Qt: Always start painter thread even if not in use

src/platform/qt/DisplayGL.cpp

@@ -51,10 +51,23 @@ DisplayGL::DisplayGL(const QSurfaceFormat& format, QWidget* parent)
 	windowHandle()->create();
 
 	m_painter = std::make_unique<PainterGL>(windowHandle(), format);
+	m_drawThread.setObjectName("Painter Thread");
+	m_painter->moveToThread(&m_drawThread);
+
+	connect(&m_drawThread, &QThread::started, m_painter.get(), &PainterGL::create);
+	connect(m_painter.get(), &PainterGL::started, this, [this] {
+		m_hasStarted = true;
+		resizePainter();
+		emit drawingStarted();
+	});
+	m_drawThread.start();
 }
 
 DisplayGL::~DisplayGL() {
 	stopDrawing();
+	QMetaObject::invokeMethod(m_painter.get(), "destroy", Qt::BlockingQueuedConnection);
+	m_drawThread.exit();
+	m_drawThread.wait();
 }
 
 bool DisplayGL::supportsShaders() const {
@@ -63,34 +76,21 @@ bool DisplayGL::supportsShaders() const {
 
 VideoShader* DisplayGL::shaders() {
 	VideoShader* shaders = nullptr;
-	if (m_drawThread) {
 	QMetaObject::invokeMethod(m_painter.get(), "shaders", Qt::BlockingQueuedConnection, Q_RETURN_ARG(VideoShader*, shaders));
-	} else {
-		shaders = m_painter->shaders();
-	}
 	return shaders;
 }
 
 void DisplayGL::startDrawing(std::shared_ptr<CoreController> controller) {
-	if (m_drawThread) {
+	if (m_isDrawing) {
 		return;
 	}
 	m_isDrawing = true;
 	m_painter->setContext(controller);
 	m_painter->setMessagePainter(messagePainter());
 	m_context = controller;
-	m_drawThread = new QThread(this);
-	m_drawThread->setObjectName("Painter Thread");
-	m_painter->moveToThread(m_drawThread);
 	if (videoProxy()) {
-		videoProxy()->moveToThread(m_drawThread);
+		videoProxy()->moveToThread(&m_drawThread);
 	}
-	connect(m_drawThread, &QThread::started, m_painter.get(), &PainterGL::start);
-	connect(m_painter.get(), &PainterGL::started, this, [this] {
-		m_hasStarted = true;
-		resizePainter();
-		emit drawingStarted();
-	});
 
 	lockAspectRatio(isAspectRatioLocked());
 	lockIntegerScaling(isIntegerScalingLocked());
@@ -98,13 +98,12 @@ void DisplayGL::startDrawing(std::shared_ptr<CoreController> controller) {
 	showOSDMessages(isShowOSD());
 	filter(isFiltered());
 
-	m_drawThread->start();
-
 #if (QT_VERSION >= QT_VERSION_CHECK(5, 6, 0))
 	messagePainter()->resize(size(), isAspectRatioLocked(), devicePixelRatioF());
 #else
 	messagePainter()->resize(size(), isAspectRatioLocked(), devicePixelRatio());
 #endif
+	QMetaObject::invokeMethod(m_painter.get(), "start");
 	setUpdatesEnabled(false);
 }
 
@@ -147,21 +146,18 @@ bool DisplayGL::supportsFormat(const QSurfaceFormat& format) {
 }
 
 void DisplayGL::stopDrawing() {
-	if (m_drawThread) {
+	if (m_hasStarted || m_isDrawing) {
 		m_isDrawing = false;
 		m_hasStarted = false;
 		CoreController::Interrupter interrupter(m_context);
 		QMetaObject::invokeMethod(m_painter.get(), "stop", Qt::BlockingQueuedConnection);
-		m_drawThread->exit();
-		m_drawThread->wait();
-		m_drawThread = nullptr;
 		setUpdatesEnabled(true);
 	}
 	m_context.reset();
 }
 
