFolder.getAbstractPath< SelectSide::left>(), &baseFolder.getFilter(), writeLeft);
+        checkReadWriteBaseFolders.emplace_back(baseFolder.getAbstractPath<SelectSide::right>(), &baseFolder.getFilter(), writeRight);
 
         //check if more than 50% of total number of files/dirs are to be created/overwritten/deleted
-        if (!AFS::isNullPath(baseFolder.getAbstractPath< LEFT_SIDE>()) &&
-            !AFS::isNullPath(baseFolder.getAbstractPath<RIGHT_SIDE>()))
+        if (!AFS::isNullPath(baseFolder.getAbstractPath< SelectSide::left>()) &&
+            !AFS::isNullPath(baseFolder.getAbstractPath<SelectSide::right>()))
             if (significantDifferenceDetected(folderPairStat))
-                checkSignificantDiffPairs.emplace_back(baseFolder.getAbstractPath< LEFT_SIDE>(),
-                                                       baseFolder.getAbstractPath<RIGHT_SIDE>());
+                checkSignificantDiffPairs.emplace_back(baseFolder.getAbstractPath< SelectSide::left>(),
+                                                       baseFolder.getAbstractPath<SelectSide::right>());
 
         //check for sufficient free diskspace
         auto checkSpace = [&](const AbstractPath& baseFolderPath, int64_t minSpaceNeeded)
@@ -2348,16 +2354,16 @@ void fff::synchronize(const std::chrono::system_clock::time_point& syncStartTime
 
                     if (0 <= freeSpace &&
                         freeSpace < minSpaceNeeded)
-                        checkDiskSpaceMissing.push_back({ baseFolderPath, { minSpaceNeeded, freeSpace } });
+                        checkDiskSpaceMissing.push_back({baseFolderPath, {minSpaceNeeded, freeSpace}});
                 }
                 catch (const FileError& e) //failure is not critical => log only
                 {
-                    callback.reportInfo(e.toString()); //throw X
+                    callback.logInfo(e.toString()); //throw X
                 }
         };
         const std::pair<int64_t, int64_t> spaceNeeded = MinimumDiskSpaceNeeded::calculate(baseFolder);
-        checkSpace(baseFolder.getAbstractPath< LEFT_SIDE>(), spaceNeeded.first);
-        checkSpace(baseFolder.getAbstractPath<RIGHT_SIDE>(), spaceNeeded.second);
+        checkSpace(baseFolder.getAbstractPath< SelectSide::left>(), spaceNeeded.first);
+        checkSpace(baseFolder.getAbstractPath<SelectSide::right>(), spaceNeeded.second);
 
         //Windows: check if recycle bin really exists; if not, Windows will silently delete, which is just wrong
         auto checkRecycler = [&](const AbstractPath& baseFolderPath)
@@ -2379,11 +2385,11 @@ void fff::synchronize(const std::chrono::system_clock::time_point& syncStartTime
         };
         if (folderPairCfg.handleDeletion == DeletionPolicy::recycler)
         {
-            if (folderPairStat.expectPhysicalDeletion<LEFT_SIDE>())
-                checkRecycler(baseFolder.getAbstractPath<LEFT_SIDE>());
+            if (folderPairStat.expectPhysicalDeletion<SelectSide::left>())
+                checkRecycler(baseFolder.getAbstractPath<SelectSide::left>());
 
-            if (folderPairStat.expectPhysicalDeletion<RIGHT_SIDE>())
-                checkRecycler(baseFolder.getAbstractPath<RIGHT_SIDE>());
+            if (folderPairStat.expectPhysicalDeletion<SelectSide::right>())
+                checkRecycler(baseFolder.getAbstractPath<SelectSide::right>());
         }
     }
     //-----------------------------------------------------------------
@@ -2399,8 +2405,8 @@ void fff::synchronize(const std::chrono::system_clock::time_point& syncStartTime
             if (conflictCount > 0)
             {
                 msg += L"\n\n" + _("Folder pair:") + L' ' +
-                       AFS::getDisplayPath(baseFolder->getAbstractPath< LEFT_SIDE>()) + L" <-> " +
-                       AFS::getDisplayPath(baseFolder->getAbstractPath<RIGHT_SIDE>());
+                       AFS::getDisplayPath(baseFolder->getAbstractPath< SelectSide::left>()) + L" <-> " +
+                       AFS::getDisplayPath(baseFolder->getAbstractPath<SelectSide::right>());
 
                 for (const SyncStatistics::ConflictInfo& item : conflictPreview)
                     msg += L'\n' + utfTo<std::wstring>(item.relPath) + L": " + item.msg;
@@ -2567,7 +2573,7 @@ void fff::synchronize(const std::chrono::system_clock::time_point& syncStartTime
             if (!scopeFail)
                 callback.reportWarning(msg, warnings.warnModificationTimeError); //throw X
             else //at least log warnings when sync is cancelled
-                try { callback.reportInfo(msg); /*throw X*/} catch (...) {};
+                try { callback.logInfo(msg); /*throw X*/} catch (...) {};
         }
         //*INDENT-ON*
     );
@@ -2575,19 +2581,19 @@ void fff::synchronize(const std::chrono::system_clock::time_point& syncStartTime
     class PcbNoThrow : public PhaseCallback
     {
     public:
-        PcbNoThrow(ProcessCallback& cb) : cb_(cb) {}
+        explicit PcbNoThrow(ProcessCallback& cb) : cb_(cb) {}
 
         void updateDataProcessed(int itemsDelta, int64_t bytesDelta) override {} //sync DB/del-handler: logically not part of sync data, so let's ignore
         void updateDataTotal    (int itemsDelta, int64_t bytesDelta) override {} //
 
         void requestUiUpdate(bool force) override { try { cb_.requestUiUpdate(force); /*throw X*/} catch (...) {}; }
 
-        void updateStatus(const std::wstring& msg) override { try { cb_.updateStatus(msg); /*throw X*/} catch (...) {}; }
-        void reportInfo  (const std::wstring& msg) override { try { cb_.reportInfo  (msg); /*throw X*/} catch (...) {}; }
+        void updateStatus(std::wstring&& msg) override { try { cb_.updateStatus(std::move(msg)); /*throw X*/} catch (...) {}; }
+        void logInfo(const std::wstring& msg) override { try { cb_.logInfo(msg); /*throw X*/} catch (...) {}; }
 
-        void reportWarning(const std::wstring& msg, bool& warningActive) override { reportInfo(msg); /*ignore*/ }
-        Response reportError     (const ErrorInfo& errorInfo)            override { reportInfo(errorInfo.msg); return Response::ignore; }
-        void     reportFatalError(const std::wstring& msg)               override { reportInfo(msg); /*ignore*/ }
+        void reportWarning(const std::wstring& msg, bool& warningActive) override { logInfo(msg); /*ignore*/ }
+        Response reportError     (const ErrorInfo& errorInfo)            override { logInfo(errorInfo.msg); return Response::ignore; }
+        void     reportFatalError(const std::wstring& msg)               override { logInfo(msg); /*ignore*/ }
 
     private:
         ProcessCallback& cb_;
@@ -2608,20 +2614,20 @@ void fff::synchronize(const std::chrono::system_clock::time_point& syncStartTime
 
             //------------------------------------------------------------------------------------------
             if (folderCmp.size() > 1)
-                callback.reportInfo(_("Synchronizing folder pair:") + L' ' + getVariantNameWithSymbol(folderPairCfg.syncVar) + L'\n' + //throw X
-                                    L"    " + AFS::getDisplayPath(baseFolder.getAbstractPath< LEFT_SIDE>()) + L'\n' +
-                                    L"    " + AFS::getDisplayPath(baseFolder.getAbstractPath<RIGHT_SIDE>()));
+                callback.logInfo(_("Synchronizing folder pair:") + L' ' + getVariantNameWithSymbol(folderPairCfg.syncVar) + L'\n' + //throw X
+                                 L"    " + AFS::getDisplayPath(baseFolder.getAbstractPath< SelectSide::left>()) + L'\n' +
+                                 L"    " + AFS::getDisplayPath(baseFolder.getAbstractPath<SelectSide::right>()));
             //------------------------------------------------------------------------------------------
 
             //checking a second time: (a long time may have passed since syncing the previous folder pairs!)
-            if (baseFolderDrop< LEFT_SIDE>(baseFolder, callback) ||
-                baseFolderDrop<RIGHT_SIDE>(baseFolder, callback))
+            if (baseFolderDrop< SelectSide::left>(baseFolder, callback) ||
+                baseFolderDrop<SelectSide::right>(baseFolder, callback))
                 continue;
 
             //create base folders if not yet existing
             if (folderPairStat.createCount() > 0 || folderPairCfg.saveSyncDB) //else: temporary network drop leading to deletions already caught by "sourceFolderMissing" check!
-                if (!createBaseFolder< LEFT_SIDE>(baseFolder, copyFilePermissions, callback) || //+ detect temporary network drop!!
-                    !createBaseFolder<RIGHT_SIDE>(baseFolder, copyFilePermissions, callback))   //
+                if (!createBaseFolder< SelectSide::left>(baseFolder, copyFilePermissions, callback) || //+ detect temporary network drop!!
+                    !createBaseFolder<SelectSide::right>(baseFolder, copyFilePermissions, callback))   //
                     continue;
 
             //------------------------------------------------------------------------------------------
@@ -2644,10 +2650,10 @@ void fff::synchronize(const std::chrono::system_clock::time_point& syncStartTime
                 tryReportingError([&]
                 {
                     copyPermissionsFp = copyFilePermissions && //copy permissions only if asked for and supported by *both* sides!
-                    !AFS::isNullPath(baseFolder.getAbstractPath< LEFT_SIDE>()) && //scenario: directory selected on one side only
-                    !AFS::isNullPath(baseFolder.getAbstractPath<RIGHT_SIDE>()) && //
-                    AFS::supportPermissionCopy(baseFolder.getAbstractPath<LEFT_SIDE>(),
-                                               baseFolder.getAbstractPath<RIGHT_SIDE>()); //throw FileError
+                    !AFS::isNullPath(baseFolder.getAbstractPath< SelectSide::left>()) && //scenario: directory selected on one side only
+                    !AFS::isNullPath(baseFolder.getAbstractPath<SelectSide::right>()) && //
+                    AFS::supportPermissionCopy(baseFolder.getAbstractPath<SelectSide::left>(),
+                                               baseFolder.getAbstractPath<SelectSide::right>()); //throw FileError
                 }, callback); //throw X
 
 
@@ -2664,14 +2670,14 @@ void fff::synchronize(const std::chrono::system_clock::time_point& syncStartTime
                 };
                 const AbstractPath versioningFolderPath = createAbstractPath(folderPairCfg.versioningFolderPhrase);
 
-                DeletionHandler delHandlerL(baseFolder.getAbstractPath<LEFT_SIDE>(),
-                                            getEffectiveDeletionPolicy(baseFolder.getAbstractPath<LEFT_SIDE>()),
+                DeletionHandler delHandlerL(baseFolder.getAbstractPath<SelectSide::left>(),
+                                            getEffectiveDeletionPolicy(baseFolder.getAbstractPath<SelectSide::left>()),
                                             versioningFolderPath,
                                             folderPairCfg.versioningStyle,
                                             std::chrono::system_clock::to_time_t(syncStartTime));
 
-                DeletionHandler delHandlerR(baseFolder.getAbstractPath<RIGHT_SIDE>(),
-                                            getEffectiveDeletionPolicy(baseFolder.getAbstractPath<RIGHT_SIDE>()),
+                DeletionHandler delHandlerR(baseFolder.getAbstractPath<SelectSide::right>(),
+                                            getEffectiveDeletionPolicy(baseFolder.getAbstractPath<SelectSide::right>()),
                                             versioningFolderPath,
                                             folderPairCfg.versioningStyle,
                                             std::chrono::system_clock::to_time_t(syncStartTime));
diff --git a/FreeFileSync/Source/base/synchronization.h b/FreeFileSync/Source/base/synchronization.h
index cb66a4ad..592760ce 100644
--- a/FreeFileSync/Source/base/synchronization.h
+++ b/FreeFileSync/Source/base/synchronization.h
@@ -23,19 +23,19 @@ public:
     SyncStatistics(const ContainerObject& hierObj);
     SyncStatistics(const FilePair& file);
 
-    template <SelectedSide side>
+    template <SelectSide side>
     int createCount() const { return SelectParam<side>::ref(createLeft_, createRight_); }
     int createCount() const { return createLeft_ + createRight_; }
 
-    template <SelectedSide side>
+    template <SelectSide side>
     int updateCount() const { return SelectParam<side>::ref(updateLeft_, updateRight_); }
     int updateCount() const { return updateLeft_ + updateRight_; }
 
-    template <SelectedSide side>
+    template <SelectSide side>
     int deleteCount() const { return SelectParam<side>::ref(deleteLeft_, deleteRight_); }
     int deleteCount() const { return deleteLeft_ + deleteRight_; }
 
-    template <SelectedSide side>
+    template <SelectSide side>
     bool expectPhysicalDeletion() const { return SelectParam<side>::ref(physicalDeleteLeft_, physicalDeleteRight_); }
 
     int64_t getBytesToProcess() const { return bytesToProcess_; }
diff --git a/FreeFileSync/Source/base/versioning.cpp b/FreeFileSync/Source/base/versioning.cpp
index ffd98261..adb8f106 100644
--- a/FreeFileSync/Source/base/versioning.cpp
+++ b/FreeFileSync/Source/base/versioning.cpp
@@ -55,7 +55,7 @@ std::pair<time_t, Zstring> fff::impl::parseVersionedFileName(const Zstring& file
     if (fileNameOrig.empty())
         return {};
 
-    return { t, std::move(fileNameOrig) };
+    return {t, std::move(fileNameOrig)};
 }
 
 
@@ -179,7 +179,7 @@ void moveExistingItemToVersioning(const AbstractPath& sourcePath, const Abstract
 }
 
 
-void FileVersioner::revisionFile(const FileDescriptor& fileDescr, const Zstring& relativePath, const IOCallback& notifyUnbufferedIO /*throw X*/) const //throw FileError, X
+void FileVersioner::revisionFile(const FileDescriptor& fileDescr, const Zstring& relativePath, const IoCallback& notifyUnbufferedIO /*throw X*/) const //throw FileError, X
 {
     if (std::optional<AFS::ItemType> type = AFS::itemStillExists(fileDescr.path)) //throw FileError
     {
@@ -194,12 +194,12 @@ void FileVersioner::revisionFile(const FileDescriptor& fileDescr, const Zstring&
 
 void FileVersioner::revisionFileImpl(const FileDescriptor& fileDescr, const Zstring& relativePath, //throw FileError, X
                                      const std::function<void(const std::wstring& displayPathFrom, const std::wstring& displayPathTo)>& onBeforeMove,
-                                     const IOCallback& notifyUnbufferedIO  /*throw X*/) const
+                                     const IoCallback& notifyUnbufferedIO  /*throw X*/) const
 {
     const AbstractPath& filePath = fileDescr.path;
 
     const AbstractPath targetPath = generateVersionedPath(relativePath);
-    const AFS::StreamAttributes fileAttr{ fileDescr.attr.modTime, fileDescr.attr.fileSize, fileDescr.attr.fileId };
+    const AFS::StreamAttributes fileAttr{fileDescr.attr.modTime, fileDescr.attr.fileSize, fileDescr.attr.filePrint};
 
     if (onBeforeMove)
         onBeforeMove(AFS::getDisplayPath(filePath), AFS::getDisplayPath(targetPath));
@@ -242,7 +242,7 @@ void FileVersioner::revisionSymlinkImpl(const AbstractPath& linkPath, const Zstr
 void FileVersioner::revisionFolder(const AbstractPath& folderPath, const Zstring& relativePath, //throw FileError, X
                                    const std::function<void(const std::wstring& displayPathFrom, const std::wstring& displayPathTo)>& onBeforeFileMove   /*throw X*/,
                                    const std::function<void(const std::wstring& displayPathFrom, const std::wstring& displayPathTo)>& onBeforeFolderMove /*throw X*/,
-                                   const IOCallback& notifyUnbufferedIO /*throw X*/) const
+                                   const IoCallback& notifyUnbufferedIO /*throw X*/) const
 {
     //no error situation if directory is not existing! manual deletion relies on it!
     if (std::optional<AFS::ItemType> type = AFS::itemStillExists(folderPath)) //throw FileError
@@ -260,7 +260,7 @@ void FileVersioner::revisionFolder(const AbstractPath& folderPath, const Zstring
 void FileVersioner::revisionFolderImpl(const AbstractPath& folderPath, const Zstring& relativePath, //throw FileError, X
                                        const std::function<void(const std::wstring& displayPathFrom, const std::wstring& displayPathTo)>& onBeforeFileMove,
                                        const std::function<void(const std::wstring& displayPathFrom, const std::wstring& displayPathTo)>& onBeforeFolderMove,
-                                       const IOCallback& notifyUnbufferedIO /*throw X*/) const
+                                       const IoCallback& notifyUnbufferedIO /*throw X*/) const
 {
 
     //create target directories only when needed in moveFileToVersioning(): avoid empty directories!
@@ -277,8 +277,8 @@ void FileVersioner::revisionFolderImpl(const AbstractPath& folderPath, const Zst
 
     for (const AFS::FileInfo& fileInfo : files)
     {
-        const FileDescriptor fileDescr{ AFS::appendRelPath(folderPath, fileInfo.itemName),
-                                        FileAttributes(fileInfo.modTime, fileInfo.fileSize, fileInfo.fileId, false /*isSymlink*/)};
+        const FileDescriptor fileDescr{AFS::appendRelPath(folderPath, fileInfo.itemName),
+                                       FileAttributes(fileInfo.modTime, fileInfo.fileSize, fileInfo.filePrint, false /*isFollowedSymlink*/)};
 
         revisionFileImpl(fileDescr, relPathPf + fileInfo.itemName, onBeforeFileMove, notifyUnbufferedIO); //throw FileError, X
     }
@@ -325,7 +325,7 @@ void findFileVersions(VersionInfoMap& versions,
         const Zstring& relPathOrig   = nativeAppendPaths(relPathOrigParent, fileNameOrig);
         const AbstractPath& filePath = AFS::appendRelPath(parentFolderPath, fileName);
 
-        versions[relPathOrig].push_back(VersionInfo{ versionTime, filePath, isSymlink });
+        versions[relPathOrig].push_back(VersionInfo{versionTime, filePath, isSymlink});
     };
 
     auto extractFileVersion = [&](const Zstring& fileName, bool isSymlink)
@@ -423,7 +423,7 @@ void fff::applyVersioningLimit(const std::set<VersioningLimitFolder>& folderLimi
                                                                    false /*allowUserInteraction*/, callback); //throw X
             foldersToRead.clear();
             for (const AbstractPath& folderPath : status.existing)
-                foldersToRead.insert(DirectoryKey({ folderPath, makeSharedRef<NullFilter>(), SymLinkHandling::direct }));
+                foldersToRead.insert(DirectoryKey({folderPath, makeSharedRef<NullFilter>(), SymLinkHandling::direct}));
 
             if (!status.failedChecks.empty())
             {
diff --git a/FreeFileSync/Source/base/versioning.h b/FreeFileSync/Source/base/versioning.h
index 7e707300..6c5d667b 100644
--- a/FreeFileSync/Source/base/versioning.h
+++ b/FreeFileSync/Source/base/versioning.h
@@ -53,7 +53,7 @@ public:
     void revisionFile(const FileDescriptor& fileDescr, //throw FileError, X
                       const Zstring& relativePath,
                       //called frequently if move has to revert to copy + delete => see zen::copyFile for limitations when throwing exceptions!
-                      const zen::IOCallback& notifyUnbufferedIO /*throw X*/) const;
+                      const zen::IoCallback& notifyUnbufferedIO /*throw X*/) const;
 
     void revisionSymlink(const AbstractPath& linkPath, const Zstring& relativePath) const; //throw FileError
 
@@ -61,7 +61,7 @@ public:
                         const std::function<void(const std::wstring& displayPathFrom, const std::wstring& displayPathTo)>& onBeforeFileMove,   /*throw X*/
                         const std::function<void(const std::wstring& displayPathFrom, const std::wstring& displayPathTo)>& onBeforeFolderMove, /*throw X*/
                         //called frequently if move has to revert to copy + delete => see zen::copyFile for limitations when throwing exceptions!
-                        const zen::IOCallback& notifyUnbufferedIO /*throw X*/) const;
+                        const zen::IoCallback& notifyUnbufferedIO /*throw X*/) const;
 
 private:
     FileVersioner           (const FileVersioner&) = delete;
@@ -69,7 +69,7 @@ private:
 
     void revisionFileImpl(const FileDescriptor& fileDescr, const Zstring& relativePath, //throw FileError, X
                           const std::function<void(const std::wstring& displayPathFrom, const std::wstring& displayPathTo)>& onBeforeMove,
-                          const zen::IOCallback& notifyUnbufferedIO) const;
+                          const zen::IoCallback& notifyUnbufferedIO) const;
 
     void revisionSymlinkImpl(const AbstractPath& linkPath, const Zstring& relativePath, //throw FileError
                              const std::function<void(const std::wstring& displayPathFrom, const std::wstring& displayPathTo)>& onBeforeMove) const;
@@ -77,7 +77,7 @@ private:
     void revisionFolderImpl(const AbstractPath& folderPath, const Zstring& relativePath,
                             const std::function<void(const std::wstring& displayPathFrom, const std::wstring& displayPathTo)>& onBeforeFileMove,
                             const std::function<void(const std::wstring& displayPathFrom, const std::wstring& displayPathTo)>& onBeforeFolderMove,
-                            const zen::IOCallback& notifyUnbufferedIO) const; //throw FileError, X
+                            const zen::IoCallback& notifyUnbufferedIO) const; //throw FileError, X
 
     AbstractPath generateVersionedPath(const Zstring& relativePath) const;
 
diff --git a/FreeFileSync/Source/base_tools.cpp b/FreeFileSync/Source/base_tools.cpp
index 8860ecef..73246dde 100644
--- a/FreeFileSync/Source/base_tools.cpp
+++ b/FreeFileSync/Source/base_tools.cpp
@@ -29,7 +29,7 @@ std::vector<unsigned int> fff::fromTimeShiftPhrase(const std::wstring& timeShift
     }
     minutes.erase(0);
 
-    return { minutes.begin(), minutes.end() };
+    return {minutes.begin(), minutes.end()};
 }
 
 
@@ -76,7 +76,7 @@ void fff::logNonDefaultSettings(const XmlGlobalSettings& activeSettings, PhaseCa
         changedSettingsMsg += L"\n    " + _("Verify copied files") + L" - " + (activeSettings.verifyFileCopy ? _("Enabled") : _("Disabled"));
 
     if (!changedSettingsMsg.empty())
-        callback.reportInfo(_("Using non-default global settings:") + changedSettingsMsg); //throw X
+        callback.logInfo(_("Using non-default global settings:") + changedSettingsMsg); //throw X
 }
 
 
diff --git a/FreeFileSync/Source/config.cpp b/FreeFileSync/Source/config.cpp
index 06f4abb6..f4d2850b 100644
--- a/FreeFileSync/Source/config.cpp
+++ b/FreeFileSync/Source/config.cpp
@@ -13,6 +13,7 @@
 #include <wx/intl.h>
 #include "ffs_paths.h"
 #include "base_tools.h"
+#include "afs/native.h"
 
 
 using namespace zen;
@@ -1099,8 +1100,9 @@ void writeStruc(const ConfigFileItem& value, XmlElement& output)
     out.attribute("Config", substituteFreeFileSyncDriveLetter(value.cfgFilePath));
     out.attribute("LastSync", value.lastSyncTime);
 
-    if (std::optional<Zstring> nativePath = AFS::getNativeItemPath(value.logFilePath))
-        out.attribute("Log", substituteFreeFileSyncDriveLetter(*nativePath));
+    if (const Zstring& nativePath = getNativeItemPath(value.logFilePath);
+        !nativePath.empty())
+        out.attribute("Log", substituteFreeFileSyncDriveLetter(nativePath));
     else
         out.attribute("Log", AFS::getInitPathPhrase(value.logFilePath));
 
@@ -1109,7 +1111,7 @@ void writeStruc(const ConfigFileItem& value, XmlElement& output)
         const auto& [highR, lowR] = hexify(value.backColor.Red  ());
         const auto& [highG, lowG] = hexify(value.backColor.Green());
         const auto& [highB, lowB] = hexify(value.backColor.Blue ());
-        out.attribute("Color", std::string({ highR, lowR, highG, lowG, highB, lowB }));
+        out.attribute("Color", std::string({highR, lowR, highG, lowG, highB, lowB}));
     }
 }
 
diff --git a/FreeFileSync/Source/config.h b/FreeFileSync/Source/config.h
index b5995318..dc2c6bd6 100644
--- a/FreeFileSync/Source/config.h
+++ b/FreeFileSync/Source/config.h
@@ -8,6 +8,7 @@
 #define PROCESS_XML_H_28345825704254262435
 
 #include <wx/gdicmn.h>
+#include <zen/file_access.h>
 #include "localization.h"
 #include "base/structures.h"
 #include "ui/file_grid_attr.h"
@@ -130,7 +131,7 @@ struct XmlGlobalSettings
     bool copyLockedFiles  = false; //safer default: avoid copies of partially written files
     bool copyFilePermissions = false;
 
-    int fileTimeTolerance = 2; //max. allowed file time deviation; < 0 means unlimited tolerance; default 2s: FAT vs NTFS
+    int fileTimeTolerance = zen::FAT_FILE_TIME_PRECISION_SEC; //max. allowed file time deviation; < 0 means unlimited tolerance; default 2s: FAT vs NTFS
     bool runWithBackgroundPriority = false;
     bool createLockFile = true;
     bool verifyFileCopy = false;
@@ -227,8 +228,8 @@ struct XmlGlobalSettings
         /* CONTRACT: first entry: show item in file browser
                      default external app descriptions will be translated "on the fly"!!!           */
         //"xdg-open \"%parent_path%\"" -> not good enough: we need %local_path% for proper MTP/Google Drive handling
-        { L"Browse directory", "xdg-open \"$(dirname \"%local_path%\")\"" },
-        { L"Open with default application", "xdg-open \"%local_path%\""   },
+        {L"Browse directory", "xdg-open \"$(dirname \"%local_path%\")\""},
+        {L"Open with default application", "xdg-open \"%local_path%\""  },
         //mark for extraction: _("Browse directory") Linux doesn't use the term "folder"
     };
 
diff --git a/FreeFileSync/Source/fatal_error.h b/FreeFileSync/Source/fatal_error.h
index eb025472..4749ac75 100644
--- a/FreeFileSync/Source/fatal_error.h
+++ b/FreeFileSync/Source/fatal_error.h
@@ -16,7 +16,7 @@
 namespace fff
 {
 //write error message to a file (even with corrupted stack)- call in desperate situations when no other means of error handling is available
-void logFatalError(const std::string& msg); //noexcept
+void logFatalError(const std::wstring& msg); //noexcept
 
 
 
@@ -28,12 +28,12 @@ void logFatalError(const std::string& msg); //noexcept
 
 //##################### implementation ############################
 inline
-void logFatalError(const std::string& msg) //noexcept
+void logFatalError(const std::wstring& msg) //noexcept
 {
     using namespace zen;
 
     assert(false); //this is stuff we like to debug
-    const std::string logEntry = '[' + utfTo<std::string>(formatTime(formatDateTimeTag)) + "] " + msg;
+    const std::string logEntry = '[' + utfTo<std::string>(formatTime(formatDateTimeTag)) + "] " + utfTo<std::string>(msg);
     try
     {
         setFileContent(getConfigDirPathPf() + Zstr("LastError.log"), logEntry, nullptr /*notifyUnbufferedIO*/); //throw FileError
diff --git a/FreeFileSync/Source/ffs_paths.cpp b/FreeFileSync/Source/ffs_paths.cpp
index 6a81257e..44b80f6f 100644
--- a/FreeFileSync/Source/ffs_paths.cpp
+++ b/FreeFileSync/Source/ffs_paths.cpp
@@ -8,8 +8,6 @@
 #include <zen/file_access.h>
 #include <zen/thread.h>
 #include <zen/sys_info.h>
-#include <wx/stdpaths.h>
-#include <wx/app.h>
 
     #include <iostream> //std::cerr
 
@@ -48,21 +46,6 @@ Zstring fff::getInstallDirPath()
 }
 
 
-//getFfsVolumeId() might be called during static destruction, e.g. async update check
-VolumeId fff::getFfsVolumeId() //throw FileError
-{
-    static VolumeId volumeId; //POD => no "magic static" code gen
-    static constinit2 std::once_flag onceFlagGetFfsVolumeId; //=> no "magic static" code gen
-    std::call_once(onceFlagGetFfsVolumeId, [] { volumeId = getVolumeId(getRealProcessPath()); }); //throw FileError
-    return volumeId;
-}
-
-
-bool fff::isPortableVersion()
-{
-    return false; //users want local installation type: https://freefilesync.org/forum/viewtopic.php?t=5750
-
-}
 
 
 Zstring fff::getResourceDirPf()
@@ -73,34 +56,37 @@ Zstring fff::getResourceDirPf()
 
 Zstring fff::getConfigDirPathPf()
 {
-    warn_static("Linux/macOS TODO: consider getuid() == 0 as request for elevation, NOT impersonation")
-
     //note: compiler generates magic-statics code => fine, we don't expect accesses during shutdown
-    static const Zstring cfgFolderPathPf = []
+    static const Zstring ffsConfigPathPf = []
     {
-        //make independent from wxWidgets global variable "appname"; support being called by RealTimeSync
-        auto appName = wxTheApp->GetAppName();
-        wxTheApp->SetAppName(L"FreeFileSync");
-        ZEN_ON_SCOPE_EXIT(wxTheApp->SetAppName(appName));
-
-        //OS standard path (XDG layout): ~/.config/FreeFileSync
-        //wxBug: wxStandardPaths::GetUserDataDir() does not honor FileLayout_XDG flag
-        wxStandardPaths::Get().SetFileLayout(wxStandardPaths::FileLayout_XDG);
-        const Zstring cfgFolderPath = appendSeparator(utfTo<Zstring>(wxStandardPaths::Get().GetUserConfigDir())) + "FreeFileSync";
+        /*  Windows:            %AppData%\FreeFileSync
+            macOS:              ~/Library/Application Support/FreeFileSync
+            Linux (XDG layout): ~/.config/FreeFileSync                        */
+        const Zstring& ffsConfigPath = []
+        {
+            try
+            {
+                return
+                appendSeparator(getUserDataPath()) + Zstr("FreeFileSync"); //throw FileError
+            }
+            catch (const FileError& e)
+            {
+                throw std::runtime_error(std::string(__FILE__) + '[' + numberTo<std::string>(__LINE__) + "] " + utfTo<std::string>(e.toString()));
+            }
+        }();
 
         try //create the config folder if not existing + create "Logs" subfolder while we're at it
         {
-            createDirectoryIfMissingRecursion(appendSeparator(cfgFolderPath) + Zstr("Logs")); //throw FileError
+            createDirectoryIfMissingRecursion(appendSeparator(ffsConfigPath) + Zstr("Logs")); //throw FileError
         }
         catch (const FileError& e)
         {
             assert(false);
             std::cerr << utfTo<std::string>(e.toString()) << '\n';
         }
-
-        return appendSeparator(cfgFolderPath);
+        return appendSeparator(ffsConfigPath);
     }();
-    return cfgFolderPathPf;
+    return ffsConfigPathPf;
 }
 
 
diff --git a/FreeFileSync/Source/ffs_paths.h b/FreeFileSync/Source/ffs_paths.h
index cbf4edb4..a2310a14 100644
--- a/FreeFileSync/Source/ffs_paths.h
+++ b/FreeFileSync/Source/ffs_paths.h
@@ -8,7 +8,6 @@
 #define FFS_PATHS_H_842759083425342534253
 
 #include <zen/zstring.h>
-#include <zen/file_id_def.h>
 
 
 namespace fff
@@ -20,11 +19,8 @@ Zstring getResourceDirPf  (); //resource directory WITH trailing path separator
 Zstring getConfigDirPathPf(); //  config directory WITH trailing path separator
 //------------------------------------------------------------------------------
 
-bool isPortableVersion();
 
-    Zstring getInstallDirPath();
-
-zen::VolumeId getFfsVolumeId(); //throw FileError
+Zstring getInstallDirPath();
 
 Zstring getFreeFileSyncLauncherPath(); //full path to application launcher C:\...\FreeFileSync.exe
 }
diff --git a/FreeFileSync/Source/icon_buffer.cpp b/FreeFileSync/Source/icon_buffer.cpp
index bdd5eab2..30ad3173 100644
--- a/FreeFileSync/Source/icon_buffer.cpp
+++ b/FreeFileSync/Source/icon_buffer.cpp
@@ -76,7 +76,7 @@ public:
             std::lock_guard dummy(lockFiles_);
             workLoad_ = newLoad;
         }
-        conditionNewWork_.notify_all(); //instead of notify_one(); workaround bug: https://svn.boost.org/trac/boost/ticket/7796
+        conditionNewWork_.notify_all(); //instead of notify_one(); work around bug: https://svn.boost.org/trac/boost/ticket/7796
         //condition handling, see: https://www.boost.org/doc/libs/1_43_0/doc/html/thread/synchronization.html#thread.synchronization.condvar_ref
     }
 
diff --git a/FreeFileSync/Source/localization.cpp b/FreeFileSync/Source/localization.cpp
index 40c7b890..b04bc3b5 100644
--- a/FreeFileSync/Source/localization.cpp
+++ b/FreeFileSync/Source/localization.cpp
@@ -49,7 +49,7 @@ public:
 
     std::wstring translate(const std::wstring& singular, const std::wstring& plural, int64_t n) const override
     {
-        auto it = transMappingPl_.find({ singular, plural });
+        auto it = transMappingPl_.find({singular, plural});
         if (it != transMappingPl_.end())
         {
             const size_t formNo = pluralParser_->getForm(n);
@@ -89,13 +89,11 @@ FFSTranslation::FFSTranslation(const std::string& lngStream) //throw lng::Parsin
         for (const std::string& pf : pluralForms)
             transPluralForms.push_back(utfTo<std::wstring>(pf));
 
-        transMappingPl_.insert(
-        {
-            {
+        transMappingPl_.insert({{
                 utfTo<std::wstring>(singAndPlural.first),
                 utfTo<std::wstring>(singAndPlural.second)
             },
-            std::move(transPluralForms) });
+            std::move(transPluralForms)});
     }
 }
 
diff --git a/FreeFileSync/Source/log_file.cpp b/FreeFileSync/Source/log_file.cpp
index 9ab69203..90eddeb9 100644
--- a/FreeFileSync/Source/log_file.cpp
+++ b/FreeFileSync/Source/log_file.cpp
@@ -399,7 +399,7 @@ void saveNewLogFile(const AbstractPath& logFilePath, //throw FileError, X
                     LogFileFormat logFormat,
                     const ProcessSummary& summary,
                     const ErrorLog& log,
-                    const std::function<void(const std::wstring& msg)>& notifyStatus /*throw X*/)
+                    const std::function<void(std::wstring&& msg)>& notifyStatus /*throw X*/)
 {
     //create logfile folder if required
     if (const std::optional<AbstractPath> parentPath = AFS::getParentPath(logFilePath))
@@ -479,7 +479,7 @@ std::vector<LogFileInfo> getLogFiles(const AbstractPath& logFolderPath) //throw
                         jobNames.pop_back();
                     }
 
-                    logfiles.push_back({ AFS::appendRelPath(logFolderPath, fi.itemName), t, utfTo<std::wstring>(jobNames) });
+                    logfiles.push_back({AFS::appendRelPath(logFolderPath, fi.itemName), t, utfTo<std::wstring>(jobNames)});
                 }
             }
         }
@@ -494,7 +494,7 @@ std::vector<LogFileInfo> getLogFiles(const AbstractPath& logFolderPath) //throw
 void limitLogfileCount(const AbstractPath& logFolderPath, //throw FileError, X
                        int logfilesMaxAgeDays, //<= 0 := no limit
                        const std::set<AbstractPath>& logFilePathsToKeep,
-                       const std::function<void(const std::wstring& msg)>& notifyStatus /*throw X*/)
+                       const std::function<void(std::wstring&& msg)>& notifyStatus /*throw X*/)
 {
     if (logfilesMaxAgeDays > 0)
     {
@@ -613,7 +613,7 @@ void fff::saveLogFile(const AbstractPath& logFilePath, //throw FileError, X
                       int logfilesMaxAgeDays,
                       LogFileFormat logFormat,
                       const std::set<AbstractPath>& logFilePathsToKeep,
-                      const std::function<void(const std::wstring& msg)>& notifyStatus /*throw X*/)
+                      const std::function<void(std::wstring&& msg)>& notifyStatus /*throw X*/)
 {
     std::exception_ptr firstError;
     try
@@ -642,7 +642,7 @@ void fff::sendLogAsEmail(const std::string& email, //throw FileError, X
                          const ProcessSummary& summary,
                          const ErrorLog& log,
                          const AbstractPath& logFilePath,
-                         const std::function<void(const std::wstring& msg)>& notifyStatus /*throw X*/)
+                         const std::function<void(std::wstring&& msg)>& notifyStatus /*throw X*/)
 {
     try
     {
diff --git a/FreeFileSync/Source/log_file.h b/FreeFileSync/Source/log_file.h
index 031be320..50dcd4c7 100644
--- a/FreeFileSync/Source/log_file.h
+++ b/FreeFileSync/Source/log_file.h
@@ -32,13 +32,13 @@ void saveLogFile(const AbstractPath& logFilePath, //throw FileError, X
                  int logfilesMaxAgeDays,
                  LogFileFormat logFormat,
                  const std::set<AbstractPath>& logFilePathsToKeep,
-                 const std::function<void(const std::wstring& msg)>& notifyStatus /*throw X*/);
+                 const std::function<void(std::wstring&& msg)>& notifyStatus /*throw X*/);
 
 void sendLogAsEmail(const std::string& email, //throw FileError, X
                     const ProcessSummary& summary,
                     const zen::ErrorLog& log,
                     const AbstractPath& logFilePath,
-                    const std::function<void(const std::wstring& msg)>& notifyStatus /*throw X*/);
+                    const std::function<void(std::wstring&& msg)>& notifyStatus /*throw X*/);
 }
 
 #endif //GENERATE_LOGFILE_H_931726432167489732164
diff --git a/FreeFileSync/Source/parse_lng.h b/FreeFileSync/Source/parse_lng.h
index 7b8e09ec..4ab4e0f7 100644
--- a/FreeFileSync/Source/parse_lng.h
+++ b/FreeFileSync/Source/parse_lng.h
@@ -211,28 +211,28 @@ private:
     const TokenMap tokens_ =
     {
         //header information
-        { Token::TK_HEADER_BEGIN,       "<header>" },
-        { Token::TK_HEADER_END,         "</header>" },
-        { Token::TK_LANG_NAME_BEGIN,    "<language>" },
-        { Token::TK_LANG_NAME_END,      "</language>" },
-        { Token::TK_TRANS_NAME_BEGIN,   "<translator>" },
-        { Token::TK_TRANS_NAME_END,     "</translator>" },
-        { Token::TK_LOCALE_NAME_BEGIN,  "<locale>" },
-        { Token::TK_LOCALE_NAME_END,    "</locale>" },
-        { Token::TK_FLAG_FILE_BEGIN,    "<image>" },
-        { Token::TK_FLAG_FILE_END,      "</image>" },
-        { Token::TK_PLURAL_COUNT_BEGIN, "<plural_count>" },
-        { Token::TK_PLURAL_COUNT_END,   "</plural_count>" },
-        { Token::TK_PLURAL_DEF_BEGIN,   "<plural_definition>" },
-        { Token::TK_PLURAL_DEF_END,     "</plural_definition>" },
+        {Token::TK_HEADER_BEGIN,       "<header>"},
+        {Token::TK_HEADER_END,         "</header>"},
+        {Token::TK_LANG_NAME_BEGIN,    "<language>"},
+        {Token::TK_LANG_NAME_END,      "</language>"},
+        {Token::TK_TRANS_NAME_BEGIN,   "<translator>"},
+        {Token::TK_TRANS_NAME_END,     "</translator>"},
+        {Token::TK_LOCALE_NAME_BEGIN,  "<locale>"},
+        {Token::TK_LOCALE_NAME_END,    "</locale>"},
+        {Token::TK_FLAG_FILE_BEGIN,    "<image>"},
+        {Token::TK_FLAG_FILE_END,      "</image>"},
+        {Token::TK_PLURAL_COUNT_BEGIN, "<plural_count>"},
+        {Token::TK_PLURAL_COUNT_END,   "</plural_count>"},
+        {Token::TK_PLURAL_DEF_BEGIN,   "<plural_definition>"},
+        {Token::TK_PLURAL_DEF_END,     "</plural_definition>"},
 
         //item level
-        { Token::TK_SRC_BEGIN,    "<source>" },
-        { Token::TK_SRC_END,      "</source>" },
-        { Token::TK_TRG_BEGIN,    "<target>" },
-        { Token::TK_TRG_END,      "</target>" },
-        { Token::TK_PLURAL_BEGIN, "<pluralform>" },
-        { Token::TK_PLURAL_END,   "</pluralform>" },
+        {Token::TK_SRC_BEGIN,    "<source>"},
+        {Token::TK_SRC_END,      "</source>"},
+        {Token::TK_TRG_BEGIN,    "<target>"},
+        {Token::TK_TRG_END,      "</target>"},
+        {Token::TK_PLURAL_BEGIN, "<pluralform>"},
+        {Token::TK_PLURAL_END,   "</pluralform>"},
     };
 };
 
