attempting at fixing Stop function. also lay base for EmuThread command queue.

src/frontend/qt_sdl/EmuInstance.cpp

@@ -180,12 +180,12 @@ bool EmuInstance::emuIsActive()
 
 void EmuInstance::emuStop(StopReason reason)
 {
-    emuThread->emuStop();
+    if (reason != StopReason::External)
+        emuThread->emuStop(false);
 
     switch (reason)
     {
         case StopReason::GBAModeNotSupported:
-            Log(LogLevel::Error, "!! GBA MODE NOT SUPPORTED\n");
             osdAddMessage(0xFFA0A0, "GBA mode not supported");
             break;
         case StopReason::BadExceptionRegion:

src/frontend/qt_sdl/EmuThread.cpp

@@ -460,6 +460,8 @@ void EmuThread::run()
                 ContextRequest = contextRequest_None;
             }
         }
+
+        handleMessages();
     }
 
     file = Platform::OpenLocalFile("rtc.bin", Platform::FileMode::Write);
@@ -476,6 +478,45 @@ void EmuThread::run()
     NDS::Current = nullptr;
 }
 
+void EmuThread::sendMessage(Message msg)
+{
+    msgMutex.lock();
+    msgQueue.enqueue(msg);
+    msgMutex.unlock();
+}
+
+void EmuThread::waitMessage()
+{
+    msgSemaphore.acquire();
+}
+
+void EmuThread::waitAllMessages()
+{
+    msgSemaphore.acquire(msgSemaphore.available());
+}
+
+void EmuThread::handleMessages()
+{
+    msgMutex.lock();
+    while (!msgQueue.empty())
+    {
+        Message msg = msgQueue.dequeue();
+        switch (msg.type)
+        {
+        case msg_EmuStop:
+            if (msg.stopExternal) emuInstance->nds->Stop();
+            EmuRunning = emuStatus_Paused;
+            emuActive = false;
+            emuInstance->audioDisable();
+            emit windowEmuStop();
+            break;
+        }
+
+        msgSemaphore.release();
+    }
+    msgMutex.unlock();
+}
+
 void EmuThread::changeWindowTitle(char* title)
 {
     emit windowTitleChange(QString(title));
@@ -528,10 +569,9 @@ void EmuThread::emuUnpause()
     emuInstance->audioEnable();
 }
 
-void EmuThread::emuStop()
+void EmuThread::emuStop(bool external)
 {
-    emuPause();
+    sendMessage({.type = msg_EmuStop, .stopExternal = external});
-    emuActive = false;
 }
 
 void EmuThread::emuExit()

src/frontend/qt_sdl/EmuThread.h

@@ -21,6 +21,8 @@
 
 #include <QThread>
 #include <QMutex>
+#include <QSemaphore>
+#include <QQueue>
 
 #include <atomic>
 #include <variant>
@@ -53,13 +55,36 @@ public:
     void attachWindow(MainWindow* window);
     void detachWindow(MainWindow* window);
 
+    enum MessageType
+    {
+        msg_EmuStop,
+    };
+
+    struct Message
+    {
+        MessageType type;
+        union
+        {
+            bool stopExternal;
+        };
+    };
+
+    void sendMessage(Message msg);
+    void waitMessage();
+    void waitAllMessages();
+
+    void sendMessage(MessageType type)
+    {
+        return sendMessage({.type = type});
+    }
+
     void changeWindowTitle(char* title);
 
     // to be called from the UI thread
     void emuRun();
     void emuPause();
     void emuUnpause();
-    void emuStop();
+    void emuStop(bool external);
     void emuExit();
     void emuFrameStep();
 
@@ -95,6 +120,8 @@ signals:
     void syncVolumeLevel();
 
 private:
+    void handleMessages();
+
     void updateRenderer();
     void compileShaders();
 
@@ -115,6 +142,10 @@ private:
     constexpr static int EmuPauseStackPauseThreshold = 1;
     int EmuPauseStack;
 
+    QMutex msgMutex;
+    QSemaphore msgSemaphore;
+    QQueue<Message> msgQueue;
+
     enum ContextRequestKind
     {
         contextRequest_None = 0,

src/frontend/qt_sdl/Window.cpp

@@ -1621,8 +1621,8 @@ void MainWindow::onStop()
 {
     if (!emuThread->emuIsActive()) return;
 
-    emuThread->emuPause();
+    emuThread->emuStop(true);
-    emuInstance->nds->Stop();
+    emuThread->waitMessage();
 }
 
 void MainWindow::onFrameStep()
@@ -2068,8 +2068,6 @@ void MainWindow::onEmuStart()
 
 void MainWindow::onEmuStop()
 {
-    emuThread->emuStop();
-
     for (int i = 0; i < 9; i++)
     {
         actSaveState[i]->setEnabled(false);