1 files changed, 147 insertions, 0 deletions
diff --git a/wx+/async_task.h b/wx+/async_task.h
new file mode 100644
index 00000000..b23f6948
--- /dev/null
+++ b/wx+/async_task.h
@@ -0,0 +1,147 @@
+// **************************************************************************
+// * This file is part of the FreeFileSync project. It is distributed under *
+// * GNU General Public License: http://www.gnu.org/licenses/gpl-3.0        *
+// * Copyright (C) Zenju (zenju AT gmx DOT de) - All Rights Reserved        *
+// **************************************************************************
+
+#ifndef ASYNC_JOB_839147839170432143214321
+#define ASYNC_JOB_839147839170432143214321
+
+#include <functional>
+#include <zen/thread.h>
+#include <zen/scope_guard.h>
+#include <zen/stl_tools.h>
+#include <wx/timer.h>
+
+
+namespace zen
+{
+/*
+Run a task in an async thread, but process result in GUI event loop
+-------------------------------------------------------------------
+1. put AsyncGuiQueue instance inside a dialog:
+    AsyncGuiQueue guiQueue;
+
+2. schedule async task and synchronous continuation:
+    guiQueue.processAsync(evalAsync, evalOnGui);
+*/
+
+namespace impl
+{
+struct Task
+{
+    virtual ~Task() {}
+    virtual bool resultReady   () const = 0;
+    virtual void evaluateResult()       = 0;
+};
+
+
+template <class ResultType, class Fun>
+class ConcreteTask : public Task
+{
+public:
+    template <class Fun2>
+    ConcreteTask(std::future<ResultType>&& asyncResult, Fun2&& evalOnGui) : asyncResult_(std::move(asyncResult)), evalOnGui_(std::forward<Fun2>(evalOnGui)) {}
+
+    bool resultReady   () const override { return isReady(asyncResult_); }
+    void evaluateResult()       override
+    {
+#ifndef NDEBUG
+        assert(resultReady() && !resultEvaluated_);
+        resultEvaluated_ = true;
+#endif
+        evalResult(IsSameType<ResultType, void>());
+    }
+
+private:
+    void evalResult(FalseType /*void result type*/) { evalOnGui_(asyncResult_.get()); }
+    void evalResult(TrueType  /*void result type*/) { asyncResult_.get(); evalOnGui_(); }
+
+    std::future<ResultType> asyncResult_;
+    Fun evalOnGui_; //keep "evalOnGui" strictly separated from async thread: in particular do not copy in thread!
+#ifndef NDEBUG
+    bool resultEvaluated_ = false;
+#endif
+};
+
+
+class AsyncTasks
+{
+public:
+    AsyncTasks() {}
+
+    template <class Fun, class Fun2>
+    void add(Fun&& evalAsync, Fun2&& evalOnGui)
+    {
+        using ResultType = decltype(evalAsync());
+        tasks.push_back(std::make_unique<ConcreteTask<ResultType, Fun2>>(zen::runAsync(std::forward<Fun>(evalAsync)), std::forward<Fun2>(evalOnGui)));
+    }
+    //equivalent to "evalOnGui(evalAsync())"
+    //  -> evalAsync: the usual thread-safety requirements apply!
+    //  -> evalOnGui: no thread-safety concerns, but must only reference variables with greater-equal lifetime than the AsyncTask instance!
+
+    void evalResults() //call from gui thread repreatedly
+    {
+        if (!inRecursion) //prevent implicit recursion, e.g. if we're called from an idle event and spawn another one via the callback below
+        {
+            inRecursion = true;
+            ZEN_ON_SCOPE_EXIT(inRecursion = false);
+
+            std::vector<std::unique_ptr<Task>> readyTasks; //Reentrancy; access to AsyncTasks::add is not protected! => evaluate outside erase_if
+
+            erase_if(tasks, [&](std::unique_ptr<Task>& task)
+            {
+                if (task->resultReady())
+                {
+                    readyTasks.push_back(std::move(task));
+                    return true;
+                }
+                return false;
+            });
+
+            for (auto& task : readyTasks)
+                task->evaluateResult();
+        }
+    }
+
+    bool empty() const { return tasks.empty(); }
+
+private:
+    AsyncTasks           (const AsyncTasks&) = delete;
+    AsyncTasks& operator=(const AsyncTasks&) = delete;
+
+    bool inRecursion = false;
+    std::vector<std::unique_ptr<Task>> tasks;
+};
+}
+
+
+class AsyncGuiQueue : private wxEvtHandler
+{
+public:
+    AsyncGuiQueue() { timer.Connect(wxEVT_TIMER, wxEventHandler(AsyncGuiQueue::onTimerEvent), nullptr, this); }
+
+    template <class Fun, class Fun2>
+    void processAsync(Fun&& evalAsync, Fun2&& evalOnGui)
+    {
+        asyncTasks.add(std::forward<Fun >(evalAsync),
+                       std::forward<Fun2>(evalOnGui));
+        if (!timer.IsRunning())
+            timer.Start(50 /*unit: [ms]*/);
+    }
+
+private:
+    void onTimerEvent(wxEvent& event) //schedule and run long-running tasks asynchronously
+    {
+        asyncTasks.evalResults(); //process results on GUI queue
+        if (asyncTasks.empty())
+            timer.Stop();
+    }
+
+    impl::AsyncTasks asyncTasks;
+    wxTimer timer; //don't use wxWidgets' idle handling => repeated idle requests/consumption hogs 100% cpu!
+};
+
+}
+
+#endif //ASYNC_JOB_839147839170432143214321