@@ -349,7 +349,7 @@ public:
         }
         catch (const plural::InvalidPluralForm&)
         {
-            throw ParsingError({ L"Invalid plural form definition", scn_.posRow(), scn_.posCol() });
+            throw ParsingError({L"Invalid plural form definition", scn_.posRow(), scn_.posCol()});
         }
     }
 
@@ -454,12 +454,12 @@ private:
         using namespace zen;
 
         if (original.empty())
-            throw ParsingError({ L"Translation source text is empty", scn_.posRow(), scn_.posCol() });
+            throw ParsingError({L"Translation source text is empty", scn_.posRow(), scn_.posCol()});
 
         if (!isValidUtf(original))
-            throw ParsingError({ L"Translation source text contains UTF-8 encoding error", scn_.posRow(), scn_.posCol() });
+            throw ParsingError({L"Translation source text contains UTF-8 encoding error", scn_.posRow(), scn_.posCol()});
         if (!isValidUtf(translation))
-            throw ParsingError({ L"Translation text contains UTF-8 encoding error", scn_.posRow(), scn_.posCol() });
+            throw ParsingError({L"Translation text contains UTF-8 encoding error", scn_.posRow(), scn_.posCol()});
 
         if (!translation.empty())
         {
@@ -468,7 +468,7 @@ private:
             {
                 if (contains(original, placeholder) &&
                     !contains(translation, placeholder))
-                    throw ParsingError({ replaceCpy<std::wstring>(L"Placeholder %x missing in translation", L"%x", utfTo<std::wstring>(placeholder)), scn_.posRow(), scn_.posCol() });
+                    throw ParsingError({replaceCpy<std::wstring>(L"Placeholder %x missing in translation", L"%x", utfTo<std::wstring>(placeholder)), scn_.posRow(), scn_.posCol()});
             };
             checkPlaceholder("%x");
             checkPlaceholder("%y");
@@ -476,41 +476,41 @@ private:
 
             //if source is a one-liner, so should be the translation
             if (!contains(original, '\n') && contains(translation, '\n'))
-                throw ParsingError({ L"Source text is a one-liner, but translation consists of multiple lines", scn_.posRow(), scn_.posCol() });
+                throw ParsingError({L"Source text is a one-liner, but translation consists of multiple lines", scn_.posRow(), scn_.posCol()});
 
             //if source contains ampersand to mark menu accellerator key, so must translation
             const size_t ampCount = ampersandTokenCount(original);
             if (ampCount > 1 || ampCount != ampersandTokenCount(translation))
-                throw ParsingError({ L"Source and translation both need exactly one & character to mark a menu item access key or none at all", scn_.posRow(), scn_.posCol() });
+                throw ParsingError({L"Source and translation both need exactly one & character to mark a menu item access key or none at all", scn_.posRow(), scn_.posCol()});
 
             //ampersand at the end makes buggy wxWidgets crash miserably
             if (endsWithSingleAmp(original) || endsWithSingleAmp(translation))
-                throw ParsingError({ L"The & character to mark a menu item access key must not occur at the end of a string", scn_.posRow(), scn_.posCol() });
+                throw ParsingError({L"The & character to mark a menu item access key must not occur at the end of a string", scn_.posRow(), scn_.posCol()});
 
             //if source ends with colon, so must translation (note: character seems to be universally used, even for asian and arabic languages)
             if (endsWith(original, ':') && !endsWithColon(translation))
-                throw ParsingError({ L"Source text ends with a colon character \":\", but translation does not", scn_.posRow(), scn_.posCol() });
+                throw ParsingError({L"Source text ends with a colon character \":\", but translation does not", scn_.posRow(), scn_.posCol()});
 
             //if source ends with a period, so must translation (note: character seems to be universally used, even for asian and arabic languages)
             if (endsWithSingleDot(original) && !endsWithSingleDot(translation))
-                throw ParsingError({ L"Source text ends with a punctuation mark character \".\", but translation does not", scn_.posRow(), scn_.posCol() });
+                throw ParsingError({L"Source text ends with a punctuation mark character \".\", but translation does not", scn_.posRow(), scn_.posCol()});
 
             //if source ends with an ellipsis, so must translation (note: character seems to be universally used, even for asian and arabic languages)
             if (endsWithEllipsis(original) && !endsWithEllipsis(translation))
-                throw ParsingError({ L"Source text ends with an ellipsis \"...\", but translation does not", scn_.posRow(), scn_.posCol() });
+                throw ParsingError({L"Source text ends with an ellipsis \"...\", but translation does not", scn_.posRow(), scn_.posCol()});
 
             //check for not-to-be-translated texts
-            for (const char* fixedStr : { "FreeFileSync", "RealTimeSync", "ffs_gui", "ffs_batch", "ffs_tmp", "GlobalSettings.xml" })
+            for (const char* fixedStr : {"FreeFileSync", "RealTimeSync", "ffs_gui", "ffs_batch", "ffs_tmp", "GlobalSettings.xml"})
                 if (contains(original, fixedStr) && !contains(translation, fixedStr))
-                    throw ParsingError({ replaceCpy<std::wstring>(L"Misspelled \"%x\" in translation", L"%x", utfTo<std::wstring>(fixedStr)), scn_.posRow(), scn_.posCol() });
+                    throw ParsingError({replaceCpy<std::wstring>(L"Misspelled \"%x\" in translation", L"%x", utfTo<std::wstring>(fixedStr)), scn_.posRow(), scn_.posCol()});
 
             //some languages (French!) put a space before punctuation mark => must be a no-brake space!
             for (const char punctChar : std::string(".!?:;$#"))
                 if (contains(original,    std::string(" ") + punctChar) ||
                     contains(translation, std::string(" ") + punctChar))
-                    throw ParsingError({ replaceCpy<std::wstring>(L"Text contains a space before the \"%x\" character. Are line-breaks really allowed here?"
-                                                                  " Maybe this should be a \"non-breaking space\" (Windows: Alt 0160    UTF8: 0xC2 0xA0)?",
-                                                                  L"%x", utfTo<std::wstring>(punctChar)), scn_.posRow(), scn_.posCol() });
+                    throw ParsingError({replaceCpy<std::wstring>(L"Text contains a space before the \"%x\" character. Are line-breaks really allowed here?"
+                                                                 " Maybe this should be a \"non-breaking space\" (Windows: Alt 0160    UTF8: 0xC2 0xA0)?",
+                                                                 L"%x", utfTo<std::wstring>(punctChar)), scn_.posRow(), scn_.posCol()});
         }
     }
 
@@ -519,30 +519,30 @@ private:
         using namespace zen;
 
         if (original.first.empty() || original.second.empty())
-            throw ParsingError({ L"Translation source text is empty", scn_.posRow(), scn_.posCol() });
+            throw ParsingError({L"Translation source text is empty", scn_.posRow(), scn_.posCol()});
 
         const std::vector<std::string> allTexts = [&]
         {
-            std::vector<std::string> at{ original.first, original.second };
+            std::vector<std::string> at{original.first, original.second};
             at.insert(at.end(), translation.begin(), translation.end());
             return at;
         }();
 
         for (const std::string& str : allTexts)
             if (!isValidUtf(str))
-                throw ParsingError({ L"Text contains UTF-8 encoding error", scn_.posRow(), scn_.posCol() });
+                throw ParsingError({L"Text contains UTF-8 encoding error", scn_.posRow(), scn_.posCol()});
 
         //check the primary placeholder is existing at least for the second english text
         if (!contains(original.second, "%x"))
-            throw ParsingError({ L"Plural form source text does not contain %x placeholder", scn_.posRow(), scn_.posCol() });
+            throw ParsingError({L"Plural form source text does not contain %x placeholder", scn_.posRow(), scn_.posCol()});
 
         if (!translation.empty())
         {
             //check for invalid number of plural forms
             if (pluralInfo.getCount() != translation.size())
-                throw ParsingError({ replaceCpy(replaceCpy<std::wstring>(L"Invalid number of plural forms; actual: %x, expected: %y",
-                                                                         L"%x", numberTo<std::wstring>(translation.size())),
-                                                L"%y", numberTo<std::wstring>(pluralInfo.getCount())), scn_.posRow(), scn_.posCol() });
+                throw ParsingError({replaceCpy(replaceCpy<std::wstring>(L"Invalid number of plural forms; actual: %x, expected: %y",
+                                                                        L"%x", numberTo<std::wstring>(translation.size())),
+                                               L"%y", numberTo<std::wstring>(pluralInfo.getCount())), scn_.posRow(), scn_.posCol()});
 
             //check for duplicate plural form translations (catch copy & paste errors for single-number form translations)
             for (auto it = translation.begin(); it != translation.end(); ++it)
@@ -550,8 +550,8 @@ private:
                 {
                     auto it2 = std::find(it + 1, translation.end(), *it);
                     if (it2 != translation.end())
-                        throw ParsingError({ replaceCpy<std::wstring>(L"Duplicate plural form translation at index position %x",
-                                                                      L"%x", numberTo<std::wstring>(it2 - translation.begin())), scn_.posRow(), scn_.posCol() });
+                        throw ParsingError({replaceCpy<std::wstring>(L"Duplicate plural form translation at index position %x",
+                                                                     L"%x", numberTo<std::wstring>(it2 - translation.begin())), scn_.posRow(), scn_.posCol()});
                 }
 
             for (size_t pos = 0; pos < translation.size(); ++pos)
@@ -564,15 +564,15 @@ private:
                         const int firstNumber = pluralInfo.getFirstNumber(pos);
                         if (!contains(translation[pos], "%x") &&
                             !contains(translation[pos], numberTo<std::string>(firstNumber)))
-                            throw ParsingError({ replaceCpy<std::wstring>(replaceCpy<std::wstring>(L"Plural form translation at index position %y needs to use the decimal number %z or the %x placeholder",
-                                                                                                   L"%y", numberTo<std::wstring>(pos)), L"%z", numberTo<std::wstring>(firstNumber)), scn_.posRow(), scn_.posCol() });
+                            throw ParsingError({replaceCpy<std::wstring>(replaceCpy<std::wstring>(L"Plural form translation at index position %y needs to use the decimal number %z or the %x placeholder",
+                                                                                                  L"%y", numberTo<std::wstring>(pos)), L"%z", numberTo<std::wstring>(firstNumber)), scn_.posRow(), scn_.posCol()});
                     }
                 }
                 else
                 {
                     //ensure the placeholder is used when needed
                     if (!contains(translation[pos], "%x"))
-                        throw ParsingError({ replaceCpy<std::wstring>(L"Plural form at index position %y is missing the %x placeholder", L"%y", numberTo<std::wstring>(pos)), scn_.posRow(), scn_.posCol() });
+                        throw ParsingError({replaceCpy<std::wstring>(L"Plural form at index position %y is missing the %x placeholder", L"%y", numberTo<std::wstring>(pos)), scn_.posRow(), scn_.posCol()});
                 }
 
             auto checkSecondaryPlaceholder = [&](const std::string& placeholder)
@@ -582,7 +582,7 @@ private:
                     contains(original.second, placeholder))
                     for (const std::string& str : allTexts)
                         if (!contains(str, placeholder))
-                            throw ParsingError({ zen::replaceCpy<std::wstring>(L"Placeholder %x missing in text", L"%x", zen::utfTo<std::wstring>(placeholder)), scn_.posRow(), scn_.posCol() });
+                            throw ParsingError({zen::replaceCpy<std::wstring>(L"Placeholder %x missing in text", L"%x", zen::utfTo<std::wstring>(placeholder)), scn_.posRow(), scn_.posCol()});
             };
             checkSecondaryPlaceholder("%y");
             checkSecondaryPlaceholder("%z");
@@ -590,51 +590,51 @@ private:
             //if source is a one-liner, so should be the translation
             if (!contains(original.first, '\n') && !contains(original.second, '\n') &&
             /**/std::any_of(translation.begin(), translation.end(), [](const std::string& pform) { return contains(pform, '\n'); }))
-            /**/throw ParsingError({ L"Source text is a one-liner, but at least one plural form translation consists of multiple lines", scn_.posRow(), scn_.posCol() });
+            /**/throw ParsingError({L"Source text is a one-liner, but at least one plural form translation consists of multiple lines", scn_.posRow(), scn_.posCol()});
 
             //if source contains ampersand to mark menu accellerator key, so must translation
             const size_t ampCount = ampersandTokenCount(original.first);
             for (const std::string& str : allTexts)
                 if (ampCount > 1 || ampersandTokenCount(str) != ampCount)
-                    throw ParsingError({ L"Source and translation both need exactly one & character to mark a menu item access key or none at all", scn_.posRow(), scn_.posCol() });
+                    throw ParsingError({L"Source and translation both need exactly one & character to mark a menu item access key or none at all", scn_.posRow(), scn_.posCol()});
 
             //ampersand at the end makes buggy wxWidgets crash miserably
             for (const std::string& str : allTexts)
                 if (endsWithSingleAmp(str))
-                    throw ParsingError({ L"The & character to mark a menu item access key must not occur at the end of a string", scn_.posRow(), scn_.posCol() });
+                    throw ParsingError({L"The & character to mark a menu item access key must not occur at the end of a string", scn_.posRow(), scn_.posCol()});
 
             //if source ends with colon, so must translation (note: character seems to be universally used, even for asian and arabic languages)
             if (endsWith(original.first, ':') || endsWith(original.second, ':'))
                 for (const std::string& str : allTexts)
                     if (!endsWithColon(str))
-                        throw ParsingError({ L"Source text ends with a colon character \":\", but translation does not", scn_.posRow(), scn_.posCol() });
+                        throw ParsingError({L"Source text ends with a colon character \":\", but translation does not", scn_.posRow(), scn_.posCol()});
 
             //if source ends with a period, so must translation (note: character seems to be universally used, even for asian and arabic languages)
             if (endsWithSingleDot(original.first) || endsWithSingleDot(original.second))
                 for (const std::string& str : allTexts)
                     if (!endsWithSingleDot(str))
-                        throw ParsingError({ L"Source text ends with a punctuation mark character \".\", but translation does not", scn_.posRow(), scn_.posCol() });
+                        throw ParsingError({L"Source text ends with a punctuation mark character \".\", but translation does not", scn_.posRow(), scn_.posCol()});
 
             //if source ends with an ellipsis, so must translation (note: character seems to be universally used, even for asian and arabic languages)
             if (endsWithEllipsis(original.first) || endsWithEllipsis(original.second))
                 for (const std::string& str : allTexts)
                     if (!endsWithEllipsis(str))
-                        throw ParsingError({ L"Source text ends with an ellipsis \"...\", but translation does not", scn_.posRow(), scn_.posCol() });
+                        throw ParsingError({L"Source text ends with an ellipsis \"...\", but translation does not", scn_.posRow(), scn_.posCol()});
 
             //check for not-to-be-translated texts
-            for (const char* fixedStr : { "FreeFileSync", "RealTimeSync", "ffs_gui", "ffs_batch", "ffs_tmp", "GlobalSettings.xml" })
+            for (const char* fixedStr : {"FreeFileSync", "RealTimeSync", "ffs_gui", "ffs_batch", "ffs_tmp", "GlobalSettings.xml"})
                 if (contains(original.first, fixedStr) || contains(original.second, fixedStr))
                     for (const std::string& str : allTexts)
                         if (!contains(str, fixedStr))
-                            throw ParsingError({ replaceCpy<std::wstring>(L"Misspelled \"%x\" in translation", L"%x", utfTo<std::wstring>(fixedStr)), scn_.posRow(), scn_.posCol() });
+                            throw ParsingError({replaceCpy<std::wstring>(L"Misspelled \"%x\" in translation", L"%x", utfTo<std::wstring>(fixedStr)), scn_.posRow(), scn_.posCol()});
 
             //some languages (French!) put a space before punctuation mark => must be a no-brake space!
             for (const char punctChar : std::string(".!?:;$#"))
                 for (const std::string& str : allTexts)
                     if (contains(str, std::string(" ") + punctChar))
-                        throw ParsingError({ replaceCpy<std::wstring>(L"Text contains a space before the \"%x\" character. Are line-breaks really allowed here?"
-                                                                      " Maybe this should be a \"non-breaking space\" (Windows: Alt 0160    UTF8: 0xC2 0xA0)?",
-                                                                      L"%x", utfTo<std::wstring>(punctChar)), scn_.posRow(), scn_.posCol() });
+                        throw ParsingError({replaceCpy<std::wstring>(L"Text contains a space before the \"%x\" character. Are line-breaks really allowed here?"
+                                                                     " Maybe this should be a \"non-breaking space\" (Windows: Alt 0160    UTF8: 0xC2 0xA0)?",
+                                                                     L"%x", utfTo<std::wstring>(punctChar)), scn_.posRow(), scn_.posCol()});
         }
     }
 
@@ -686,7 +686,7 @@ private:
     void expectToken(Token::Type t) //throw ParsingError
     {
         if (token().type != t)
-            throw ParsingError({ L"Unexpected token", scn_.posRow(), scn_.posCol() });
+            throw ParsingError({L"Unexpected token", scn_.posRow(), scn_.posCol()});
     }
 
     void consumeToken(Token::Type t) //throw ParsingError
diff --git a/FreeFileSync/Source/parse_plural.h b/FreeFileSync/Source/parse_plural.h
index bbf635f1..67f70b27 100644
--- a/FreeFileSync/Source/parse_plural.h
+++ b/FreeFileSync/Source/parse_plural.h
@@ -241,21 +241,21 @@ private:
     using TokenList = std::vector<std::pair<std::string, Token::Type>>;
     const TokenList tokens_
     {
-        { "?",  Token::TK_TERNARY_QUEST },
-        { ":",  Token::TK_TERNARY_COLON },
-        { "||", Token::TK_OR            },
-        { "&&", Token::TK_AND           },
-        { "==", Token::TK_EQUAL         },
-        { "!=", Token::TK_NOT_EQUAL     },
-        { "<=", Token::TK_LESS_EQUAL    },
-        { "<",  Token::TK_LESS          },
-        { ">=", Token::TK_GREATER_EQUAL },
-        { ">",  Token::TK_GREATER       },
-        { "%",  Token::TK_MODULUS       },
-        { "n",  Token::TK_VARIABLE_N    },
-        { "N",  Token::TK_VARIABLE_N    },
-        { "(",  Token::TK_BRACKET_LEFT  },
-        { ")",  Token::TK_BRACKET_RIGHT },
+        {"?",  Token::TK_TERNARY_QUEST},
+        {":",  Token::TK_TERNARY_COLON},
+        {"||", Token::TK_OR           },
+        {"&&", Token::TK_AND          },
+        {"==", Token::TK_EQUAL        },
+        {"!=", Token::TK_NOT_EQUAL    },
+        {"<=", Token::TK_LESS_EQUAL   },
+        {"<",  Token::TK_LESS         },
+        {">=", Token::TK_GREATER_EQUAL},
+        {">",  Token::TK_GREATER      },
+        {"%",  Token::TK_MODULUS      },
+        {"n",  Token::TK_VARIABLE_N   },
+        {"N",  Token::TK_VARIABLE_N   },
+        {"(",  Token::TK_BRACKET_LEFT },
+        {")",  Token::TK_BRACKET_RIGHT},
     };
 
     const std::string stream_;
diff --git a/FreeFileSync/Source/perf_check.cpp b/FreeFileSync/Source/perf_check.cpp
index 9905cc7d..7a0f43ab 100644
--- a/FreeFileSync/Source/perf_check.cpp
+++ b/FreeFileSync/Source/perf_check.cpp
@@ -22,7 +22,7 @@ PerfCheck::PerfCheck(std::chrono::milliseconds windowSizeRemTime,
 
 void PerfCheck::addSample(std::chrono::nanoseconds timeElapsed, int itemsCurrent, int64_t bytesCurrent)
 {
-    samples_.insert(samples_.end(), { timeElapsed, { itemsCurrent, bytesCurrent }}); //use fact that time is monotonously ascending
+    samples_.insert(samples_.end(), {timeElapsed, { itemsCurrent, bytesCurrent}}); //use fact that time is monotonously ascending
 
     //remove all records earlier than "now - windowMax"
     auto it = samples_.upper_bound(timeElapsed - windowMax_);
@@ -45,7 +45,7 @@ std::tuple<double /*timeDelta*/, int /*itemsDelta*/, int64_t /*bytesDelta*/> Per
     const int     itemsDelta = itBack->second.items - itFront->second.items;
     const int64_t bytesDelta = itBack->second.bytes - itFront->second.bytes;
 
-    return { timeDelta, itemsDelta, bytesDelta };
+    return {timeDelta, itemsDelta, bytesDelta};
 }
 
 
diff --git a/FreeFileSync/Source/status_handler.cpp b/FreeFileSync/Source/status_handler.cpp
index b86c104d..38c488f8 100644
--- a/FreeFileSync/Source/status_handler.cpp
+++ b/FreeFileSync/Source/status_handler.cpp
@@ -5,8 +5,10 @@
 // *****************************************************************************
 
 #include "status_handler.h"
-#include <chrono>
-//#include <zen/basic_math.h>
+#include <zen/basic_math.h>
+#include <zen/process_exec.h>
+
+using namespace zen;
 
 
 namespace
@@ -26,3 +28,42 @@ bool fff::uiUpdateDue(bool force)
     }
     return false;
 }
+
+
+void fff::runCommandAndLogErrors(const Zstring& cmdLine, ErrorLog& errorLog)
+{
+    try
+    {
+        //give consoleExecute() some "time to fail", but not too long to hang our process
+        const int DEFAULT_APP_TIMEOUT_MS = 100;
+
+        if (const auto& [exitCode, output] = consoleExecute(cmdLine, DEFAULT_APP_TIMEOUT_MS); //throw SysError, SysErrorTimeOut
+            exitCode != 0)
+            throw SysError(formatSystemError("", replaceCpy(_("Exit code %x"), L"%x", numberTo<std::wstring>(exitCode)), utfTo<std::wstring>(output)));
+
+        errorLog.logMsg(_("Executing command:") + L' ' + utfTo<std::wstring>(cmdLine) + L" [" + replaceCpy(_("Exit code %x"), L"%x", L"0") + L']', MSG_TYPE_INFO);
+    }
+    catch (SysErrorTimeOut&) //child process not failed yet => probably fine :>
+    {
+        errorLog.logMsg(_("Executing command:") + L' ' + utfTo<std::wstring>(cmdLine), MSG_TYPE_INFO);
+    }
+    catch (const SysError& e)
+    {
+        errorLog.logMsg(replaceCpy(_("Command %x failed."), L"%x", fmtPath(cmdLine)) + L"\n\n" + e.toString(), MSG_TYPE_ERROR);
+    }
+}
+
+
+void fff::delayAndCountDown(std::chrono::steady_clock::time_point delayUntil, const std::function<void(const std::wstring& timeRemMsg)>& notifyStatus)
+{
+    for (auto now = std::chrono::steady_clock::now(); now < delayUntil; now = std::chrono::steady_clock::now())
+    {
+        if (notifyStatus)
+        {
+            const auto timeRemMs = std::chrono::duration_cast<std::chrono::milliseconds>(delayUntil - now).count();
+            notifyStatus(_P("1 sec", "%x sec", numeric::intDivCeil(timeRemMs, 1000)));
+        }
+
+        std::this_thread::sleep_for(UI_UPDATE_INTERVAL / 2);
+    }
+}
diff --git a/FreeFileSync/Source/status_handler.h b/FreeFileSync/Source/status_handler.h
index faac4e99..36a74a2e 100644
--- a/FreeFileSync/Source/status_handler.h
+++ b/FreeFileSync/Source/status_handler.h
@@ -7,21 +7,19 @@
 #ifndef STATUS_HANDLER_H_81704805908341534
 #define STATUS_HANDLER_H_81704805908341534
 
-#include <vector>
+#include <thread>
+#include <functional>
+#include <zen/error_log.h>
 #include "base/process_callback.h"
 #include "return_codes.h"
 
-
 namespace fff
 {
 bool uiUpdateDue(bool force = false); //test if a specific amount of time is over
 
-/*
-Updating GUI is fast!
-    time per single call to ProcessCallback::forceUiRefresh()
+/*  Updating GUI is fast! time per call to ProcessCallback::forceUiRefresh()
     - Comparison       0.025 ms
-    - Synchronization  0.74 ms (despite complex graph control!)
-*/
+    - Synchronization  0.74 ms (despite complex graph control!)               */
 
 //Exception class used to abort the "compare" and "sync" process
 class AbortProcess {};
@@ -88,7 +86,7 @@ public:
         assert((itemsTotal < 0) == (bytesTotal < 0));
         currentPhase_ = phase;
         statsCurrent_ = {};
-        statsTotal_ = { itemsTotal, bytesTotal };
+        statsTotal_ = {itemsTotal, bytesTotal};
     }
 
     void updateDataProcessed(int itemsDelta, int64_t bytesDelta) override { updateData(statsCurrent_, itemsDelta, bytesDelta); } //note: these methods MUST NOT throw in order
@@ -116,10 +114,10 @@ public:
 
     virtual void forceUiUpdateNoThrow() = 0; //noexcept
 
-    void updateStatus(const std::wstring& msg) final //throw AbortProcess
+    void updateStatus(std::wstring&& msg) final //throw AbortProcess
     {
         //assert(!msg.empty()); -> possible, e.g. start of parallel scan
-        statusText_ = msg; //update *before* running operations that can throw
+        statusText_ = std::move(msg); //update *before* running operations that can throw
         requestUiUpdate(false /*force*/); //throw AbortProcess
     }
 
@@ -160,11 +158,15 @@ private:
 
     ProcessPhase currentPhase_ = ProcessPhase::none;
     ProgressStats statsCurrent_;
-    ProgressStats statsTotal_ { -1, -1 };
+    ProgressStats statsTotal_ {-1, -1};
     std::wstring statusText_;
 
     std::optional<AbortTrigger> abortRequested_;
 };
+
+
+void delayAndCountDown(std::chrono::steady_clock::time_point delayUntil, const std::function<void(const std::wstring& timeRemMsg)>& notifyStatus);
+void runCommandAndLogErrors(const Zstring& cmdLine, zen::ErrorLog& errorLog);
 }
 
 #endif //STATUS_HANDLER_H_81704805908341534
diff --git a/FreeFileSync/Source/ui/abstract_folder_picker.cpp b/FreeFileSync/Source/ui/abstract_folder_picker.cpp
index 1465d8b1..914b2358 100644
--- a/FreeFileSync/Source/ui/abstract_folder_picker.cpp
+++ b/FreeFileSync/Source/ui/abstract_folder_picker.cpp
@@ -74,7 +74,7 @@ private:
         error
     };
 
-    AsyncGuiQueue guiQueue_{ 25 /*polling [ms]*/ }; //schedule and run long-running tasks asynchronously, but process results on GUI queue
+    AsyncGuiQueue guiQueue_{25 /*polling [ms]*/}; //schedule and run long-running tasks asynchronously, but process results on GUI queue
 
     //output-only parameters:
     AbstractPath& folderPathOut_;
@@ -157,9 +157,9 @@ struct FlatTraverserCallback : public AFS::TraverserCallback
 private:
     void                               onFile   (const AFS::FileInfo&    fi) override {}
     std::shared_ptr<TraverserCallback> onFolder (const AFS::FolderInfo&  fi) override { result_.folderNames.emplace(fi.itemName, fi.isFollowedSymlink); return nullptr; }
-    HandleLink                         onSymlink(const AFS::SymlinkInfo& si) override { return LINK_FOLLOW; }
-    HandleError reportDirError (const ErrorInfo& errorInfo)                          override { logError(errorInfo.msg); return ON_ERROR_CONTINUE; }
-    HandleError reportItemError(const ErrorInfo& errorInfo, const Zstring& itemName) override { logError(errorInfo.msg); return ON_ERROR_CONTINUE; }
+    HandleLink                         onSymlink(const AFS::SymlinkInfo& si) override { return HandleLink::follow; }
+    HandleError reportDirError (const ErrorInfo& errorInfo)                          override { logError(errorInfo.msg); return HandleError::ignore; }
+    HandleError reportItemError(const ErrorInfo& errorInfo, const Zstring& itemName) override { logError(errorInfo.msg); return HandleError::ignore; }
 
     void logError(const std::wstring& msg)
     {
@@ -189,7 +189,7 @@ void AbstractFolderPickerDlg::populateNodeThen(const wxTreeItemId& itemId, const
                 guiQueue_.processAsync([folderPath = itemData->folderPath] //AbstractPath is thread-safe like an int!
                 {
                     auto ft = std::make_shared<FlatTraverserCallback>(); //noexcept, traverse directory one level deep
-                    AFS::traverseFolderRecursive(folderPath.afsDevice, {{ folderPath.afsPath, ft }}, 1 /*parallelOps*/);
+                    AFS::traverseFolderRecursive(folderPath.afsDevice, {{folderPath.afsPath, ft}}, 1 /*parallelOps*/);
                     return ft->getResult();
                 },
 
@@ -290,8 +290,8 @@ void AbstractFolderPickerDlg::navigateToExistingPath(const wxTreeItemId& itemId,
 
     populateNodeThen(itemId, [this, itemId, nodeRelPath, leafType]
     {
-        const             Zstring  childFolderName   = nodeRelPath.front();
-        const std::vector<Zstring> childFolderRelPath{ nodeRelPath.begin() + 1, nodeRelPath.end() };
+        const             Zstring  childFolderName  = nodeRelPath.front();
+        const std::vector<Zstring> childFolderRelPath{nodeRelPath.begin() + 1, nodeRelPath.end()};
 
         wxTreeItemId childIdMatch;
         size_t insertPos = 0; //let's not use the wxTreeCtrl::OnCompareItems() abomination to implement sorting
diff --git a/FreeFileSync/Source/ui/batch_config.cpp b/FreeFileSync/Source/ui/batch_config.cpp
index 77ce2f9e..a2351cc9 100644
--- a/FreeFileSync/Source/ui/batch_config.cpp
+++ b/FreeFileSync/Source/ui/batch_config.cpp
@@ -167,7 +167,7 @@ ConfirmationButton fff::showBatchConfigDialog(wxWindow* parent,
                                               BatchExclusiveConfig& batchExCfg,
                                               bool& ignoreErrors)
 {
-    BatchDialogConfig dlgCfg = { batchExCfg, ignoreErrors };
+    BatchDialogConfig dlgCfg = {batchExCfg, ignoreErrors};
 
     BatchDialog batchDlg(parent, dlgCfg);
 
diff --git a/FreeFileSync/Source/ui/batch_status_handler.cpp b/FreeFileSync/Source/ui/batch_status_handler.cpp
index a79b894e..7950f76d 100644
--- a/FreeFileSync/Source/ui/batch_status_handler.cpp
+++ b/FreeFileSync/Source/ui/batch_status_handler.cpp
@@ -5,7 +5,6 @@
 // *****************************************************************************
 
 #include "batch_status_handler.h"
-#include <zen/process_exec.h>
 #include <zen/shutdown.h>
 #include <zen/resolve_path.h>
 #include <wx+/popup_dlg.h>
@@ -13,7 +12,7 @@
 #include <wx/sound.h>
 #include "../afs/concrete.h"
 #include "../log_file.h"
-#include "status_handler_impl.h"
+#include "../fatal_error.h"
 
 using namespace zen;
 using namespace fff;
@@ -36,7 +35,7 @@ BatchStatusHandler::BatchStatusHandler(bool showProgress,
     autoRetryDelay_(autoRetryDelay),
     soundFileSyncComplete_(soundFileSyncComplete),
     progressDlg_(SyncProgressDialog::create(progressDlgSize, dlgMaximize, [this] { userRequestAbort(); }, *this, nullptr /*parentWindow*/, showProgress, autoCloseDialog,
-{ jobName }, startTime, ignoreErrors, autoRetryCount, [&]
+{jobName}, startTime, ignoreErrors, autoRetryCount, [&]
 {
     switch (postSyncAction)
     {
@@ -96,7 +95,7 @@ BatchStatusHandler::Result BatchStatusHandler::reportResults(const Zstring& post
 
     const ProcessSummary summary
     {
-        startTime_, syncResult, { jobName_ },
+        startTime_, syncResult, {jobName_},
         getStatsCurrent(),
         getStatsTotal  (),
         totalTime
@@ -105,7 +104,7 @@ BatchStatusHandler::Result BatchStatusHandler::reportResults(const Zstring& post
     const AbstractPath logFilePath = generateLogFilePath(logFormat, summary, altLogFolderPathPhrase);
     //e.g. %AppData%\FreeFileSync\Logs\Backup FreeFileSync 2013-09-15 015052.123 [Error].log
 
-    auto notifyStatusNoThrow = [&](const std::wstring& msg) { try { updateStatus(msg); /*throw AbortProcess*/ } catch (AbortProcess&) {} };
+    auto notifyStatusNoThrow = [&](std::wstring&& msg) { try { updateStatus(std::move(msg)); /*throw AbortProcess*/ } catch (AbortProcess&) {} };
 
     bool autoClose = false;
     FinalRequest finalRequest = FinalRequest::none;
@@ -212,7 +211,7 @@ BatchStatusHandler::Result BatchStatusHandler::reportResults(const Zstring& post
         //do NOT use tryReportingError()! saving log files should not be cancellable!
         saveLogFile(logFilePath, summary, errorLog_, logfilesMaxAgeDays, logFormat, logFilePathsToKeep, notifyStatusNoThrow); //throw FileError
     }
-    catch (const FileError& e) { errorLog_.logMsg(e.toString(), MSG_TYPE_ERROR); }
+    catch (const FileError& e) { errorLog_.logMsg(e.toString(), MSG_TYPE_ERROR); logFatalError(e.toString()); }
     //----------------------------------------------------------
 
 
@@ -236,7 +235,7 @@ BatchStatusHandler::Result BatchStatusHandler::reportResults(const Zstring& post
                                                                                   syncResult, errorLogFinal);
     progressDlg_ = nullptr;
 
-    return { syncResult, errorLogFinal.ref().getStats(), finalRequest, logFilePath, dlgSize, dlgIsMaximized };
+    return {syncResult, errorLogFinal.ref().getStats(), finalRequest, logFilePath, dlgSize, dlgIsMaximized};
 }
 
 
@@ -260,10 +259,10 @@ void BatchStatusHandler::updateDataProcessed(int itemsDelta, int64_t bytesDelta)
 }
 
 
-void BatchStatusHandler::reportInfo(const std::wstring& msg)
+void BatchStatusHandler::logInfo(const std::wstring& msg)
 {
     errorLog_.logMsg(msg, MSG_TYPE_INFO);
-    updateStatus(msg); //throw AbortProcess
+    requestUiUpdate(false /*force*/); //throw AbortProcess
 }
 
 
diff --git a/FreeFileSync/Source/ui/batch_status_handler.h b/FreeFileSync/Source/ui/batch_status_handler.h
index edea7480..91c1d78d 100644
--- a/FreeFileSync/Source/ui/batch_status_handler.h
+++ b/FreeFileSync/Source/ui/batch_status_handler.h
@@ -34,7 +34,7 @@ public:
     ~BatchStatusHandler();
 
     void     initNewPhase    (int itemsTotal, int64_t bytesTotal, ProcessPhase phaseID) override; //
-    void     reportInfo      (const std::wstring& msg)                                  override; //
+    void     logInfo         (const std::wstring& msg)                                  override; //
     void     reportWarning   (const std::wstring& msg, bool& warningActive)             override; //throw AbortProcess
     Response reportError     (const ErrorInfo& errorInfo)                               override; //
     void     reportFatalError(const std::wstring& msg)                                  override; //
diff --git a/FreeFileSync/Source/ui/cfg_grid.cpp b/FreeFileSync/Source/ui/cfg_grid.cpp
index c0d153c1..98a8d50b 100644
--- a/FreeFileSync/Source/ui/cfg_grid.cpp
+++ b/FreeFileSync/Source/ui/cfg_grid.cpp
@@ -16,6 +16,7 @@
 #include <wx/settings.h>
 #include "../icon_buffer.h"
 #include "../ffs_paths.h"
+#include "../afs/native.h"
 
 using namespace zen;
 using namespace fff;
@@ -199,7 +200,7 @@ void ConfigView::sortListViewImpl()
         if (lhs->second.isLastRunCfg != rhs->second.isLastRunCfg)
             return lhs->second.isLastRunCfg < rhs->second.isLastRunCfg; //"last session" label should be (always) last
 
-        return makeSortDirection(std::greater<>(), std::bool_constant<ascending>())(lhs->second.cfgItem.lastSyncTime, rhs->second.cfgItem.lastSyncTime);
+        return makeSortDirection(std::greater(), std::bool_constant<ascending>())(lhs->second.cfgItem.lastSyncTime, rhs->second.cfgItem.lastSyncTime);
         //[!] ascending lastSync shows lowest "days past" first <=> highest lastSyncTime first
     };
 
@@ -215,7 +216,7 @@ void ConfigView::sortListViewImpl()
 
         //primary sort order
         if (hasLogL && lhs->second.cfgItem.logResult != rhs->second.cfgItem.logResult)
-            return makeSortDirection(std::greater<>(), std::bool_constant<ascending>())(lhs->second.cfgItem.logResult, rhs->second.cfgItem.logResult);
+            return makeSortDirection(std::greater(), std::bool_constant<ascending>())(lhs->second.cfgItem.logResult, rhs->second.cfgItem.logResult);
 
         //secondary sort order
         return LessNaturalSort()(lhs->second.name, rhs->second.name);
@@ -480,9 +481,7 @@ private:
                     break;
                 case ColumnTypeCfg::lastLog:
 
-                    if (!item->isLastRunCfg &&
-                        !AFS::isNullPath(item->cfgItem.logFilePath) &&
-                        AFS::getNativeItemPath(item->cfgItem.logFilePath))
+                    if (!item->isLastRunCfg && !getNativeItemPath(item->cfgItem.logFilePath).empty())
                         return static_cast<HoverArea>(HoverAreaLog::link);
                     break;
             }
@@ -588,8 +587,9 @@ private:
                 case HoverAreaLog::link:
                     try
                     {
-                        if (std::optional<Zstring> nativePath = AFS::getNativeItemPath(item->cfgItem.logFilePath))
-                            openWithDefaultApp(*nativePath); //throw FileError
+                        if (const Zstring& nativePath = getNativeItemPath(item->cfgItem.logFilePath);
+                            !nativePath.empty())
+                            openWithDefaultApp(nativePath); //throw FileError
                         else
                             assert(false);
                         assert(!AFS::isNullPath(item->cfgItem.logFilePath)); //see getMouseHover()
diff --git a/FreeFileSync/Source/ui/cfg_grid.h b/FreeFileSync/Source/ui/cfg_grid.h
index 19a7b427..84364584 100644
--- a/FreeFileSync/Source/ui/cfg_grid.h
+++ b/FreeFileSync/Source/ui/cfg_grid.h
@@ -59,9 +59,9 @@ std::vector<ColAttributesCfg> getCfgGridDefaultColAttribs()
     using namespace zen;
     return
     {
-        { ColumnTypeCfg::name,     -fastFromDIP(75) - fastFromDIP(42), 1, true },
-        { ColumnTypeCfg::lastSync, fastFromDIP(75), 0, true },
-        { ColumnTypeCfg::lastLog,  fastFromDIP(42), 0, true }, //leave some room for the sort direction indicator
+        {ColumnTypeCfg::name,     -fastFromDIP(75) - fastFromDIP(42), 1, true},
+        {ColumnTypeCfg::lastSync, fastFromDIP(75), 0, true},
+        {ColumnTypeCfg::lastLog,  fastFromDIP(42), 0, true}, //leave some room for the sort direction indicator
     };
 }
 
@@ -126,7 +126,7 @@ public:
     size_t getRowCount() const { assert(cfgList_.size() == cfgListView_.size()); return cfgListView_.size(); }
 
     void setSortDirection(ColumnTypeCfg colType, bool ascending);
-    std::pair<ColumnTypeCfg, bool> getSortDirection() { return { sortColumn_, sortAscending_ }; }
+    std::pair<ColumnTypeCfg, bool> getSortDirection() { return {sortColumn_, sortAscending_}; }
 
 private:
     ConfigView           (const ConfigView&) = delete;
diff --git a/FreeFileSync/Source/ui/command_box.cpp b/FreeFileSync/Source/ui/command_box.cpp
index 4c1b177f..c0637b10 100644
--- a/FreeFileSync/Source/ui/command_box.cpp
+++ b/FreeFileSync/Source/ui/command_box.cpp
@@ -112,9 +112,9 @@ void CommandBox::setValueAndUpdateList(const wxString& value)
     if (std::find(items.begin(), items.end(), value) == items.end())
     {
         if (!items.empty() && !value.empty())
-            items.insert(items.begin(), { value, getSeparationLine() });
+            items.insert(items.begin(), {value, getSeparationLine()});
         else
-            items.insert(items.begin(), { value });
+            items.insert(items.begin(), {value});
     }
 
