1 files changed, 77 insertions, 0 deletions
diff --git a/zen/scroll_window_under_cursor.cpp b/zen/scroll_window_under_cursor.cpp
new file mode 100644
index 00000000..6031cd88
--- /dev/null
+++ b/zen/scroll_window_under_cursor.cpp
@@ -0,0 +1,77 @@
+// **************************************************************************
+// * This file is part of the FreeFileSync project. It is distributed under *
+// * GNU General Public License: http://www.gnu.org/licenses/gpl.html       *
+// * Copyright (C) Zenju (zenju AT gmx DOT de) - All Rights Reserved        *
+// **************************************************************************
+
+#include <cassert>
+#include "win.h"     //includes "windows.h"
+#include "Windowsx.h" //WM_MOUSEWHEEL
+
+//redirect mouse wheel events directly to window under cursor rather than window having input focus
+//implementing new Windows Vista UI guidelines: http://msdn.microsoft.com/en-us/library/bb545459.aspx#wheel
+//this is confirmed to be required for at least Windows 2000 to Windows 8
+//on Ubuntu Linux, this is already the default behavior
+
+//Usage: just include this file into a Windows project
+
+namespace
+{
+#ifndef WM_MOUSEHWHEEL //MinGW is clueless...
+#define WM_MOUSEHWHEEL                  0x020E
+#endif
+
+LRESULT CALLBACK mouseInputHook(int nCode, WPARAM wParam, LPARAM lParam)
+{
+    //"if nCode is less than zero, the hook procedure must pass the message to the CallNextHookEx function
+    //without further processing and should return the value returned by CallNextHookEx"
+    if (nCode >= 0)
+    {
+        MSG& msgInfo = *reinterpret_cast<MSG*>(lParam);
+
+        if (msgInfo.message == WM_MOUSEWHEEL ||
+            msgInfo.message == WM_MOUSEHWHEEL)
+        {
+            POINT pt = {};
+            pt.x = GET_X_LPARAM(msgInfo.lParam); //yes, there's also msgInfo.pt, but let's not take chances
+            pt.y = GET_Y_LPARAM(msgInfo.lParam); //
+
+            //visible child window directly under cursor; attention: not necessarily from our process!
+            //http://blogs.msdn.com/b/oldnewthing/archive/2010/12/30/10110077.aspx
+            if (HWND hWin = ::WindowFromPoint(pt))
+                if (msgInfo.hwnd != hWin && ::GetCapture() == nullptr)
+                {
+                    DWORD winProcessId = 0;
+                    ::GetWindowThreadProcessId( //no-fail!
+                        hWin,           //_In_       HWND hWnd,
+                        &winProcessId); //_Out_opt_  LPDWORD lpdwProcessId
+                    if (winProcessId == ::GetCurrentProcessId()) //no-fail!
+                        msgInfo.hwnd = hWin; //it would be a bug to set handle from another process here
+                }
+        }
+    }
+
+    return ::CallNextHookEx(nullptr, nCode, wParam, lParam);
+}
+
+struct Dummy
+{
+    Dummy()
+    {
+        hHook = ::SetWindowsHookEx(WH_GETMESSAGE,  //__in  int idHook,
+                                   mouseInputHook, //__in  HOOKPROC lpfn,
+                                   nullptr,        //__in  HINSTANCE hMod,
+                                   ::GetCurrentThreadId()); //__in  DWORD dwThreadId
+        assert(hHook);
+    }
+
+    ~Dummy()
+    {
+        if (hHook)
+            ::UnhookWindowsHookEx(hHook);
+    }
+
+private:
+    HHOOK hHook;
+} dummy;
+}