Qt: Improve sync code

CHANGES

@@ -70,6 +70,7 @@ Misc:
  - FFmpeg: Support audio-only recording
  - Qt: Increase maximum magnifications and scaling
  - Qt: Add native FPS button to settings view
+ - Qt: Improve sync code
 
 0.7.1: (2019-02-24)
 Bugfixes:

src/platform/qt/Display.cpp

@@ -20,7 +20,7 @@ Display* Display::create(QWidget* parent) {
 #if defined(BUILD_GL) || defined(BUILD_GLES2) || defined(USE_EPOXY)
 	QSurfaceFormat format;
 	format.setSwapInterval(1);
-	format.setSwapBehavior(QSurfaceFormat::SingleBuffer);
+	format.setSwapBehavior(QSurfaceFormat::DoubleBuffer);
 #endif
 
 	switch (s_driver) {

src/platform/qt/DisplayGL.cpp

@@ -1,4 +1,4 @@
-/* Copyright (c) 2013-2015 Jeffrey Pfau
+/* Copyright (c) 2013-2019 Jeffrey Pfau
  *
  * This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
@@ -261,15 +261,9 @@ PainterGL::PainterGL(VideoProxy* proxy, QWindow* surface, QOpenGLContext* parent
 #endif
 	m_backend->swap = [](VideoBackend* v) {
 		PainterGL* painter = static_cast<PainterGL*>(v->user);
-		if (!painter->m_gl->isValid()) {
-			return;
+		if (!painter->m_swapTimer.isActive()) {
+			QMetaObject::invokeMethod(&painter->m_swapTimer, "start");
 		}
-		painter->m_gl->swapBuffers(painter->m_surface);
-		painter->m_gl->doneCurrent();
-		painter->m_gl->makeCurrent(painter->m_surface);
-#if defined(_WIN32) && defined(USE_EPOXY)
-		epoxy_handle_external_wglMakeCurrent();
-#endif
 	};
 
 	m_backend->init(m_backend, 0);
@@ -287,6 +281,10 @@ PainterGL::PainterGL(VideoProxy* proxy, QWindow* surface, QOpenGLContext* parent
 	for (int i = 0; i < 2; ++i) {
 		m_free.append(new uint32_t[1024 * 2048]);
 	}
+
+	m_swapTimer.setInterval(16);
+	m_swapTimer.setSingleShot(true);
+	connect(&m_swapTimer, &QTimer::timeout, this, &PainterGL::swap);
 }
 
 PainterGL::~PainterGL() {
@@ -375,27 +373,22 @@ void PainterGL::draw() {
 		return;
 	}
 
+	if (m_needsUnlock) {
+		QTimer::singleShot(0, this, &PainterGL::draw);
+		return;
+	}
+
 	if (mCoreSyncWaitFrameStart(&m_context->thread()->impl->sync) || !m_queue.isEmpty()) {
 		dequeue();
-		mCoreSyncWaitFrameEnd(&m_context->thread()->impl->sync);
-		m_painter.begin(m_window);
-		performDraw();
-		m_painter.end();
-		m_backend->swap(m_backend);
-		if (!m_delayTimer.isValid()) {
-			m_delayTimer.start();
-		} else if (m_gl->format().swapInterval() && m_context->videoSync()) {
-			while (m_delayTimer.elapsed() < 15) {
-				QThread::usleep(100);
-			}
-			m_delayTimer.restart();
+		forceDraw();
+		if (m_context->thread()->impl->sync.videoFrameWait) {
+			m_needsUnlock = true;
+		} else {
+			mCoreSyncWaitFrameEnd(&m_context->thread()->impl->sync);
 		}
 	} else {
 		mCoreSyncWaitFrameEnd(&m_context->thread()->impl->sync);
 	}
-	if (!m_queue.isEmpty()) {
-		QMetaObject::invokeMethod(this, "draw", Qt::QueuedConnection);
-	}
 }
 
 void PainterGL::forceDraw() {
@@ -438,6 +431,30 @@ void PainterGL::performDraw() {
 	if (m_messagePainter) {
 		m_messagePainter->paint(&m_painter);
 	}
+	m_frameReady = true;
+}
+
+void PainterGL::swap() {
+	if (!m_gl->isValid()) {
+		return;
+	}
+	if (m_frameReady) {
+		m_gl->swapBuffers(m_surface);
+		m_gl->makeCurrent(m_surface);
+#if defined(_WIN32) && defined(USE_EPOXY)
+		epoxy_handle_external_wglMakeCurrent();
+#endif
+		m_frameReady = false;
+	}
+	if (m_needsUnlock) {
+		mCoreSyncWaitFrameEnd(&m_context->thread()->impl->sync);
+		m_needsUnlock = false;
+	}
+	if (!m_queue.isEmpty()) {
+		QMetaObject::invokeMethod(this, "draw", Qt::QueuedConnection);
+	} else {
+		m_swapTimer.start();
+	}
 }
 
 void PainterGL::enqueue(const uint32_t* backing) {

src/platform/qt/DisplayGL.h

@@ -16,13 +16,13 @@
 #endif
 #endif
 
-#include <QElapsedTimer>
 #include <QOpenGLContext>
 #include <QList>
 #include <QMouseEvent>
 #include <QPainter>
 #include <QQueue>
 #include <QThread>
+#include <QTimer>
 
 #include "VideoProxy.h"
 
@@ -105,6 +105,9 @@ public slots:
 
 	int glTex();
 
+private slots:
+	void swap();
+
 private:
 	void performDraw();
 	void dequeue();
@@ -125,7 +128,9 @@ private:
 	VideoBackend* m_backend = nullptr;
 	QSize m_size;
 	MessagePainter* m_messagePainter = nullptr;
-	QElapsedTimer m_delayTimer;
+	QTimer m_swapTimer{this};
+	bool m_needsUnlock = false;
+	bool m_frameReady = false;
 	VideoProxy* m_videoProxy;
 };