     //this->Clear(); -> NO! emits yet another wxEVT_COMMAND_TEXT_UPDATED!!!
diff --git a/FreeFileSync/Source/ui/file_grid.cpp b/FreeFileSync/Source/ui/file_grid.cpp
index b65786d1..d54a9368 100644
--- a/FreeFileSync/Source/ui/file_grid.cpp
+++ b/FreeFileSync/Source/ui/file_grid.cpp
@@ -34,17 +34,17 @@ wxDEFINE_EVENT(EVENT_GRID_SYNC_DIRECTION, SyncDirectionEvent);
 namespace
 {
 //let's NOT create wxWidgets objects statically:
-inline wxColor getColorSyncBlue (bool faint) { if (faint) return { 0xed, 0xee, 0xff }; return { 185, 188, 255 }; }
-inline wxColor getColorSyncGreen(bool faint) { if (faint) return { 0xf1, 0xff, 0xed }; return { 196, 255, 185 }; }
+inline wxColor getColorSyncBlue (bool faint) { if (faint) return {0xed, 0xee, 0xff}; return {185, 188, 255}; }
+inline wxColor getColorSyncGreen(bool faint) { if (faint) return {0xf1, 0xff, 0xed}; return {196, 255, 185}; }
 
-inline wxColor getColorConflictBackground (bool faint) { if (faint) return { 0xfe, 0xfe, 0xda }; return { 247, 252,  62 }; } //yellow
-inline wxColor getColorDifferentBackground(bool faint) { if (faint) return { 0xff, 0xed, 0xee }; return { 255, 185, 187 }; } //red
+inline wxColor getColorConflictBackground (bool faint) { if (faint) return {0xfe, 0xfe, 0xda}; return {247, 252,  62}; } //yellow
+inline wxColor getColorDifferentBackground(bool faint) { if (faint) return {0xff, 0xed, 0xee}; return {255, 185, 187}; } //red
 
-inline wxColor getColorSymlinkBackground() { return { 238, 201, 0 }; } //orange
-//inline wxColor getColorItemMissing() { return { 212, 208, 200 }; } //medium grey
+inline wxColor getColorSymlinkBackground() { return {238, 201, 0}; } //orange
+//inline wxColor getColorItemMissing() { return {212, 208, 200}; } //medium grey
 
-inline wxColor getColorInactiveBack(bool faint) { if (faint) return { 0xf6, 0xf6, 0xf6}; return { 0xe4, 0xe4, 0xe4 }; } //light grey
-inline wxColor getColorInactiveText() { return { 0x40, 0x40, 0x40 }; } //dark grey
+inline wxColor getColorInactiveBack(bool faint) { if (faint) return {0xf6, 0xf6, 0xf6}; return {0xe4, 0xe4, 0xe4}; } //light grey
+inline wxColor getColorInactiveText() { return {0x40, 0x40, 0x40}; } //dark grey
 
 inline wxColor getColorGridLine() { return wxSystemSettings::GetColour(wxSYS_COLOUR_BTNSHADOW); }
 
@@ -73,7 +73,7 @@ std::pair<ptrdiff_t, ptrdiff_t> getVisibleRows(const Grid& grid) //returns range
         const ptrdiff_t rowFrom  = grid.getRowAtPos(topLeft.y); //return -1 for invalid position, rowCount if out of range
         const ptrdiff_t rowTo    = grid.getRowAtPos(bottom.y);
         if (rowFrom >= 0 && rowTo >= 0)
-            return { rowFrom, std::min(rowTo + 1, rowCount) };
+            return {rowFrom, std::min(rowTo + 1, rowCount)};
     }
     return {};
 }
@@ -125,36 +125,36 @@ enum class CudAction
     update,
     destroy,
 };
-std::pair<CudAction, SelectedSide> getCudAction(SyncOperation so)
+std::pair<CudAction, SelectSide> getCudAction(SyncOperation so)
 {
     switch (so)
     {
         //*INDENT-OFF*
         case SO_CREATE_NEW_LEFT:
-        case SO_MOVE_LEFT_TO: return {CudAction::create, LEFT_SIDE};
+        case SO_MOVE_LEFT_TO: return {CudAction::create, SelectSide::left};
 
         case SO_CREATE_NEW_RIGHT:
-        case SO_MOVE_RIGHT_TO: return {CudAction::create, RIGHT_SIDE};
+        case SO_MOVE_RIGHT_TO: return {CudAction::create, SelectSide::right};
 
         case SO_DELETE_LEFT:
-        case SO_MOVE_LEFT_FROM: return {CudAction::destroy, LEFT_SIDE};
+        case SO_MOVE_LEFT_FROM: return {CudAction::destroy, SelectSide::left};
 
         case SO_DELETE_RIGHT:
-        case SO_MOVE_RIGHT_FROM: return {CudAction::destroy, RIGHT_SIDE};
+        case SO_MOVE_RIGHT_FROM: return {CudAction::destroy, SelectSide::right};
 
         case SO_OVERWRITE_LEFT:
-        case SO_COPY_METADATA_TO_LEFT: return {CudAction::update, LEFT_SIDE};
+        case SO_COPY_METADATA_TO_LEFT: return {CudAction::update, SelectSide::left};
 
         case SO_OVERWRITE_RIGHT:
-        case SO_COPY_METADATA_TO_RIGHT: return {CudAction::update, RIGHT_SIDE};
+        case SO_COPY_METADATA_TO_RIGHT: return {CudAction::update, SelectSide::right};
 
         case SO_DO_NOTHING:
         case SO_EQUAL:
-        case SO_UNRESOLVED_CONFLICT: return {CudAction::doNothing, LEFT_SIDE};
+        case SO_UNRESOLVED_CONFLICT: return {CudAction::doNothing, SelectSide::left};
         //*INDENT-ON*
     }
     assert(false);
-    return {CudAction::doNothing, LEFT_SIDE};
+    return {CudAction::doNothing, SelectSide::left};
 }
 
 
@@ -375,7 +375,7 @@ private:
 
 //########################################################################################################
 
-template <SelectedSide side>
+template <SelectSide side>
 class GridDataRim : public GridDataBase
 {
 public:
@@ -503,7 +503,7 @@ private:
                     case ColumnTypeRim::size:
                         visitFSObject(*fsObj, [&](const FolderPair& folder) { value = L'<' + _("Folder") + L'>'; },
                         [&](const FilePair& file) { value = formatNumber(file.getFileSize<side>()); },
-                        //[&](const FilePair& file) { value = utfTo<std::wstring>(formatAsHexString(file.getFileId<side>())); }, // -> test file id
+                        //[&](const FilePair& file) { value = numberTo<std::wstring>(file.getFilePrint<side>()); }, // -> test file id
                         [&](const SymlinkPair& symlink) { value = L'<' + _("Symlink") + L'>'; });
                         break;
 
@@ -1194,7 +1194,7 @@ private:
         //draw sort marker
         if (auto sortInfo = getDataView().getSortConfig())
             if (const ColumnTypeRim* sortType = std::get_if<ColumnTypeRim>(&sortInfo->sortCol))
-                if (*sortType == static_cast<ColumnTypeRim>(colType) && sortInfo->onLeft == (side == LEFT_SIDE))
+                if (*sortType == static_cast<ColumnTypeRim>(colType) && sortInfo->onLeft == (side == SelectSide::left))
                 {
                     const wxImage sortMarker = loadImage(sortInfo->ascending ? "sort_ascending" : "sort_descending");
                     drawBitmapRtlNoMirror(dc, enabled ? sortMarker : sortMarker.ConvertToDisabled(), rectInner, wxALIGN_CENTER_HORIZONTAL);
@@ -1293,16 +1293,16 @@ private:
 };
 
 
-class GridDataLeft : public GridDataRim<LEFT_SIDE>
+class GridDataLeft : public GridDataRim<SelectSide::left>
 {
 public:
-    GridDataLeft(Grid& grid, const SharedRef<SharedComponents>& sharedComp) : GridDataRim<LEFT_SIDE>(grid, sharedComp) {}
+    GridDataLeft(Grid& grid, const SharedRef<SharedComponents>& sharedComp) : GridDataRim<SelectSide::left>(grid, sharedComp) {}
 };
 
-class GridDataRight : public GridDataRim<RIGHT_SIDE>
+class GridDataRight : public GridDataRim<SelectSide::right>
 {
 public:
-    GridDataRight(Grid& grid, const SharedRef<SharedComponents>& sharedComp) : GridDataRim<RIGHT_SIDE>(grid, sharedComp) {}
+    GridDataRight(Grid& grid, const SharedRef<SharedComponents>& sharedComp) : GridDataRim<SelectSide::right>(grid, sharedComp) {}
 };
 
 //########################################################################################################
@@ -1480,7 +1480,7 @@ private:
                     {
                         //draw notch on left side
                         if (notch_.GetHeight() != rectTmp.height)
-                            notch_.Rescale(notch_.GetWidth(), rectTmp.height);
+                            notch_ = notch_.Scale(notch_.GetWidth(), rectTmp.height);
 
                         //wxWidgets screws up again and has wxALIGN_RIGHT off by one pixel! -> use wxALIGN_LEFT instead
                         const wxRect rectNotch(rectTmp.x + rectTmp.width - notch_.GetWidth(), rectTmp.y, notch_.GetWidth(), rectTmp.height);
@@ -2008,9 +2008,9 @@ void filegrid::init(Grid& gridLeft, Grid& gridCenter, Grid& gridRight)
 
     gridCenter.setColumnConfig(
     {
-        { static_cast<ColumnType>(ColumnTypeCenter::checkbox),   widthCheckbox,   0, true },
-        { static_cast<ColumnType>(ColumnTypeCenter::difference), widthDifference, 0, true },
-        { static_cast<ColumnType>(ColumnTypeCenter::action),     widthAction,     0, true },
+        {static_cast<ColumnType>(ColumnTypeCenter::checkbox),   widthCheckbox,   0, true},
+        {static_cast<ColumnType>(ColumnTypeCenter::difference), widthDifference, 0, true},
+        {static_cast<ColumnType>(ColumnTypeCenter::action),     widthAction,     0, true},
     });
 }
 
diff --git a/FreeFileSync/Source/ui/file_grid_attr.h b/FreeFileSync/Source/ui/file_grid_attr.h
index 13c4dab9..012724ad 100644
--- a/FreeFileSync/Source/ui/file_grid_attr.h
+++ b/FreeFileSync/Source/ui/file_grid_attr.h
@@ -42,10 +42,10 @@ std::vector<ColAttributesRim> getFileGridDefaultColAttribsLeft()
     using namespace zen;
     return //harmonize with main_dlg.cpp::onGridLabelContextRim() => expects stretched path and non-stretched other columns!
     {
-        { ColumnTypeRim::path,      -fastFromDIP(100), 1, true  },
-        { ColumnTypeRim::extension, fastFromDIP(  60), 0, false },
-        { ColumnTypeRim::date,      fastFromDIP( 140), 0, false },
-        { ColumnTypeRim::size,      fastFromDIP( 100), 0, true  },
+        {ColumnTypeRim::path,      -fastFromDIP(100), 1, true },
+        {ColumnTypeRim::extension, fastFromDIP(  60), 0, false},
+        {ColumnTypeRim::date,      fastFromDIP( 140), 0, false},
+        {ColumnTypeRim::size,      fastFromDIP( 100), 0, true },
     };
 }
 
diff --git a/FreeFileSync/Source/ui/file_view.cpp b/FreeFileSync/Source/ui/file_view.cpp
index 8d06b266..fbea502e 100644
--- a/FreeFileSync/Source/ui/file_view.cpp
+++ b/FreeFileSync/Source/ui/file_view.cpp
@@ -62,8 +62,8 @@ FileView::FileView(FolderComparison& folderCmp)
         serializeHierarchy(baseObj, sortedRef_);
 
         folderPairs_.emplace_back(&baseObj,
-                                  baseObj.getAbstractPath< LEFT_SIDE>(),
-                                  baseObj.getAbstractPath<RIGHT_SIDE>());
+                                  baseObj.getAbstractPath< SelectSide::left>(),
+                                  baseObj.getAbstractPath<SelectSide::right>());
     });
 }
 
@@ -123,7 +123,7 @@ void FileView::updateView(Predicate pred)
                 assert(!groupDetails_.empty());
                 const size_t groupIdx = groupDetails_.size() - 1;
                 //-----------------------------------------------------------
-                viewRef_.push_back({ objId, groupIdx });
+                viewRef_.push_back({objId, groupIdx});
             }
 }
 
@@ -149,33 +149,33 @@ void addNumbers(const FileSystemObject& fsObj, ViewStats& stats)
 {
     visitFSObject(fsObj, [&](const FolderPair& folder)
     {
-        if (!folder.isEmpty<LEFT_SIDE>())
+        if (!folder.isEmpty<SelectSide::left>())
             ++stats.fileStatsLeft.folderCount;
 
-        if (!folder.isEmpty<RIGHT_SIDE>())
+        if (!folder.isEmpty<SelectSide::right>())
             ++stats.fileStatsRight.folderCount;
     },
 
     [&](const FilePair& file)
     {
-        if (!file.isEmpty<LEFT_SIDE>())
+        if (!file.isEmpty<SelectSide::left>())
         {
-            stats.fileStatsLeft.bytes += file.getFileSize<LEFT_SIDE>();
+            stats.fileStatsLeft.bytes += file.getFileSize<SelectSide::left>();
             ++stats.fileStatsLeft.fileCount;
         }
-        if (!file.isEmpty<RIGHT_SIDE>())
+        if (!file.isEmpty<SelectSide::right>())
         {
-            stats.fileStatsRight.bytes += file.getFileSize<RIGHT_SIDE>();
+            stats.fileStatsRight.bytes += file.getFileSize<SelectSide::right>();
             ++stats.fileStatsRight.fileCount;
         }
     },
 
     [&](const SymlinkPair& symlink)
     {
-        if (!symlink.isEmpty<LEFT_SIDE>())
+        if (!symlink.isEmpty<SelectSide::left>())
             ++stats.fileStatsLeft.fileCount;
 
-        if (!symlink.isEmpty<RIGHT_SIDE>())
+        if (!symlink.isEmpty<SelectSide::right>())
             ++stats.fileStatsRight.fileCount;
     });
 }
@@ -345,7 +345,7 @@ FileView::PathDrawInfo FileView::getDrawInfo(size_t row)
         if (fsObj && !folderGroupObj)
             folderGroupObj = dynamic_cast<FolderPair*>(&fsObj->parent());
 
-        return { groupFirstRow, groupLastRow, groupIdx, viewUpdateId_, folderGroupObj, fsObj };
+        return {groupFirstRow, groupLastRow, groupIdx, viewUpdateId_, folderGroupObj, fsObj};
     }
     assert(false); //unexpected: check rowsOnView()!
     return {};
@@ -394,7 +394,7 @@ bool isDirectoryPair(const FileSystemObject& fsObj)
 }
 
 
-template <bool ascending, SelectedSide side> inline
+template <bool ascending, SelectSide side> inline
 bool lessFileName(const FileSystemObject& lhs, const FileSystemObject& rhs)
 {
     //sort order: first files/symlinks, then directories then empty rows
@@ -445,7 +445,7 @@ bool lessFilePath(const FileSystemObject::ObjectId& lhs, const FileSystemObject:
         const size_t basePosR = itR->second;
 
         if (basePosL != basePosR)
-            return zen::makeSortDirection(std::less<>(), std::bool_constant<ascending>())(basePosL, basePosR);
+            return zen::makeSortDirection(std::less(), std::bool_constant<ascending>())(basePosL, basePosR);
     }
 
     //------- sort component-wise ----------
@@ -507,7 +507,7 @@ bool lessFilePath(const FileSystemObject::ObjectId& lhs, const FileSystemObject:
         else
             return std::is_gt(cmp);
     }
-    //return zen::makeSortDirection(std::less<>(), std::bool_constant<ascending>())(rv, 0);
+    //return zen::makeSortDirection(std::less(), std::bool_constant<ascending>())(rv, 0);
 
     /*...with equivalent names:
         1. functional correctness => must not compare equal!  e.g. a/a/x and a/A/y
@@ -516,7 +516,7 @@ bool lessFilePath(const FileSystemObject::ObjectId& lhs, const FileSystemObject:
 }
 
 
-template <bool ascending, SelectedSide side> inline
+template <bool ascending, SelectSide side> inline
 bool lessFilesize(const FileSystemObject& lhs, const FileSystemObject& rhs)
 {
     //empty rows always last
@@ -541,11 +541,11 @@ bool lessFilesize(const FileSystemObject& lhs, const FileSystemObject& rhs)
         return true;
 
     //return list beginning with largest files first
-    return zen::makeSortDirection(std::less<>(), std::bool_constant<ascending>())(fileL->getFileSize<side>(), fileR->getFileSize<side>());
+    return zen::makeSortDirection(std::less(), std::bool_constant<ascending>())(fileL->getFileSize<side>(), fileR->getFileSize<side>());
 }
 
 
-template <bool ascending, SelectedSide side> inline
+template <bool ascending, SelectSide side> inline
 bool lessFiletime(const FileSystemObject& lhs, const FileSystemObject& rhs)
 {
     if (lhs.isEmpty<side>())
@@ -568,11 +568,11 @@ bool lessFiletime(const FileSystemObject& lhs, const FileSystemObject& rhs)
     const int64_t dateR = fileR ? fileR->getLastWriteTime<side>() : symlinkR->getLastWriteTime<side>();
 
     //return list beginning with newest files first
-    return zen::makeSortDirection(std::less<>(), std::bool_constant<ascending>())(dateL, dateR);
+    return zen::makeSortDirection(std::less(), std::bool_constant<ascending>())(dateL, dateR);
 }
 
 
-template <bool ascending, SelectedSide side> inline
+template <bool ascending, SelectSide side> inline
 bool lessExtension(const FileSystemObject& lhs, const FileSystemObject& rhs)
 {
     if (lhs.isEmpty<side>())
@@ -613,11 +613,11 @@ bool lessCmpResult(const FileSystemObject& lhs, const FileSystemObject& rhs)
 template <bool ascending> inline
 bool lessSyncDirection(const FileSystemObject& lhs, const FileSystemObject& rhs)
 {
-    return zen::makeSortDirection(std::less<>(), std::bool_constant<ascending>())(lhs.getSyncOperation(), rhs.getSyncOperation());
+    return zen::makeSortDirection(std::less(), std::bool_constant<ascending>())(lhs.getSyncOperation(), rhs.getSyncOperation());
 }
 
 
-template <bool ascending, SelectedSide side>
+template <bool ascending, SelectSide side>
 struct LessFullPath
 {
     LessFullPath(std::vector<std::tuple<const void* /*BaseFolderPair*/, AbstractPath, AbstractPath>> folderPairs)
@@ -673,7 +673,7 @@ private:
 };
 
 
-template <bool ascending, SelectedSide side>
+template <bool ascending, SelectSide side>
 struct LessFileName
 {
     bool operator()(const FileSystemObject::ObjectId& lhs, const FileSystemObject::ObjectId& rhs) const
@@ -690,7 +690,7 @@ struct LessFileName
 };
 
 
-template <bool ascending, SelectedSide side>
+template <bool ascending, SelectSide side>
 struct LessFilesize
 {
     bool operator()(const FileSystemObject::ObjectId& lhs, const FileSystemObject::ObjectId& rhs) const
@@ -707,7 +707,7 @@ struct LessFilesize
 };
 
 
-template <bool ascending, SelectedSide side>
+template <bool ascending, SelectSide side>
 struct LessFiletime
 {
     bool operator()(const FileSystemObject::ObjectId& lhs, const FileSystemObject::ObjectId& rhs) const
@@ -724,7 +724,7 @@ struct LessFiletime
 };
 
 
-template <bool ascending, SelectedSide side>
+template <bool ascending, SelectSide side>
 struct LessExtension
 {
     bool operator()(const FileSystemObject::ObjectId& lhs, const FileSystemObject::ObjectId& rhs) const
@@ -783,7 +783,7 @@ void FileView::sortView(ColumnTypeRim type, ItemPathFormat pathFmt, bool onLeft,
     groupDetails_          .clear();
     rowPositions_          .clear();
     rowPositionsFirstChild_.clear();
-    currentSort_ = SortInfo({ type, onLeft, ascending });
+    currentSort_ = SortInfo({type, onLeft, ascending});
 
     switch (type)
     {
@@ -791,10 +791,10 @@ void FileView::sortView(ColumnTypeRim type, ItemPathFormat pathFmt, bool onLeft,
             switch (pathFmt)
             {
                 case ItemPathFormat::name:
-                    if      ( ascending &&  onLeft) std::sort(sortedRef_.begin(), sortedRef_.end(), LessFileName<true,   LEFT_SIDE>());
-                    else if ( ascending && !onLeft) std::sort(sortedRef_.begin(), sortedRef_.end(), LessFileName<true,  RIGHT_SIDE>());
-                    else if (!ascending &&  onLeft) std::sort(sortedRef_.begin(), sortedRef_.end(), LessFileName<false,  LEFT_SIDE>());
-                    else if (!ascending && !onLeft) std::sort(sortedRef_.begin(), sortedRef_.end(), LessFileName<false, RIGHT_SIDE>());
+                    if      ( ascending &&  onLeft) std::sort(sortedRef_.begin(), sortedRef_.end(), LessFileName<true,   SelectSide::left>());
+                    else if ( ascending && !onLeft) std::sort(sortedRef_.begin(), sortedRef_.end(), LessFileName<true,  SelectSide::right>());
+                    else if (!ascending &&  onLeft) std::sort(sortedRef_.begin(), sortedRef_.end(), LessFileName<false,  SelectSide::left>());
+                    else if (!ascending && !onLeft) std::sort(sortedRef_.begin(), sortedRef_.end(), LessFileName<false, SelectSide::right>());
                     break;
 
                 case ItemPathFormat::relative:
@@ -803,31 +803,31 @@ void FileView::sortView(ColumnTypeRim type, ItemPathFormat pathFmt, bool onLeft,
                     break;
 
                 case ItemPathFormat::full:
-                    if      ( ascending &&  onLeft) std::sort(sortedRef_.begin(), sortedRef_.end(), LessFullPath<true,   LEFT_SIDE>(folderPairs_));
-                    else if ( ascending && !onLeft) std::sort(sortedRef_.begin(), sortedRef_.end(), LessFullPath<true,  RIGHT_SIDE>(folderPairs_));
-                    else if (!ascending &&  onLeft) std::sort(sortedRef_.begin(), sortedRef_.end(), LessFullPath<false,  LEFT_SIDE>(folderPairs_));
-                    else if (!ascending && !onLeft) std::sort(sortedRef_.begin(), sortedRef_.end(), LessFullPath<false, RIGHT_SIDE>(folderPairs_));
+                    if      ( ascending &&  onLeft) std::sort(sortedRef_.begin(), sortedRef_.end(), LessFullPath<true,   SelectSide::left>(folderPairs_));
+                    else if ( ascending && !onLeft) std::sort(sortedRef_.begin(), sortedRef_.end(), LessFullPath<true,  SelectSide::right>(folderPairs_));
+                    else if (!ascending &&  onLeft) std::sort(sortedRef_.begin(), sortedRef_.end(), LessFullPath<false,  SelectSide::left>(folderPairs_));
+                    else if (!ascending && !onLeft) std::sort(sortedRef_.begin(), sortedRef_.end(), LessFullPath<false, SelectSide::right>(folderPairs_));
                     break;
             }
             break;
 
         case ColumnTypeRim::size:
-            if      ( ascending &&  onLeft) std::sort(sortedRef_.begin(), sortedRef_.end(), LessFilesize<true,   LEFT_SIDE>());
-            else if ( ascending && !onLeft) std::sort(sortedRef_.begin(), sortedRef_.end(), LessFilesize<true,  RIGHT_SIDE>());
-            else if (!ascending &&  onLeft) std::sort(sortedRef_.begin(), sortedRef_.end(), LessFilesize<false,  LEFT_SIDE>());
-            else if (!ascending && !onLeft) std::sort(sortedRef_.begin(), sortedRef_.end(), LessFilesize<false, RIGHT_SIDE>());
+            if      ( ascending &&  onLeft) std::sort(sortedRef_.begin(), sortedRef_.end(), LessFilesize<true,   SelectSide::left>());
+            else if ( ascending && !onLeft) std::sort(sortedRef_.begin(), sortedRef_.end(), LessFilesize<true,  SelectSide::right>());
+            else if (!ascending &&  onLeft) std::sort(sortedRef_.begin(), sortedRef_.end(), LessFilesize<false,  SelectSide::left>());
+            else if (!ascending && !onLeft) std::sort(sortedRef_.begin(), sortedRef_.end(), LessFilesize<false, SelectSide::right>());
             break;
         case ColumnTypeRim::date:
-            if      ( ascending &&  onLeft) std::sort(sortedRef_.begin(), sortedRef_.end(), LessFiletime<true,   LEFT_SIDE>());
-            else if ( ascending && !onLeft) std::sort(sortedRef_.begin(), sortedRef_.end(), LessFiletime<true,  RIGHT_SIDE>());
-            else if (!ascending &&  onLeft) std::sort(sortedRef_.begin(), sortedRef_.end(), LessFiletime<false,  LEFT_SIDE>());
-            else if (!ascending && !onLeft) std::sort(sortedRef_.begin(), sortedRef_.end(), LessFiletime<false, RIGHT_SIDE>());
+            if      ( ascending &&  onLeft) std::sort(sortedRef_.begin(), sortedRef_.end(), LessFiletime<true,   SelectSide::left>());
+            else if ( ascending && !onLeft) std::sort(sortedRef_.begin(), sortedRef_.end(), LessFiletime<true,  SelectSide::right>());
+            else if (!ascending &&  onLeft) std::sort(sortedRef_.begin(), sortedRef_.end(), LessFiletime<false,  SelectSide::left>());
+            else if (!ascending && !onLeft) std::sort(sortedRef_.begin(), sortedRef_.end(), LessFiletime<false, SelectSide::right>());
             break;
         case ColumnTypeRim::extension:
-            if      ( ascending &&  onLeft) std::stable_sort(sortedRef_.begin(), sortedRef_.end(), LessExtension<true,   LEFT_SIDE>());
-            else if ( ascending && !onLeft) std::stable_sort(sortedRef_.begin(), sortedRef_.end(), LessExtension<true,  RIGHT_SIDE>());
-            else if (!ascending &&  onLeft) std::stable_sort(sortedRef_.begin(), sortedRef_.end(), LessExtension<false,  LEFT_SIDE>());
-            else if (!ascending && !onLeft) std::stable_sort(sortedRef_.begin(), sortedRef_.end(), LessExtension<false, RIGHT_SIDE>());
+            if      ( ascending &&  onLeft) std::stable_sort(sortedRef_.begin(), sortedRef_.end(), LessExtension<true,   SelectSide::left>());
+            else if ( ascending && !onLeft) std::stable_sort(sortedRef_.begin(), sortedRef_.end(), LessExtension<true,  SelectSide::right>());
+            else if (!ascending &&  onLeft) std::stable_sort(sortedRef_.begin(), sortedRef_.end(), LessExtension<false,  SelectSide::left>());
+            else if (!ascending && !onLeft) std::stable_sort(sortedRef_.begin(), sortedRef_.end(), LessExtension<false, SelectSide::right>());
             break;
     }
 }
@@ -839,7 +839,7 @@ void FileView::sortView(ColumnTypeCenter type, bool ascending)
     groupDetails_          .clear();
     rowPositions_          .clear();
     rowPositionsFirstChild_.clear();
-    currentSort_ = SortInfo({ type, false, ascending });
+    currentSort_ = SortInfo({type, false, ascending});
 
     switch (type)
     {
diff --git a/FreeFileSync/Source/ui/folder_pair.h b/FreeFileSync/Source/ui/folder_pair.h
index 5940e25e..0357ae4c 100644
--- a/FreeFileSync/Source/ui/folder_pair.h
+++ b/FreeFileSync/Source/ui/folder_pair.h
@@ -84,7 +84,7 @@ private:
 
         zen::ContextMenu menu;
         menu.addItem(_("Remove local settings"), removeLocalCompCfg, wxNullImage, static_cast<bool>(localCmpCfg_));
-        menu.popup(*basicPanel_.m_bpButtonLocalCompCfg, { basicPanel_.m_bpButtonLocalCompCfg->GetSize().x, 0 });
+        menu.popup(*basicPanel_.m_bpButtonLocalCompCfg, {basicPanel_.m_bpButtonLocalCompCfg->GetSize().x, 0});
     }
 
     void onLocalSyncCfgContext(wxEvent& event)
@@ -98,7 +98,7 @@ private:
 
         zen::ContextMenu menu;
         menu.addItem(_("Remove local settings"), removeLocalSyncCfg, wxNullImage, static_cast<bool>(localSyncCfg_));
-        menu.popup(*basicPanel_.m_bpButtonLocalSyncCfg, { basicPanel_.m_bpButtonLocalSyncCfg->GetSize().x, 0 });
+        menu.popup(*basicPanel_.m_bpButtonLocalSyncCfg, {basicPanel_.m_bpButtonLocalSyncCfg->GetSize().x, 0});
     }
 
     void onLocalFilterCfgContext(wxEvent& event)
@@ -128,7 +128,7 @@ private:
         menu.addSeparator();
         menu.addItem( _("Copy"),  copyFilter,  wxNullImage, !isNullFilter(localFilter_));
         menu.addItem( _("Paste"), pasteFilter, wxNullImage, filterCfgOnClipboard.get() != nullptr);
-        menu.popup(*basicPanel_.m_bpButtonLocalFilter, { basicPanel_.m_bpButtonLocalFilter->GetSize().x, 0 });
+        menu.popup(*basicPanel_.m_bpButtonLocalFilter, {basicPanel_.m_bpButtonLocalFilter->GetSize().x, 0});
     }
 
 
diff --git a/FreeFileSync/Source/ui/folder_selector.cpp b/FreeFileSync/Source/ui/folder_selector.cpp
index 061b603f..99c0bbe4 100644
--- a/FreeFileSync/Source/ui/folder_selector.cpp
+++ b/FreeFileSync/Source/ui/folder_selector.cpp
@@ -201,6 +201,9 @@ void FolderSelector::onSelectFolder(wxCommandEvent& event)
         //make sure default folder exists: don't let folder picker hang on non-existing network share!
         auto folderExistsTimed = [waitEndTime = std::chrono::steady_clock::now() + FOLDER_SELECTED_EXISTENCE_CHECK_TIME_MAX](const AbstractPath& folderPath)
         {
+            if (AFS::isNullPath(folderPath))
+                return false;
+
             auto ft = runAsync([folderPath]
             {
                 try
@@ -218,8 +221,9 @@ void FolderSelector::onSelectFolder(wxCommandEvent& event)
             {
                 const AbstractPath folderPath = createItemPathNative(folderPathPhrase);
                 if (folderExistsTimed(folderPath))
-                    if (std::optional<Zstring> nativeFolderPath = AFS::getNativeItemPath(folderPath))
-                        defaultFolderNative = *nativeFolderPath;
+                    if (const Zstring& nativePath = getNativeItemPath(folderPath);
+                        !nativePath.empty())
+                        defaultFolderNative = nativePath;
             }
         };
         const Zstring& currentFolderPath = getPath();
diff --git a/FreeFileSync/Source/ui/gui_status_handler.cpp b/FreeFileSync/Source/ui/gui_status_handler.cpp
index ef82679f..861ea810 100644
--- a/FreeFileSync/Source/ui/gui_status_handler.cpp
+++ b/FreeFileSync/Source/ui/gui_status_handler.cpp
@@ -15,7 +15,7 @@
 #include "main_dlg.h"
 #include "../afs/concrete.h"
 #include "../log_file.h"
-#include "status_handler_impl.h"
+#include "../fatal_error.h"
 
 using namespace zen;
 using namespace fff;
@@ -172,7 +172,7 @@ StatusHandlerTemporaryPanel::Result StatusHandlerTemporaryPanel::reportResults()
     auto errorLogFinal = std::make_shared<const ErrorLog>(std::move(errorLog_));
     errorLog_ = ErrorLog(); //see check in ~StatusHandlerTemporaryPanel()
 
-    return { summary, errorLogFinal };
+    return {summary, errorLogFinal};
 }
 
 
@@ -187,10 +187,10 @@ void StatusHandlerTemporaryPanel::initNewPhase(int itemsTotal, int64_t bytesTota
 }
 
 
-void StatusHandlerTemporaryPanel::reportInfo(const std::wstring& msg)
+void StatusHandlerTemporaryPanel::logInfo(const std::wstring& msg)
 {
     errorLog_.logMsg(msg, MSG_TYPE_INFO);
-    updateStatus(msg); //throw AbortProcess
+    requestUiUpdate(false /*force*/); //throw AbortProcess
 }
 
 
@@ -405,7 +405,7 @@ StatusHandlerFloatingDialog::Result StatusHandlerFloatingDialog::reportResults(c
     const AbstractPath logFilePath = generateLogFilePath(logFormat, summary, altLogFolderPathPhrase);
     //e.g. %AppData%\FreeFileSync\Logs\Backup FreeFileSync 2013-09-15 015052.123 [Error].log
 
-    auto notifyStatusNoThrow = [&](const std::wstring& msg) { try { updateStatus(msg); /*throw AbortProcess*/ } catch (AbortProcess&) {} };
+    auto notifyStatusNoThrow = [&](std::wstring&& msg) { try { updateStatus(std::move(msg)); /*throw AbortProcess*/ } catch (AbortProcess&) {} };
 
     bool autoClose = false;
     FinalRequest finalRequest = FinalRequest::none;
@@ -513,7 +513,7 @@ StatusHandlerFloatingDialog::Result StatusHandlerFloatingDialog::reportResults(c
         //do NOT use tryReportingError()! saving log files should not be cancellable!
         saveLogFile(logFilePath, summary, errorLog_, logfilesMaxAgeDays, logFormat, logFilePathsToKeep, notifyStatusNoThrow); //throw FileError
     }
-    catch (const FileError& e) { errorLog_.logMsg(e.toString(), MSG_TYPE_ERROR); }
+    catch (const FileError& e) { errorLog_.logMsg(e.toString(), MSG_TYPE_ERROR); logFatalError(e.toString()); }
     //----------------------------------------------------------
 
 
@@ -532,7 +532,7 @@ StatusHandlerFloatingDialog::Result StatusHandlerFloatingDialog::reportResults(c
                                                                                  syncResult, errorLogFinal);
     progressDlg_ = nullptr;
 
-    return { summary, errorLogFinal, finalRequest, logFilePath, dlgSize, dlgIsMaximized, autoCloseFinal };
+    return {summary, errorLogFinal, finalRequest, logFilePath, dlgSize, dlgIsMaximized, autoCloseFinal};
 }
 
 
@@ -547,10 +547,10 @@ void StatusHandlerFloatingDialog::initNewPhase(int itemsTotal, int64_t bytesTota
 }
 
 
-void StatusHandlerFloatingDialog::reportInfo(const std::wstring& msg)
+void StatusHandlerFloatingDialog::logInfo(const std::wstring& msg)
 {
     errorLog_.logMsg(msg, MSG_TYPE_INFO);
-    updateStatus(msg); //throw AbortProcess
+    requestUiUpdate(false /*force*/); //throw AbortProcess
 }
 
 
diff --git a/FreeFileSync/Source/ui/gui_status_handler.h b/FreeFileSync/Source/ui/gui_status_handler.h
index 643714a2..8f74e77d 100644
--- a/FreeFileSync/Source/ui/gui_status_handler.h
+++ b/FreeFileSync/Source/ui/gui_status_handler.h
@@ -26,7 +26,7 @@ public:
     ~StatusHandlerTemporaryPanel();
 
     void     initNewPhase    (int itemsTotal, int64_t bytesTotal, ProcessPhase phaseID) override; //
-    void     reportInfo      (const std::wstring& msg)                                  override; //
+    void     logInfo         (const std::wstring& msg)                                  override; //
     void     reportWarning   (const std::wstring& msg, bool& warningActive)             override; //throw AbortProcess
     Response reportError     (const ErrorInfo& errorInfo)                               override; //
     void     reportFatalError(const std::wstring& msg)                                  override; //
@@ -71,7 +71,7 @@ public:
     ~StatusHandlerFloatingDialog();
 
     void     initNewPhase    (int itemsTotal, int64_t bytesTotal, ProcessPhase phaseID) override; //
-    void     reportInfo      (const std::wstring& msg)                                  override; //
+    void     logInfo         (const std::wstring& msg)                                  override; //
     void     reportWarning   (const std::wstring& msg, bool& warningActive)             override; //throw AbortProcess
     Response reportError     (const ErrorInfo& errorInfo)                               override; //
     void     reportFatalError(const std::wstring& msg)                                  override; //
diff --git a/FreeFileSync/Source/ui/log_panel.cpp b/FreeFileSync/Source/ui/log_panel.cpp
index 3bea6506..cd61b9bd 100644
--- a/FreeFileSync/Source/ui/log_panel.cpp
+++ b/FreeFileSync/Source/ui/log_panel.cpp
@@ -18,7 +18,7 @@ using namespace fff;
 
 namespace
 {
-inline wxColor getColorGridLine() { return { 192, 192, 192 }; } //light grey
+inline wxColor getColorGridLine() { return {192, 192, 192}; } //light grey
 
 
 inline
@@ -320,9 +320,9 @@ LogPanel::LogPanel(wxWindow* parent) : LogPanelGenerated(parent)
     m_gridMessages->setRowHeight(rowHeight);
     m_gridMessages->setColumnConfig(
     {
-        { static_cast<ColumnType>(ColumnTypeLog::time    ), colMsgTimeWidth,                        0, true },
-        { static_cast<ColumnType>(ColumnTypeLog::severity), colMsgSeverityWidth,                    0, true },
-        { static_cast<ColumnType>(ColumnTypeLog::text    ), -colMsgTimeWidth - colMsgSeverityWidth, 1, true },
+        {static_cast<ColumnType>(ColumnTypeLog::time    ), colMsgTimeWidth,                        0, true},
+        {static_cast<ColumnType>(ColumnTypeLog::severity), colMsgSeverityWidth,                    0, true},
+        {static_cast<ColumnType>(ColumnTypeLog::text    ), -colMsgTimeWidth - colMsgSeverityWidth, 1, true},
     });
 
     //support for CTRL + C
diff --git a/FreeFileSync/Source/ui/main_dlg.cpp b/FreeFileSync/Source/ui/main_dlg.cpp
index be302be0..3fe046fb 100644
--- a/FreeFileSync/Source/ui/main_dlg.cpp
+++ b/FreeFileSync/Source/ui/main_dlg.cpp
@@ -49,6 +49,7 @@
 #include "../ffs_paths.h"
 #include "../localization.h"
 #include "../version/version.h"
+#include "../afs/gdrive.h"
 
 using namespace zen;
 using namespace fff;
@@ -1350,8 +1351,8 @@ std::vector<FileSystemObject*> MainDialog::getTreeSelection() const
 void MainDialog::copyToAlternateFolder(const std::vector<FileSystemObject*>& selectionLeft,
                                        const std::vector<FileSystemObject*>& selectionRight)
 {
-    if (std::all_of(selectionLeft .begin(), selectionLeft .end(), [](const FileSystemObject* fsObj) { return fsObj->isEmpty< LEFT_SIDE>(); }) &&
-    /**/std::all_of(selectionRight.begin(), selectionRight.end(), [](const FileSystemObject* fsObj) { return fsObj->isEmpty<RIGHT_SIDE>(); }))
+    if (std::all_of(selectionLeft .begin(), selectionLeft .end(), [](const FileSystemObject* fsObj) { return fsObj->isEmpty< SelectSide::left>(); }) &&
+    /**/std::all_of(selectionRight.begin(), selectionRight.end(), [](const FileSystemObject* fsObj) { return fsObj->isEmpty<SelectSide::right>(); }))
     /**/return; //harmonize with onGridContextRim(): this function should be a no-op iff context menu option is disabled!
 
     FocusPreserver fp;
@@ -1399,8 +1400,8 @@ void MainDialog::copyToAlternateFolder(const std::vector<FileSystemObject*>& sel
 void MainDialog::deleteSelectedFiles(const std::vector<FileSystemObject*>& selectionLeft,
                                      const std::vector<FileSystemObject*>& selectionRight, bool moveToRecycler)
 {
-    if (std::all_of(selectionLeft .begin(), selectionLeft .end(), [](const FileSystemObject* fsObj) { return fsObj->isEmpty< LEFT_SIDE>(); }) &&
-    /**/std::all_of(selectionRight.begin(), selectionRight.end(), [](const FileSystemObject* fsObj) { return fsObj->isEmpty<RIGHT_SIDE>(); }))
+    if (std::all_of(selectionLeft .begin(), selectionLeft .end(), [](const FileSystemObject* fsObj) { return fsObj->isEmpty< SelectSide::left>(); }) &&
+    /**/std::all_of(selectionRight.begin(), selectionRight.end(), [](const FileSystemObject* fsObj) { return fsObj->isEmpty<SelectSide::right>(); }))
     /**/return; //harmonize with onGridContextRim(): this function should be a no-op iff context menu option is disabled!
 