 void DisplayGL::pauseDrawing() {
-	if (m_drawThread) {
+	if (m_hasStarted) {
 		m_isDrawing = false;
 		CoreController::Interrupter interrupter(m_context);
 		QMetaObject::invokeMethod(m_painter.get(), "pause", Qt::BlockingQueuedConnection);
@@ -172,7 +168,7 @@ void DisplayGL::pauseDrawing() {
 }
 
 void DisplayGL::unpauseDrawing() {
-	if (m_drawThread) {
+	if (m_hasStarted) {
 		m_isDrawing = true;
 		CoreController::Interrupter interrupter(m_context);
 		QMetaObject::invokeMethod(m_painter.get(), "unpause", Qt::BlockingQueuedConnection);
@@ -183,78 +179,59 @@ void DisplayGL::unpauseDrawing() {
 }
 
 void DisplayGL::forceDraw() {
-	if (m_drawThread) {
+	if (m_hasStarted) {
 		QMetaObject::invokeMethod(m_painter.get(), "forceDraw");
 	}
 }
 
 void DisplayGL::lockAspectRatio(bool lock) {
 	Display::lockAspectRatio(lock);
-	if (m_drawThread) {
 	QMetaObject::invokeMethod(m_painter.get(), "lockAspectRatio", Q_ARG(bool, lock));
-	}
 }
 
 void DisplayGL::lockIntegerScaling(bool lock) {
 	Display::lockIntegerScaling(lock);
-	if (m_drawThread) {
 	QMetaObject::invokeMethod(m_painter.get(), "lockIntegerScaling", Q_ARG(bool, lock));
-	}
 }
 
 void DisplayGL::interframeBlending(bool enable) {
 	Display::interframeBlending(enable);
-	if (m_drawThread) {
 	QMetaObject::invokeMethod(m_painter.get(), "interframeBlending", Q_ARG(bool, enable));
-	}
 }
 
 void DisplayGL::showOSDMessages(bool enable) {
 	Display::showOSDMessages(enable);
-	if (m_drawThread) {
 	QMetaObject::invokeMethod(m_painter.get(), "showOSD", Q_ARG(bool, enable));
-	}
 }
 
 void DisplayGL::filter(bool filter) {
 	Display::filter(filter);
-	if (m_drawThread) {
 	QMetaObject::invokeMethod(m_painter.get(), "filter", Q_ARG(bool, filter));
-	}
 }
 
 void DisplayGL::framePosted() {
-	if (m_drawThread) {
 	m_painter->enqueue(m_context->drawContext());
 	QMetaObject::invokeMethod(m_painter.get(), "draw");
-	}
 }
 
 void DisplayGL::setShaders(struct VDir* shaders) {
-	if (m_drawThread) {
 	QMetaObject::invokeMethod(m_painter.get(), "setShaders", Qt::BlockingQueuedConnection, Q_ARG(struct VDir*, shaders));
-	} else {
-		m_painter->setShaders(shaders);
-	}
 }
 
 void DisplayGL::clearShaders() {
-	QMetaObject::invokeMethod(m_painter.get(), "clearShaders");
+	QMetaObject::invokeMethod(m_painter.get(), "clearShaders", Qt::BlockingQueuedConnection);
 }
 
 void DisplayGL::resizeContext() {
-	if (m_drawThread) {
-		CoreController::Interrupter interrupter(m_context);
 	QMetaObject::invokeMethod(m_painter.get(), "resizeContext");
-	}
 }
 
 void DisplayGL::setVideoScale(int scale) {
-	if (m_drawThread) {
+	if (m_context) {
 		CoreController::Interrupter interrupter(m_context);
 		mCoreConfigSetIntValue(&m_context->thread()->core->config, "videoScale", scale);
-		QMetaObject::invokeMethod(m_painter.get(), "resizeContext");
 	}
+	QMetaObject::invokeMethod(m_painter.get(), "resizeContext");
 }
 
 void DisplayGL::resizeEvent(QResizeEvent* event) {
@@ -263,15 +240,15 @@ void DisplayGL::resizeEvent(QResizeEvent* event) {
 }
 
 void DisplayGL::resizePainter() {
-	if (m_drawThread && m_hasStarted) {
+	if (m_hasStarted) {
 		QMetaObject::invokeMethod(m_painter.get(), "resize", Qt::BlockingQueuedConnection, Q_ARG(QSize, size()));
 	}
 }
 
