For Qt GUI, add video buffer mutex to ensure clean transfer between emulation and GUI threads. Use common FCEU::mutex wrapper for cleaner code.

src/drivers/Qt/ConsoleWindow.cpp

@@ -170,11 +170,6 @@ consoleWin_t::consoleWin_t(QWidget *parent)
 	setAcceptDrops(true);
 
 	gameTimer  = new QTimer( this );
-#if QT_VERSION >= QT_VERSION_CHECK(6,0,0)
-	mutex      = new QRecursiveMutex();
-#else
-	mutex      = new QMutex( QMutex::Recursive );
-#endif
 	emulatorThread = new emulatorThread_t(this);
 
 	connect(emulatorThread, &QThread::finished, emulatorThread, &QObject::deleteLater);
@@ -336,8 +331,6 @@ consoleWin_t::~consoleWin_t(void)
 
 	unloadVideoDriver();
 
-	delete mutex;
-
 	// LoadGame() checks for an IP and if it finds one begins a network session
 	// clear the NetworkIP field so this doesn't happen unintentionally
 	//g_config->setOption ("SDL.NetworkIP", "");
@@ -4564,19 +4557,30 @@ int consoleWin_t::getPeriodicInterval(void)
 
 void consoleWin_t::transferVideoBuffer(void)
 {
+	bool redraw = false;
 	FCEU_PROFILE_FUNC(prof, "VideoXfer");
+
+	{
+		FCEU::autoScopedLock lock(videoBufferMutex);
 		if ( nes_shm->blitUpdated )
 		{
 			nes_shm->blitUpdated = 0;
 
-		if (viewport_Interface)
+			if (viewport_Interface != nullptr)
 			{
 				viewport_Interface->transfer2LocalBuffer();
-			viewport_Interface->queueRedraw();
+				redraw = true;
 			}
 		}
 	}
 
+	// Don't queue redraw in mutex lock scope
+	if (redraw && (viewport_Interface != nullptr))
+	{
+		viewport_Interface->queueRedraw();
+	}
+}
+
 void consoleWin_t::emuFrameFinish(void)
 {
 	static bool eventProcessingInProg = false;

src/drivers/Qt/ConsoleWindow.h

@@ -27,6 +27,7 @@
 #include <QRecursiveMutex>
 #endif
 
+#include "utils/mutex.h"
 #include "Qt/ColorMenu.h"
 #include "Qt/ConsoleViewerGL.h"
 #include "Qt/ConsoleViewerSDL.h"
@@ -134,11 +135,8 @@ class  consoleWin_t : public QMainWindow
 
 		void setCyclePeriodms( int ms );
 
-#if QT_VERSION >= QT_VERSION_CHECK(6,0,0)
-		QRecursiveMutex *mutex;
-#else
-		QMutex *mutex;
-#endif
+		FCEU::mutex emulatorMutex;
+		FCEU::mutex videoBufferMutex;
 
 		int  videoInit(void);
 		void videoReset(void);

src/drivers/Qt/fceuWrapper.cpp

@@ -1382,7 +1382,7 @@ void fceuWrapperLock(void)
 	mutexPending++;
 	if ( consoleWindow != NULL )
 	{
-		consoleWindow->mutex->lock();
+		consoleWindow->emulatorMutex.lock();
 	}
 	mutexPending--;
 	mutexLocks++;
@@ -1412,7 +1412,7 @@ bool fceuWrapperTryLock(int timeout)
 	mutexPending++;
 	if ( consoleWindow != NULL )
 	{
-		lockAcq = consoleWindow->mutex->tryLock( timeout );
+		lockAcq = consoleWindow->emulatorMutex.tryLock( timeout );
 	}
 	mutexPending--;
 
@@ -1430,7 +1430,7 @@ void fceuWrapperUnLock(void)
 		mutexLocks--;
 		if ( consoleWindow != NULL )
 		{
-			consoleWindow->mutex->unlock();
+			consoleWindow->emulatorMutex.unlock();
 		}
 	}
 	else

src/drivers/Qt/sdl-video.cpp

@@ -496,8 +496,6 @@ doBlitScreen(uint8_t *XBuf, uint8_t *dest)
 void
 BlitScreen(uint8 *XBuf)
 {
-	int i = nes_shm->pixBufIdx;
-
 	if (usePaletteForVideoBg)
 	{
 		unsigned char r, g, b;
@@ -511,12 +509,19 @@ BlitScreen(uint8 *XBuf)
 		}
 	}
 
+	if (consoleWindow != nullptr)
+	{
+		FCEU::autoScopedLock lock(consoleWindow->videoBufferMutex);
+
+		int i = nes_shm->pixBufIdx;
+
 		doBlitScreen(XBuf, (uint8_t*)nes_shm->pixbuf[i]);
 
 		nes_shm->pixBufIdx = (i+1) % NES_VIDEO_BUFLEN;
 		nes_shm->blit_count++;
 		nes_shm->blitUpdated = 1;
 	}
+}
 
 void FCEUI_AviVideoUpdate(const unsigned char* buffer)
 {	// This is not used by Qt Emulator, avi recording pulls from the post processed video buffer

src/utils/mutex.cpp

@@ -48,6 +48,24 @@ void mutex::unlock(void)
 #endif
 }
 
+bool mutex::tryLock()
+{
+	bool success = false;
+#ifdef __QT_DRIVER__
+	success = mtx->tryLock();
+#endif
+	return success;
+}
+
+bool mutex::tryLock(int timeout)
+{
+	bool success = false;
+#ifdef __QT_DRIVER__
+	success = mtx->tryLock(timeout);
+#endif
+	return success;
+}
+
 //-----------------------------------------------------
 // Scoped AutoLock
 //-----------------------------------------------------

src/utils/mutex.h

@@ -18,6 +18,8 @@ namespace FCEU
 	
 			void lock(void);
 			void unlock(void);
+			bool tryLock(void);
+			bool tryLock(int timeout);
 	
 		private:
 	#ifdef __QT_DRIVER__