     FocusPreserver fp;
@@ -1444,7 +1445,7 @@ void MainDialog::deleteSelectedFiles(const std::vector<FileSystemObject*>& selec
 
 namespace
 {
-template <SelectedSide side>
+template <SelectSide side>
 AbstractPath getExistingParentFolder(const FileSystemObject& fsObj)
 {
     auto folder = dynamic_cast<const FolderPair*>(&fsObj);
@@ -1462,41 +1463,40 @@ AbstractPath getExistingParentFolder(const FileSystemObject& fsObj)
 }
 
 
-template <SelectedSide side, class Function>
+template <SelectSide side, class Function>
 void extractFileDescriptor(const FileSystemObject& fsObj, Function onDescriptor)
 {
     if (!fsObj.isEmpty<side>())
         visitFSObject(fsObj, [](const FolderPair& folder) {},
     [&](const FilePair& file)
     {
-        const FileDescriptor descr = { file.getAbstractPath<side>(), file.getAttributes<side>() };
-        onDescriptor(descr);
+        onDescriptor(FileDescriptor{file.getAbstractPath<side>(), file.getAttributes<side>()});
     },
     [](const SymlinkPair& symlink) {});
 }
 
 
-template <SelectedSide side>
+template <SelectSide side>
 void collectNonNativeFiles(const std::vector<FileSystemObject*>& selectedRows, const TempFileBuffer& tempFileBuf,
                            std::set<FileDescriptor>& workLoad)
 {
     for (const FileSystemObject* fsObj : selectedRows)
         extractFileDescriptor<side>(*fsObj, [&](const FileDescriptor& descr)
     {
-        if (!AFS::getNativeItemPath(descr.path))
-            if (tempFileBuf.getTempPath(descr).empty()) //TempFileBuffer::createTempFiles() contract!
-                workLoad.insert(descr);
+        if (getNativeItemPath(descr.path).empty() &&
+            tempFileBuf.getTempPath(descr).empty()) //TempFileBuffer::createTempFiles() contract!
+            workLoad.insert(descr);
     });
 }
 
 
-template <SelectedSide side>
+template <SelectSide side>
 void invokeCommandLine(const Zstring& commandLinePhrase, //throw FileError
                        bool openWithDefaultAppRequested,
                        const std::vector<FileSystemObject*>& selection,
                        const TempFileBuffer& tempFileBuf)
 {
-    constexpr SelectedSide side2 = OtherSide<side>::value;
+    constexpr SelectSide side2 = OtherSide<side>::value;
 
     for (const FileSystemObject* fsObj : selection) //context menu calls this function only if selection is not empty!
     {
@@ -1514,13 +1514,15 @@ void invokeCommandLine(const Zstring& commandLinePhrase, //throw FileError
         Zstring localPath;
         Zstring localPath2;
 
-        if (AFS::getNativeItemPath(basePath))
-            localPath = itemPath; //no matter if item exists or not
+        if (const Zstring& nativePath = getNativeItemPath(fsObj->getAbstractPath<side>());
+            !nativePath.empty())
+            localPath = nativePath; //no matter if item exists or not
         else //returns empty if not available (item not existing, error during copy):
             extractFileDescriptor<side>(*fsObj, [&](const FileDescriptor& descr) { localPath = tempFileBuf.getTempPath(descr); });
 
-        if (AFS::getNativeItemPath(basePath2))
-            localPath2 = itemPath2;
+        if (const Zstring& nativePath = getNativeItemPath(fsObj->getAbstractPath<side2>());
+            !nativePath.empty())
+            localPath2 = nativePath;
         else
             extractFileDescriptor<side2>(*fsObj, [&](const FileDescriptor& descr) { localPath2 = tempFileBuf.getTempPath(descr); });
 
@@ -1568,113 +1570,124 @@ void MainDialog::openExternalApplication(const Zstring& commandLinePhrase, bool
     const bool showInFileBrowserRequested  = commandLinePhrase == defaultCfg.externalApps[0].cmdLine;
     const bool openWithDefaultAppRequested = commandLinePhrase == defaultCfg.externalApps[1].cmdLine;
 
-    auto openFolderInFileBrowser = [this](const AbstractPath& folderPath)
+    try
     {
-        try
+        auto openFolderInFileBrowser = [](const AbstractPath& folderPath) //throw FileError
         {
-                openWithDefaultApp(utfTo<Zstring>(AFS::getDisplayPath(folderPath))); //throw FileError
-        }
-        catch (const FileError& e) { showNotificationDialog(this, DialogInfoType::error, PopupDialogCfg().setDetailInstructions(e.toString())); }
-    };
+                if (const Zstring& gdriveUrl = getGoogleDriveFolderUrl(folderPath); //throw FileError
+                    !gdriveUrl.empty())
+                    return openWithDefaultApp(gdriveUrl); //throw FileError
+                else
+                    openWithDefaultApp(utfTo<Zstring>(AFS::getDisplayPath(folderPath))); //throw FileError
+        };
 
-    //support fallback instead of an error in this special case
-    if (showInFileBrowserRequested)
-    {
-        if (selectionLeft.size() + selectionRight.size() > 1) //do not open more than one Explorer instance!
+        //support fallback instead of an error in this special case
+        if (showInFileBrowserRequested)
         {
-            if ((leftSide && !selectionLeft .empty()) ||
-                (!leftSide && selectionRight.empty()))
-                return openExternalApplication(commandLinePhrase, leftSide, { selectionLeft[0] }, {});
+            if (selectionLeft.size() + selectionRight.size() > 1) //do not open more than one Explorer instance!
+            {
+                if ((leftSide && !selectionLeft .empty()) ||
+                    (!leftSide && selectionRight.empty()))
+                    return openExternalApplication(commandLinePhrase, leftSide, {selectionLeft[0]}, {});
+                else
+                    return openExternalApplication(commandLinePhrase, leftSide, {}, {selectionRight[0]});
+            }
+
+            //either left or right selection is filled with exactly one item (or no selection at all)
+            AbstractPath itemPath = getNullPath();
+            if (!selectionLeft.empty())
+            {
+                if (selectionLeft[0]->isEmpty<SelectSide::left>())
+                    return openFolderInFileBrowser(getExistingParentFolder<SelectSide::left>(*selectionLeft[0])); //throw FileError
+
+                itemPath = selectionLeft[0]->getAbstractPath<SelectSide::left>();
+            }
+            else if (!selectionRight.empty())
+            {
+                if (selectionRight[0]->isEmpty<SelectSide::right>())
+                    return openFolderInFileBrowser(getExistingParentFolder<SelectSide::right>(*selectionRight[0])); //throw FileError
+
+                itemPath = selectionRight[0]->getAbstractPath<SelectSide::right>();
+            }
             else
-                return openExternalApplication(commandLinePhrase, leftSide, {}, { selectionRight[0] });
+                return openFolderInFileBrowser(leftSide ? //throw FileError
+                                               createAbstractPath(firstFolderPair_->getValues().folderPathPhraseLeft) :
+                                               createAbstractPath(firstFolderPair_->getValues().folderPathPhraseRight));
+
+            //itemPath != base folder in this context
+            if (const Zstring& gdriveUrl = getGoogleDriveFolderUrl(*AFS::getParentPath(itemPath)); //throw FileError
+                !gdriveUrl.empty())
+                return openWithDefaultApp(gdriveUrl); //throw FileError
         }
 
-        if (selectionLeft.empty() && selectionRight.empty())
-            return openFolderInFileBrowser(leftSide ?
-                                           createAbstractPath(firstFolderPair_->getValues().folderPathPhraseLeft) :
-                                           createAbstractPath(firstFolderPair_->getValues().folderPathPhraseRight));
-        //in this context either left or right selection is filled with exactly one item
-        if (!selectionLeft.empty())
+        //regular command evaluation:
+        const size_t invokeCount = selectionLeft.size() + selectionRight.size();
+        if (invokeCount > EXT_APP_MASS_INVOKE_THRESHOLD)
+            if (globalCfg_.confirmDlgs.confirmCommandMassInvoke)
+            {
+                bool dontAskAgain = false;
+                switch (showConfirmationDialog(this, DialogInfoType::warning, PopupDialogCfg().
+                                               setTitle(_("Confirm")).
+                                               setMainInstructions(replaceCpy(_P("Do you really want to execute the command %y for one item?",
+                                                                                 "Do you really want to execute the command %y for %x items?", invokeCount),
+                                                                              L"%y", fmtPath(commandLinePhrase))).
+                                               setCheckBox(dontAskAgain, _("&Don't show this warning again")),
+                                               _("&Execute")))
+                {
+                    case ConfirmationButton::accept:
+                        globalCfg_.confirmDlgs.confirmCommandMassInvoke = !dontAskAgain;
+                        break;
+                    case ConfirmationButton::cancel:
+                        return;
+                }
+            }
+
+        std::set<FileDescriptor> nonNativeFiles;
+        if (contains(commandLinePhrase, Zstr("%local_path%")))
         {
-            if (selectionLeft[0]->isEmpty<LEFT_SIDE>())
-                return openFolderInFileBrowser(getExistingParentFolder<LEFT_SIDE>(*selectionLeft[0]));
+            collectNonNativeFiles< SelectSide::left>(selectionLeft,  tempFileBuf_, nonNativeFiles);
+            collectNonNativeFiles<SelectSide::right>(selectionRight, tempFileBuf_, nonNativeFiles);
         }
-        else
+        if (contains(commandLinePhrase, Zstr("%local_path2%")))
         {
-            if (selectionRight[0]->isEmpty<RIGHT_SIDE>())
-                return openFolderInFileBrowser(getExistingParentFolder<RIGHT_SIDE>(*selectionRight[0]));
+            collectNonNativeFiles<SelectSide::right>(selectionLeft,  tempFileBuf_, nonNativeFiles);
+            collectNonNativeFiles< SelectSide::left>(selectionRight, tempFileBuf_, nonNativeFiles);
         }
-    }
 
-    //regular command evaluation:
-    const size_t invokeCount = selectionLeft.size() + selectionRight.size();
-    if (invokeCount > EXT_APP_MASS_INVOKE_THRESHOLD)
-        if (globalCfg_.confirmDlgs.confirmCommandMassInvoke)
+        //##################### create temporary files for non-native paths ######################
+        if (!nonNativeFiles.empty())
         {
-            bool dontAskAgain = false;
-            switch (showConfirmationDialog(this, DialogInfoType::warning, PopupDialogCfg().
-                                           setTitle(_("Confirm")).
-                                           setMainInstructions(replaceCpy(_P("Do you really want to execute the command %y for one item?",
-                                                                             "Do you really want to execute the command %y for %x items?", invokeCount),
-                                                                          L"%y", fmtPath(commandLinePhrase))).
-                                           setCheckBox(dontAskAgain, _("&Don't show this warning again")),
-                                           _("&Execute")))
-            {
-                case ConfirmationButton::accept:
-                    globalCfg_.confirmDlgs.confirmCommandMassInvoke = !dontAskAgain;
-                    break;
-                case ConfirmationButton::cancel:
-                    return;
-            }
-        }
+            FocusPreserver fp;
 
-    std::set<FileDescriptor> nonNativeFiles;
-    if (contains(commandLinePhrase, Zstr("%local_path%")))
-    {
-        collectNonNativeFiles< LEFT_SIDE>(selectionLeft,  tempFileBuf_, nonNativeFiles);
-        collectNonNativeFiles<RIGHT_SIDE>(selectionRight, tempFileBuf_, nonNativeFiles);
-    }
-    if (contains(commandLinePhrase, Zstr("%local_path2%")))
-    {
-        collectNonNativeFiles<RIGHT_SIDE>(selectionLeft,  tempFileBuf_, nonNativeFiles);
-        collectNonNativeFiles< LEFT_SIDE>(selectionRight, tempFileBuf_, nonNativeFiles);
-    }
+            disableGuiElements(true /*enableAbort*/); //StatusHandlerTemporaryPanel will internally process Window messages, so avoid unexpected callbacks!
+            auto app = wxTheApp; //fix lambda/wxWigets/VC fuck up
+            ZEN_ON_SCOPE_EXIT(app->Yield(); enableGuiElements()); //ui update before enabling buttons again: prevent strange behaviour of delayed button clicks
 
-    //##################### create temporary files for non-native paths ######################
-    if (!nonNativeFiles.empty())
-    {
-        FocusPreserver fp;
+            const auto& guiCfg = getConfig();
 
-        disableGuiElements(true /*enableAbort*/); //StatusHandlerTemporaryPanel will internally process Window messages, so avoid unexpected callbacks!
-        auto app = wxTheApp; //fix lambda/wxWigets/VC fuck up
-        ZEN_ON_SCOPE_EXIT(app->Yield(); enableGuiElements()); //ui update before enabling buttons again: prevent strange behaviour of delayed button clicks
+            StatusHandlerTemporaryPanel statusHandler(*this, std::chrono::system_clock::now() /*startTime*/,
+                                                      false /*ignoreErrors*/,
+                                                      guiCfg.mainCfg.autoRetryCount,
+                                                      guiCfg.mainCfg.autoRetryDelay); //handle status display and error messages
+            try
+            {
+                tempFileBuf_.createTempFiles(nonNativeFiles, statusHandler); //throw AbortProcess
+                //"clearSelection" not needed/desired
+            }
+            catch (AbortProcess&) {}
 
-        const auto& guiCfg = getConfig();
+            const StatusHandlerTemporaryPanel::Result r = statusHandler.reportResults(); //noexcept
+            setLastOperationLog(r.summary, r.errorLog);
 
-        StatusHandlerTemporaryPanel statusHandler(*this, std::chrono::system_clock::now() /*startTime*/,
-                                                  false /*ignoreErrors*/,
-                                                  guiCfg.mainCfg.autoRetryCount,
-                                                  guiCfg.mainCfg.autoRetryDelay); //handle status display and error messages
-        try
-        {
-            tempFileBuf_.createTempFiles(nonNativeFiles, statusHandler); //throw AbortProcess
-            //"clearSelection" not needed/desired
-        }
-        catch (AbortProcess&) {}
-
-        const StatusHandlerTemporaryPanel::Result r = statusHandler.reportResults(); //noexcept
-        setLastOperationLog(r.summary, r.errorLog);
+            if (r.summary.syncResult == SyncResult::aborted)
+                return;
 
-        if (r.summary.syncResult == SyncResult::aborted)
-            return;
+            //updateGui(); -> not needed
+        }
+        //########################################################################################
 
-        //updateGui(); -> not needed
-    }
-    //########################################################################################
-    try
-    {
-        invokeCommandLine< LEFT_SIDE>(commandLinePhrase, openWithDefaultAppRequested, selectionLeft,  tempFileBuf_); //throw FileError
-        invokeCommandLine<RIGHT_SIDE>(commandLinePhrase, openWithDefaultAppRequested, selectionRight, tempFileBuf_); //
+        invokeCommandLine< SelectSide::left>(commandLinePhrase, openWithDefaultAppRequested, selectionLeft,  tempFileBuf_); //throw FileError
+        invokeCommandLine<SelectSide::right>(commandLinePhrase, openWithDefaultAppRequested, selectionRight, tempFileBuf_); //
     }
     catch (const FileError& e) { showNotificationDialog(this, DialogInfoType::error, PopupDialogCfg().setDetailInstructions(e.toString())); }
 }
@@ -1898,7 +1911,7 @@ void MainDialog::onTreeKeyEvent(wxKeyEvent& event)
         {
             case 'C':
             case WXK_INSERT: //CTRL + C || CTRL + INS
-                copySelectionToClipboard({ m_gridOverview });
+                copySelectionToClipboard({m_gridOverview});
                 return;
         }
 
@@ -2142,16 +2155,13 @@ void MainDialog::onLocalKeyEvent(wxKeyEvent& event) //process key events without
         break;
 
         case WXK_ESCAPE: //let's do something useful and hide the log panel
-        {
-            const wxWindow* focus = wxWindow::FindFocus();
-            if (!isComponentOf(focus, m_panelSearch)  && //search panel also handles ESC!
+            if (!isComponentOf(wxWindow::FindFocus(), m_panelSearch)  && //search panel also handles ESC!
                 m_panelLog->IsEnabled())
             {
                 if (auiMgr_.GetPane(m_panelLog).IsShown()) //else: let it "ding"
                     return showLogPanel(false /*show*/);
             }
-        }
-        break;
+            break;
     }
 
     event.Skip();
@@ -2308,7 +2318,7 @@ void MainDialog::onTreeGridContext(GridContextMenuEvent& event)
     menu.addSeparator();
     menu.addItem(_("&Synchronize selection") + L"\tEnter", [&] { startSyncForSelecction(selection); }, loadImage("start_sync_selection_sicon"), selectionContainsItemsToSync);
     //----------------------------------------------------------------------------------------------------
-    const bool haveNonEmptyItems = std::any_of(selection.begin(), selection.end(), [](const FileSystemObject* fsObj) { return !fsObj->isEmpty<LEFT_SIDE>() || !fsObj->isEmpty<RIGHT_SIDE>(); });
+    const bool haveNonEmptyItems = std::any_of(selection.begin(), selection.end(), [](const FileSystemObject* fsObj) { return !fsObj->isEmpty<SelectSide::left>() || !fsObj->isEmpty<SelectSide::right>(); });
     //menu.addSeparator();
     //menu.addItem(_("&Copy to...") + L"\tCtrl+T", [&] { copyToAlternateFolder(selection, selection); }, wxNullImage, haveNonEmptyItems);
     //----------------------------------------------------------------------------------------------------
@@ -2485,8 +2495,8 @@ void MainDialog::onGridContextRim(const std::vector<FileSystemObject*>& selectio
         }
     }
     //----------------------------------------------------------------------------------------------------
-    const bool haveNonEmptyItemsL = std::any_of(selectionLeft .begin(), selectionLeft .end(), [](const FileSystemObject* fsObj) { return !fsObj->isEmpty<LEFT_SIDE >(); });
-    const bool haveNonEmptyItemsR = std::any_of(selectionRight.begin(), selectionRight.end(), [](const FileSystemObject* fsObj) { return !fsObj->isEmpty<RIGHT_SIDE>(); });
+    const bool haveNonEmptyItemsL = std::any_of(selectionLeft .begin(), selectionLeft .end(), [](const FileSystemObject* fsObj) { return !fsObj->isEmpty< SelectSide::left>(); });
+    const bool haveNonEmptyItemsR = std::any_of(selectionRight.begin(), selectionRight.end(), [](const FileSystemObject* fsObj) { return !fsObj->isEmpty<SelectSide::right>(); });
 
     menu.addSeparator();
     menu.addItem(_("&Copy to...") + L"\tCtrl+T", [&] { copyToAlternateFolder(selectionLeft, selectionRight); }, wxNullImage, haveNonEmptyItemsL || haveNonEmptyItemsR);
@@ -2594,7 +2604,7 @@ void MainDialog::onGridLabelContextC(GridLabelClickEvent& event)
     const GridViewType viewType = m_bpButtonViewType->isActive() ? GridViewType::action : GridViewType::difference;
     menu.addItem(_("Difference") + (viewType != GridViewType::difference ? L"\tF11" : L""), [&] { setGridViewType(GridViewType::difference); }, greyScaleIfDisabled(loadImage("compare_sicon"   ), viewType == GridViewType::difference));
     menu.addItem(_("Action")     + (viewType != GridViewType::action     ? L"\tF11" : L""), [&] { setGridViewType(GridViewType::action    ); }, greyScaleIfDisabled(loadImage("start_sync_sicon"), viewType == GridViewType::action));
-    menu.popup(*m_gridMainC, { m_gridMainC->GetSize().x, 0 });
+    menu.popup(*m_gridMainC, {m_gridMainC->GetSize().x, 0});
 }
 
 
@@ -2703,7 +2713,7 @@ void MainDialog::onGridLabelContextRim(GridLabelClickEvent& event, bool leftSide
         menu.addItem(_("Select time span..."), selectTimeSpan);
     }
     //--------------------------------------------------------------------------------------------------------
-    menu.popup(grid, { event.mousePos_.x, grid.getColumnLabelHeight() });
+    menu.popup(grid, {event.mousePos_.x, grid.getColumnLabelHeight()});
     //event.Skip();
 }
 
@@ -2800,7 +2810,7 @@ void MainDialog::onCompSettingsContext(wxEvent& event)
     addVariantItem(CompareVariant::content,  "cmp_content");
     addVariantItem(CompareVariant::size,     "cmp_size");
 
-    menu.popup(*m_bpButtonCmpContext, { m_bpButtonCmpContext->GetSize().x, 0 });
+    menu.popup(*m_bpButtonCmpContext, {m_bpButtonCmpContext->GetSize().x, 0});
 }
 
 
@@ -2827,7 +2837,7 @@ void MainDialog::onSyncSettingsContext(wxEvent& event)
     addVariantItem(SyncVariant::update, "sync_update");
     addVariantItem(SyncVariant::custom, "sync_custom");
 
-    menu.popup(*m_bpButtonSyncContext, { m_bpButtonSyncContext->GetSize().x, 0 });
+    menu.popup(*m_bpButtonSyncContext, {m_bpButtonSyncContext->GetSize().x, 0});
 }
 
 
@@ -3004,7 +3014,7 @@ bool MainDialog::trySaveConfig(const Zstring* guiCfgPath) //return true if saved
     try
     {
         writeConfig(guiCfg, cfgFilePath); //throw FileError
-        setLastUsedConfig(guiCfg, { cfgFilePath });
+        setLastUsedConfig(guiCfg, {cfgFilePath});
 
         flashStatusInformation(_("Configuration saved"));
         return true;
@@ -3086,7 +3096,7 @@ bool MainDialog::trySaveBatchConfig(const Zstring* batchCfgPath)
     try
     {
         writeConfig(batchCfg, cfgFilePath); //throw FileError
-        setLastUsedConfig(guiCfg, { cfgFilePath }); //[!] behave as if we had saved guiCfg
+        setLastUsedConfig(guiCfg, {cfgFilePath}); //[!] behave as if we had saved guiCfg
 
         flashStatusInformation(_("Configuration saved"));
         return true;
@@ -3351,7 +3361,7 @@ void MainDialog::renameSelectedCfgHistoryItem()
 
         //FIRST: 1. consolidate unsaved changes using the *old* config file name, if any!
         //2. get rid of multiple-selection if exists 3. load cfg to allow non-failing(!) setLastUsedConfig() below
-        if (!loadConfiguration({ cfgPathOld }))
+        if (!loadConfiguration({cfgPathOld}))
             return; //error/cancel
 
         const Zstring fileName     =  afterLast(cfgPathOld, FILE_NAME_SEPARATOR, IfNotFoundReturn::all);
@@ -3394,11 +3404,11 @@ void MainDialog::renameSelectedCfgHistoryItem()
                 continue;
             }
 
-            cfggrid::getDataView(*m_gridCfgHistory).removeItems({ cfgPathOld });
+            cfggrid::getDataView(*m_gridCfgHistory).removeItems({cfgPathOld});
             m_gridCfgHistory->Refresh(); //grid size changed => clears selection!
 
-            //keep current cfg and just swap the file name: see previous "loadConfiguration({ cfgPathOld }"!
-            setLastUsedConfig(lastSavedCfg_, { cfgPathNew });
+            //keep current cfg and just swap the file name: see previous "loadConfiguration({cfgPathOld}"!
+            setLastUsedConfig(lastSavedCfg_, {cfgPathNew});
             return;
         }
     }
@@ -3478,13 +3488,13 @@ void MainDialog::onCfgGridContext(GridContextMenuEvent& event)
         submenu.addItem(name, applyBackColor, bmpSquare.ConvertToImage(), !selectedRows.empty());
     };
     addColorOption(wxNullColour, L'(' + _("&Default") + L')'); //meta options should be enclosed in parentheses
-    addColorOption({ 0xff, 0xd8, 0xcb }, _("Red"));
-    addColorOption({ 0xff, 0xf9, 0x99 }, _("Yellow"));
-    addColorOption({ 0xcc, 0xff, 0x99 }, _("Green"));
-    addColorOption({ 0xcc, 0xff, 0xff }, _("Cyan"));
-    addColorOption({ 0xcc, 0xcc, 0xff }, _("Blue"));
-    addColorOption({ 0xf2, 0xcb, 0xff }, _("Purple"));
-    addColorOption({ 0xdd, 0xdd, 0xdd }, _("Grey"));
+    addColorOption({0xff, 0xd8, 0xcb}, _("Red"));
+    addColorOption({0xff, 0xf9, 0x99}, _("Yellow"));
+    addColorOption({0xcc, 0xff, 0x99}, _("Green"));
+    addColorOption({0xcc, 0xff, 0xff}, _("Cyan"));
+    addColorOption({0xcc, 0xcc, 0xff}, _("Blue"));
+    addColorOption({0xf2, 0xcb, 0xff}, _("Purple"));
+    addColorOption({0xdd, 0xdd, 0xdd}, _("Grey"));
 
     menu.addSubmenu(_("Background color"), submenu, loadImage("color_sicon"), !selectedRows.empty());
     menu.addSeparator();
@@ -3586,7 +3596,7 @@ void MainDialog::onCfgGridLabelContext(GridLabelClickEvent& event)
     menu.addItem(_("Highlight..."), setCfgHighlight);
     //--------------------------------------------------------------------------------------------------------
 
-    menu.popup(*m_gridCfgHistory, { event.mousePos_.x, m_gridCfgHistory->getColumnLabelHeight() });
+    menu.popup(*m_gridCfgHistory, {event.mousePos_.x, m_gridCfgHistory->getColumnLabelHeight()});
     //event.Skip();
 }
 
@@ -3867,7 +3877,7 @@ void MainDialog::onGlobalFilterContext(wxEvent& event)
     menu.addItem( _("Copy"),  copyFilter,  wxNullImage, !isNullFilter(currentCfg_.mainCfg.globalFilter));
     menu.addItem( _("Paste"), pasteFilter, wxNullImage, filterCfgOnClipboard_.get() != nullptr);
 
-    menu.popup(*m_bpButtonFilterContext, { m_bpButtonFilterContext->GetSize().x, 0 });
+    menu.popup(*m_bpButtonFilterContext, {m_bpButtonFilterContext->GetSize().x, 0});
 }
 
 
@@ -3922,7 +3932,7 @@ void MainDialog::onViewTypeContextMouse(wxMouseEvent&   event)
     menu.addItem(_("Difference") + (viewType != GridViewType::difference ? L"\tF11" : L""), [&] { setGridViewType(GridViewType::difference); }, greyScaleIfDisabled(loadImage("compare_sicon"   ), viewType == GridViewType::difference));
     menu.addItem(_("Action")     + (viewType != GridViewType::action     ? L"\tF11" : L""), [&] { setGridViewType(GridViewType::action    ); }, greyScaleIfDisabled(loadImage("start_sync_sicon"), viewType == GridViewType::action));
 
-    menu.popup(*m_bpButtonViewType, { m_bpButtonViewType->GetSize().x, 0 });
+    menu.popup(*m_bpButtonViewType, {m_bpButtonViewType->GetSize().x, 0});
 }
 
 
@@ -3961,7 +3971,7 @@ void MainDialog::onViewFilterContext(wxEvent& event)
     };
 
     menu.addItem( _("Save as default"), saveDefault, loadImage("cfg_save_sicon"));
-    menu.popup(*m_bpButtonViewFilterContext, { m_bpButtonViewFilterContext->GetSize().x, 0 });
+    menu.popup(*m_bpButtonViewFilterContext, {m_bpButtonViewFilterContext->GetSize().x, 0});
 }
 
 
@@ -4166,12 +4176,12 @@ void MainDialog::updateStatistics()
     const SyncStatistics st(folderCmp_);
 
     setValue(*m_staticTextData, st.getBytesToProcess() == 0, formatFilesizeShort(st.getBytesToProcess()), *m_bitmapData, "data");
-    setIntValue(*m_staticTextCreateLeft,  st.createCount< LEFT_SIDE>(), *m_bitmapCreateLeft,  "so_create_left_sicon");
-    setIntValue(*m_staticTextUpdateLeft,  st.updateCount< LEFT_SIDE>(), *m_bitmapUpdateLeft,  "so_update_left_sicon");
-    setIntValue(*m_staticTextDeleteLeft,  st.deleteCount< LEFT_SIDE>(), *m_bitmapDeleteLeft,  "so_delete_left_sicon");
-    setIntValue(*m_staticTextCreateRight, st.createCount<RIGHT_SIDE>(), *m_bitmapCreateRight, "so_create_right_sicon");
-    setIntValue(*m_staticTextUpdateRight, st.updateCount<RIGHT_SIDE>(), *m_bitmapUpdateRight, "so_update_right_sicon");
-    setIntValue(*m_staticTextDeleteRight, st.deleteCount<RIGHT_SIDE>(), *m_bitmapDeleteRight, "so_delete_right_sicon");
+    setIntValue(*m_staticTextCreateLeft,  st.createCount< SelectSide::left>(), *m_bitmapCreateLeft,  "so_create_left_sicon");
+    setIntValue(*m_staticTextUpdateLeft,  st.updateCount< SelectSide::left>(), *m_bitmapUpdateLeft,  "so_update_left_sicon");
+    setIntValue(*m_staticTextDeleteLeft,  st.deleteCount< SelectSide::left>(), *m_bitmapDeleteLeft,  "so_delete_left_sicon");
+    setIntValue(*m_staticTextCreateRight, st.createCount<SelectSide::right>(), *m_bitmapCreateRight, "so_create_right_sicon");
+    setIntValue(*m_staticTextUpdateRight, st.updateCount<SelectSide::right>(), *m_bitmapUpdateRight, "so_update_right_sicon");
+    setIntValue(*m_staticTextDeleteRight, st.deleteCount<SelectSide::right>(), *m_bitmapDeleteRight, "so_delete_right_sicon");
 
     m_panelStatistics->Layout();
     m_panelStatistics->Refresh(); //fix small mess up on RTL layout
@@ -4270,13 +4280,15 @@ void MainDialog::onStartSync(wxCommandEvent& event)
                 std::set<Zstring> folderPathsToLock;
                 for (auto it = begin(folderCmp_); it != end(folderCmp_); ++it)
                 {
-                    if (it->isAvailable<LEFT_SIDE>()) //do NOT check directory existence again!
-                        if (std::optional<Zstring> nativeFolderPath = AFS::getNativeItemPath(it->getAbstractPath<LEFT_SIDE>())) //restrict directory locking to native paths until further
-                            folderPathsToLock.insert(*nativeFolderPath);
-
-                    if (it->isAvailable<RIGHT_SIDE>())
-                        if (std::optional<Zstring> nativeFolderPath = AFS::getNativeItemPath(it->getAbstractPath<RIGHT_SIDE>()))
-                            folderPathsToLock.insert(*nativeFolderPath);
+                    if (it->isAvailable<SelectSide::left>()) //do NOT check directory existence again!
+                        if (const Zstring& nativePath = getNativeItemPath(it->getAbstractPath<SelectSide::left>()); //restrict directory locking to native paths until further
+                            !nativePath.empty())
+                            folderPathsToLock.insert(nativePath);
+
+                    if (it->isAvailable<SelectSide::right>())
+                        if (const Zstring& nativePath = getNativeItemPath(it->getAbstractPath<SelectSide::right>());
+                            !nativePath.empty())
+                            folderPathsToLock.insert(nativePath);
                 }
                 dirLocks = std::make_unique<LockHolder>(folderPathsToLock, globalCfg_.warnDlgs.warnDirectoryLockFailed, statusHandler); //throw AbortProcess
             }
@@ -4497,7 +4509,7 @@ void MainDialog::startSyncForSelecction(const std::vector<FileSystemObject*>& se
 
 void MainDialog::updateConfigLastRunStats(time_t lastRunTime, SyncResult result, const AbstractPath& logFilePath)
 {
-    cfggrid::getDataView(*m_gridCfgHistory).setLastRunStats(activeConfigFiles_, { lastRunTime, result, logFilePath });
+    cfggrid::getDataView(*m_gridCfgHistory).setLastRunStats(activeConfigFiles_, {lastRunTime, result, logFilePath});
 
     //re-apply selection: sort order changed if sorted by last sync time
     cfggrid::addAndSelect(*m_gridCfgHistory, activeConfigFiles_, false /*scrollToSelection*/);
@@ -4576,21 +4588,14 @@ void MainDialog::setLastOperationLog(const ProcessSummary& summary, const std::s
 
 void MainDialog::onToggleLog(wxCommandEvent& event)
 {
-    const bool show = !auiMgr_.GetPane(m_panelLog).IsShown();
-    showLogPanel(show);
-    if (show)
-        logPanel_->SetFocus();
+    showLogPanel(!auiMgr_.GetPane(m_panelLog).IsShown());
 }
 
 
 void MainDialog::showLogPanel(bool show)
 {
-    warn_static("add 'FocusPreserver fp' when showing andclosing log!?     similar implementation like focusIdAfterSearch_")
-
-
-
-    wxAuiPaneInfo& logPane = auiMgr_.GetPane(m_panelLog);
-    if (show != logPane.IsShown())
+    if (wxAuiPaneInfo& logPane = auiMgr_.GetPane(m_panelLog);
+        logPane.IsShown() != show)
     {
         if (!show)
         {
@@ -4602,7 +4607,23 @@ void MainDialog::showLogPanel(bool show)
 
         logPane.Show(show);
         auiMgr_.Update();
-        m_panelLog->Refresh(); //macOS: fix background corruption for the statistics boxes (call *after* wxAuiManager::Update()
+        m_panelLog->Refresh(); //macOS: fix background corruption for the statistics boxes; call *after* wxAuiManager::Update()
+    }
+
+    if (show)
+    {
+        if (wxWindow* focus = wxWindow::FindFocus()) //restore when closing panel!
+            if (!isComponentOf(focus, m_panelLog))
+                focusAfterCloseLog_ = focus->GetId();
+
+        logPanel_->SetFocus();
+    }
+    else
+    {
+        if (isComponentOf(wxWindow::FindFocus(), m_panelLog))
+            if (wxWindow* oldFocusWin = wxWindow::FindWindowById(focusAfterCloseLog_))
+                oldFocusWin->SetFocus();
+        focusAfterCloseLog_ = wxID_ANY;
     }
 }
 
@@ -4614,7 +4635,7 @@ void MainDialog::onGridDoubleClickRim(GridClickEvent& event, bool leftSide)
         std::vector<FileSystemObject*> selectionLeft;
         std::vector<FileSystemObject*> selectionRight;
         if (FileSystemObject* fsObj = filegrid::getDataView(*m_gridMainC).getFsObject(event.row_)) //selection must be a list of BOUND pointers!
-            (leftSide ? selectionLeft : selectionRight) = { fsObj };
+            (leftSide ? selectionLeft : selectionRight) = {fsObj};
 
         openExternalApplication(globalCfg_.externalApps[0].cmdLine, leftSide, selectionLeft, selectionRight);
     }
@@ -5007,7 +5028,7 @@ void MainDialog::onSearchGridEnter(wxCommandEvent& event)
 
 void MainDialog::onHideSearchPanel(wxCommandEvent& event)
 {
-    hideFindPanel();
+    showFindPanel(false /*show*/);
 }
 
 
@@ -5020,43 +5041,39 @@ void MainDialog::onSearchPanelKeyPressed(wxKeyEvent& event)
             startFindNext(true /*searchAscending*/);
             return;
         case WXK_ESCAPE:
-            hideFindPanel();
+            showFindPanel(false /*show*/);
             return;
     }
     event.Skip();
 }
 
 
-void MainDialog::showFindPanel() //CTRL + F or F3 with empty search phrase
+void MainDialog::showFindPanel(bool show) //CTRL + F or F3 with empty search phrase
 {
-    if (!auiMgr_.GetPane(m_panelSearch).IsShown())
+    if (auiMgr_.GetPane(m_panelSearch).IsShown() != show)
     {
-        auiMgr_.GetPane(m_panelSearch).Show();
+        auiMgr_.GetPane(m_panelSearch).Show(show);
         auiMgr_.Update();
     }
 
-    m_textCtrlSearchTxt->SelectAll();
-
-    if (wxWindow* focus = wxWindow::FindFocus()) //restore when closing panel!
-        if (!isComponentOf(focus, m_panelSearch))
-            focusIdAfterSearch_ = focus->GetId();
-    //don't save wxWindow* to arbitrary window: it might not exist anymore when hideFindPanel() uses it!!! (e.g. some folder pair panel)
-
-    m_textCtrlSearchTxt->SetFocus();
-}
+    if (show)
+    {
+        m_textCtrlSearchTxt->SelectAll();
 
+        if (wxWindow* focus = wxWindow::FindFocus()) //restore when closing panel!
+            if (!isComponentOf(focus, m_panelSearch))
+                focusAfterCloseSearch_ = focus->GetId();
 
-void MainDialog::hideFindPanel()
-{
-    if (auiMgr_.GetPane(m_panelSearch).IsShown())
-    {
-        auiMgr_.GetPane(m_panelSearch).Hide();
-        auiMgr_.Update();
+        m_textCtrlSearchTxt->SetFocus();
     }
+    else
+    {
+        if (isComponentOf(wxWindow::FindFocus(), m_panelSearch))
+            if (wxWindow* oldFocusWin = wxWindow::FindWindowById(focusAfterCloseSearch_))
+                oldFocusWin->SetFocus();
 
-    if (wxWindow* oldFocusWin = wxWindow::FindWindowById(focusIdAfterSearch_))
-        oldFocusWin->SetFocus();
-    focusIdAfterSearch_ = wxID_ANY;
+        focusAfterCloseSearch_ = wxID_ANY;
+    }
 }
 
 
@@ -5065,14 +5082,14 @@ void MainDialog::startFindNext(bool searchAscending) //F3 or ENTER in m_textCtrl
     const std::wstring& searchString = utfTo<std::wstring>(trimCpy(m_textCtrlSearchTxt->GetValue()));
 
     if (searchString.empty())
-        showFindPanel();
+        showFindPanel(true /*show*/);
     else
     {
         Grid* grid1 = m_gridMainL;
         Grid* grid2 = m_gridMainR;
 
         wxWindow* focus = wxWindow::FindFocus();
-        if ((isComponentOf(focus, m_panelSearch) ? focusIdAfterSearch_ : focus->GetId()) == m_gridMainR->getMainWin().GetId())
+        if ((isComponentOf(focus, m_panelSearch) ? focusAfterCloseSearch_ : focus->GetId()) == m_gridMainR->getMainWin().GetId())
             std::swap(grid1, grid2); //select side to start search at grid cursor position
 
         wxBeginBusyCursor(wxHOURGLASS_CURSOR);
@@ -5080,21 +5097,21 @@ void MainDialog::startFindNext(bool searchAscending) //F3 or ENTER in m_textCtrl
                                                                        m_checkBoxMatchCase->GetValue(), searchAscending); //parameter owned by GUI, *not* globalCfg structure! => we should better implement a getGlocalCfg()!
         wxEndBusyCursor();
 
-        if (Grid* grid = const_cast<Grid*>(result.first)) //grid wasn't const when passing to findAndSelectNext(), so this is safe
+        if (Grid* grid = const_cast<Grid*>(result.first)) //grid wasn't const when passing to findAndSelectNext(), so this is legal
         {
             assert(result.second >= 0);
 
             filegrid::setScrollMaster(*grid);
             grid->setGridCursor(result.second, GridEventPolicy::allow);
 
-            focusIdAfterSearch_ = grid->getMainWin().GetId();
+            focusAfterCloseSearch_ = grid->getMainWin().GetId();
 
             if (!isComponentOf(wxWindow::FindFocus(), m_panelSearch))
                 grid->getMainWin().SetFocus();
         }
         else
         {
-            showFindPanel();
+            showFindPanel(true /*show*/);
             showNotificationDialog(this, DialogInfoType::info, PopupDialogCfg().
                                    setTitle(_("Find")).
                                    setMainInstructions(replaceCpy(_("Cannot find %x"), L"%x", fmtPath(searchString))));
@@ -5105,7 +5122,7 @@ void MainDialog::startFindNext(bool searchAscending) //F3 or ENTER in m_textCtrl
 
 void MainDialog::onTopFolderPairAdd(wxCommandEvent& event)
 {
-    insertAddFolderPair({ LocalPairConfig() }, 0);
+    insertAddFolderPair({LocalPairConfig()}, 0);
     moveAddFolderPairUp(0);
 }
 
@@ -5178,12 +5195,12 @@ void MainDialog::onShowFolderPairOptions(wxEvent& event)
             const ptrdiff_t pos = it - additionalFolderPairs_.begin();
 
             ContextMenu menu;
-            menu.addItem(_("Add folder pair"), [this, pos] { insertAddFolderPair({ LocalPairConfig() },  pos); }, loadImage("item_add_sicon"));
+            menu.addItem(_("Add folder pair"), [this, pos] { insertAddFolderPair({LocalPairConfig()},  pos); }, loadImage("item_add_sicon"));
             menu.addSeparator();
             menu.addItem(_("Move up"  ) + L"\tAlt+Page Up",   [this, pos] { moveAddFolderPairUp(pos);     }, loadImage("move_up_sicon"));
             menu.addItem(_("Move down") + L"\tAlt+Page Down", [this, pos] { moveAddFolderPairUp(pos + 1); }, loadImage("move_down_sicon"), pos + 1 < makeSigned(additionalFolderPairs_.size()));
 