 void DisplayGL::setVideoProxy(std::shared_ptr<VideoProxy> proxy) {
 	Display::setVideoProxy(proxy);
-	if (m_drawThread && proxy) {
-		proxy->moveToThread(m_drawThread);
+	if (proxy) {
+		proxy->moveToThread(&m_drawThread);
 	}
 	m_painter->setVideoProxy(proxy);
 }
@@ -361,15 +338,6 @@ void PainterGL::destroy() {
 		return;
 	}
 	makeCurrent();
-	if (m_context) {
-		if (m_videoProxy) {
-			m_videoProxy->detach(m_context.get());
-		}
-		m_context->setFramebufferHandle(-1);
-		if (m_videoProxy) {
-			m_videoProxy->processData();
-		}
-	}
 #ifdef BUILD_GLES2
 	if (m_shader.passes) {
 		mGLES2ShaderFree(&m_shader);
@@ -394,6 +362,7 @@ void PainterGL::resizeContext() {
 	}
 
 	if (m_started) {
+		CoreController::Interrupter interrupter(m_context);
 		mCore* core = m_context->thread()->core;
 		core->reloadConfigOption(core, "videoScale", NULL);
 	}
@@ -440,9 +409,6 @@ void PainterGL::filter(bool filter) {
 }
 
 void PainterGL::start() {
-	if (!m_gl) {
-		create();
-	}
 	makeCurrent();
 
 #ifdef BUILD_GLES2
@@ -510,16 +476,23 @@ void PainterGL::stop() {
 	m_active = false;
 	m_started = false;
 	dequeueAll();
-	m_backend->clear(m_backend);
-	m_backend->swap(m_backend);
+	if (m_context) {
+		if (m_videoProxy) {
+			m_videoProxy->detach(m_context.get());
+		}
+		m_context->setFramebufferHandle(-1);
+		m_context.reset();
+		if (m_videoProxy) {
+			m_videoProxy->processData();
+		}
+	}
 	if (m_videoProxy) {
 		m_videoProxy->reset();
-	}
-	destroy();
-	moveToThread(m_surface->thread());
-	if (m_videoProxy) {
 		m_videoProxy->moveToThread(m_surface->thread());
+		m_videoProxy.reset();
 	}
+	m_backend->clear(m_backend);
+	m_backend->swap(m_backend);
 }
 
 void PainterGL::pause() {
@@ -606,9 +579,6 @@ void PainterGL::setShaders(struct VDir* dir) {
 		return;
 	}
 #ifdef BUILD_GLES2
-	if (!m_started) {
-		return; // TODO
-	}
 	if (m_shader.passes) {
 		mGLES2ShaderDetach(reinterpret_cast<mGLES2Context*>(m_backend));
 		mGLES2ShaderFree(&m_shader);
@@ -623,9 +593,6 @@ void PainterGL::clearShaders() {
 		return;
 	}
 #ifdef BUILD_GLES2
-	if (!m_started) {
-		return; // TODO
-	}
 	if (m_shader.passes) {
 		mGLES2ShaderDetach(reinterpret_cast<mGLES2Context*>(m_backend));
 		mGLES2ShaderFree(&m_shader);

src/platform/qt/DisplayGL.h

@@ -84,7 +84,7 @@ private:
 	bool m_isDrawing = false;
 	bool m_hasStarted = false;
 	std::unique_ptr<PainterGL> m_painter;
-	QThread* m_drawThread = nullptr;
+	QThread m_drawThread;
 	std::shared_ptr<CoreController> m_context;
 };
 
@@ -104,6 +104,9 @@ public:
 	void setVideoProxy(std::shared_ptr<VideoProxy>);
 
 public slots:
+	void create();
+	void destroy();
+
 	void forceDraw();
 	void draw();
 	void start();
@@ -132,8 +135,6 @@ private:
 	void performDraw();
 	void dequeue();
 	void dequeueAll();
-	void create();
-	void destroy();
 
 	std::array<std::array<uint32_t, 0x100000>, 3> m_buffers;
 	QList<uint32_t*> m_free;