-            menu.popup(*(*it)->m_bpButtonFolderPairOptions, { (*it)->m_bpButtonFolderPairOptions->GetSize().x, 0 });
+            menu.popup(*(*it)->m_bpButtonFolderPairOptions, {(*it)->m_bpButtonFolderPairOptions->GetSize().x, 0});
             break;
         }
 }
@@ -5228,27 +5245,23 @@ void MainDialog::onAddFolderPairKeyEvent(wxKeyEvent& event)
         {
             case WXK_PAGEUP: //Alt + Page Up
             case WXK_NUMPAD_PAGEUP:
-            {
-                const ptrdiff_t pos = getAddFolderPairPos();
-                if (pos >= 0)
+                if (const ptrdiff_t pos = getAddFolderPairPos();
+                    pos >= 0)
                 {
                     moveAddFolderPairUp(pos);
                     (pos == 0 ? m_folderPathLeft : additionalFolderPairs_[pos - 1]->m_folderPathLeft)->SetFocus();
                 }
-            }
-            return;
+                return;
 
             case WXK_PAGEDOWN: //Alt + Page Down
             case WXK_NUMPAD_PAGEDOWN:
-            {
-                const ptrdiff_t pos = getAddFolderPairPos();
-                if (0 <= pos && pos + 1 < makeSigned(additionalFolderPairs_.size()))
+                if (const ptrdiff_t pos = getAddFolderPairPos();
+                    0 <= pos && pos + 1 < makeSigned(additionalFolderPairs_.size()))
                 {
                     moveAddFolderPairUp(pos + 1);
                     additionalFolderPairs_[pos + 1]->m_folderPathLeft->SetFocus();
                 }
-            }
-            return;
+                return;
         }
 
     event.Skip();
@@ -5507,8 +5520,8 @@ void MainDialog::onMenuExportFileList(wxCommandEvent& event)
     header += fmtValue(_("Folder Pairs")) + LINE_BREAK;
     std::for_each(begin(folderCmp_), end(folderCmp_), [&](BaseFolderPair& baseFolder)
     {
-        header += fmtValue(AFS::getDisplayPath(baseFolder.getAbstractPath< LEFT_SIDE>())) + CSV_SEP;
-        header += fmtValue(AFS::getDisplayPath(baseFolder.getAbstractPath<RIGHT_SIDE>())) + LINE_BREAK;
+        header += fmtValue(AFS::getDisplayPath(baseFolder.getAbstractPath< SelectSide::left>())) + CSV_SEP;
+        header += fmtValue(AFS::getDisplayPath(baseFolder.getAbstractPath<SelectSide::right>())) + LINE_BREAK;
     });
     header += LINE_BREAK;
 
diff --git a/FreeFileSync/Source/ui/main_dlg.h b/FreeFileSync/Source/ui/main_dlg.h
index e22bad6f..dc0ea8d1 100644
--- a/FreeFileSync/Source/ui/main_dlg.h
+++ b/FreeFileSync/Source/ui/main_dlg.h
@@ -251,8 +251,7 @@ private:
     void applyFilterConfig();
     void applySyncDirections();
 
-    void showFindPanel(); //CTRL + F
-    void hideFindPanel();
+    void showFindPanel(bool show); //CTRL + F
     void startFindNext(bool searchAscending); //F3
 
     void resetLayout();
@@ -266,7 +265,7 @@ private:
     void onMenuOptions        (wxCommandEvent& event) override;
     void onMenuExportFileList (wxCommandEvent& event) override;
     void onMenuResetLayout    (wxCommandEvent& event) override { resetLayout(); }
-    void onMenuFindItem       (wxCommandEvent& event) override { showFindPanel(); } //CTRL + F
+    void onMenuFindItem       (wxCommandEvent& event) override { showFindPanel(true /*show*/); } //CTRL + F
     void onMenuCheckVersion   (wxCommandEvent& event) override;
     void onMenuCheckVersionAutomatically(wxCommandEvent& event) override;
     void onMenuAbout          (wxCommandEvent& event) override;
@@ -347,7 +346,9 @@ private:
 
     std::unique_ptr<FilterConfig> filterCfgOnClipboard_; //copy/paste of filter config
 
-    wxWindowID focusIdAfterSearch_ = wxID_ANY; //used to restore focus after search panel is closed
+    wxWindowID focusAfterCloseLog_    = wxID_ANY; //
+    wxWindowID focusAfterCloseSearch_ = wxID_ANY; //restore focus after panel is closed
+    //don't save wxWindow* to arbitrary window: might not exist anymore when hideFindPanel() uses it!!! (e.g. some folder pair panel)
 
     //mitigate reentrancy:
     bool localKeyEventsEnabled_ = true;
diff --git a/FreeFileSync/Source/ui/progress_indicator.cpp b/FreeFileSync/Source/ui/progress_indicator.cpp
index 0ab39dab..fc97858e 100644
--- a/FreeFileSync/Source/ui/progress_indicator.cpp
+++ b/FreeFileSync/Source/ui/progress_indicator.cpp
@@ -47,17 +47,17 @@ constexpr std::chrono::seconds      GRAPH_TOTAL_TIME_UPDATE_INTERVAL(2);
 
 const size_t PROGRESS_GRAPH_SAMPLE_SIZE_MAX = 2'500'000; //sizeof(single node) worst case ~ 3 * 8 byte ptr + 16 byte key/value = 40 byte
 
-inline wxColor getColorBytes() { return { 111, 255,  99 }; } //light green
-inline wxColor getColorItems() { return { 127, 147, 255 }; } //light blue
+inline wxColor getColorBytes() { return {111, 255,  99}; } //light green
+inline wxColor getColorItems() { return {127, 147, 255}; } //light blue
 
-inline wxColor getColorBytesRim() { return { 20, 200,   0 }; } //medium green
-inline wxColor getColorItemsRim() { return { 90, 120, 255 }; } //medium blue
+inline wxColor getColorBytesRim() { return {20, 200,   0}; } //medium green
+inline wxColor getColorItemsRim() { return {90, 120, 255}; } //medium blue
 
-//inline wxColor getColorBytesFaint() { return { 205, 255, 202 }; } //faint green
-//inline wxColor getColorItemsFaint() { return { 198, 206, 255 }; } //faint blue
+//inline wxColor getColorBytesFaint() { return {205, 255, 202}; } //faint green
+//inline wxColor getColorItemsFaint() { return {198, 206, 255}; } //faint blue
 
-inline wxColor getColorBytesDark() { return { 12, 128,   0 }; } //dark green
-inline wxColor getColorItemsDark() { return { 53,  25, 255 }; } //dark blue
+inline wxColor getColorBytesDark() { return {12, 128,   0}; } //dark green
+inline wxColor getColorItemsDark() { return {53,  25, 255}; } //dark blue
 
 inline wxColor getColorLightGrey() { return {0xf2, 0xf2, 0xf2}; }
 inline wxColor getColorDarkGrey () { return {0x8f, 0x8f, 0x8f}; }
@@ -95,7 +95,7 @@ public:
     void setFraction(double fraction) { fraction_ = fraction; } //value between [0, 1]
 
 private:
-    std::pair<double, double> getRangeX() const override { return { 0, 1 }; }
+    std::pair<double, double> getRangeX() const override { return {0, 1}; }
 
     std::vector<CurvePoint> getPoints(double minX, double maxX, const wxSize& areaSizePx) const override
     {
@@ -104,10 +104,10 @@ private:
 
         return
         {
-            { 0,         yHigh },
-            { fraction_, yHigh },
-            { fraction_, yLow  },
-            { 0,         yLow  },
+            {0,         yHigh},
+            {fraction_, yHigh},
+            {fraction_, yLow },
+            {0,         yLow },
         };
     }
 
@@ -117,14 +117,14 @@ private:
 
 class CurveDataProgressSeparatorLine : public CurveData
 {
-    std::pair<double, double> getRangeX() const override { return { 0, 1 }; }
+    std::pair<double, double> getRangeX() const override { return {0, 1}; }
 
     std::vector<CurvePoint> getPoints(double minX, double maxX, const wxSize& areaSizePx) const override
     {
         return
         {
-            { 0, 1 },
-            { 1, 1 },
+            {0, 1},
+            {1, 1},
         };
     }
 };
@@ -168,13 +168,13 @@ private:
     const Statistics* syncStat_ = nullptr; //only bound while sync is running
 
     std::unique_ptr<Taskbar> taskbar_;
-    PerfCheck perf_{ WINDOW_REMAINING_TIME, WINDOW_BYTES_PER_SEC }; //estimate remaining time
+    PerfCheck perf_{WINDOW_REMAINING_TIME, WINDOW_BYTES_PER_SEC}; //estimate remaining time
 
     std::chrono::nanoseconds timeLastSpeedEstimate_ = std::chrono::seconds(-100); //used for calculating intervals between showing and collecting perf samples
     //initial value: just some big number
 
-    std::shared_ptr<CurveDataProgressBar> curveDataBytes_{ std::make_shared<CurveDataProgressBar>(true  /*drawTop*/) };
-    std::shared_ptr<CurveDataProgressBar> curveDataItems_{ std::make_shared<CurveDataProgressBar>(false /*drawTop*/) };
+    std::shared_ptr<CurveDataProgressBar> curveDataBytes_{std::make_shared<CurveDataProgressBar>(true  /*drawTop*/)};
+    std::shared_ptr<CurveDataProgressBar> curveDataItems_{std::make_shared<CurveDataProgressBar>(false /*drawTop*/)};
 
     bool ignoreErrors_ = false;
 };
@@ -422,14 +422,14 @@ public:
     {
         assert(!samples_.empty() || (lastSample_ == std::pair<std::chrono::nanoseconds, double>()));
 
-        lastSample_ = { timeElapsed, value };
+        lastSample_ = {timeElapsed, value};
 
         //allow for at most one sample per 100ms (handles duplicate inserts, too!) => this is unrelated to UI_UPDATE_INTERVAL!
         if (!samples_.empty()) //always unconditionally insert first sample!
             if (numeric::dist(timeElapsed, samples_.rbegin()->first) < std::chrono::milliseconds(100))
                 return;
 
-        samples_.insert(samples_.end(), { timeElapsed, value }); //time is "expected" to be monotonously ascending
+        samples_.insert(samples_.end(), {timeElapsed, value}); //time is "expected" to be monotonously ascending
         //documentation differs about whether "hint" should be before or after the to be inserted element!
         //however "std::map<>::end()" is interpreted correctly by GCC and VS2010
 
@@ -452,8 +452,8 @@ private:
         upperEndMs += 0.05 *(upperEndMs - samples.begin()->first);
         */
 
-        return { std::chrono::duration<double>(samples_.begin()->first).count(), //need not start with 0, e.g. "binary comparison, graph reset, followed by sync"
-                 std::chrono::duration<double>(upperEnd).count() };
+        return {std::chrono::duration<double>(samples_.begin()->first).count(), //need not start with 0, e.g. "binary comparison, graph reset, followed by sync"
+                std::chrono::duration<double>(upperEnd).count()};
     }
 
     std::optional<CurvePoint> getLessEq(double x) const override //x: seconds since begin
@@ -504,14 +504,14 @@ public:
     double getTotalTime() const { return x2_; }
 
 private:
-    std::pair<double, double> getRangeX() const override { return { x1_, x2_ }; }
+    std::pair<double, double> getRangeX() const override { return {x1_, x2_}; }
 
     std::vector<CurvePoint> getPoints(double minX, double maxX, const wxSize& areaSizePx) const override
     {
         return
         {
-            { x1_, y1_ },
-            { x2_, y2_ },
+            {x1_, y1_},
+            {x2_, y2_},
         };
     }
 
@@ -529,14 +529,14 @@ public:
     void setTime(double x) { x_ = x; }
 
 private:
-    std::pair<double, double> getRangeX() const override { return { x_, x_ }; }
+    std::pair<double, double> getRangeX() const override { return {x_, x_}; }
 
     std::vector<CurvePoint> getPoints(double minX, double maxX, const wxSize& areaSizePx) const override
     {
         return
         {
-            { x_, y_ },
-            { x_, 0  },
+            {x_, y_},
+            {x_, 0 },
         };
     }
 
@@ -564,7 +564,7 @@ struct LabelFormatterBytes : public LabelFormatter
             return 0;
         const double a = bytesProposed / e; //bytesProposed = a * 2^k with a in [1, 2)
         assert(1 <= a && a < 2);
-        const double steps[] = { 1, 2 };
+        const double steps[] = {1, 2};
         return e * numeric::nearMatch(a, std::begin(steps), std::end(steps));
     }
 
@@ -578,7 +578,7 @@ struct LabelFormatterItemCount : public LabelFormatter
     {
         itemsProposed *= stretchDefaultBlockSize; //enlarge block default size
 
-        const double steps[] = { 1, 2, 5, 10 };
+        const double steps[] = {1, 2, 5, 10};
         if (itemsProposed <= 10)
             return numeric::nearMatch(itemsProposed, std::begin(steps), std::end(steps)); //like nextNiceNumber(), but without the 2.5 step!
         return nextNiceNumber(itemsProposed);
@@ -598,11 +598,11 @@ struct LabelFormatterTimeElapsed : public LabelFormatter
     double getOptimalBlockSize(double secProposed) const override
     {
         //5 sec minimum block size
-        const double stepsSec[] = { 5, 10, 20, 30, 60 }; //nice numbers for seconds
+        const double stepsSec[] = {5, 10, 20, 30, 60}; //nice numbers for seconds
         if (secProposed <= 60)
             return numeric::nearMatch(secProposed, std::begin(stepsSec), std::end(stepsSec));
 
-        const double stepsMin[] = { 1, 2, 5, 10, 15, 20, 30, 60 }; //nice numbers for minutes
+        const double stepsMin[] = {1, 2, 5, 10, 15, 20, 30, 60}; //nice numbers for minutes
         if (secProposed <= 3600)
             return 60 * numeric::nearMatch(secProposed / 60, std::begin(stepsMin), std::end(stepsMin));
 
@@ -716,7 +716,7 @@ private:
     bool closePressed_ = false;
 
     //remaining time
-    PerfCheck perf_{ WINDOW_REMAINING_TIME, WINDOW_BYTES_PER_SEC };
+    PerfCheck perf_{WINDOW_REMAINING_TIME, WINDOW_BYTES_PER_SEC};
     std::chrono::nanoseconds timeLastSpeedEstimate_    = std::chrono::seconds(-100); //used for calculating intervals between collecting perf samples
     std::chrono::nanoseconds timeLastGraphTotalUpdate_ = std::chrono::seconds(-100);
 
@@ -1513,7 +1513,7 @@ auto SyncProgressDialogImpl<TopLevelDialog>::destroy(bool autoClose, bool restor
 
     this->Destroy(); //wxWidgets macOS: simple "delete"!!!!!!!
 
-    return { autoCloseDialog, dlgSizeBuf_, isMaximized };
+    return {autoCloseDialog, dlgSizeBuf_, isMaximized};
 }
 
 
diff --git a/FreeFileSync/Source/ui/search_grid.cpp b/FreeFileSync/Source/ui/search_grid.cpp
index 8c102d97..c3f459f4 100644
--- a/FreeFileSync/Source/ui/search_grid.cpp
+++ b/FreeFileSync/Source/ui/search_grid.cpp
@@ -123,7 +123,7 @@ std::pair<const Grid*, ptrdiff_t> fff::findGridMatch(const Grid& grid1, const Gr
                                     findRow<false>(grid, searchString, searchAscending, rowFirst, rowLast);
         if (targetRow >= 0)
         {
-            result = { &grid, targetRow };
+            result = {&grid, targetRow};
             return true;
         }
         return false;
diff --git a/FreeFileSync/Source/ui/small_dlgs.cpp b/FreeFileSync/Source/ui/small_dlgs.cpp
index fbd0cbf9..1f569467 100644
--- a/FreeFileSync/Source/ui/small_dlgs.cpp
+++ b/FreeFileSync/Source/ui/small_dlgs.cpp
@@ -1082,12 +1082,12 @@ SyncConfirmationDlg::SyncConfirmationDlg(wxWindow* parent,
     };
 
     setValue(*m_staticTextData, st.getBytesToProcess() == 0, formatFilesizeShort(st.getBytesToProcess()), *m_bitmapData, "data");
-    setIntValue(*m_staticTextCreateLeft,  st.createCount< LEFT_SIDE>(), *m_bitmapCreateLeft,  "so_create_left_sicon");
-    setIntValue(*m_staticTextUpdateLeft,  st.updateCount< LEFT_SIDE>(), *m_bitmapUpdateLeft,  "so_update_left_sicon");
-    setIntValue(*m_staticTextDeleteLeft,  st.deleteCount< LEFT_SIDE>(), *m_bitmapDeleteLeft,  "so_delete_left_sicon");
-    setIntValue(*m_staticTextCreateRight, st.createCount<RIGHT_SIDE>(), *m_bitmapCreateRight, "so_create_right_sicon");
-    setIntValue(*m_staticTextUpdateRight, st.updateCount<RIGHT_SIDE>(), *m_bitmapUpdateRight, "so_update_right_sicon");
-    setIntValue(*m_staticTextDeleteRight, st.deleteCount<RIGHT_SIDE>(), *m_bitmapDeleteRight, "so_delete_right_sicon");
+    setIntValue(*m_staticTextCreateLeft,  st.createCount< SelectSide::left>(), *m_bitmapCreateLeft,  "so_create_left_sicon");
+    setIntValue(*m_staticTextUpdateLeft,  st.updateCount< SelectSide::left>(), *m_bitmapUpdateLeft,  "so_update_left_sicon");
+    setIntValue(*m_staticTextDeleteLeft,  st.deleteCount< SelectSide::left>(), *m_bitmapDeleteLeft,  "so_delete_left_sicon");
+    setIntValue(*m_staticTextCreateRight, st.createCount<SelectSide::right>(), *m_bitmapCreateRight, "so_create_right_sicon");
+    setIntValue(*m_staticTextUpdateRight, st.updateCount<SelectSide::right>(), *m_bitmapUpdateRight, "so_update_right_sicon");
+    setIntValue(*m_staticTextDeleteRight, st.deleteCount<SelectSide::right>(), *m_bitmapDeleteRight, "so_delete_right_sicon");
 
     GetSizer()->SetSizeHints(this); //~=Fit() + SetMinSize()
     //=> works like a charm for GTK2 with window resizing problems and title bar corruption; e.g. Debian!!!
@@ -1426,7 +1426,7 @@ std::vector<ExternalApp> OptionsDlg::getExtApp() const
             description = it->second;
 
         if (!description.empty() || !commandline.empty())
-            output.push_back({ description, commandline });
+            output.push_back({description, commandline});
     }
     return output;
 }
diff --git a/FreeFileSync/Source/ui/status_handler_impl.h b/FreeFileSync/Source/ui/status_handler_impl.h
deleted file mode 100644
index c52df76e..00000000
--- a/FreeFileSync/Source/ui/status_handler_impl.h
+++ /dev/null
@@ -1,63 +0,0 @@
-// *****************************************************************************
-// * This file is part of the FreeFileSync project. It is distributed under    *
-// * GNU General Public License: https://www.gnu.org/licenses/gpl-3.0          *
-// * Copyright (C) Zenju (zenju AT freefilesync DOT org) - All Rights Reserved *
-// *****************************************************************************
-
-#ifndef STATUS_HANDLER_IMPL_H_145234543248059083415565
-#define STATUS_HANDLER_IMPL_H_145234543248059083415565
-
-#include <chrono>
-#include <thread>
-#include <zen/basic_math.h>
-#include <zen/zstring.h>
-#include <zen/i18n.h>
-
-
-namespace fff
-{
-namespace
-{
-void delayAndCountDown(std::chrono::steady_clock::time_point delayUntil, const std::function<void(const std::wstring& timeRemMsg)>& notifyStatus)
-{
-    for (auto now = std::chrono::steady_clock::now(); now < delayUntil; now = std::chrono::steady_clock::now())
-    {
-        if (notifyStatus)
-        {
-            const auto timeRemMs = std::chrono::duration_cast<std::chrono::milliseconds>(delayUntil - now).count();
-            notifyStatus(_P("1 sec", "%x sec", numeric::intDivCeil(timeRemMs, 1000)));
-        }
-
-        std::this_thread::sleep_for(UI_UPDATE_INTERVAL / 2);
-    }
-}
-
-
-void runCommandAndLogErrors(const Zstring& cmdLine, zen::ErrorLog& errorLog)
-{
-    using namespace zen;
-
-    try
-    {
-        //give consoleExecute() some "time to fail", but not too long to hang our process
-        const int DEFAULT_APP_TIMEOUT_MS = 100;
-
-        if (const auto& [exitCode, output] = consoleExecute(cmdLine, DEFAULT_APP_TIMEOUT_MS); //throw SysError, SysErrorTimeOut
-            exitCode != 0)
-            throw SysError(formatSystemError("", replaceCpy(_("Exit code %x"), L"%x", numberTo<std::wstring>(exitCode)), utfTo<std::wstring>(output)));
-
-        errorLog.logMsg(_("Executing command:") + L' ' + utfTo<std::wstring>(cmdLine) + L" [" + replaceCpy(_("Exit code %x"), L"%x", L"0") + L']', MSG_TYPE_INFO);
-    }
-    catch (SysErrorTimeOut&) //child process not failed yet => probably fine :>
-    {
-        errorLog.logMsg(_("Executing command:") + L' ' + utfTo<std::wstring>(cmdLine), MSG_TYPE_INFO);
-    }
-    catch (const SysError& e)
-    {
-        errorLog.logMsg(replaceCpy(_("Command %x failed."), L"%x", fmtPath(cmdLine)) + L"\n\n" + e.toString(), MSG_TYPE_ERROR);
-    }
-}
-}
-}
-
-#endif //STATUS_HANDLER_IMPL_H_145234543248059083415565
diff --git a/FreeFileSync/Source/ui/tree_grid.cpp b/FreeFileSync/Source/ui/tree_grid.cpp
index 9e6ec23c..ff261ef4 100644
--- a/FreeFileSync/Source/ui/tree_grid.cpp
+++ b/FreeFileSync/Source/ui/tree_grid.cpp
@@ -29,8 +29,8 @@ namespace
 const int PERCENTAGE_BAR_WIDTH_DIP = 60;
 const int TREE_GRID_GAP_SIZE_DIP   = 2;
 
-inline wxColor getColorPercentBorder    () { return { 198, 198, 198 }; }
-inline wxColor getColorPercentBackground() { return { 0xf8, 0xf8, 0xf8 }; }
+inline wxColor getColorPercentBorder    () { return {198, 198, 198}; }
+inline wxColor getColorPercentBackground() { return {0xf8, 0xf8, 0xf8}; }
 }
 
 
@@ -39,8 +39,8 @@ TreeView::TreeView(FolderComparison& folderCmp, const SortInfo& si) : folderCmp_
     //remove truly empty folder pairs as early as this: we want to distinguish single/multiple folder pair cases by looking at "folderCmp"
     std::erase_if(folderCmp_, [](const std::shared_ptr<BaseFolderPair>& baseObj)
     {
-        return AFS::isNullPath(baseObj->getAbstractPath< LEFT_SIDE>()) &&
-               AFS::isNullPath(baseObj->getAbstractPath<RIGHT_SIDE>());
+        return AFS::isNullPath(baseObj->getAbstractPath< SelectSide::left>()) &&
+               AFS::isNullPath(baseObj->getAbstractPath<SelectSide::right>());
     });
 }
 
@@ -73,16 +73,16 @@ void TreeView::extractVisibleSubtree(ContainerObject& hierObj,  //in
         //    switch (file.getSyncDir())
         //    {
         //        case SyncDirection::left:
-        //            return file.getFileSize<RIGHT_SIDE>();
+        //            return file.getFileSize<SelectSide::right>();
         //        case SyncDirection::right:
-        //            return file.getFileSize<LEFT_SIDE>();
+        //            return file.getFileSize<SelectSide::left>();
         //        case SyncDirection::none:
         //            break;
         //    }
 
         //prefer file-browser semantics over sync preview (=> always show useful numbers, even for SyncDirection::none)
         //discussion: https://freefilesync.org/forum/viewtopic.php?t=1595
-        return std::max(file.getFileSize<LEFT_SIDE>(), file.getFileSize<RIGHT_SIDE>());
+        return std::max(file.getFileSize<SelectSide::left>(), file.getFileSize<SelectSide::right>());
     };
 
     cont.firstFileId = nullptr;
@@ -275,13 +275,13 @@ void TreeView::getChildren(const Container& cont, unsigned int level, std::vecto
 
     for (const DirNodeImpl& subDir : cont.subDirs)
     {
-        output.push_back({ level, 0, &subDir, NodeType::folder});
+        output.push_back({level, 0, &subDir, NodeType::folder});
         workList.emplace_back(subDir.bytesGross, &output.back().percent);
     }
 
     if (cont.firstFileId)
     {
-        output.push_back({ level, 0, &cont, NodeType::files });
+        output.push_back({level, 0, &cont, NodeType::files});
         workList.emplace_back(cont.bytesNet, &output.back().percent);
     }
     calcPercentage(workList);
@@ -345,7 +345,7 @@ void TreeView::applySubView(std::vector<RootNodeImpl>&& newView)
 
         for (const RootNodeImpl& root : folderCmpView_)
         {
-            flatTree_.push_back({ 0, 0, &root, NodeType::root });
+            flatTree_.push_back({0, 0, &root, NodeType::root});
             workList.emplace_back(root.bytesGross, &flatTree_.back().percent);
         }
 
@@ -394,8 +394,8 @@ void TreeView::updateView(Predicate pred)
         else
         {
             root.baseFolder = baseObj;
-            root.displayName = getShortDisplayNameForFolderPair(baseObj->getAbstractPath< LEFT_SIDE>(),
-                                                                baseObj->getAbstractPath<RIGHT_SIDE>());
+            root.displayName = getShortDisplayNameForFolderPair(baseObj->getAbstractPath< SelectSide::left>(),
+                                                                baseObj->getAbstractPath<SelectSide::right>());
 
             this->compressNode(root); //"this->" required by two-pass lookup as enforced by GCC 4.7
         }
@@ -663,18 +663,18 @@ wxColor getColorForLevel(size_t level)
     switch (level % 12)
     {
         //*INDENT-OFF*
-        case  0: return { 0xcc, 0xcc, 0xff };
-        case  1: return { 0xcc, 0xff, 0xcc };
-        case  2: return { 0xff, 0xff, 0x99 };
-        case  3: return { 0xdd, 0xdd, 0xdd };
-        case  4: return { 0xff, 0xcc, 0xff };
-        case  5: return { 0x99, 0xff, 0xcc };
-        case  6: return { 0xcc, 0xcc, 0x99 };
-        case  7: return { 0xff, 0xcc, 0xcc };
-        case  8: return { 0xcc, 0xff, 0x99 };
-        case  9: return { 0xff, 0xff, 0xcc };
-        case 10: return { 0xcc, 0xff, 0xff };
-        case 11: return { 0xff, 0xcc, 0x99 };
+        case  0: return {0xcc, 0xcc, 0xff};
+        case  1: return {0xcc, 0xff, 0xcc};
+        case  2: return {0xff, 0xff, 0x99};
+        case  3: return {0xdd, 0xdd, 0xdd};
+        case  4: return {0xff, 0xcc, 0xff};
+        case  5: return {0x99, 0xff, 0xcc};
+        case  6: return {0xcc, 0xcc, 0x99};
+        case  7: return {0xff, 0xcc, 0xcc};
+        case  8: return {0xcc, 0xff, 0x99};
+        case  9: return {0xff, 0xff, 0xcc};
+        case 10: return {0xcc, 0xff, 0xff};
+        case 11: return {0xff, 0xcc, 0x99};
         //*INDENT-ON*
     }
     assert(false);
@@ -724,8 +724,8 @@ private:
                 if (std::unique_ptr<TreeView::Node> node = getDataView().getLine(row))
                     if (const TreeView::RootNode* root = dynamic_cast<const TreeView::RootNode*>(node.get()))
                     {
-                        const std::wstring& dirLeft  = AFS::getDisplayPath(root->baseFolder.getAbstractPath< LEFT_SIDE>());
-                        const std::wstring& dirRight = AFS::getDisplayPath(root->baseFolder.getAbstractPath<RIGHT_SIDE>());
+                        const std::wstring& dirLeft  = AFS::getDisplayPath(root->baseFolder.getAbstractPath< SelectSide::left>());
+                        const std::wstring& dirRight = AFS::getDisplayPath(root->baseFolder.getAbstractPath<SelectSide::right>());
                         if (dirLeft.empty())
                             return dirRight;
                         else if (dirRight.empty())
@@ -1131,7 +1131,7 @@ private:
         menu.addItem(_("&Default"), setDefaultColumns); //'&' -> reuse text from "default" buttons elsewhere
         //--------------------------------------------------------------------------------------------------------
 
-        menu.popup(grid_, { event.mousePos_.x, grid_.getColumnLabelHeight() });
+        menu.popup(grid_, {event.mousePos_.x, grid_.getColumnLabelHeight()});
         //event.Skip();
     }
 
diff --git a/FreeFileSync/Source/ui/tree_grid_attr.h b/FreeFileSync/Source/ui/tree_grid_attr.h
index eff14c4e..4cd0f2f1 100644
--- a/FreeFileSync/Source/ui/tree_grid_attr.h
+++ b/FreeFileSync/Source/ui/tree_grid_attr.h
@@ -36,9 +36,9 @@ std::vector<ColAttributesTree> getTreeGridDefaultColAttribs()
     using namespace zen;
     return //harmonize with tree_view.cpp::onGridLabelContext() => expects stretched folder and non-stretched other columns!
     {
-        { ColumnTypeTree::folder,    - 2 * fastFromDIP(60), 1, true }, //stretch to full width and substract sum of fixed size widths
-        { ColumnTypeTree::itemCount, fastFromDIP(60), 0, true },
-        { ColumnTypeTree::bytes,     fastFromDIP(60), 0, true }, //GTK needs a few pixels more width
+        {ColumnTypeTree::folder,    - 2 * fastFromDIP(60), 1, true}, //stretch to full width and substract sum of fixed size widths
+        {ColumnTypeTree::itemCount, fastFromDIP(60), 0, true},
+        {ColumnTypeTree::bytes,     fastFromDIP(60), 0, true}, //GTK needs a few pixels more width
     };
 }
 
diff --git a/FreeFileSync/Source/ui/version_check.cpp b/FreeFileSync/Source/ui/version_check.cpp
index c81c0582..087582ee 100644
--- a/FreeFileSync/Source/ui/version_check.cpp
+++ b/FreeFileSync/Source/ui/version_check.cpp
@@ -10,7 +10,7 @@
 #include <zen/string_tools.h>
 #include <zen/i18n.h>
 #include <zen/utf.h>
-#include <zen/file_access.h>
+//#include <zen/file_access.h>
 #include <zen/scope_guard.h>
 #include <zen/build_info.h>
 #include <zen/basic_math.h>
@@ -27,6 +27,7 @@
 #include "../version/version.h"
 #include "small_dlgs.h"
 
+    #include <zen/symlink_target.h>
 
 
 using namespace zen;
@@ -117,11 +118,10 @@ std::wstring getIso3166Country()
 //coordinate with get_latest_version_number.php
 std::vector<std::pair<std::string, std::string>> geHttpPostParameters(wxWindow& parent) //throw SysError
 {
-    assert(runningOnMainThread()); //this function is not thread-safe, e.g. consider wxWidgets usage in isPortableVersion()
+    assert(runningOnMainThread()); //this function is not thread-safe, e.g. consider wxWidgets usage in getIso639Language()
     std::vector<std::pair<std::string, std::string>> params;
 
     params.emplace_back("ffs_version", ffsVersion);
-    params.emplace_back("installation_type", isPortableVersion() ? "Portable" : "Local");
 
 
     params.emplace_back("os_name", "Linux");
@@ -159,7 +159,7 @@ void showUpdateAvailableDialog(wxWindow* parent, const std::string& onlineVersio
     std::wstring updateDetailsMsg;
     try
     {
-        updateDetailsMsg = utfTo<std::wstring>(sendHttpGet(utfTo<Zstring>("https://api.freefilesync.org/latest_changes?" + xWwwFormUrlEncode({ { "since", ffsVersion } })),
+        updateDetailsMsg = utfTo<std::wstring>(sendHttpGet(utfTo<Zstring>("https://api.freefilesync.org/latest_changes?" + xWwwFormUrlEncode({{"since", ffsVersion}})),
         ffsUpdateCheckUserAgent, nullptr /*caCertFilePath*/, nullptr /*notifyUnbufferedIO*/).readAll()); //throw SysError
     }
     catch (const SysError& e) { updateDetailsMsg = _("Failed to retrieve update information.") + + L"\n\n" + e.toString(); }
diff --git a/FreeFileSync/Source/version/version.h b/FreeFileSync/Source/version/version.h
index e75db779..c621b68c 100644
--- a/FreeFileSync/Source/version/version.h
+++ b/FreeFileSync/Source/version/version.h
@@ -3,7 +3,7 @@
 
 namespace fff
 {
-const char ffsVersion[] = "11.6"; //internal linkage!
+const char ffsVersion[] = "11.7"; //internal linkage!
 const char FFS_VERSION_SEPARATOR = '.';
 }
 
diff --git a/libcurl/rest.cpp b/libcurl/rest.cpp
index 60fcb8eb..0964f63a 100644
--- a/libcurl/rest.cpp
+++ b/libcurl/rest.cpp
@@ -181,5 +181,5 @@ HttpSession::Result HttpSession::perform(const std::string& serverRelPath,
     }
 
     lastSuccessfulUseTime_ = std::chrono::steady_clock::now();
-    return { static_cast<int>(httpStatus) /*, contentType ? contentType : ""*/ };
+    return {static_cast<int>(httpStatus) /*, contentType ? contentType : ""*/};
 }
diff --git a/wx+/choice_enum.h b/wx+/choice_enum.h
index 626aa39a..a590861a 100644
--- a/wx+/choice_enum.h
+++ b/wx+/choice_enum.h
@@ -41,7 +41,7 @@ struct EnumDescrList
 {
     EnumDescrList& add(Enum value, const wxString& text, const wxString& tooltip = {})
     {
-        descrList.push_back({ value, { text, tooltip } });
+        descrList.push_back({value, {text, tooltip}});
         return *this;
     }
 
diff --git a/wx+/graph.cpp b/wx+/graph.cpp
index ba87299e..be75ac4d 100644
--- a/wx+/graph.cpp
+++ b/wx+/graph.cpp
@@ -36,7 +36,7 @@ double zen::nextNiceNumber(double blockSize) //round to next number which is a c
     assert(1 <= a && a < 10);
 
     //have a look at leading two digits: "nice" numbers start with 1, 2, 2.5 and 5
-    const double steps[] = { 1, 2, 2.5, 5, 10 };
+    const double steps[] = {1, 2, 2.5, 5, 10};
     return e * numeric::nearMatch(a, std::begin(steps), std::end(steps));
 }
 
@@ -48,16 +48,16 @@ wxColor getDefaultColor(size_t pos)
     switch (pos % 10)
     {
         //*INDENT-OFF*
-        case 0: return {   0,  69, 134 }; //blue
-        case 1: return { 255,  66,  14 }; //red
-        case 2: return { 255, 211,  32 }; //yellow
-        case 3: return {  87, 157,  28 }; //green
-        case 4: return { 126,   0,  33 }; //royal
-        case 5: return { 131, 202, 255 }; //light blue
-        case 6: return {  49,  64,   4 }; //dark green
-        case 7: return { 174, 207,   0 }; //light green
-        case 8: return {  75,  31, 111 }; //purple
-        case 9: return { 255, 149,  14 }; //orange
+        case 0: return {  0,  69, 134}; //blue
+        case 1: return {255,  66,  14}; //red
+        case 2: return {255, 211,  32}; //yellow
+        case 3: return { 87, 157,  28}; //green
+        case 4: return {126,   0,  33}; //royal
+        case 5: return {131, 202, 255}; //light blue
+        case 6: return { 49,  64,   4}; //dark green
+        case 7: return {174, 207,   0}; //light green
+        case 8: return { 75,  31, 111}; //purple
+        case 9: return {255, 149,  14}; //orange
         //*INDENT-ON*
     }
     assert(false);
diff --git a/wx+/graph.h b/wx+/graph.h
index c843b09b..288ef9e7 100644
--- a/wx+/graph.h
+++ b/wx+/graph.h
@@ -218,7 +218,7 @@ public:
     void addCurve(const std::shared_ptr<CurveData>& data, const CurveAttributes& ca = CurveAttributes());
     void clearCurves() { curves_.clear(); }
 
-    static wxColor getBorderColor() { return { 130, 135, 144 }; } //medium grey, the same Win7 uses for other frame borders => not accessible! but no big deal...
+    static wxColor getBorderColor() { return {130, 135, 144}; } //medium grey, the same Win7 uses for other frame borders => not accessible! but no big deal...
 
     class MainAttributes
     {
@@ -330,7 +330,7 @@ private:
     CurveList curves_;
 
     //perf!!! generating the font is *very* expensive! => buffer for Graph2D::render()!
-    const wxFont labelFont_ { wxNORMAL_FONT->GetPointSize(), wxFONTFAMILY_DEFAULT, wxFONTSTYLE_NORMAL, wxFONTWEIGHT_NORMAL, false, L"Arial" };
+    const wxFont labelFont_{wxNORMAL_FONT->GetPointSize(), wxFONTFAMILY_DEFAULT, wxFONTSTYLE_NORMAL, wxFONTWEIGHT_NORMAL, false, L"Arial"};
 };
 }
 
diff --git a/wx+/grid.cpp b/wx+/grid.cpp
index cd91b1af..0111ccf7 100644
--- a/wx+/grid.cpp
+++ b/wx+/grid.cpp
@@ -27,8 +27,8 @@ using namespace zen;
 
 
 //let's NOT create wxWidgets objects statically:
-wxColor GridData::getColorSelectionGradientFrom() { return { 137, 172, 255 }; } //blue: HSL: 158, 255, 196   HSV: 222, 0.46, 1
-wxColor GridData::getColorSelectionGradientTo  () { return { 225, 234, 255 }; } //      HSL: 158, 255, 240   HSV: 222, 0.12, 1
+wxColor GridData::getColorSelectionGradientFrom() { return {137, 172, 255}; } //blue: HSL: 158, 255, 196   HSV: 222, 0.46, 1
+wxColor GridData::getColorSelectionGradientTo  () { return {225, 234, 255}; } //      HSL: 158, 255, 240   HSV: 222, 0.12, 1
 
 int GridData::getColumnGapLeft() { return fastFromDIP(4); }
 
@@ -493,8 +493,8 @@ public:
         const int yFrom = refParent().CalcUnscrolledPosition(clientRect.GetTopLeft    ()).y;
         const int yTo   = refParent().CalcUnscrolledPosition(clientRect.GetBottomRight()).y;
 
-        return { std::max(yFrom / rowHeight_, 0),
-                 std::min<ptrdiff_t>((yTo  / rowHeight_) + 1, refParent().getRowCount()) };
+        return {std::max(yFrom / rowHeight_, 0),
+                std::min<ptrdiff_t>((yTo  / rowHeight_) + 1, refParent().getRowCount())};
     }
 
 private:
@@ -1351,6 +1351,7 @@ private:
                 return;
 
             const double mouseDragSpeedIncScrollU = MOUSE_DRAG_ACCELERATION_DIP * wnd_.rowLabelWin_.getRowHeight() / pixelsPerUnitY; //unit: [scroll units / (DIP * sec)]
+            //design alternative: "Dynamic autoscroll based on escape velocity": https://devblogs.microsoft.com/oldnewthing/20210128-00/?p=104768
 
             auto autoScroll = [&](int overlapPix, double& toScroll)
             {
@@ -1986,7 +1987,7 @@ void Grid::setColumnConfig(const std::vector<Grid::ColAttributes>& attr)
         assert(ca.type != ColumnType::none);
 
         if (ca.visible)
-            visCols.push_back({ ca.type, ca.offset, std::max(ca.stretch, 0) });
+            visCols.push_back({ca.type, ca.offset, std::max(ca.stretch, 0)});
     }
 
     //"ownership" of visible columns is now within Grid
@@ -2101,10 +2102,10 @@ Grid::ColumnPosInfo Grid::getColumnAtPos(int posX) const
         {
             accWidth += cw.width;
             if (posX < accWidth)
-                return { cw.type, posX + cw.width - accWidth, cw.width };
+                return {cw.type, posX + cw.width - accWidth, cw.width};
         }
     }
-    return { ColumnType::none, 0, 0 };
+    return {ColumnType::none, 0, 0};
 }
 
 
@@ -2386,7 +2387,7 @@ std::vector<Grid::ColumnWidth> Grid::getColWidths(int mainWinWidth) const //eval
         else
             width = std::max(width, 0); //support smaller width than COLUMN_MIN_WIDTH_DIP if set via configuration
 
-        output.push_back({ vc.type, width });
+        output.push_back({vc.type, width});
     }
     return output;
 }
diff --git a/wx+/grid.h b/wx+/grid.h
index 8d68ffd7..4de76b66 100644
--- a/wx+/grid.h
+++ b/wx+/grid.h
@@ -387,7 +387,7 @@ std::vector<Grid::ColAttributes> convertColAttributes(const std::vector<ColAttrR
 {
     std::vector<Grid::ColAttributes> output;
     for (const ColAttrReal& ca : makeConsistent(attribs, defaults))
-        output.push_back({ static_cast<ColumnType>(ca.type), ca.offset, ca.stretch, ca.visible });
+        output.push_back({static_cast<ColumnType>(ca.type), ca.offset, ca.stretch, ca.visible});
     return output;
 }
 
@@ -399,7 +399,7 @@ std::vector<ColAttrReal> convertColAttributes(const std::vector<Grid::ColAttribu
 
     std::vector<ColAttrReal> output;
     for (const Grid::ColAttributes& ca : attribs)
-        output.push_back({ static_cast<ColTypeReal>(ca.type), ca.offset, ca.stretch, ca.visible });
+        output.push_back({static_cast<ColTypeReal>(ca.type), ca.offset, ca.stretch, ca.visible});
     return output;
 }
 }
diff --git a/wx+/image_resources.cpp b/wx+/image_resources.cpp
index 42114ebb..fbfeb0d8 100644
--- a/wx+/image_resources.cpp
+++ b/wx+/image_resources.cpp
@@ -50,27 +50,23 @@ ImageHolder xbrzScale(int width, int height, const unsigned char* imageRgb, cons
             *out++ = xbrz::makePixel(*alpha++, rgb[0], rgb[1], rgb[2]);
     }
     //-----------------------------------------------------
-    xbrz::scale(hqScale,       //size_t factor, //valid range: 2 - SCALE_FACTOR_MAX
-                argbSrc,       //const uint32_t* src,
-                xbrTrg,        //uint32_t* trg,
-                width, height, //int srcWidth, int srcHeight,
-                xbrz::ColorFormat::ARGB_UNBUFFERED); //ColorFormat colFmt,
-    //test: total xBRZ scaling time with ARGB: 300ms, ARGB_UNBUFFERED: 50ms
+    xbrz::scale(hqScale,       //size_t factor - valid range: 2 - SCALE_FACTOR_MAX
+                argbSrc,       //const uint32_t* src
+                xbrTrg,        //uint32_t* trg
+                width, height, //int srcWidth, int srcHeight
+                xbrz::ColorFormat::argbUnbuffered); //ColorFormat colFmt
+    //test: total xBRZ scaling time with ARGB: 300ms, ARGB unbuffered: 50ms
     //-----------------------------------------------------
     //convert BGRA to RGB + alpha
     ImageHolder trgImg(hqWidth, hqHeight, true /*withAlpha*/);
-    {
-        unsigned char* rgb   = trgImg.getRgb();
-        unsigned char* alpha = trgImg.getAlpha();
 
-        std::for_each(xbrTrg, xbrTrg + hqWidth * hqHeight, [&](uint32_t col)
-        {
-            *alpha++ = xbrz::getAlpha(col);
-            *rgb++   = xbrz::getRed  (col);
-            *rgb++   = xbrz::getGreen(col);
-            *rgb++   = xbrz::getBlue (col);
-        });
-    }
+    std::for_each(xbrTrg, xbrTrg + hqWidth * hqHeight, [rgb = trgImg.getRgb(), alpha = trgImg.getAlpha()](uint32_t col) mutable
+    {
+        *alpha++ = xbrz::getAlpha(col);
+        *rgb++   = xbrz::getRed  (col);
+        *rgb++   = xbrz::getGreen(col);
+        *rgb++   = xbrz::getBlue (col);
+    });
     return trgImg;
 }
 
@@ -128,7 +124,7 @@ private:
     Protected<std::vector<std::pair<std::string, ImageHolder>>> result_;
 
     using TaskType = FunctionReturnTypeT<decltype(&getScalerTask)>;
-    std::optional<ThreadGroup<TaskType>> threadGroup_{ ThreadGroup<TaskType>(std::max<int>(std::thread::hardware_concurrency(), 1), Zstr("xBRZ Scaler")) };
+    std::optional<ThreadGroup<TaskType>> threadGroup_{ThreadGroup<TaskType>(std::max<int>(std::thread::hardware_concurrency(), 1), Zstr("xBRZ Scaler"))};
     //hardware_concurrency() == 0 if "not computable or well defined"
 };
 
@@ -296,8 +292,8 @@ const wxImage& ImageBuffer::getImage(const std::string& name, int maxWidth /*opt
         if (rawImg.GetHeight() >= outHeight) //=> skip needless xBRZ upscaling
             it = imagesOut_.emplace(imkey, shrinkImage(rawImg, -1 /*maxWidth*/, outHeight)).first;
         else if (rawImg.GetHeight() >= 0.9 * outHeight) //almost there: also no need for xBRZ-scale
-            //however: for 125% DPI scaling, "2xBRZ + bilinear downscale" gives a better result than mere "125% bilinear upscale"!
-            it = imagesOut_.emplace(imkey, rawImg.Scale(numeric::intDivRound(outHeight * rawImg.GetWidth(), rawImg.GetHeight()), outHeight, wxIMAGE_QUALITY_BILINEAR)).first;
+            it = imagesOut_.emplace(imkey, bilinearScale(rawImg, numeric::intDivRound(outHeight * rawImg.GetWidth(), rawImg.GetHeight()), outHeight)).first;
+        //however: for 125% DPI scaling, "2xBRZ + bilinear downscale" gives a better result than mere "125% bilinear upscale"
         else
             it = imagesOut_.emplace(imkey, shrinkImage(getScaledImage(name), -1 /*maxWidth*/, outHeight)).first;
     }
diff --git a/wx+/image_tools.cpp b/wx+/image_tools.cpp
index 6ba95c5e..bbc8cee7 100644
--- a/wx+/image_tools.cpp
+++ b/wx+/image_tools.cpp
@@ -8,6 +8,7 @@
 #include <zen/string_tools.h>
 #include <zen/zstring.h>
 #include <wx/app.h>
+#include <xBRZ/src/xbrz_tools.h>
 
 using namespace zen;
 
@@ -91,12 +92,12 @@ void copyImageLayover(const wxImage& src,
         for (int x = 0; x < srcWidth; ++x)
         {
             const int w1 = *srcAlpha; //alpha-composition interpreted as weighted average
-            const int w2 = *trgAlpha * (255 - w1) / 255;
+            const int w2 = numeric::intDivRound(*trgAlpha * (255 - w1), 255);
             const int wSum = w1 + w2;
 
             auto calcColor = [w1, w2, wSum](unsigned char colsrc, unsigned char colTrg)
             {
-                return static_cast<unsigned char>(wSum == 0 ? 0 : (colsrc * w1 + colTrg * w2) / wSum);
+                return static_cast<unsigned char>(wSum == 0 ? 0 : numeric::intDivRound(colsrc * w1 + colTrg * w2, wSum));
             };
             trgRgb[0] = calcColor(srcRgb[0], trgRgb[0]);
             trgRgb[1] = calcColor(srcRgb[1], trgRgb[1]);
@@ -138,7 +139,7 @@ wxImage zen::stackImages(const wxImage& img1, const wxImage& img2, ImageStackLay
     const int img2Height = img2.GetHeight();
 
     const wxSize newSize = dir == ImageStackLayout::horizontal ?
-                           wxSize(img1Width + gap + img2Width,    std::max(img1Height, img2Height)) :
+                           wxSize(img1Width + gap + img2Width, std::max(img1Height, img2Height)) :
                            wxSize(std::max(img1Width, img2Width), img1Height + gap + img2Height);
 
     wxImage output(newSize);
@@ -181,7 +182,7 @@ wxImage zen::createImageFromText(const wxString& text, const wxFont& font, const
     //assert(!contains(text, L"&")); //accelerator keys not supported here
     wxString textFmt = replaceCpy(text, L"&", L"", false);
 
-        const std::vector<std::pair<wxString, wxSize>> lineInfo = getTextExtentInfo(textFmt, font);
+    const std::vector<std::pair<wxString, wxSize>> lineInfo = getTextExtentInfo(textFmt, font);
 
     int maxWidth   = 0;
     int lineHeight = 0;
@@ -197,8 +198,8 @@ wxImage zen::createImageFromText(const wxString& text, const wxFont& font, const
     {
         wxMemoryDC dc(newBitmap);
 
-            if (wxTheApp->GetLayoutDirection() == wxLayout_RightToLeft)
-                dc.SetLayoutDirection(wxLayout_RightToLeft); //handle e.g. "weak" bidi characters: -> arrows in hebrew/arabic
+        if (wxTheApp->GetLayoutDirection() == wxLayout_RightToLeft)
+            dc.SetLayoutDirection(wxLayout_RightToLeft); //handle e.g. "weak" bidi characters: -> arrows in hebrew/arabic
 
         dc.SetBackground(*wxWHITE_BRUSH);
         dc.Clear();
@@ -238,7 +239,7 @@ wxImage zen::createImageFromText(const wxString& text, const wxFont& font, const
     for (int i = 0; i < pixelCount; ++i)
     {
         //black(0,0,0) becomes wxIMAGE_ALPHA_OPAQUE(255), while white(255,255,255) becomes wxIMAGE_ALPHA_TRANSPARENT(0)
-        *alpha++ = static_cast<unsigned char>((255 - rgb[0] + 255 - rgb[1] + 255 - rgb[2]) / 3); //mixed-mode arithmetics!
+        *alpha++ = static_cast<unsigned char>(numeric::intDivRound(3 * 255 - rgb[0] - rgb[1] - rgb[2], 3)); //mixed-mode arithmetics!
 
         *rgb++ = col.Red  (); //
         *rgb++ = col.Green(); //apply actual text color
@@ -312,6 +313,46 @@ wxImage zen::resizeCanvas(const wxImage& img, wxSize newSize, int alignment)
 }
 
 
+wxImage zen::bilinearScale(const wxImage& img, int width, int height)
+{
+    assert(img.HasAlpha());
+    const auto imgReader = [rgb = img.GetData(), alpha = img.GetAlpha(), srcWidth = img.GetSize().x](int x, int y, xbrz::BytePixel& pix)
+    {
+        const int idx = y * srcWidth + x;
+        const unsigned char* const ptr = rgb + idx * 3;
+
+        const unsigned char a = alpha[idx];
+        pix[0] = a;
+        pix[1] = xbrz::premultiply(ptr[0], a); //r
+        pix[2] = xbrz::premultiply(ptr[1], a); //g
+        pix[3] = xbrz::premultiply(ptr[2], a); //b
+    };
+
+    wxImage imgOut(width, height);
+    imgOut.SetAlpha();
+
+    const auto imgWriter = [rgb = imgOut.GetData(), alpha = imgOut.GetAlpha()](const xbrz::BytePixel& pix) mutable
+    {
+        const unsigned char a = pix[0];
+        * alpha++ = a;
+        * rgb++ = xbrz::demultiply(pix[1], a); //r
+        *rgb++ = xbrz::demultiply(pix[2], a); //g
+        *rgb++ = xbrz::demultiply(pix[3], a); //b
+    };
+
+    xbrz::bilinearScaleSimple(imgReader,       //PixReader srcReader
+                              img.GetSize().x, //int srcWidth
+                              img.GetSize().y, //int srcHeight
+                              imgWriter,       //PixWriter trgWriter
+                              width,           //int trgWidth
+                              height,          //int trgHeight
+                              0,               //int yFirst
+                              height);         //int yLast
+    return imgOut;
+    //return img.Scale(width, height, wxIMAGE_QUALITY_BILINEAR);
+}
+
+
 wxImage zen::shrinkImage(const wxImage& img, int maxWidth /*optional*/, int maxHeight /*optional*/)
 {
     wxSize newSize = img.GetSize();
@@ -330,8 +371,7 @@ wxImage zen::shrinkImage(const wxImage& img, int maxWidth /*optional*/, int maxH
     if (newSize == img.GetSize())
         return img;
 
-    return img.Scale(newSize.x, newSize.y, wxIMAGE_QUALITY_BILINEAR); //looks sharper than wxIMAGE_QUALITY_HIGH!
-    //perf: use xbrz::bilinearScale instead? only about 10% shorter runtime
+    return bilinearScale(img, newSize.x, newSize.y); //looks sharper than wxIMAGE_QUALITY_HIGH!
 }
 
 
diff --git a/wx+/image_tools.h b/wx+/image_tools.h
index 0f0fb9c2..c2fed4c1 100644
--- a/wx+/image_tools.h
+++ b/wx+/image_tools.h
@@ -50,6 +50,9 @@ void convertToVanillaImage(wxImage& img); //add alpha channel if missing + remov
 
 //wxColor hsvColor(double h, double s, double v); //h within [0, 360), s, v within [0, 1]
 
+//does *not* fuck up alpha channel like naive bilinear implementations, e.g. wxImage::Scale()
+wxImage bilinearScale(const wxImage& img, int width, int height);
+
 wxImage shrinkImage(const wxImage& img, int maxWidth /*optional*/, int maxHeight /*optional*/);
 inline wxImage shrinkImage(const wxImage& img, int maxSize) { return shrinkImage(img, maxSize, maxSize); }
 
diff --git a/xBRZ/src/xbrz.cpp b/xBRZ/src/xbrz.cpp
index 50660b84..6c015aa1 100644
--- a/xBRZ/src/xbrz.cpp
+++ b/xBRZ/src/xbrz.cpp
@@ -32,7 +32,10 @@ uint32_t gradientRGB(uint32_t pixFront, uint32_t pixBack) //blend front color wi
 {
     static_assert(0 < M && M < N && N <= 1000);
 
-    auto calcColor = [](unsigned char colFront, unsigned char colBack) -> unsigned char { return (colFront * M + colBack * (N - M)) / N; };
+    auto calcColor = [](unsigned char colFront, unsigned char colBack)
+    {
+        return static_cast<unsigned char>(uintDivRound(colFront * M + colBack * (N - M), N));
+    };
 
     return makePixel(calcColor(getRed  (pixFront), getRed  (pixBack)),
                      calcColor(getGreen(pixFront), getGreen(pixBack)),
@@ -53,10 +56,10 @@ uint32_t gradientARGB(uint32_t pixFront, uint32_t pixBack) //find intermediate c
 
     auto calcColor = [=](unsigned char colFront, unsigned char colBack)
     {
-        return static_cast<unsigned char>((colFront * weightFront + colBack * weightBack) / weightSum);
+        return static_cast<unsigned char>(uintDivRound(colFront * weightFront + colBack * weightBack, weightSum));
     };
 
-    return makePixel(static_cast<unsigned char>(weightSum / N),
+    return makePixel(static_cast<unsigned char>(uintDivRound(weightSum, N)),
                      calcColor(getRed  (pixFront), getRed  (pixBack)),
                      calcColor(getGreen(pixFront), getGreen(pixBack)),
                      calcColor(getBlue (pixFront), getBlue (pixBack)));
@@ -154,7 +157,7 @@ double distYCbCr(uint32_t pix1, uint32_t pix2, double lumaWeight)
 {
     //https://en.wikipedia.org/wiki/YCbCr#ITU-R_BT.601_conversion
     //YCbCr conversion is a matrix multiplication => take advantage of linearity by subtracting first!
-    const int r_diff = static_cast<int>(getRed  (pix1)) - getRed  (pix2); //we may delay division by 255 to after matrix multiplication
+    const int r_diff = static_cast<int>(getRed  (pix1)) - getRed  (pix2); //defer division by 255 to after matrix multiplication
     const int g_diff = static_cast<int>(getGreen(pix1)) - getGreen(pix2); //
     const int b_diff = static_cast<int>(getBlue (pix1)) - getBlue (pix2); //substraction for int is noticeable faster than for double!
 
@@ -1094,23 +1097,23 @@ struct ColorDistanceARGB
     {
         const double a1 = getAlpha(pix1) / 255.0 ;
         const double a2 = getAlpha(pix2) / 255.0 ;
-        /*
-        Requirements for a color distance handling alpha channel: with a1, a2 in [0, 1]
+
+        /*  Requirements for a color distance handling alpha channel: with a1, a2 in [0, 1]
 
             1. if a1 = a2, distance should be: a1 * distYCbCr()
             2. if a1 = 0,  distance should be: a2 * distYCbCr(black, white) = a2 * 255
             3. if a1 = 1,  ??? maybe: 255 * (1 - a2) + a2 * distYCbCr()
-        */
 
-        //return std::min(a1, a2) * distYCbCrBuffered(pix1, pix2) + 255 * abs(a1 - a2);
+            std::min(a1, a2) * distYCbCrBuffered(pix1, pix2) + 255 * abs(a1 - a2);
+
+            alternative? std::sqrt(a1 * a2 * square(distYCbCrBuffered(pix1, pix2)) + square(255 * (a1 - a2)));   */
+
         //=> following code is 15% faster:
         const double d = distYCbCrBuffered(pix1, pix2);
         if (a1 < a2)
             return a1 * d + 255 * (a2 - a1);
         else
             return a2 * d + 255 * (a1 - a2);
-
-        //alternative? return std::sqrt(a1 * a2 * square(distYCbCrBuffered(pix1, pix2)) + square(255 * (a1 - a2)));
     }
 };
 
@@ -1163,7 +1166,7 @@ void xbrz::scale(size_t factor, const uint32_t* src, uint32_t* trg, int srcWidth
     switch (colFmt)
     {
         //*INDENT-OFF*
-        case ColorFormat::RGB:
+        case ColorFormat::rgb:
             switch (factor)
             {
                 case 2: return scaleImage<Scaler2x<ColorGradientRGB>, ColorDistanceRGB, OobReaderDuplicate>(src, trg, srcWidth, srcHeight, cfg, yFirst, yLast);
@@ -1174,7 +1177,7 @@ void xbrz::scale(size_t factor, const uint32_t* src, uint32_t* trg, int srcWidth
             }
             break;
 
-        case ColorFormat::ARGB:
+        case ColorFormat::argb:
             switch (factor)
             {
                 case 2: return scaleImage<Scaler2x<ColorGradientARGB>, ColorDistanceARGB, OobReaderTransparent>(src, trg, srcWidth, srcHeight, cfg, yFirst, yLast);
@@ -1185,7 +1188,7 @@ void xbrz::scale(size_t factor, const uint32_t* src, uint32_t* trg, int srcWidth
             }
             break;
 
-        case ColorFormat::ARGB_UNBUFFERED:
+        case ColorFormat::argbUnbuffered:
             switch (factor)
             {
                 case 2: return scaleImage<Scaler2x<ColorGradientARGB>, ColorDistanceUnbufferedARGB, OobReaderTransparent>(src, trg, srcWidth, srcHeight, cfg, yFirst, yLast);
@@ -1205,11 +1208,11 @@ bool xbrz::equalColorTest(uint32_t col1, uint32_t col2, ColorFormat colFmt, doub
 {
     switch (colFmt)
     {
-        case ColorFormat::RGB:
+        case ColorFormat::rgb:
             return ColorDistanceRGB::dist(col1, col2, luminanceWeight) < equalColorTolerance;
-        case ColorFormat::ARGB:
+        case ColorFormat::argb:
             return ColorDistanceARGB::dist(col1, col2, luminanceWeight) < equalColorTolerance;
-        case ColorFormat::ARGB_UNBUFFERED:
+        case ColorFormat::argbUnbuffered:
             return ColorDistanceUnbufferedARGB::dist(col1, col2, luminanceWeight) < equalColorTolerance;
     }
     assert(false);
@@ -1223,13 +1226,26 @@ void xbrz::bilinearScale(const uint32_t* src, int srcWidth, int srcHeight,
     const auto imgReader = [src, srcWidth](int x, int y, BytePixel& pix)
     {
         static_assert(sizeof(pix) == sizeof(uint32_t));
-        std::memcpy(pix, src + y * srcWidth + x, sizeof(pix));
+        const uint32_t pixSrc = src[y * srcWidth + x];
+
+        const unsigned char a = getAlpha(pixSrc);
+        pix[0] = a;
+        pix[1] = xbrz::premultiply(getRed  (pixSrc), a); //r
+        pix[2] = xbrz::premultiply(getGreen(pixSrc), a); //g
+        pix[3] = xbrz::premultiply(getBlue (pixSrc), a); //b
     };
 
-    const auto imgWriter = [trg](const xbrz::BytePixel& pix) mutable { std::memcpy(trg++, pix, sizeof(pix)); };
+    const auto imgWriter = [trg](const xbrz::BytePixel& pix) mutable
+    {
+        const unsigned char a = pix[0];
+        * trg++ = makePixel(a,
+                            xbrz::demultiply(pix[1], a),  //r
+                            xbrz::demultiply(pix[2], a),  //g
+                            xbrz::demultiply(pix[3], a)); //b
+    };
 
-    bilinearScale(imgReader, srcWidth, srcHeight,
-                  imgWriter, trgWidth, trgHeight, 0, trgHeight);
+    bilinearScaleSimple(imgReader, srcWidth, srcHeight,
+                        imgWriter, trgWidth, trgHeight, 0, trgHeight);
 }
 
 
@@ -1262,8 +1278,8 @@ void bilinearScaleCpu(const uint32_t* src, int srcWidth, int srcHeight,
         tg.run([=]
     {
         const int iLast = std::min(i + TASK_GRANULARITY, trgHeight);
-        xbrz::bilinearScale(src, srcWidth, srcHeight, srcWidth * sizeof(uint32_t),
-                            trg, trgWidth, trgHeight, trgWidth * sizeof(uint32_t),
+        xbrz::bilinearScaleSimple(src, srcWidth, srcHeight, srcWidth * sizeof(uint32_t),
+                                  trg, trgWidth, trgHeight, trgWidth * sizeof(uint32_t),
         i, iLast, [](uint32_t pix) { return pix; });
     });
     tg.wait();
diff --git a/xBRZ/src/xbrz.h b/xBRZ/src/xbrz.h
index c0778cf1..b3a496ba 100644
--- a/xBRZ/src/xbrz.h
+++ b/xBRZ/src/xbrz.h
@@ -26,26 +26,24 @@
 
 namespace xbrz
 {
-/*
--------------------------------------------------------------------------
-| xBRZ: "Scale by rules" - high quality image upscaling filter by Zenju |
--------------------------------------------------------------------------
-using a modified approach of xBR:
-http://board.byuu.org/viewtopic.php?f=10&t=2248
-- new rule set preserving small image features
-- highly optimized for performance
-- support alpha channel
-- support multithreading
-- support 64-bit architectures
-- support processing image slices
-- support scaling up to 6xBRZ
-*/
+/*  -------------------------------------------------------------------------
+    | xBRZ: "Scale by rules" - high quality image upscaling filter by Zenju |
+    -------------------------------------------------------------------------
+    using a modified approach of xBR:
+    http://board.byuu.org/viewtopic.php?f=10&t=2248
+    - new rule set preserving small image features
+    - highly optimized for performance
+    - support alpha channel
+    - support multithreading
+    - support 64-bit architectures
+    - support processing image slices
+    - support scaling up to 6xBRZ                                             */
 
 enum class ColorFormat //from high bits -> low bits, 8 bit per channel
 {
-    RGB,  //8 bit for each red, green, blue, upper 8 bits unused
-    ARGB, //including alpha channel, BGRA byte order on little-endian machines
-    ARGB_UNBUFFERED, //like ARGB, but without the one-time buffer creation overhead (ca. 100 - 300 ms) at the expense of a slightly slower scaling time
+    rgb,  //8 bit for each red, green, blue, upper 8 bits unused
+    argb, //including alpha channel, BGRA byte order on little-endian machines
+    argbUnbuffered, //like ARGB, but without the one-time buffer creation overhead (ca. 100 - 300 ms) at the expense of a slightly slower scaling time
 };
 
 const int SCALE_FACTOR_MAX = 6;
@@ -66,6 +64,7 @@ void scale(size_t factor, //valid range: 2 - SCALE_FACTOR_MAX
            const ScalerCfg& cfg = ScalerCfg(),
            int yFirst = 0, int yLast = std::numeric_limits<int>::max()); //slice of source image
 
+//BGRA byte order
 void bilinearScale(const uint32_t* src, int srcWidth, int srcHeight,
                    /**/  uint32_t* trg, int trgWidth, int trgHeight);
 
diff --git a/xBRZ/src/xbrz_tools.h b/xBRZ/src/xbrz_tools.h
index 98164678..d6e48c0c 100644
--- a/xBRZ/src/xbrz_tools.h
+++ b/xBRZ/src/xbrz_tools.h
@@ -87,10 +87,35 @@ void nearestNeighborScale(PixReader srcReader /* (int x, int y, BytePixel& pix)
 }
 
 
+inline
+unsigned int uintDivRound(unsigned int num, unsigned int den)
+{
+    assert(den != 0);
+    return (num + den / 2) / den;
+}
+
+
+inline
+unsigned char premultiply(unsigned char c, unsigned char alpha)
+{
+    return static_cast<unsigned char>(uintDivRound(static_cast<unsigned int>(c) * alpha, 255));
+    //premultiply/demultiply using int div round is more accurate than int div floor/ceil pair
+}
+
+
+inline
+unsigned char demultiply(unsigned char c, unsigned char alpha)
+{
+    return static_cast<unsigned char>(alpha == 0 ? 0 :
+                                      std::clamp(uintDivRound(static_cast<unsigned int>(c) * 255, alpha), 0U, 255U));
+}
+
+
+//caveat: treats alpha channel like regular color! => caller needs to pre/de-multiply alpha!
 template <class PixReader, class PixWriter>
-void bilinearScale(PixReader srcReader /* (int x, int y, BytePixel& pix) */, int srcWidth, int srcHeight,
-                   PixWriter trgWriter /* (const BytePixel& pix)         */, int trgWidth, int trgHeight,
-                   int yFirst, int yLast)
+void bilinearScaleSimple(PixReader srcReader /* (int x, int y, BytePixel& pix) */, int srcWidth, int srcHeight,
+                         PixWriter trgWriter /* (const BytePixel& pix)         */, int trgWidth, int trgHeight,
+                         int yFirst, int yLast)
 {
     yFirst = std::max(yFirst, 0);
     yLast  = std::min(yLast, trgHeight);
@@ -121,7 +146,7 @@ void bilinearScale(PixReader srcReader /* (int x, int y, BytePixel& pix) */, int
         const double xx1 = x / scaleX - x1;
         const double x2x = 1 - xx1;
 
-        buf[x] = { x1, x2, xx1, x2x };
+        buf[x] = {x1, x2, xx1, x2x};
     }
 
     for (int y = yFirst; y < yLast; ++y)
diff --git a/zen/basic_math.h b/zen/basic_math.h
index a4feb83e..944a0f53 100644
--- a/zen/basic_math.h
+++ b/zen/basic_math.h
@@ -111,14 +111,14 @@ std::pair<InputIterator, InputIterator> minMaxElement(InputIterator first, Input
             }
         }
     }
-    return { lowest, largest };
+    return {lowest, largest};
 }
 
 
 template <class InputIterator> inline
 std::pair<InputIterator, InputIterator> minMaxElement(InputIterator first, InputIterator last)
 {
-    return minMaxElement(first, last, std::less<typename std::iterator_traits<InputIterator>::value_type>());
+    return minMaxElement(first, last, std::less());
 }
 */
 
@@ -152,10 +152,10 @@ template <class N, class D> inline
 auto intDivRound(N num, D den)
 {
     using namespace zen;
-    static_assert(IsInteger<N>::value && IsInteger<D>::value);
-    static_assert(IsSignedInt<N>::value == IsSignedInt<D>::value); //until further
+    static_assert(IsIntegerV<N>&& IsIntegerV<D>);
+    static_assert(IsSignedIntV<N> == IsSignedIntV<D>); //until further
     assert(den != 0);
-    if constexpr (IsSignedInt<N>::value)
+    if constexpr (IsSignedIntV<N>)
     {
         if ((num < 0) != (den < 0))
             return (num - den / 2) / den;
@@ -168,10 +168,10 @@ template <class N, class D> inline
 auto intDivCeil(N num, D den)
 {
     using namespace zen;
-    static_assert(IsInteger<N>::value && IsInteger<D>::value);
-    static_assert(IsSignedInt<N>::value == IsSignedInt<D>::value); //until further
+    static_assert(IsIntegerV<N>&& IsIntegerV<D>);
+    static_assert(IsSignedIntV<N> == IsSignedIntV<D>); //until further
     assert(den != 0);
-    if constexpr (IsSignedInt<N>::value)
+    if constexpr (IsSignedIntV<N>)
     {
         if ((num < 0) != (den < 0))
             return num / den;
@@ -187,10 +187,10 @@ template <class N, class D> inline
 auto intDivFloor(N num, D den)
 {
     using namespace zen;
-    static_assert(IsInteger<N>::value && IsInteger<D>::value);
-    static_assert(IsSignedInt<N>::value == IsSignedInt<D>::value); //until further
+    static_assert(IsIntegerV<N>&& IsIntegerV<D>);
+    static_assert(IsSignedIntV<N> == IsSignedIntV<D>); //until further
     assert(den != 0);
-    if constexpr (IsSignedInt<N>::value)
+    if constexpr (IsSignedIntV<N>)
     {
         if ((num < 0) != (den < 0))
         {
diff --git a/zen/dir_watcher.cpp b/zen/dir_watcher.cpp
index dc416b34..191ffd64 100644
--- a/zen/dir_watcher.cpp
+++ b/zen/dir_watcher.cpp
@@ -9,7 +9,6 @@
 #include <set>
 #include "thread.h"
 #include "scope_guard.h"
-//#include "basic_math.h"
 
     #include <map>
     #include <sys/inotify.h>
@@ -34,7 +33,7 @@ DirWatcher::DirWatcher(const Zstring& dirPath) : //throw FileError
     pimpl_(std::make_unique<Impl>())
 {
     //get all subdirectories
-    std::vector<Zstring> fullFolderList { baseDirPath_ };
+    std::vector<Zstring> fullFolderList {baseDirPath_};
     {
         std::function<void (const Zstring& path)> traverse;
 
@@ -102,7 +101,7 @@ DirWatcher::~DirWatcher()
 
 std::vector<DirWatcher::Change> DirWatcher::fetchChanges(const std::function<void()>& requestUiUpdate, std::chrono::milliseconds cbInterval) //throw FileError
 {
-    std::vector<std::byte> buffer(512 * (sizeof(struct ::inotify_event) + NAME_MAX + 1));
+    std::vector<std::byte> buffer(512 * (sizeof(inotify_event) + NAME_MAX + 1));
 
     ssize_t bytesRead = 0;
     do
@@ -125,7 +124,7 @@ std::vector<DirWatcher::Change> DirWatcher::fetchChanges(const std::function<voi
     ssize_t bytePos = 0;
     while (bytePos < bytesRead)
     {
-        struct ::inotify_event& evt = reinterpret_cast<struct ::inotify_event&>(buffer[bytePos]);
+        inotify_event& evt = reinterpret_cast<inotify_event&>(buffer[bytePos]);
 
         if (evt.len != 0) //exclude case: deletion of "self", already reported by parent directory watch
         {
@@ -138,18 +137,18 @@ std::vector<DirWatcher::Change> DirWatcher::fetchChanges(const std::function<voi
 
                 if ((evt.mask & IN_CREATE) ||
                     (evt.mask & IN_MOVED_TO))
-                    output.push_back({ ChangeType::create, itemPath });
+                    output.push_back({ChangeType::create, itemPath});
                 else if ((evt.mask & IN_MODIFY) ||
                          (evt.mask & IN_CLOSE_WRITE))
-                    output.push_back({ ChangeType::update, itemPath });
+                    output.push_back({ChangeType::update, itemPath});
                 else if ((evt.mask & IN_DELETE     ) ||
                          (evt.mask & IN_DELETE_SELF) ||
                          (evt.mask & IN_MOVE_SELF  ) ||
                          (evt.mask & IN_MOVED_FROM))
-                    output.push_back({ ChangeType::remove, itemPath });
+                    output.push_back({ChangeType::remove, itemPath});
             }
         }
-        bytePos += sizeof(struct ::inotify_event) + evt.len;
+        bytePos += sizeof(inotify_event) + evt.len;
     }
 
     return output;
diff --git a/zen/error_log.h b/zen/error_log.h
index 6d9f80ae..a24dfe5a 100644
--- a/zen/error_log.h
+++ b/zen/error_log.h
@@ -68,7 +68,7 @@ private:
 inline
 void ErrorLog::logMsg(const std::wstring& msg, MessageType type)
 {
-    entries_.push_back({ std::time(nullptr), type, utfTo<Zstringc>(msg) });
+    entries_.push_back({std::time(nullptr), type, utfTo<Zstringc>(msg)});
 }
 
 
diff --git a/zen/file_access.cpp b/zen/file_access.cpp
index 4c9af652..fb770f19 100644
--- a/zen/file_access.cpp
+++ b/zen/file_access.cpp
@@ -12,7 +12,6 @@
 #include "file_traverser.h"
 #include "scope_guard.h"
 #include "symlink_target.h"
-#include "file_id_def.h"
 #include "file_io.h"
 #include "crc.h"
 #include "guid.h"
@@ -45,7 +44,7 @@ std::optional<PathComponents> zen::parsePathComponents(const Zstring& itemPath)
                     Zstring relPath(it + 1, itemPathFmt.end());
                     trim(relPath, true, true, [](Zchar c) { return c == FILE_NAME_SEPARATOR; });
 
-                    return PathComponents({ rootPath, relPath });
+                    return PathComponents({rootPath, relPath});
                 }
         return {};
     };
@@ -100,7 +99,7 @@ std::optional<Zstring> zen::getParentFolderPath(const Zstring& itemPath)
 
 ItemType zen::getItemType(const Zstring& itemPath) //throw FileError
 {
-    struct ::stat itemInfo = {};
+    struct stat itemInfo = {};
     if (::lstat(itemPath.c_str(), &itemInfo) != 0)
         THROW_LAST_FILE_ERROR(replaceCpy(_("Cannot read file attributes of %x."), L"%x", fmtPath(itemPath)), "lstat");
 
@@ -153,7 +152,7 @@ std::optional<ItemType> zen::itemStillExists(const Zstring& itemPath) //throw Fi
 bool zen::fileAvailable(const Zstring& filePath) //noexcept
 {
     //symbolic links (broken or not) are also treated as existing files!
-    struct ::stat fileInfo = {};
+    struct stat fileInfo = {};
     if (::stat(filePath.c_str(), &fileInfo) == 0) //follow symlinks!
         return S_ISREG(fileInfo.st_mode);
     return false;
@@ -163,7 +162,7 @@ bool zen::fileAvailable(const Zstring& filePath) //noexcept
 bool zen::dirAvailable(const Zstring& dirPath) //noexcept
 {
     //symbolic links (broken or not) are also treated as existing directories!
-    struct ::stat dirInfo = {};
+    struct stat dirInfo = {};
     if (::stat(dirPath.c_str(), &dirInfo) == 0) //follow symlinks!
         return S_ISDIR(dirInfo.st_mode);
     return false;
@@ -177,29 +176,22 @@ namespace
 
 int64_t zen::getFreeDiskSpace(const Zstring& path) //throw FileError, returns < 0 if not available
 {
-    struct ::statfs info = {};
-    if (::statfs(path.c_str(), &info) != 0)
+    struct statfs info = {};
+    if (::statfs(path.c_str(), &info) != 0) //follows symlinks!
         THROW_LAST_FILE_ERROR(replaceCpy(_("Cannot determine free disk space for %x."), L"%x", fmtPath(path)), "statfs");
+    //Linux: "Fields that are undefined for a particular file system are set to 0."
+    //macOS: "Fields that are undefined for a particular file system are set to -1." - mkay :>
+    if (makeSigned(info.f_bsize)  <= 0 ||
+        makeSigned(info.f_bavail) <= 0)
+        return -1;
 
     return static_cast<int64_t>(info.f_bsize) * info.f_bavail;
 }
 
 
-VolumeId zen::getVolumeId(const Zstring& itemPath) //throw FileError
-{
-    struct ::stat fileInfo = {};
-    if (::stat(itemPath.c_str(), &fileInfo) != 0)
-        THROW_LAST_FILE_ERROR(replaceCpy(_("Cannot read file attributes of %x."), L"%x", fmtPath(itemPath)), "stat");
-
-    warn_static("NOT STABLE!")
-
-    return fileInfo.st_dev;
-}
-
-
 uint64_t zen::getFileSize(const Zstring& filePath) //throw FileError
 {
-    struct ::stat fileInfo = {};
+    struct stat fileInfo = {};
     if (::stat(filePath.c_str(), &fileInfo) != 0)
         THROW_LAST_FILE_ERROR(replaceCpy(_("Cannot read file attributes of %x."), L"%x", fmtPath(filePath)), "stat");
 
@@ -207,6 +199,8 @@ uint64_t zen::getFileSize(const Zstring& filePath) //throw FileError
 }
 
 
+
+
 Zstring zen::getTempFolderPath() //throw FileError
 {
     if (const char* tempPath = ::getenv("TMPDIR")) //no extended error reporting
@@ -336,15 +330,15 @@ void moveAndRenameFileSub(const Zstring& pathFrom, const Zstring& pathTo, bool r
     //macOS: no solution https://developer.apple.com/legacy/library/documentation/Darwin/Reference/ManPages/man2/rename.2.html
     if (!replaceExisting)
     {
-        struct ::stat infoSrc = {};
-        if (::lstat(pathFrom.c_str(), &infoSrc) != 0)
+        struct stat sourceInfo = {};
+        if (::lstat(pathFrom.c_str(), &sourceInfo) != 0)
             THROW_LAST_FILE_ERROR(replaceCpy(_("Cannot read file attributes of %x."), L"%x", fmtPath(pathFrom)), "stat");
 
-        struct ::stat infoTrg = {};
-        if (::lstat(pathTo.c_str(), &infoTrg) == 0)
+        struct stat targetInfo = {};
+        if (::lstat(pathTo.c_str(), &targetInfo) == 0)
         {
-            if (infoSrc.st_dev != infoTrg.st_dev ||
-                infoSrc.st_ino != infoTrg.st_ino)
+            if (sourceInfo.st_dev != targetInfo.st_dev ||
+                sourceInfo.st_ino != targetInfo.st_ino)
                 throwException(EEXIST); //that's what we're really here for
             //else: continue with a rename in case
             //caveat: if we have a hardlink referenced by two different paths, the source one will be unlinked => fine, but not exactly a "rename"...
@@ -376,7 +370,7 @@ void zen::moveAndRenameItem(const Zstring& pathFrom, const Zstring& pathTo, bool
 
 namespace
 {
-void setWriteTimeNative(const Zstring& itemPath, const struct ::timespec& modTime, ProcSymlink procSl) //throw FileError
+void setWriteTimeNative(const Zstring& itemPath, const timespec& modTime, ProcSymlink procSl) //throw FileError
 {
     /*
     [2013-05-01] sigh, we can't use utimensat() on NTFS volumes on Ubuntu: silent failure!!! what morons are programming this shit???
@@ -388,12 +382,12 @@ void setWriteTimeNative(const Zstring& itemPath, const struct ::timespec& modTim
         => let's give utimensat another chance:
         using open()/futimens() for regular files and utimensat(AT_SYMLINK_NOFOLLOW) for symlinks is consistent with "cp" and "touch"!
     */
-    struct ::timespec newTimes[2] = {};
+    timespec newTimes[2] = {};
     newTimes[0].tv_sec = ::time(nullptr); //access time; using UTIME_OMIT for tv_nsec would trigger even more bugs: https://freefilesync.org/forum/viewtopic.php?t=1701
     newTimes[1] = modTime; //modification time
     //test: even modTime == 0 is correctly applied (no NOOP!) test2: same behavior for "utime()"
 
-    if (procSl == ProcSymlink::FOLLOW)
+    if (procSl == ProcSymlink::follow)
     {
         //hell knows why files on gvfs-mounted Samba shares fail to open(O_WRONLY) returning EOPNOTSUPP:
         //https://freefilesync.org/forum/viewtopic.php?t=2803 => utimensat() works (but not for gvfs SFTP)
@@ -422,10 +416,8 @@ void setWriteTimeNative(const Zstring& itemPath, const struct ::timespec& modTim
 
 void zen::setFileTime(const Zstring& filePath, time_t modTime, ProcSymlink procSl) //throw FileError
 {
-    struct ::timespec writeTime = {};
-    writeTime.tv_sec = modTime;
-    setWriteTimeNative(filePath, writeTime, procSl); //throw FileError
-
+    setWriteTimeNative(filePath, timetToNativeFileTime(modTime),
+                       procSl); //throw FileError
 }
 
 
@@ -442,7 +434,7 @@ namespace
 void copySecurityContext(const Zstring& source, const Zstring& target, ProcSymlink procSl) //throw FileError
 {
     security_context_t contextSource = nullptr;
-    const int rv = procSl == ProcSymlink::FOLLOW ?
+    const int rv = procSl == ProcSymlink::follow ?
                    ::getfilecon (source.c_str(), &contextSource) :
                    ::lgetfilecon(source.c_str(), &contextSource);
     if (rv < 0)
@@ -457,7 +449,7 @@ void copySecurityContext(const Zstring& source, const Zstring& target, ProcSymli
 
     {
         security_context_t contextTarget = nullptr;
-        const int rv2 = procSl == ProcSymlink::FOLLOW ?
+        const int rv2 = procSl == ProcSymlink::follow ?
                         ::getfilecon(target.c_str(), &contextTarget) :
                         ::lgetfilecon(target.c_str(), &contextTarget);
         if (rv2 < 0)
@@ -475,7 +467,7 @@ void copySecurityContext(const Zstring& source, const Zstring& target, ProcSymli
         }
     }
 
-    const int rv3 = procSl == ProcSymlink::FOLLOW ?
+    const int rv3 = procSl == ProcSymlink::follow ?
                     ::setfilecon(target.c_str(), contextSource) :
                     ::lsetfilecon(target.c_str(), contextSource);
     if (rv3 < 0)
@@ -493,8 +485,8 @@ void zen::copyItemPermissions(const Zstring& sourcePath, const Zstring& targetPa
     copySecurityContext(sourcePath, targetPath, procSl); //throw FileError
 #endif
 
-    struct ::stat fileInfo = {};
-    if (procSl == ProcSymlink::FOLLOW)
+    struct stat fileInfo = {};
+    if (procSl == ProcSymlink::follow)
     {
         if (::stat(sourcePath.c_str(), &fileInfo) != 0)
             THROW_LAST_FILE_ERROR(replaceCpy(_("Cannot read permissions of %x."), L"%x", fmtPath(sourcePath)), "stat");
@@ -614,22 +606,22 @@ void zen::copySymlink(const Zstring& sourcePath, const Zstring& targetPath) //th
     catch (FileError&) {});
 
     //file times: essential for syncing a symlink: enforce this! (don't just try!)
-    struct ::stat sourceInfo = {};
+    struct stat sourceInfo = {};
     if (::lstat(sourcePath.c_str(), &sourceInfo) != 0)
         THROW_LAST_FILE_ERROR(replaceCpy(_("Cannot read file attributes of %x."), L"%x", fmtPath(sourcePath)), "lstat");
 
-    setWriteTimeNative(targetPath, sourceInfo.st_mtim, ProcSymlink::DIRECT); //throw FileError
+    setWriteTimeNative(targetPath, sourceInfo.st_mtim, ProcSymlink::direct); //throw FileError
 }
 
 
 FileCopyResult zen::copyNewFile(const Zstring& sourceFile, const Zstring& targetFile, //throw FileError, ErrorTargetExisting, (ErrorFileLocked), X
-                                const IOCallback& notifyUnbufferedIO /*throw X*/)
+                                const IoCallback& notifyUnbufferedIO /*throw X*/)
 {
     int64_t totalUnbufferedIO = 0;
 
     FileInput fileIn(sourceFile, IOCallbackDivider(notifyUnbufferedIO, totalUnbufferedIO)); //throw FileError, (ErrorFileLocked -> Windows-only)
 
-    struct ::stat sourceInfo = {};
+    struct stat sourceInfo = {};
     if (::fstat(fileIn.getHandle(), &sourceInfo) != 0)
         THROW_LAST_FILE_ERROR(replaceCpy(_("Cannot read file attributes of %x."), L"%x", fmtPath(sourceFile)), "fstat");
 
@@ -637,7 +629,7 @@ FileCopyResult zen::copyNewFile(const Zstring& sourceFile, const Zstring& target
     //it seems we don't need S_IWUSR, not even for the setFileTime() below! (tested with source file having different user/group!)
 
     //=> need copyItemPermissions() only for "chown" and umask-agnostic permissions
-    const int fdTarget = ::open(targetFile.c_str(), O_WRONLY | O_CREAT | O_EXCL | O_CLOEXEC, mode);
+    const int fdTarget = ::open(targetFile.c_str(), O_CREAT | O_EXCL | O_WRONLY | O_CLOEXEC, mode);
     if (fdTarget == -1)
     {
         const int ec = errno; //copy before making other system calls!
@@ -659,7 +651,7 @@ FileCopyResult zen::copyNewFile(const Zstring& sourceFile, const Zstring& target
     //flush intermediate buffers before fiddling with the raw file handle
     fileOut.flushBuffers(); //throw FileError, X
 
-    struct ::stat targetInfo = {};
+    struct stat targetInfo = {};
     if (::fstat(fileOut.getHandle(), &targetInfo) != 0)
         THROW_LAST_FILE_ERROR(replaceCpy(_("Cannot read file attributes of %x."), L"%x", fmtPath(targetFile)), "fstat");
 
@@ -673,12 +665,12 @@ FileCopyResult zen::copyNewFile(const Zstring& sourceFile, const Zstring& target
     std::optional<FileError> errorModTime;
     try
     {
-        //we cannot set the target file times (::futimes) while the file descriptor is still open after a write operation:
-        //this triggers bugs on samba shares where the modification time is set to current time instead.
-        //Linux: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=340236
-        //       http://comments.gmane.org/gmane.linux.file-systems.cifs/2854
-        //OS X:  https://freefilesync.org/forum/viewtopic.php?t=356
-        setWriteTimeNative(targetFile, sourceInfo.st_mtim, ProcSymlink::FOLLOW); //throw FileError
+        /*  we cannot set the target file times (::futimes) while the file descriptor is still open after a write operation:
+            this triggers bugs on Samba shares where the modification time is set to current time instead.
+            Linux: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=340236
+                    http://comments.gmane.org/gmane.linux.file-systems.cifs/2854
+            macOS: https://freefilesync.org/forum/viewtopic.php?t=356             */
+        setWriteTimeNative(targetFile, sourceInfo.st_mtim, ProcSymlink::follow); //throw FileError
     }
     catch (const FileError& e)
     {
@@ -687,9 +679,9 @@ FileCopyResult zen::copyNewFile(const Zstring& sourceFile, const Zstring& target
 
     FileCopyResult result;
     result.fileSize = sourceInfo.st_size;
-    result.modTime = sourceInfo.st_mtim.tv_sec; //
-    result.sourceFileId = generateFileId(sourceInfo);
-    result.targetFileId = generateFileId(targetInfo);
+    result.sourceModTime = sourceInfo.st_mtim;
+    result.sourceFileIdx = sourceInfo.st_ino;
+    result.targetFileIdx = targetInfo.st_ino;
     result.errorModTime = errorModTime;
     return result;
 }
diff --git a/zen/file_access.h b/zen/file_access.h
index a3fa56d7..f3ea6c00 100644
--- a/zen/file_access.h
+++ b/zen/file_access.h
@@ -10,9 +10,8 @@
 #include <functional>
 #include "zstring.h"
 #include "file_error.h"
-#include "file_id_def.h"
-#include "serialize.h"
-
+#include "serialize.h" //IoCallback
+    #include <sys/stat.h>
 
 namespace zen
 {
@@ -31,6 +30,21 @@ std::optional<Zstring> getParentFolderPath(const Zstring& itemPath);
 bool fileAvailable(const Zstring& filePath); //noexcept
 bool dirAvailable (const Zstring& dirPath ); //
 
+//FAT/FAT32: "Why does the timestamp of a file *increase* by up to 2 seconds when I copy it to a USB thumb drive?"
+const int FAT_FILE_TIME_PRECISION_SEC = 2; //https://devblogs.microsoft.com/oldnewthing/?p=83
+//https://web.archive.org/web/20141127143832/http://support.microsoft.com/kb/127830
+
+using FileIndex = ino_t;
+using FileTimeNative = timespec;
+
+inline time_t nativeFileTimeToTimeT(const timespec& ft) { return ft.tv_sec; } //follow Windows Explorer and always round down!
+inline timespec timetToNativeFileTime(time_t utcTime)
+{
+    timespec natTime = {};
+    natTime.tv_sec = utcTime;
+    return natTime;
+}
+
 enum class ItemType
 {
     file,
@@ -47,14 +61,13 @@ std::optional<ItemType> itemStillExists(const Zstring& itemPath); //throw FileEr
 
 enum class ProcSymlink
 {
-    DIRECT,
-    FOLLOW
+    direct,
+    follow
 };
 void setFileTime(const Zstring& filePath, time_t modTime, ProcSymlink procSl); //throw FileError
 
 //symlink handling: follow
 int64_t getFreeDiskSpace(const Zstring& path); //throw FileError, returns < 0 if not available
-VolumeId getVolumeId(const Zstring& itemPath); //throw FileError
 uint64_t getFileSize(const Zstring& filePath); //throw FileError
 
 //get per-user directory designated for temporary files:
@@ -87,16 +100,15 @@ void copySymlink(const Zstring& sourcePath, const Zstring& targetPath); //throw
 struct FileCopyResult
 {
     uint64_t fileSize = 0;
-    time_t modTime = 0; //number of seconds since Jan. 1st 1970 UTC
-    FileId sourceFileId;
-    FileId targetFileId;
+    FileTimeNative sourceModTime = {};
+    FileIndex sourceFileIdx = 0;
+    FileIndex targetFileIdx = 0;
     std::optional<FileError> errorModTime; //failure to set modification time
 };
 
 FileCopyResult copyNewFile(const Zstring& sourceFile, const Zstring& targetFile, //throw FileError, ErrorTargetExisting, ErrorFileLocked, X
                            //accummulated delta != file size! consider ADS, sparse, compressed files
-                           const IOCallback& notifyUnbufferedIO /*throw X*/);
-
+                           const IoCallback& notifyUnbufferedIO /*throw X*/);
 }
 
 #endif //FILE_ACCESS_H_8017341345614857
diff --git a/zen/file_id_def.h b/zen/file_id_def.h
deleted file mode 100644
index d2d104d5..00000000
--- a/zen/file_id_def.h
+++ /dev/null
@@ -1,46 +0,0 @@
-// *****************************************************************************
-// * This file is part of the FreeFileSync project. It is distributed under    *
-// * GNU General Public License: https://www.gnu.org/licenses/gpl-3.0          *
-// * Copyright (C) Zenju (zenju AT freefilesync DOT org) - All Rights Reserved *
-// *****************************************************************************
-
-#ifndef FILE_ID_DEF_H_013287632486321493
-#define FILE_ID_DEF_H_013287632486321493
-
-    #include <sys/stat.h>
-
-
-namespace zen
-{
-namespace impl { typedef struct ::stat StatDummy; } //sigh...
-
-using VolumeId  = decltype(impl::StatDummy::st_dev);
-using FileIndex = decltype(impl::StatDummy::st_ino);
-
-
-struct FileId //always available on Linux, and *generally* available on Windows)
-{
-    FileId() {}
-    FileId(VolumeId volId, FileIndex fIdx) : volumeId(volId), fileIndex(fIdx)
-    {
-        if (volId == 0 || fIdx == 0)
-        {
-            volumeId  = 0;
-            fileIndex = 0;
-        }
-    }
-    VolumeId  volumeId  = 0;
-    FileIndex fileIndex = 0;
-
-    bool operator==(const FileId&) const = default;
-};
-
-
-inline
-FileId generateFileId(const struct ::stat& fileInfo)
-{
-    return FileId(fileInfo.st_dev, fileInfo.st_ino);
-}
-}
-
-#endif //FILE_ID_DEF_H_013287632486321493
diff --git a/zen/file_io.cpp b/zen/file_io.cpp
index e081335d..f575a366 100644
--- a/zen/file_io.cpp
+++ b/zen/file_io.cpp
@@ -41,7 +41,7 @@ namespace
 FileBase::FileHandle openHandleForRead(const Zstring& filePath) //throw FileError, ErrorFileLocked
 {
     //caveat: check for file types that block during open(): character device, block device, named pipe
-    struct ::stat fileInfo = {};
+    struct stat fileInfo = {};
     if (::stat(filePath.c_str(), &fileInfo) == 0) //follows symlinks
     {
         if (!S_ISREG(fileInfo.st_mode) &&
@@ -74,11 +74,11 @@ FileBase::FileHandle openHandleForRead(const Zstring& filePath) //throw FileErro
 }
 
 
-FileInput::FileInput(FileHandle handle, const Zstring& filePath, const IOCallback& notifyUnbufferedIO) :
+FileInput::FileInput(FileHandle handle, const Zstring& filePath, const IoCallback& notifyUnbufferedIO) :
     FileBase(handle, filePath), notifyUnbufferedIO_(notifyUnbufferedIO) {}
 
 
-FileInput::FileInput(const Zstring& filePath, const IOCallback& notifyUnbufferedIO) :
+FileInput::FileInput(const Zstring& filePath, const IoCallback& notifyUnbufferedIO) :
     FileBase(openHandleForRead(filePath), filePath), //throw FileError, ErrorFileLocked
     notifyUnbufferedIO_(notifyUnbufferedIO)
 {
@@ -166,8 +166,13 @@ FileBase::FileHandle openHandleForWrite(const Zstring& filePath) //throw FileErr
 {
     //checkForUnsupportedType(filePath); -> not needed, open() + O_WRONLY should fail fast
 
-    const int fdFile = ::open(filePath.c_str(), O_WRONLY | O_CREAT | O_CLOEXEC | /*access == FileOutput::ACC_OVERWRITE ? O_TRUNC : */ O_EXCL,
-                              S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH); //0666 => umask will be applied implicitly!
+    const mode_t lockFileMode = S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH; //0666 => umask will be applied implicitly!
+
+    //O_EXCL contains a race condition on NFS file systems: https://linux.die.net/man/2/open
+    const int fdFile = ::open(filePath.c_str(), //const char* pathname
+                              O_CREAT |         //int flags     
+                              /*access == FileOutput::ACC_OVERWRITE ? O_TRUNC : */ O_EXCL | O_WRONLY  | O_CLOEXEC, 
+                              lockFileMode);    //mode_t mode
     if (fdFile == -1)
     {
         const int ec = errno; //copy before making other system calls!
@@ -185,13 +190,13 @@ FileBase::FileHandle openHandleForWrite(const Zstring& filePath) //throw FileErr
 }
 
 
-FileOutput::FileOutput(FileHandle handle, const Zstring& filePath, const IOCallback& notifyUnbufferedIO) :
+FileOutput::FileOutput(FileHandle handle, const Zstring& filePath, const IoCallback& notifyUnbufferedIO) :
     FileBase(handle, filePath), notifyUnbufferedIO_(notifyUnbufferedIO)
 {
 }
 
 
-FileOutput::FileOutput(const Zstring& filePath, const IOCallback& notifyUnbufferedIO) :
+FileOutput::FileOutput(const Zstring& filePath, const IoCallback& notifyUnbufferedIO) :
     FileBase(openHandleForWrite(filePath), filePath), notifyUnbufferedIO_(notifyUnbufferedIO) {} //throw FileError, ErrorTargetExisting
 
 
@@ -298,8 +303,8 @@ void FileOutput::reserveSpace(uint64_t expectedSize) //throw FileError
 
     //don't use ::posix_fallocate which uses horribly inefficient fallback if FS doesn't support it (EOPNOTSUPP) and changes files size!
     //FALLOC_FL_KEEP_SIZE => allocate only, file size is NOT changed!
-    if (::fallocate(getHandle(),         //int fd,
-                    FALLOC_FL_KEEP_SIZE, //int mode,
+    if (::fallocate(getHandle(),         //int fd
+                    FALLOC_FL_KEEP_SIZE, //int mode
                     0,                   //off_t offset
                     expectedSize) != 0)  //off_t len
         if (errno != EOPNOTSUPP) //possible, unlike with posix_fallocate()
@@ -308,19 +313,19 @@ void FileOutput::reserveSpace(uint64_t expectedSize) //throw FileError
 }
 
 
-std::string zen::getFileContent(const Zstring& filePath, const IOCallback& notifyUnbufferedIO /*throw X*/) //throw FileError, X
+std::string zen::getFileContent(const Zstring& filePath, const IoCallback& notifyUnbufferedIO /*throw X*/) //throw FileError, X
 {
     FileInput streamIn(filePath, notifyUnbufferedIO); //throw FileError, ErrorFileLocked
     return bufferedLoad<std::string>(streamIn); //throw FileError, X
 }
 
 
-void zen::setFileContent(const Zstring& filePath, const std::string& byteStream, const IOCallback& notifyUnbufferedIO /*throw X*/) //throw FileError, X
+void zen::setFileContent(const Zstring& filePath, const std::string& byteStream, const IoCallback& notifyUnbufferedIO /*throw X*/) //throw FileError, X
 {
     TempFileOutput fileOut(filePath, notifyUnbufferedIO); //throw FileError
     if (!byteStream.empty())
     {
-        //preallocate disk space + reduce fragmentation
+        //preallocate disk space & reduce fragmentation
         fileOut.reserveSpace(byteStream.size()); //throw FileError
         fileOut.write(&byteStream[0], byteStream.size()); //throw FileError, X
     }
diff --git a/zen/file_io.h b/zen/file_io.h
index a7385241..3d1dfee7 100644
--- a/zen/file_io.h
+++ b/zen/file_io.h
@@ -32,8 +32,7 @@ public:
     FileHandle getHandle() { return hFile_; }
 
     //Windows: use 64kB ?? https://docs.microsoft.com/en-us/previous-versions/windows/it-pro/windows-2000-server/cc938632%28v=technet.10%29
-    //Linux: use st_blksize?
-    //macOS: use f_iosize?
+    //macOS, Linux: use st_blksize?
     static size_t getBlockSize() { return 128 * 1024; };
 
     const Zstring& getFilePath() const { return filePath_; }
@@ -57,15 +56,15 @@ private:
 class FileInput : public FileBase
 {
 public:
-    FileInput(                   const Zstring& filePath, const IOCallback& notifyUnbufferedIO /*throw X*/); //throw FileError, ErrorFileLocked
-    FileInput(FileHandle handle, const Zstring& filePath, const IOCallback& notifyUnbufferedIO /*throw X*/); //takes ownership!
+    FileInput(                   const Zstring& filePath, const IoCallback& notifyUnbufferedIO /*throw X*/); //throw FileError, ErrorFileLocked
+    FileInput(FileHandle handle, const Zstring& filePath, const IoCallback& notifyUnbufferedIO /*throw X*/); //takes ownership!
 
     size_t read(void* buffer, size_t bytesToRead); //throw FileError, ErrorFileLocked, X; return "bytesToRead" bytes unless end of stream!
 
 private:
     size_t tryRead(void* buffer, size_t bytesToRead); //throw FileError, ErrorFileLocked; may return short, only 0 means EOF! =>  CONTRACT: bytesToRead > 0!
 
-    const IOCallback notifyUnbufferedIO_; //throw X
+    const IoCallback notifyUnbufferedIO_; //throw X
 
     std::vector<std::byte> memBuf_ = std::vector<std::byte>(getBlockSize());
     size_t bufPos_   = 0;
@@ -76,8 +75,8 @@ private:
 class FileOutput : public FileBase
 {
 public:
-    FileOutput(                   const Zstring& filePath, const IOCallback& notifyUnbufferedIO /*throw X*/); //throw FileError, ErrorTargetExisting
-    FileOutput(FileHandle handle, const Zstring& filePath, const IOCallback& notifyUnbufferedIO /*throw X*/); //takes ownership!
+    FileOutput(                   const Zstring& filePath, const IoCallback& notifyUnbufferedIO /*throw X*/); //throw FileError, ErrorTargetExisting
+    FileOutput(FileHandle handle, const Zstring& filePath, const IoCallback& notifyUnbufferedIO /*throw X*/); //takes ownership!
     ~FileOutput();
 
     void reserveSpace(uint64_t expectedSize); //throw FileError
@@ -91,7 +90,7 @@ public:
 private:
     size_t tryWrite(const void* buffer, size_t bytesToWrite); //throw FileError; may return short! CONTRACT: bytesToWrite > 0
 
-    IOCallback notifyUnbufferedIO_; //throw X
+    IoCallback notifyUnbufferedIO_; //throw X
     std::vector<std::byte> memBuf_ = std::vector<std::byte>(getBlockSize());
     size_t bufPos_    = 0;
     size_t bufPosEnd_ = 0;
@@ -102,7 +101,7 @@ private:
 class TempFileOutput
 {
 public:
-    TempFileOutput( const Zstring& filePath, const IOCallback& notifyUnbufferedIO /*throw X*/) : //throw FileError
+    TempFileOutput( const Zstring& filePath, const IoCallback& notifyUnbufferedIO /*throw X*/) : //throw FileError
         filePath_(filePath),
         tmpFile_(tmpFilePath_, notifyUnbufferedIO) {} //throw FileError, (ErrorTargetExisting)
 
@@ -110,7 +109,7 @@ public:
 
     void write(const void* buffer, size_t bytesToWrite) { tmpFile_.write(buffer, bytesToWrite); } //throw FileError, X
 
-     FileOutput& refTempFile() { return tmpFile_; }
+    FileOutput& refTempFile() { return tmpFile_; }
 
     void commit() //throw FileError, X
     {
@@ -133,10 +132,10 @@ private:
 };
 
 
-[[nodiscard]] std::string getFileContent(const Zstring& filePath, const IOCallback& notifyUnbufferedIO /*throw X*/); //throw FileError, X
+[[nodiscard]] std::string getFileContent(const Zstring& filePath, const IoCallback& notifyUnbufferedIO /*throw X*/); //throw FileError, X
 
 //overwrites if existing + transactional! :)
-void setFileContent(const Zstring& filePath, const std::string& bytes, const IOCallback& notifyUnbufferedIO /*throw X*/); //throw FileError, X
+void setFileContent(const Zstring& filePath, const std::string& bytes, const IoCallback& notifyUnbufferedIO /*throw X*/); //throw FileError, X
 }
 
 #endif //FILE_IO_H_89578342758342572345
diff --git a/zen/file_traverser.cpp b/zen/file_traverser.cpp
index aa48cb85..f1b5519b 100644
--- a/zen/file_traverser.cpp
+++ b/zen/file_traverser.cpp
@@ -31,7 +31,7 @@ void zen::traverseFolder(const Zstring& dirPath,
         for (;;)
         {
             errno = 0;
-            const struct ::dirent* dirEntry = ::readdir(folder); //don't use readdir_r(), see comment in native.cpp
+            const dirent* dirEntry = ::readdir(folder); //don't use readdir_r(), see comment in native.cpp
             if (!dirEntry)
             {
                 if (errno == 0) //errno left unchanged => no more items
@@ -54,7 +54,7 @@ void zen::traverseFolder(const Zstring& dirPath,
 
             const Zstring& itemPath = appendSeparator(dirPath) + itemName;
 
-            struct ::stat statData = {};
+            struct stat statData = {};
             try
             {
                 if (::lstat(itemPath.c_str(), &statData) != 0) //lstat() does not resolve symlinks
@@ -75,12 +75,12 @@ void zen::traverseFolder(const Zstring& dirPath,
             else if (S_ISDIR(statData.st_mode)) //a directory
             {
                 if (onFolder)
-                    onFolder({ itemName, itemPath });
+                    onFolder({itemName, itemPath});
             }
             else //a file or named pipe, etc.
             {
                 if (onFile)
-                    onFile({ itemName, itemPath, makeUnsigned(statData.st_size), statData.st_mtime });
+                    onFile({itemName, itemPath, makeUnsigned(statData.st_size), statData.st_mtime});
             }
 
             /* It may be a good idea to not check "S_ISREG(statData.st_mode)" explicitly and to not issue an error message on other types to support these scenarios:
diff --git a/zen/format_unit.cpp b/zen/format_unit.cpp
index 28943de7..b2d1b59a 100644
--- a/zen/format_unit.cpp
+++ b/zen/format_unit.cpp
@@ -128,9 +128,9 @@ std::wstring roundToBlock(double timeInHigh,
 
 std::wstring zen::formatRemainingTime(double timeInSec)
 {
-    const int steps10[] = { 1, 2, 5, 10 };
-    const int steps24[] = { 1, 2, 3, 4, 6, 8, 12, 24 };
-    const int steps60[] = { 1, 2, 5, 10, 15, 20, 30, 60 };
+    const int steps10[] = {1, 2, 5, 10};
+    const int steps24[] = {1, 2, 3, 4, 6, 8, 12, 24};
+    const int steps60[] = {1, 2, 5, 10, 15, 20, 30, 60};
 
     //determine preferred unit
     double timeInUnit = timeInSec;
@@ -178,7 +178,7 @@ std::wstring zen::formatUtcToLocalTime(time_t utcTime)
 {
     auto errorMsg = [&] { return _("Error") + L" (time_t: " + numberTo<std::wstring>(utcTime) + L')'; };
 
-    TimeComp loc = getLocalTime(utcTime);
+    const TimeComp& loc = getLocalTime(utcTime);
 
     std::wstring dateString = utfTo<std::wstring>(formatTime(Zstr("%x  %X"), loc));
     return !dateString.empty() ? dateString : errorMsg();
diff --git a/zen/http.cpp b/zen/http.cpp
index 5d389719..f8fb24a3 100644
--- a/zen/http.cpp
+++ b/zen/http.cpp
@@ -23,7 +23,7 @@ public:
          bool disableGetCache /*not relevant for POST (= never cached)*/,
          const Zstring& userAgent,
          const Zstring* caCertFilePath /*optional: enable certificate validation*/,
-         const IOCallback& notifyUnbufferedIO) : //throw SysError, X
+         const IoCallback& notifyUnbufferedIO) : //throw SysError, X
         notifyUnbufferedIO_(notifyUnbufferedIO)
     {
         ZEN_ON_SCOPE_FAIL(cleanup(); /*destructor call would lead to member double clean-up!!!*/);
@@ -214,7 +214,7 @@ private:
 
     int64_t contentRemaining_ = -1; //consider "Content-Length" if available
 
-    const IOCallback notifyUnbufferedIO_; //throw X
+    const IoCallback notifyUnbufferedIO_; //throw X
 
     std::vector<std::byte> memBuf_ = std::vector<std::byte>(getBlockSize());
     size_t bufPos_    = 0; //buffered I/O; see file_io.cpp
@@ -240,7 +240,7 @@ std::unique_ptr<HttpInputStream::Impl> sendHttpRequestImpl(const Zstring& url,
                                                            const std::string& contentType, //required for POST
                                                            const Zstring& userAgent,
                                                            const Zstring* caCertFilePath /*optional: enable certificate validation*/,
-                                                           const IOCallback& notifyUnbufferedIO) //throw SysError, X
+                                                           const IoCallback& notifyUnbufferedIO) //throw SysError, X
 {
     Zstring urlRed = url;
     //"A user agent should not automatically redirect a request more than five times, since such redirections usually indicate an infinite loop."
@@ -339,14 +339,14 @@ std::vector<std::pair<std::string, std::string>> zen::xWwwFormUrlDecode(const st
 }
 
 
-HttpInputStream zen::sendHttpGet(const Zstring& url, const Zstring& userAgent, const Zstring* caCertFilePath, const IOCallback& notifyUnbufferedIO) //throw SysError, X
+HttpInputStream zen::sendHttpGet(const Zstring& url, const Zstring& userAgent, const Zstring* caCertFilePath, const IoCallback& notifyUnbufferedIO) //throw SysError, X
 {
     return sendHttpRequestImpl(url, nullptr /*postBuf*/, "" /*contentType*/, userAgent, caCertFilePath, notifyUnbufferedIO); //throw SysError, X, X
 }
 
 
 HttpInputStream zen::sendHttpPost(const Zstring& url, const std::vector<std::pair<std::string, std::string>>& postParams,
-                                  const Zstring& userAgent, const Zstring* caCertFilePath, const IOCallback& notifyUnbufferedIO) //throw SysError, X
+                                  const Zstring& userAgent, const Zstring* caCertFilePath, const IoCallback& notifyUnbufferedIO) //throw SysError, X
 {
     return sendHttpPost(url, xWwwFormUrlEncode(postParams), "application/x-www-form-urlencoded", userAgent, caCertFilePath, notifyUnbufferedIO); //throw SysError, X
 }
@@ -354,7 +354,7 @@ HttpInputStream zen::sendHttpPost(const Zstring& url, const std::vector<std::pai
 
 
 HttpInputStream zen::sendHttpPost(const Zstring& url, const std::string& postBuf, const std::string& contentType,
-                                  const Zstring& userAgent, const Zstring* caCertFilePath, const IOCallback& notifyUnbufferedIO) //throw SysError, X
+                                  const Zstring& userAgent, const Zstring* caCertFilePath, const IoCallback& notifyUnbufferedIO) //throw SysError, X
 {
     return sendHttpRequestImpl(url, &postBuf, contentType, userAgent, caCertFilePath, notifyUnbufferedIO); //throw SysError, X
 }
diff --git a/zen/http.h b/zen/http.h
index 6cb107bf..07c3f28c 100644
--- a/zen/http.h
+++ b/zen/http.h
@@ -39,19 +39,19 @@ private:
 HttpInputStream sendHttpGet(const Zstring& url,
                             const Zstring& userAgent,
                             const Zstring* caCertFilePath /*optional: enable certificate validation*/,
-                            const IOCallback& notifyUnbufferedIO /*throw X*/); //throw SysError, X
+                            const IoCallback& notifyUnbufferedIO /*throw X*/); //throw SysError, X
 
 HttpInputStream sendHttpPost(const Zstring& url,
                              const std::vector<std::pair<std::string, std::string>>& postParams,
                              const Zstring& userAgent,
                              const Zstring* caCertFilePath /*optional: enable certificate validation*/,
-                             const IOCallback& notifyUnbufferedIO /*throw X*/); //throw SysError, X
+                             const IoCallback& notifyUnbufferedIO /*throw X*/); //throw SysError, X
 
 HttpInputStream sendHttpPost(const Zstring& url,
                              const std::string& postBuf, const std::string& contentType,
                              const Zstring& userAgent,
                              const Zstring* caCertFilePath /*optional: enable certificate validation*/,
-                             const IOCallback& notifyUnbufferedIO /*throw X*/); //throw SysError, X
+                             const IoCallback& notifyUnbufferedIO /*throw X*/); //throw SysError, X
 
 bool internetIsAlive(); //noexcept
 std::wstring formatHttpError(int httpStatus);
diff --git a/zen/json.h b/zen/json.h
index a3740664..f6458d6a 100644
--- a/zen/json.h
+++ b/zen/json.h
@@ -372,7 +372,7 @@ public:
                 if (*it == '"')
                 {
                     Token tk(Token::Type::string);
-                    tk.primVal = jsonUnescape({ pos_, it });
+                    tk.primVal = jsonUnescape({pos_, it});
                     pos_ = ++it;
                     return tk;
                 }
diff --git a/zen/open_ssl.cpp b/zen/open_ssl.cpp
index ea77db43..7c94263a 100644
--- a/zen/open_ssl.cpp
+++ b/zen/open_ssl.cpp
@@ -79,7 +79,7 @@ std::wstring formatLastOpenSSLError(const char* functionName)
 
 std::shared_ptr<EVP_PKEY> generateRsaKeyPair(int bits) //throw SysError
 {
-    EVP_PKEY_CTX* keyCtx = ::EVP_PKEY_CTX_new_id(EVP_PKEY_RSA, //int id,
+    EVP_PKEY_CTX* keyCtx = ::EVP_PKEY_CTX_new_id(EVP_PKEY_RSA, //int id
                                                  nullptr);     //ENGINE* e
     if (!keyCtx)
         throw SysError(formatLastOpenSSLError("EVP_PKEY_CTX_new_id"));
@@ -110,9 +110,9 @@ std::shared_ptr<EVP_PKEY> streamToEvpKey(const std::string& keyStream, BioToEvpF
         throw SysError(formatLastOpenSSLError("BIO_new_mem_buf"));
     ZEN_ON_SCOPE_EXIT(::BIO_free_all(bio));
 
-    if (EVP_PKEY* evp = bioToEvp(bio,      //BIO* bp,
-                                 nullptr,  //EVP_PKEY** x,
-                                 nullptr,  //pem_password_cb* cb,
+    if (EVP_PKEY* evp = bioToEvp(bio,      //BIO* bp
+                                 nullptr,  //EVP_PKEY** x
+                                 nullptr,  //pem_password_cb* cb
                                  nullptr)) //void* u
         return std::shared_ptr<EVP_PKEY>(evp, ::EVP_PKEY_free);
     throw SysError(formatLastOpenSSLError(functionName));
@@ -128,9 +128,9 @@ std::shared_ptr<EVP_PKEY> streamToEvpKey(const std::string& keyStream, BioToRsaF
         throw SysError(formatLastOpenSSLError("BIO_new_mem_buf"));
     ZEN_ON_SCOPE_EXIT(::BIO_free_all(bio));
 
-    RSA* rsa = bioToRsa(bio,      //BIO* bp,
-                        nullptr,  //RSA** x,
-                        nullptr,  //pem_password_cb* cb,
+    RSA* rsa = bioToRsa(bio,      //BIO* bp
+                        nullptr,  //RSA** x
+                        nullptr,  //pem_password_cb* cb
                         nullptr); //void* u
     if (!rsa)
         throw SysError(formatLastOpenSSLError(functionName));
@@ -168,9 +168,9 @@ std::shared_ptr<EVP_PKEY> streamToKey(const std::string& keyStream, RsaStreamTyp
     }
 
     auto tmp = reinterpret_cast<const unsigned char*>(keyStream.c_str());
-    EVP_PKEY* evp = (publicKey ? ::d2i_PublicKey : ::d2i_PrivateKey)(EVP_PKEY_RSA,                         //int type,
-                                                                     nullptr,                              //EVP_PKEY** a,
-                                                                     &tmp, /*changes tmp pointer itself!*/ //const unsigned char** pp,
+    EVP_PKEY* evp = (publicKey ? ::d2i_PublicKey : ::d2i_PrivateKey)(EVP_PKEY_RSA,                         //int type
+                                                                     nullptr,                              //EVP_PKEY** a
+                                                                     &tmp, /*changes tmp pointer itself!*/ //const unsigned char** pp
                                                                      static_cast<long>(keyStream.size())); //long length
     if (!evp)
         throw SysError(formatLastOpenSSLError(publicKey ? "d2i_PublicKey" : "d2i_PrivateKey"));
@@ -238,23 +238,23 @@ std::string evpKeyToStream(EVP_PKEY* evp, RsaToBioFunc rsaToBio, const char* fun
 //fix OpenSSL API inconsistencies:
 int PEM_write_bio_PrivateKey2(BIO* bio, EVP_PKEY* key)
 {
-    return ::PEM_write_bio_PrivateKey(bio,      //BIO* bp,
-                                      key,      //EVP_PKEY* x,
-                                      nullptr,  //const EVP_CIPHER* enc,
-                                      nullptr,  //unsigned char* kstr,
-                                      0,        //int klen,
-                                      nullptr,  //pem_password_cb* cb,
+    return ::PEM_write_bio_PrivateKey(bio,      //BIO* bp
+                                      key,      //EVP_PKEY* x
+                                      nullptr,  //const EVP_CIPHER* enc
+                                      nullptr,  //unsigned char* kstr
+                                      0,        //int klen
+                                      nullptr,  //pem_password_cb* cb
                                       nullptr); //void* u
 }
 
 int PEM_write_bio_RSAPrivateKey2(BIO* bio, RSA* rsa)
 {
-    return ::PEM_write_bio_RSAPrivateKey(bio,      //BIO* bp,
-                                         rsa,      //RSA* x,
-                                         nullptr,  //const EVP_CIPHER* enc,
-                                         nullptr,  //unsigned char* kstr,
-                                         0,        //int klen,
-                                         nullptr,  //pem_password_cb* cb,
+    return ::PEM_write_bio_RSAPrivateKey(bio,      //BIO* bp
+                                         rsa,      //RSA* x
+                                         nullptr,  //const EVP_CIPHER* enc
+                                         nullptr,  //unsigned char* kstr
+                                         0,        //int klen
+                                         nullptr,  //pem_password_cb* cb
                                          nullptr); //void* u
 }
 
@@ -286,7 +286,7 @@ std::string keyToStream(EVP_PKEY* evp, RsaStreamType streamType, bool publicKey)
         throw SysError(formatLastOpenSSLError(publicKey ? "i2d_PublicKey" : "i2d_PrivateKey"));
     ZEN_ON_SCOPE_EXIT(::OPENSSL_free(buf)); //memory is only allocated for bufSize > 0
 
-    return { reinterpret_cast<const char*>(buf), static_cast<size_t>(bufSize) };
+    return {reinterpret_cast<const char*>(buf), static_cast<size_t>(bufSize)};
 }
 
 //================================================================================
@@ -299,29 +299,29 @@ std::string createSignature(const std::string& message, EVP_PKEY* privateKey) //
         throw SysError(formatSystemError("EVP_MD_CTX_create", L"", L"Unexpected failure.")); //no more error details
     ZEN_ON_SCOPE_EXIT(::EVP_MD_CTX_destroy(mdctx));
 
-    if (::EVP_DigestSignInit(mdctx,            //EVP_MD_CTX* ctx,
-                             nullptr,          //EVP_PKEY_CTX** pctx,
-                             EVP_sha256(),     //const EVP_MD* type,
-                             nullptr,          //ENGINE* e,
+    if (::EVP_DigestSignInit(mdctx,            //EVP_MD_CTX* ctx
+                             nullptr,          //EVP_PKEY_CTX** pctx
+                             EVP_sha256(),     //const EVP_MD* type
+                             nullptr,          //ENGINE* e
                              privateKey) != 1) //EVP_PKEY* pkey
         throw SysError(formatLastOpenSSLError("EVP_DigestSignInit"));
 
-    if (::EVP_DigestSignUpdate(mdctx,                //EVP_MD_CTX* ctx,
-                               message.c_str(),      //const void* d,
+    if (::EVP_DigestSignUpdate(mdctx,                //EVP_MD_CTX* ctx
+                               message.c_str(),      //const void* d
                                message.size()) != 1) //size_t cnt
         throw SysError(formatLastOpenSSLError("EVP_DigestSignUpdate"));
 
     size_t sigLenMax = 0; //"first call to EVP_DigestSignFinal returns the maximum buffer size required"
-    if (::EVP_DigestSignFinal(mdctx,            //EVP_MD_CTX* ctx,
-                              nullptr,          //unsigned char* sigret,
+    if (::EVP_DigestSignFinal(mdctx,            //EVP_MD_CTX* ctx
+                              nullptr,          //unsigned char* sigret
                               &sigLenMax) != 1) //size_t* siglen
         throw SysError(formatLastOpenSSLError("EVP_DigestSignFinal"));
 
     std::string signature(sigLenMax, '\0');
     size_t sigLen = sigLenMax;
 
-    if (::EVP_DigestSignFinal(mdctx,                                           //EVP_MD_CTX* ctx,
-                              reinterpret_cast<unsigned char*>(&signature[0]), //unsigned char* sigret,
+    if (::EVP_DigestSignFinal(mdctx,                                           //EVP_MD_CTX* ctx
+                              reinterpret_cast<unsigned char*>(&signature[0]), //unsigned char* sigret
                               &sigLen) != 1)                                   //size_t* siglen
         throw SysError(formatLastOpenSSLError("EVP_DigestSignFinal"));
 
@@ -338,20 +338,20 @@ void verifySignature(const std::string& message, const std::string& signature, E
         throw SysError(formatSystemError("EVP_MD_CTX_create", L"", L"Unexpected failure.")); //no more error details
     ZEN_ON_SCOPE_EXIT(::EVP_MD_CTX_destroy(mdctx));
 
-    if (::EVP_DigestVerifyInit(mdctx,           //EVP_MD_CTX* ctx,
-                               nullptr,         //EVP_PKEY_CTX** pctx,
-                               EVP_sha256(),    //const EVP_MD* type,
-                               nullptr,         //ENGINE* e,
+    if (::EVP_DigestVerifyInit(mdctx,           //EVP_MD_CTX* ctx
+                               nullptr,         //EVP_PKEY_CTX** pctx
+                               EVP_sha256(),    //const EVP_MD* type
+                               nullptr,         //ENGINE* e
                                publicKey) != 1) //EVP_PKEY* pkey
         throw SysError(formatLastOpenSSLError("EVP_DigestVerifyInit"));
 
-    if (::EVP_DigestVerifyUpdate(mdctx,                //EVP_MD_CTX* ctx,
-                                 message.c_str(),      //const void* d,
+    if (::EVP_DigestVerifyUpdate(mdctx,                //EVP_MD_CTX* ctx
+                                 message.c_str(),      //const void* d
                                  message.size()) != 1) //size_t cnt
         throw SysError(formatLastOpenSSLError("EVP_DigestVerifyUpdate"));
 
-    if (::EVP_DigestVerifyFinal(mdctx,                                                     //EVP_MD_CTX* ctx,
-                                reinterpret_cast<const unsigned char*>(signature.c_str()), //const unsigned char* sig,
+    if (::EVP_DigestVerifyFinal(mdctx,                                                     //EVP_MD_CTX* ctx
+                                reinterpret_cast<const unsigned char*>(signature.c_str()), //const unsigned char* sig
                                 signature.size()) != 1)                                    //size_t siglen
         throw SysError(formatLastOpenSSLError("EVP_DigestVerifyFinal"));
 }
@@ -735,10 +735,10 @@ std::string zen::convertPuttyKeyToPkix(const std::string& keyStream, const std::
             throw SysError(formatSystemError("EVP_CIPHER_CTX_new", L"", L"Unexpected failure.")); //no more error details
         ZEN_ON_SCOPE_EXIT(::EVP_CIPHER_CTX_free(cipCtx));
 
-        if (::EVP_DecryptInit_ex(cipCtx,            //EVP_CIPHER_CTX* ctx,
-                                 EVP_aes_256_cbc(), //const EVP_CIPHER* type,
-                                 nullptr,           //ENGINE* impl,
-                                 key,               //const unsigned char* key, => implied length of 256 bit!
+        if (::EVP_DecryptInit_ex(cipCtx,            //EVP_CIPHER_CTX* ctx
+                                 EVP_aes_256_cbc(), //const EVP_CIPHER* type
+                                 nullptr,           //ENGINE* impl
+                                 key,               //const unsigned char* key => implied length of 256 bit!
                                  nullptr) != 1)     //const unsigned char* iv
             throw SysError(formatLastOpenSSLError("EVP_DecryptInit_ex"));
 
@@ -749,16 +749,16 @@ std::string zen::convertPuttyKeyToPkix(const std::string& keyStream, const std::
         //"EVP_DecryptUpdate() should have room for (inl + cipher_block_size) bytes"
 
         int decLen1 = 0;
-        if (::EVP_DecryptUpdate(cipCtx,                                                         //EVP_CIPHER_CTX* ctx,
-                                reinterpret_cast<unsigned char*>(&privateBlob[0]),              //unsigned char* out,
-                                &decLen1,                                                       //int* outl,
-                                reinterpret_cast<const unsigned char*>(privateBlobEnc.c_str()), //const unsigned char* in,
+        if (::EVP_DecryptUpdate(cipCtx,                                                         //EVP_CIPHER_CTX* ctx
+                                reinterpret_cast<unsigned char*>(&privateBlob[0]),              //unsigned char* out
+                                &decLen1,                                                       //int* outl
+                                reinterpret_cast<const unsigned char*>(privateBlobEnc.c_str()), //const unsigned char* in
                                 static_cast<int>(privateBlobEnc.size())) != 1)                  //int inl
             throw SysError(formatLastOpenSSLError("EVP_DecryptUpdate"));
 
         int decLen2 = 0;
-        if (::EVP_DecryptFinal_ex(cipCtx,                                                  //EVP_CIPHER_CTX* ctx,
-                                  reinterpret_cast<unsigned char*>(&privateBlob[decLen1]), //unsigned char* outm,
+        if (::EVP_DecryptFinal_ex(cipCtx,                                                  //EVP_CIPHER_CTX* ctx
+                                  reinterpret_cast<unsigned char*>(&privateBlob[decLen1]), //unsigned char* outm
                                   &decLen2) != 1)                                          //int* outl
             throw SysError(formatLastOpenSSLError("EVP_DecryptFinal_ex"));
 
@@ -777,7 +777,7 @@ std::string zen::convertPuttyKeyToPkix(const std::string& keyStream, const std::
     {
         static_assert(std::endian::native == std::endian::little&& sizeof(n) >= 4);
         const char* numStr = reinterpret_cast<const char*>(&n);
-        return { numStr[3], numStr[2], numStr[1], numStr[0] }; //big endian!
+        return {numStr[3], numStr[2], numStr[1], numStr[0]}; //big endian!
     };
 
     const std::string macData = numToBeString(algorithm    .size()) + algorithm +
@@ -787,13 +787,13 @@ std::string zen::convertPuttyKeyToPkix(const std::string& keyStream, const std::
                                 numToBeString(privateBlob  .size()) + privateBlob;
     char md[EVP_MAX_MD_SIZE] = {};
     unsigned int mdLen = 0;
-    if (!::HMAC(EVP_sha1(),      //const EVP_MD* evp_md,
-                macKey,          //const void* key,
-                sizeof(macKey),  //int key_len,
-                reinterpret_cast<const unsigned char*>(macData.c_str()), //const unsigned char* d,
-                static_cast<int>(macData.size()),     //int n,
-                reinterpret_cast<unsigned char*>(md), //unsigned char* md,
-                &mdLen))         //unsigned int* md_len
+    if (!::HMAC(EVP_sha1(),                           //const EVP_MD* evp_md
+                macKey,                               //const void* key
+                sizeof(macKey),                       //int key_len
+                reinterpret_cast<const unsigned char*>(macData.c_str()), //const unsigned char* d
+                static_cast<int>(macData.size()),     //int n
+                reinterpret_cast<unsigned char*>(md), //unsigned char* md
+                &mdLen))                              //unsigned int* md_len
         throw SysError(formatSystemError("HMAC", L"", L"Unexpected failure.")); //no more error details
 
     const bool hashValid = mac == std::string_view(md, mdLen);
@@ -979,10 +979,10 @@ std::string zen::convertPuttyKeyToPkix(const std::string& keyStream, const std::
             throw SysError(formatLastOpenSSLError("EC_POINT_new"));
         ZEN_ON_SCOPE_EXIT(::EC_POINT_free(ecPoint));
 
-        if (::EC_POINT_oct2point(ecGroup,            //const EC_GROUP* group,
-                                 ecPoint,            //EC_POINT* p,
-                                 reinterpret_cast<const unsigned char*>(&pointStream[0]), //const unsigned char* buf,
-                                 pointStream.size(), //size_t len,
+        if (::EC_POINT_oct2point(ecGroup,            //const EC_GROUP* group
+                                 ecPoint,            //EC_POINT* p
+                                 reinterpret_cast<const unsigned char*>(&pointStream[0]), //const unsigned char* buf
+                                 pointStream.size(), //size_t len
                                  nullptr) != 1)      //BN_CTX* ctx
             throw SysError(formatLastOpenSSLError("EC_POINT_oct2point"));
 
@@ -1008,9 +1008,9 @@ std::string zen::convertPuttyKeyToPkix(const std::string& keyStream, const std::
         //const std::string pubStream = extractStringPub(); -> we don't need the public key
         const std::string priStream = extractStringPriv();
 
-        EVP_PKEY* evpPriv = ::EVP_PKEY_new_raw_private_key(EVP_PKEY_ED25519,  //int type,
-                                                           nullptr,           //ENGINE* e,
-                                                           reinterpret_cast<const unsigned char*>(&priStream[0]), //const unsigned char* priv,
+        EVP_PKEY* evpPriv = ::EVP_PKEY_new_raw_private_key(EVP_PKEY_ED25519,  //int type
+                                                           nullptr,           //ENGINE* e
+                                                           reinterpret_cast<const unsigned char*>(&priStream[0]), //const unsigned char* priv
                                                            priStream.size()); //size_t len
         if (!evpPriv)
             throw SysError(formatLastOpenSSLError("EVP_PKEY_new_raw_private_key"));
diff --git a/zen/perf.h b/zen/perf.h
index 6bc328bb..2ebf1955 100644
--- a/zen/perf.h
+++ b/zen/perf.h
@@ -23,21 +23,20 @@
 
     static zen::PerfTimer perfTest(true); //startPaused
     perfTest.resume();
-    ZEN_ON_SCOPE_EXIT(perfTest.pause());
-*/
+    ZEN_ON_SCOPE_EXIT(perfTest.pause());                      */
 
 namespace zen
 {
-//issue with wxStopWatch? https://freefilesync.org/forum/viewtopic.php?t=1426
-// => wxStopWatch implementation uses QueryPerformanceCounter: https://github.com/wxWidgets/wxWidgets/blob/17d72a48ffd4d8ff42eed070ac48ee2de50ceabd/src/common/stopwatch.cpp
-// => whatever the problem was, it's almost certainly not caused by QueryPerformanceCounter():
-//      MSDN: "How often does QPC roll over? Not less than 100 years from the most recent system boot"
-//      https://docs.microsoft.com/en-us/windows/win32/sysinfo/acquiring-high-resolution-time-stamps#general-faq-about-qpc-and-tsc
-//
-// => using the system clock is problematic: https://freefilesync.org/forum/viewtopic.php?t=5280
-//
-//    std::chrono::system_clock wraps ::GetSystemTimePreciseAsFileTime()
-//    std::chrono::steady_clock wraps ::QueryPerformanceCounter()
+/* issue with wxStopWatch? https://freefilesync.org/forum/viewtopic.php?t=1426
+     - wxStopWatch implementation uses QueryPerformanceCounter: https://github.com/wxWidgets/wxWidgets/blob/17d72a48ffd4d8ff42eed070ac48ee2de50ceabd/src/common/stopwatch.cpp
+     - whatever the problem was, it's almost certainly not caused by QueryPerformanceCounter():
+          MSDN: "How often does QPC roll over? Not less than 100 years from the most recent system boot"
+          https://docs.microsoft.com/en-us/windows/win32/sysinfo/acquiring-high-resolution-time-stamps#general-faq-about-qpc-and-tsc
+
+     - using the system clock is problematic: https://freefilesync.org/forum/viewtopic.php?t=5280
+
+       std::chrono::system_clock wraps ::GetSystemTimePreciseAsFileTime()
+       std::chrono::steady_clock wraps ::QueryPerformanceCounter()                       */
 class StopWatch
 {
 public:
diff --git a/zen/process_exec.cpp b/zen/process_exec.cpp
index bbc87c51..b82c2565 100644
--- a/zen/process_exec.cpp
+++ b/zen/process_exec.cpp
@@ -117,7 +117,7 @@ std::pair<int /*exit code*/, std::string> processExecuteImpl(const Zstring& file
             if (::dup(fdLifeSignW) == -1) //O_CLOEXEC does NOT propagate with dup()
                 THROW_LAST_SYS_ERROR("dup(fdLifeSignW)");
 
-            std::vector<const char*> argv{ filePath.c_str() };
+            std::vector<const char*> argv{filePath.c_str()};
             for (const Zstring& arg : arguments)
                 argv.push_back(arg.c_str());
             argv.push_back(nullptr);
@@ -147,6 +147,8 @@ std::pair<int /*exit code*/, std::string> processExecuteImpl(const Zstring& file
         if (flags == -1)
             THROW_LAST_SYS_ERROR("fcntl(F_GETFL)");
 
+        //fcntl() success: Linux: 0
+        //                 macOS: "Value other than -1."
         if (::fcntl(fdLifeSignR, F_SETFL, flags | O_NONBLOCK) == -1)
             THROW_LAST_SYS_ERROR("fcntl(F_SETFL, O_NONBLOCK)");
 
@@ -174,7 +176,7 @@ std::pair<int /*exit code*/, std::string> processExecuteImpl(const Zstring& file
 
             const auto waitTimeMs = std::chrono::duration_cast<std::chrono::milliseconds>(endTime - now).count();
 
-            struct ::timeval tv = {};
+            timeval tv = {};
             tv.tv_sec  = static_cast<long>(waitTimeMs / 1000);
             tv.tv_usec = static_cast<long>(waitTimeMs - tv.tv_sec * 1000) * 1000;
 
@@ -219,7 +221,7 @@ std::pair<int /*exit code*/, std::string> processExecuteImpl(const Zstring& file
         exitCode == 127) //details should have been streamed to STDERR: used by /bin/sh, e.g. failure to execute due to missing .so file
         throw SysError(utfTo<std::wstring>(trimCpy(output)));
 
-    return { exitCode, output };
+    return {exitCode, output};
 }
 }
 
diff --git a/zen/resolve_path.cpp b/zen/resolve_path.cpp
index 76999500..0e714528 100644
--- a/zen/resolve_path.cpp
+++ b/zen/resolve_path.cpp
@@ -5,17 +5,12 @@
 // *****************************************************************************
 
 #include "resolve_path.h"
-//#include <set> //not necessarily included by <map>!
-//#include <map>
 #include "time.h"
 #include "thread.h"
-//#include "utf.h"
-//#include "scope_guard.h"
-//#include "globals.h"
 #include "file_access.h"
 
     #include <stdlib.h> //getenv()
-    #include <unistd.h> //getcwd
+    #include <unistd.h> //getcwd()
 
 using namespace zen;
 
@@ -251,7 +246,7 @@ std::vector<Zstring> zen::getFolderPathAliases(const Zstring& folderPathPhrase)
     tmp.erase(dirPath);
     tmp.erase(Zstring());
 
-    return { tmp.begin(), tmp.end() };
+    return {tmp.begin(), tmp.end()};
 }
 
 
diff --git a/zen/ring_buffer.h b/zen/ring_buffer.h
index 240262fa..ae2377d8 100644
--- a/zen/ring_buffer.h
+++ b/zen/ring_buffer.h
@@ -196,11 +196,11 @@ public:
     using iterator        = Iterator<      RingBuffer,       T>;
     using const_iterator  = Iterator<const RingBuffer, const T>;
 
-    iterator begin() { return { *this, 0     }; }
-    iterator end  () { return { *this, size_ }; }
+    iterator begin() { return {*this, 0    }; }
+    iterator end  () { return {*this, size_}; }
 
-    const_iterator begin() const { return { *this, 0     }; }
-    const_iterator end  () const { return { *this, size_ }; }
+    const_iterator begin() const { return {*this, 0    }; }
+    const_iterator end  () const { return {*this, size_}; }
 
     const_iterator cbegin() const { return begin(); }
     const_iterator cend  () const { return end  (); }
diff --git a/zen/serialize.h b/zen/serialize.h
index 6c57e4ee..f9677630 100644
--- a/zen/serialize.h
+++ b/zen/serialize.h
@@ -35,7 +35,7 @@ struct BufferedInputStream
 Optional: support stream-copying
 --------------------------------
     size_t getBlockSize() const;
-    const IOCallback& notifyUnbufferedIO
+    const IoCallback& notifyUnbufferedIO
 };
 
 --------------------------------
@@ -47,9 +47,9 @@ struct BufferedOutputStream
 
 Optional: support stream-copying
 --------------------------------
-    const IOCallback& notifyUnbufferedIO
+    const IoCallback& notifyUnbufferedIO
 };                                                                           */
-using IOCallback = std::function<void(int64_t bytesDelta)>; //throw X
+using IoCallback = std::function<void(int64_t bytesDelta)>; //throw X
 
 
 //functions based on buffered stream abstraction
@@ -75,7 +75,7 @@ template <         class BufferedInputStream> void readArray    (BufferedInputSt
 
 struct IOCallbackDivider
 {
-    IOCallbackDivider(const IOCallback& notifyUnbufferedIO, int64_t& totalUnbufferedIO) : totalUnbufferedIO_(totalUnbufferedIO), notifyUnbufferedIO_(notifyUnbufferedIO) {}
+    IOCallbackDivider(const IoCallback& notifyUnbufferedIO, int64_t& totalUnbufferedIO) : totalUnbufferedIO_(totalUnbufferedIO), notifyUnbufferedIO_(notifyUnbufferedIO) {}
 
     void operator()(int64_t bytesDelta)
     {
@@ -85,7 +85,7 @@ struct IOCallbackDivider
 
 private:
     int64_t& totalUnbufferedIO_;
-    const IOCallback& notifyUnbufferedIO_;
+    const IoCallback& notifyUnbufferedIO_;
 };
 
 
@@ -206,7 +206,7 @@ void writeArray(BufferedOutputStream& stream, const void* buffer, size_t len)
 template <class N, class BufferedOutputStream> inline
 void writeNumber(BufferedOutputStream& stream, const N& num)
 {
-    static_assert(IsArithmetic<N>::value || std::is_same_v<N, bool> || std::is_enum_v<N>);
+    static_assert(IsArithmeticV<N> || std::is_same_v<N, bool> || std::is_enum_v<N>);
     writeArray(stream, &num, sizeof(N));
 }
 
@@ -234,7 +234,7 @@ void readArray(BufferedInputStream& stream, void* buffer, size_t len) //throw Sy
 template <class N, class BufferedInputStream> inline
 N readNumber(BufferedInputStream& stream) //throw SysErrorUnexpectedEos
 {
-    static_assert(IsArithmetic<N>::value || std::is_same_v<N, bool> || std::is_enum_v<N>);
+    static_assert(IsArithmeticV<N> || std::is_same_v<N, bool> || std::is_enum_v<N>);
     N num{};
     readArray(stream, &num, sizeof(N)); //throw SysErrorUnexpectedEos
     return num;
diff --git a/zen/stl_tools.h b/zen/stl_tools.h
index 495ff8d1..53b95241 100644
--- a/zen/stl_tools.h
+++ b/zen/stl_tools.h
@@ -128,7 +128,7 @@ void removeDuplicates(std::vector<T, Alloc>& v, CompLess less)
 template <class T, class Alloc> inline
 void removeDuplicates(std::vector<T, Alloc>& v)
 {
-    removeDuplicates(v, std::less<T>(), std::equal_to<T>());
+    removeDuplicates(v, std::less(), std::equal_to());
 }
 
 
@@ -233,6 +233,7 @@ class FNV1aHash
 {
 public:
     FNV1aHash() {}
+    explicit FNV1aHash(Num startVal) : hashVal_(startVal) {}
 
     void add(Num n)
     {
@@ -243,8 +244,8 @@ public:
     Num get() const { return hashVal_; }
 
 private:
-    static_assert(IsUnsignedInt<Num>::value);
-    static_assert(sizeof(Num) == 4 || sizeof(Num) == 8); //macOS: size_t is "unsigned long"
+    static_assert(IsUnsignedIntV<Num>);
+    static_assert(sizeof(Num) == 4 || sizeof(Num) == 8);
     static constexpr Num base_  = sizeof(Num) == 4 ? 2166136261U : 14695981039346656037ULL;
     static constexpr Num prime_ = sizeof(Num) == 4 ?   16777619U :        1099511628211ULL;
 
@@ -257,7 +258,7 @@ Num hashArray(ByteIterator first, ByteIterator last)
 {
     using ValType = typename std::iterator_traits<ByteIterator>::value_type;
     static_assert(sizeof(ValType) <= sizeof(Num));
-    static_assert(IsInteger<ValType>::value || std::is_same_v<ValType, char> || std::is_same_v<ValType, wchar_t>);
+    static_assert(IsIntegerV<ValType> || std::is_same_v<ValType, char> || std::is_same_v<ValType, wchar_t>);
 
     FNV1aHash<Num> hash;
     std::for_each(first, last, [&hash](ValType v) { hash.add(v); });
@@ -265,8 +266,7 @@ Num hashArray(ByteIterator first, ByteIterator last)
 }
 
 
-//support for custom string classes in std::unordered_set/map
-struct StringHash
+struct StringHash //support for custom string classes with std::unordered_set/map
 {
     template <class String>
     size_t operator()(const String& str) const
diff --git a/zen/string_tools.h b/zen/string_tools.h
index 883c45b8..8150df05 100644
--- a/zen/string_tools.h
+++ b/zen/string_tools.h
@@ -395,7 +395,7 @@ std::vector<S> split(const S& str, const T& delimiter, SplitOnEmpty soe)
     {
         if (str.empty() && soe == SplitOnEmpty::skip)
             return {};
-        return { str };
+        return {str};
     }
 
     const auto* const delimFirst = strBegin(delimiter);
@@ -800,9 +800,9 @@ template <class S, class Num> inline
 S numberTo(const Num& number)
 {
     using TypeTag = std::integral_constant<impl::NumberType,
-                                           IsSignedInt  <Num>::value ? impl::NumberType::signedInt :
-                                           IsUnsignedInt<Num>::value ? impl::NumberType::unsignedInt :
-                                           IsFloat      <Num>::value ? impl::NumberType::floatingPoint :
+                                           IsSignedIntV  <Num> ? impl::NumberType::signedInt :
+                                           IsUnsignedIntV<Num> ? impl::NumberType::unsignedInt :
+                                           IsFloatV      <Num> ? impl::NumberType::floatingPoint :
                                            impl::NumberType::other>;
 
     return impl::numberTo<S>(number, TypeTag());
@@ -813,9 +813,9 @@ template <class Num, class S> inline
 Num stringTo(const S& str)
 {
     using TypeTag = std::integral_constant<impl::NumberType,
-                                           IsSignedInt  <Num>::value ? impl::NumberType::signedInt :
-                                           IsUnsignedInt<Num>::value ? impl::NumberType::unsignedInt :
-                                           IsFloat      <Num>::value ? impl::NumberType::floatingPoint :
+                                           IsSignedIntV  <Num> ? impl::NumberType::signedInt :
+                                           IsUnsignedIntV<Num> ? impl::NumberType::unsignedInt :
+                                           IsFloatV      <Num> ? impl::NumberType::floatingPoint :
                                            impl::NumberType::other>;
 
     return impl::stringTo<Num>(str, TypeTag());
@@ -836,7 +836,7 @@ std::pair<char, char> hexify(unsigned char c, bool upperCase)
         else
             return static_cast<char>('a' + (num - 10));
     };
-    return { hexifyDigit(c / 16), hexifyDigit(c % 16) };
+    return {hexifyDigit(c / 16), hexifyDigit(c % 16)};
 }
 
 
diff --git a/zen/string_traits.h b/zen/string_traits.h
index d9ce589c..ca40f7d6 100644
--- a/zen/string_traits.h
+++ b/zen/string_traits.h
@@ -120,19 +120,12 @@ public:
 };
 }
 
-template <class T>
-struct IsStringLike : std::bool_constant<impl::StringTraits<T>::isStringLike> {};
 
-template <class T>
-struct GetCharType { using Type = typename impl::StringTraits<T>::CharType; };
-
-
-//template alias helpers:
 template<class T>
-constexpr bool IsStringLikeV = IsStringLike<T>::value;
+constexpr bool IsStringLikeV = impl::StringTraits<T>::isStringLike;
 
 template<class T>
-using GetCharTypeT = typename GetCharType<T>::Type;
+using GetCharTypeT = typename impl::StringTraits<T>::CharType;
 
 
 namespace impl
diff --git a/zen/symlink_target.h b/zen/symlink_target.h
index 42010fd2..32b1211d 100644
--- a/zen/symlink_target.h
+++ b/zen/symlink_target.h
@@ -70,11 +70,11 @@ Zstring getResolvedSymlinkPath_impl(const Zstring& linkPath) //throw FileError
 namespace zen
 {
 inline
-SymlinkRawContent getSymlinkRawContent(const Zstring& linkPath) { return getSymlinkRawContent_impl(linkPath); }
+SymlinkRawContent getSymlinkRawContent(const Zstring& linkPath) { return getSymlinkRawContent_impl(linkPath); } //throw FileError
 
 
 inline
-Zstring getSymlinkResolvedPath(const Zstring& linkPath) { return getResolvedSymlinkPath_impl(linkPath); }
+Zstring getSymlinkResolvedPath(const Zstring& linkPath) { return getResolvedSymlinkPath_impl(linkPath); } //throw FileError
 
 }
 
diff --git a/zen/sys_info.cpp b/zen/sys_info.cpp
index f6045f7e..1a0d18f5 100644
--- a/zen/sys_info.cpp
+++ b/zen/sys_info.cpp
@@ -25,17 +25,14 @@ using namespace zen;
 
 std::wstring zen::getUserName() //throw FileError
 {
-    const uid_t userIdNo = ::getuid(); //"real user ID"; never fails
-
-    std::vector<char> buffer(std::max<long>(10000, ::sysconf(_SC_GETPW_R_SIZE_MAX))); //::sysconf may return long(-1)
-    struct passwd buffer2 = {};
-    struct passwd* pwsEntry = nullptr;
-    if (::getpwuid_r(userIdNo, &buffer2, &buffer[0], buffer.size(), &pwsEntry) != 0) //getlogin() is deprecated and not working on Ubuntu at all!!!
-        THROW_LAST_FILE_ERROR(_("Cannot get process information."), "getpwuid_r");
-    if (!pwsEntry)
-        throw FileError(_("Cannot get process information."), L"no login found"); //should not happen?
-
-    return utfTo<std::wstring>(pwsEntry->pw_name);
+    //https://linux.die.net/man/3/getlogin
+    //https://developer.apple.com/library/archive/documentation/System/Conceptual/ManPages_iPhoneOS/man2/getlogin.2.html
+    const char* loginUser = ::getlogin();
+    if (!loginUser)
+        THROW_LAST_FILE_ERROR(_("Cannot get process information."), "getlogin");
+    //getlogin() is smarter than simply evaluating $LOGNAME! even in contexts without
+    //$LOGNAME, e.g. "sudo su" on Ubuntu, it returns the correct non-root user!
+    return utfTo<std::wstring>(loginUser);
 }
 
 
@@ -64,7 +61,7 @@ ComputerModel zen::getComputerModel() //throw FileError
         cm.vendor = tryGetInfo("/sys/devices/virtual/dmi/id/sys_vendor");   //
 
         //clean up:
-        cm.model  = beforeFirst(cm.model, L'\u00ff', IfNotFoundReturn::all);  //fix broken BIOS entries:
+        cm.model  = beforeFirst(cm.model,  L'\u00ff', IfNotFoundReturn::all); //fix broken BIOS entries:
         cm.vendor = beforeFirst(cm.vendor, L'\u00ff', IfNotFoundReturn::all); //0xff can be considered 0
 
         for (const char* dummyModel :
@@ -119,21 +116,25 @@ Zstring zen::getRealProcessPath() //throw FileError
 }
 
 
+Zstring zen::getUserDataPath() //throw FileError
+{
+    if (::getuid() != 0) //nofail; root(0) => consider as request for elevation, NOT impersonation
+        if (const char* xdgCfgPath = ::getenv("XDG_CONFIG_HOME"); //no extended error reporting
+            xdgCfgPath && xdgCfgPath[0] != 0)
+            return xdgCfgPath;
+
+    return Zstring("/home/") + utfTo<Zstring>(getUserName()) + "/.config"; //throw FileError
+}
+
+
 Zstring zen::getUserDownloadsPath() //throw FileError
 {
     try
     {
-        Zstring cmdLine;
-        if (getuid() == 0) //nofail; root(0) => consider as request for elevation, NOT impersonation
-        {
-            const char* loginUser = getlogin(); //https://linux.die.net/man/3/getlogin
-            if (!loginUser)
-                THROW_LAST_SYS_ERROR("getlogin");
-
-            cmdLine = Zstring("sudo -u ") + loginUser + " xdg-user-dir DOWNLOAD"; //sudo better be installed :>
-        }
-        else
-            cmdLine = "xdg-user-dir DOWNLOAD";
+        const Zstring cmdLine = ::getuid() == 0 ? //nofail; root(0) => consider as request for elevation, NOT impersonation
+                                //sudo better be installed :>
+                                "sudo -u " + utfTo<Zstring>(getUserName()) + " xdg-user-dir DOWNLOAD" : //throw FileError
+                                "xdg-user-dir DOWNLOAD";
 
         const auto& [exitCode, output] = consoleExecute(cmdLine, std::nullopt /*timeoutMs*/); //throw SysError
         if (exitCode != 0)
@@ -145,4 +146,3 @@ Zstring zen::getUserDownloadsPath() //throw FileError
     }
     catch (const SysError& e) { throw FileError(_("Cannot get process information."), e.toString()); }
 }
-
diff --git a/zen/sys_info.h b/zen/sys_info.h
index 1b046fb6..4f83a9a3 100644
--- a/zen/sys_info.h
+++ b/zen/sys_info.h
@@ -31,6 +31,7 @@ std::wstring getOsDescription(); //throw FileError
 Zstring getRealProcessPath(); //throw FileError
 
 Zstring getUserDownloadsPath(); //throw FileError
+Zstring getUserDataPath(); //throw FileError
 
 }
 
diff --git a/zen/thread.cpp b/zen/thread.cpp
index 89fa0233..e14afac7 100644
--- a/zen/thread.cpp
+++ b/zen/thread.cpp
@@ -28,7 +28,7 @@ const std::thread::id globalMainThreadId = std::this_thread::get_id();
 
 bool zen::runningOnMainThread()
 {
-    if (globalMainThreadId == std::thread::id()) //called during static initialization!
+    if (globalMainThreadId == std::thread::id()) //if called during static initialization!
         return true;
 
     return std::this_thread::get_id() == globalMainThreadId;
diff --git a/zen/thread.h b/zen/thread.h
index 1bea95ea..136c7a5c 100644
--- a/zen/thread.h
+++ b/zen/thread.h
@@ -173,18 +173,18 @@ public:
     void run(Function&& wi /*should throw ThreadStopRequest when needed*/, bool insertFront = false)
     {
         {
-            std::lock_guard dummy(workLoad_->lock);
+            std::lock_guard dummy(workLoad_.ref().lock);
 
             if (insertFront)
-                workLoad_->tasks.push_front(std::move(wi));
+                workLoad_.ref().tasks.push_front(std::move(wi));
             else
-                workLoad_->tasks.push_back(std::move(wi));
-            const size_t tasksPending = ++(workLoad_->tasksPending);
+                workLoad_.ref().tasks.push_back(std::move(wi));
+            const size_t tasksPending = ++(workLoad_.ref().tasksPending);
 
             if (worker_.size() < std::min(tasksPending, threadCountMax_))
                 addWorkerThread();
         }
-        workLoad_->conditionNewTask.notify_all();
+        workLoad_.ref().conditionNewTask.notify_all();
     }
 
     //context of controlling thread, blocking:
@@ -203,12 +203,12 @@ public:
     //non-blocking wait()-alternative: context of controlling thread:
     void notifyWhenDone(const std::function<void()>& onCompletion /*noexcept! runs on worker thread!*/)
     {
-        std::lock_guard dummy(workLoad_->lock);
+        std::lock_guard dummy(workLoad_.ref().lock);
 
-        if (workLoad_->tasksPending == 0)
+        if (workLoad_.ref().tasksPending == 0)
             onCompletion();
         else
-            workLoad_->onCompletionCallbacks.push_back(onCompletion);
+            workLoad_.ref().onCompletionCallbacks.push_back(onCompletion);
     }
 
     //context of controlling thread:
@@ -222,27 +222,28 @@ private:
     {
         Zstring threadName = groupName_ + Zstr('[') + numberTo<Zstring>(worker_.size() + 1) + Zstr('/') + numberTo<Zstring>(threadCountMax_) + Zstr(']');
 
-        worker_.emplace_back([wl = workLoad_, threadName = std::move(threadName)] //don't capture "this"! consider detach() and move operations
+        worker_.emplace_back([workLoad_ /*clang bug*/= workLoad_ /*share ownership!*/, threadName = std::move(threadName)]() mutable //don't capture "this"! consider detach() and move operations
         {
             setCurrentThreadName(threadName);
+            WorkLoad& workLoad = workLoad_.ref();
 
-            std::unique_lock dummy(wl->lock);
+            std::unique_lock dummy(workLoad.lock);
             for (;;)
             {
-                interruptibleWait(wl->conditionNewTask, dummy, [&tasks = wl->tasks] { return !tasks.empty(); }); //throw ThreadStopRequest
+                interruptibleWait(workLoad.conditionNewTask, dummy, [&tasks = workLoad.tasks] { return !tasks.empty(); }); //throw ThreadStopRequest
 
-                Function task = std::move(wl->tasks.    front()); //noexcept thanks to move
-                /**/                      wl->tasks.pop_front();  //
+                Function task = std::move(workLoad.tasks.    front()); //noexcept thanks to move
+                /**/                      workLoad.tasks.pop_front();  //
 
                 dummy.unlock();
                 task(); //throw ThreadStopRequest?
                 dummy.lock();
 
-                if (--(wl->tasksPending) == 0)
-                    if (!wl->onCompletionCallbacks.empty())
+                if (--(workLoad.tasksPending) == 0)
+                    if (!workLoad.onCompletionCallbacks.empty())
                     {
                         std::vector<std::function<void()>> callbacks;
-                        callbacks.swap(wl->onCompletionCallbacks);
+                        callbacks.swap(workLoad.onCompletionCallbacks);
 
                         dummy.unlock();
                         for (const auto& cb : callbacks)
@@ -263,7 +264,7 @@ private:
     };
 
     std::vector<InterruptibleThread> worker_;
-    std::shared_ptr<WorkLoad> workLoad_ = std::make_shared<WorkLoad>();
+    SharedRef<WorkLoad> workLoad_ = makeSharedRef<WorkLoad>();
     bool detach_ = false;
     size_t threadCountMax_;
     Zstring groupName_;
@@ -446,7 +447,7 @@ private:
         activeCondition_ = cv;
     }
 
-    std::atomic<bool> stopRequested_{ false }; //std:atomic is uninitialized by default!!!
+    std::atomic<bool> stopRequested_{false}; //std:atomic is uninitialized by default!!!
     //"The default constructor is trivial: no initialization takes place other than zero initialization of static and thread-local objects."
 
     std::condition_variable* activeCondition_ = nullptr;
diff --git a/zen/time.h b/zen/time.h
index aaf36983..903b2e87 100644
--- a/zen/time.h
+++ b/zen/time.h
@@ -271,7 +271,7 @@ TimeComp parseTime(const String& format, const String2& str)
                     if (strLast - itStr < 3)
                         return TimeComp();
 
-                    const char* months[] = { "jan", "feb", "mar", "apr", "may", "jun", "jul", "aug", "sep", "oct", "nov", "dec" };
+                    const char* months[] = {"jan", "feb", "mar", "apr", "may", "jun", "jul", "aug", "sep", "oct", "nov", "dec"};
                     auto itMonth = std::find_if(std::begin(months), std::end(months), [&](const char* month)
                     {
                         return equalAsciiNoCase(makeStringView(itStr, 3), month);
diff --git a/zen/type_traits.h b/zen/type_traits.h
index 03fbd768..a4194c05 100644
--- a/zen/type_traits.h
+++ b/zen/type_traits.h
@@ -20,6 +20,7 @@ struct GetFirstOf
 };
 template<class... T> using GetFirstOfT = typename GetFirstOf<T...>::Type;
 
+
 template <class F>
 class FunctionReturnType
 {
@@ -48,40 +49,40 @@ template<class T> inline auto makeSigned  (T t) { return static_cast<std::make_s
 template<class T> inline auto makeUnsigned(T t) { return static_cast<std::make_unsigned_t<T>>(t); }
 
 //################# Built-in Types  ########################
-//Example: "IsSignedInt<int>::value" evaluates to "true"
-
 //unfortunate standardized nonsense: std::is_integral<> includes bool, char, wchar_t! => roll our own:
-template <class T> struct IsUnsignedInt;
-template <class T> struct IsSignedInt;
-
-template <class T> using IsFloat      = std::is_floating_point<T>;
-template <class T> using IsInteger    = std::bool_constant<IsUnsignedInt<T>::value || IsSignedInt<T>::value>;
-template <class T> using IsArithmetic = std::bool_constant<IsInteger    <T>::value || IsFloat    <T>::value>;
-
-//remaining non-arithmetic types: bool, char, wchar_t
-
-
-//optional: specialize new types like:
-//template <> struct IsUnsignedInt<UInt64> : std::true_type {};
+template<class T> constexpr bool IsUnsignedIntV = std::is_same_v<std::remove_cv_t<T>, unsigned char>      ||
+                                                  std::is_same_v<std::remove_cv_t<T>, unsigned short int> ||
+                                                  std::is_same_v<std::remove_cv_t<T>, unsigned int>       ||
+                                                  std::is_same_v<std::remove_cv_t<T>, unsigned long int>  ||
+                                                  std::is_same_v<std::remove_cv_t<T>, unsigned long long int>;
+
+template<class T> constexpr bool IsSignedIntV = std::is_same_v<std::remove_cv_t<T>, signed char> ||
+                                                std::is_same_v<std::remove_cv_t<T>, short int>   ||
+                                                std::is_same_v<std::remove_cv_t<T>, int>         ||
+                                                std::is_same_v<std::remove_cv_t<T>, long int>    ||
+                                                std::is_same_v<std::remove_cv_t<T>, long long int>;
+
+template<class T> constexpr bool IsIntegerV    = IsUnsignedIntV<T> || IsSignedIntV<T>;
+template<class T> constexpr bool IsFloatV      = std::is_floating_point_v<T>;
+template<class T> constexpr bool IsArithmeticV = IsIntegerV<T> || IsFloatV<T>;
 
 //################# Class Members ########################
 
 /*  Detect data or function members of a class by name: ZEN_INIT_DETECT_MEMBER + HasMember_
     Example: 1. ZEN_INIT_DETECT_MEMBER(c_str);
              2. HasMemberV_c_str<T>    -> use boolean
-*/
 
-/*  Detect data or function members of a class by name *and* type: ZEN_INIT_DETECT_MEMBER2 + HasMember_
+
+    Detect data or function members of a class by name *and* type: ZEN_INIT_DETECT_MEMBER2 + HasMember_
 
     Example: 1. ZEN_INIT_DETECT_MEMBER2(size, size_t (T::*)() const);
              2. HasMember_size<T>::value    -> use as boolean
-*/
 
-/*  Detect member type of a class: ZEN_INIT_DETECT_MEMBER_TYPE + HasMemberType_
+
+    Detect member type of a class: ZEN_INIT_DETECT_MEMBER_TYPE + HasMemberType_
 
     Example: 1. ZEN_INIT_DETECT_MEMBER_TYPE(value_type);
-             2. HasMemberTypeV_value_type<T>    -> use as boolean
-*/
+             2. HasMemberTypeV_value_type<T>    -> use as boolean                       */
 
 //########## Sorting ##############################
 /*
@@ -114,25 +115,6 @@ LessDescending<Predicate> makeSortDirection(Predicate pred, std::false_type) { r
 
 
 //################ implementation ######################
-template <class T>
-struct IsUnsignedInt : std::false_type {};
-
-template <> struct IsUnsignedInt<unsigned char         > : std::true_type {};
-template <> struct IsUnsignedInt<unsigned short int    > : std::true_type {};
-template <> struct IsUnsignedInt<unsigned int          > : std::true_type {};
-template <> struct IsUnsignedInt<unsigned long int     > : std::true_type {};
-template <> struct IsUnsignedInt<unsigned long long int> : std::true_type {};
-
-template <class T>
-struct IsSignedInt : std::false_type {};
-
-template <> struct IsSignedInt<signed char  > : std::true_type {};
-template <> struct IsSignedInt<short int    > : std::true_type {};
-template <> struct IsSignedInt<int          > : std::true_type {};
-template <> struct IsSignedInt<long int     > : std::true_type {};
-template <> struct IsSignedInt<long long int> : std::true_type {};
-//####################################################################
-
 #define ZEN_INIT_DETECT_MEMBER(NAME)        \
     \
     template<bool isClass, class T>         \
diff --git a/zenXml/zenxml/cvrt_text.h b/zenXml/zenxml/cvrt_text.h
index 51b23173..058ffa30 100644
--- a/zenXml/zenxml/cvrt_text.h
+++ b/zenXml/zenxml/cvrt_text.h
@@ -131,7 +131,7 @@ template <class T>
 struct GetTextType : std::integral_constant<TextType,
     std::is_same_v<T, bool>    ? TEXT_TYPE_BOOL   :
     IsStringLikeV<T>           ? TEXT_TYPE_STRING : //string before number to correctly handle char/wchar_t -> this was an issue with Loki only!
-    IsArithmetic<T>::value     ? TEXT_TYPE_NUMBER : //
+    IsArithmeticV<T>           ? TEXT_TYPE_NUMBER : //
     IsChronoDuration<T>::value ? TEXT_TYPE_CHRONO :
     TEXT_TYPE_OTHER> {};
 
diff --git a/zenXml/zenxml/dom.h b/zenXml/zenxml/dom.h
index cfbd14c9..e77509bf 100644
--- a/zenXml/zenxml/dom.h
+++ b/zenXml/zenxml/dom.h
@@ -85,7 +85,7 @@ public:
             it->second->value = std::move(attrValue);
         else
         {
-            auto itBack = attributes_.insert(attributes_.end(), { attrName, std::move(attrValue) });
+            auto itBack = attributes_.insert(attributes_.end(), {attrName, std::move(attrValue)});
             attributesSorted_.emplace(std::move(attrName), itBack);
         }
     }
@@ -207,10 +207,10 @@ public:
       \endcode
       \return A pair of STL begin/end iterators to access all child elements sequentially.
     */
-    std::pair<ChildIterConst, ChildIterConst> getChildren() const { return { childElements_.begin(), childElements_.end() }; }
+    std::pair<ChildIterConst, ChildIterConst> getChildren() const { return {childElements_.begin(), childElements_.end()}; }
 
     ///\sa getChildren
-    std::pair<ChildIter, ChildIter> getChildren() { return { childElements_.begin(), childElements_.end() }; }
+    std::pair<ChildIter, ChildIter> getChildren() { return {childElements_.begin(), childElements_.end()}; }
 
     ///Get parent XML element, may be nullptr for root element
     XmlElement* parent() { return parent_; }
@@ -231,9 +231,8 @@ public:
         for (auto it = iterPair.first; it != iterPair.second; ++it)
            std::cout << "name: " << it->name << " value: " << it->value << '\n';
       \endcode
-      \return A pair of STL begin/end iterators to access all attributes sequentially as a list of name/value pairs of std::string.
-    */
-    std::pair<AttrIter, AttrIter> getAttributes() const { return { attributes_.begin(), attributes_.end() }; }
+      \return A pair of STL begin/end iterators to access all attributes sequentially as a list of name/value pairs of std::string.   */
+    std::pair<AttrIter, AttrIter> getAttributes() const { return {attributes_.begin(), attributes_.end()}; }
 
     //swap two elements while keeping references to parent.  -> disabled documentation extraction
     void swapSubtree(XmlElement& other) noexcept
@@ -329,11 +328,11 @@ private:
     XmlDoc           (const XmlDoc&) = delete; //not implemented, thanks to XmlElement::parent_
     XmlDoc& operator=(const XmlDoc&) = delete;
 
-    std::string version_ { "1.0" };
-    std::string encoding_{ "utf-8" };
+    std::string version_ {"1.0"};
+    std::string encoding_{"utf-8"};
     std::string standalone_;
 
-    XmlElement root_{ "Root" };
+    XmlElement root_{"Root"};
 };
 
 }
diff --git a/zenXml/zenxml/parser.h b/zenXml/zenxml/parser.h
index 7ec2433b..a4800ab3 100644
--- a/zenXml/zenxml/parser.h
+++ b/zenXml/zenxml/parser.h
@@ -423,15 +423,15 @@ private:
     using TokenList = std::vector<std::pair<std::string, Token::Type>>;
     const TokenList tokens_
     {
-        { "<?xml", Token::TK_DECL_BEGIN    },
-        { "?>",    Token::TK_DECL_END      },
-        { "</",    Token::TK_LESS_SLASH    },
-        { "/>",    Token::TK_SLASH_GREATER },
-        { "<",     Token::TK_LESS          }, //evaluate after TK_DECL_BEGIN!
-        { ">",     Token::TK_GREATER       },
-        { "=",     Token::TK_EQUAL         },
-        { "\"",    Token::TK_QUOTE         },
-        { "\'",    Token::TK_QUOTE         },
+        {"<?xml", Token::TK_DECL_BEGIN   },
+        {"?>",    Token::TK_DECL_END     },
+        {"</",    Token::TK_LESS_SLASH   },
+        {"/>",    Token::TK_SLASH_GREATER},
+        {"<",     Token::TK_LESS         }, //evaluate after TK_DECL_BEGIN!
+        {">",     Token::TK_GREATER      },
+        {"=",     Token::TK_EQUAL        },
+        {"\"",    Token::TK_QUOTE        },
+        {"\'",    Token::TK_QUOTE        },
     };
 
     const std::string xmlCommentBegin_ = "<!--";