From 8997eda005d1e1d289aa07c16fddd1edb4d7b40d Mon Sep 17 00:00:00 2001
From: Vicki Pfau <vi@endrift.com>
Date: Wed, 13 Jul 2022 19:27:38 -0700
Subject: [PATCH] Revert "Qt: Improve frame pacing, maybe"

This reverts commit 76d6055bb0095caf57431f7250bc0e965aa49e5e.
---
 src/core/sync.c               |  4 +--
 src/platform/qt/DisplayGL.cpp | 48 ++++++++++++-----------------------
 src/platform/qt/DisplayGL.h   |  4 +--
 3 files changed, 19 insertions(+), 37 deletions(-)

diff --git a/src/core/sync.c b/src/core/sync.c
index 78b04ea3e..b2a65493b 100644
--- a/src/core/sync.c
+++ b/src/core/sync.c
@@ -25,10 +25,10 @@ void mCoreSyncPostFrame(struct mCoreSync* sync) {
 	MutexLock(&sync->videoFrameMutex);
 	++sync->videoFramePending;
 	do {
+		ConditionWake(&sync->videoFrameAvailableCond);
 		if (sync->videoFrameWait) {
 			ConditionWait(&sync->videoFrameRequiredCond, &sync->videoFrameMutex);
 		}
-		ConditionWake(&sync->videoFrameAvailableCond);
 	} while (sync->videoFrameWait && sync->videoFramePending);
 	MutexUnlock(&sync->videoFrameMutex);
 }
@@ -54,7 +54,7 @@ bool mCoreSyncWaitFrameStart(struct mCoreSync* sync) {
 	}
 	if (sync->videoFrameWait) {
 		ConditionWake(&sync->videoFrameRequiredCond);
-		if (ConditionWaitTimed(&sync->videoFrameAvailableCond, &sync->videoFrameMutex, 4)) {
+		if (ConditionWaitTimed(&sync->videoFrameAvailableCond, &sync->videoFrameMutex, 50)) {
 			return false;
 		}
 	}
diff --git a/src/platform/qt/DisplayGL.cpp b/src/platform/qt/DisplayGL.cpp
index 4175505b5..740604b82 100644
--- a/src/platform/qt/DisplayGL.cpp
+++ b/src/platform/qt/DisplayGL.cpp
@@ -619,12 +619,11 @@ void PainterGL::start() {
 	m_buffer = nullptr;
 	m_active = true;
 	m_started = true;
-	resetTiming();
 	emit started();
 }
 
 void PainterGL::draw() {
-	if (!m_started) {
+	if (!m_started || m_queue.isEmpty()) {
 		return;
 	}
 
@@ -637,16 +636,14 @@ void PainterGL::draw() {
 	}
 
 	mCoreSync* sync = &m_context->thread()->impl->sync;
-
-	qint64 targetNsec = 1000000000 / sync->fpsTarget;
-	qint64 refreshNsec = 1000000000 / m_window->screen()->refreshRate();
-	qint64 delay = m_timerResidue;
-
 	if (!mCoreSyncWaitFrameStart(sync)) {
 		mCoreSyncWaitFrameEnd(sync);
 		if (!sync->audioWait && !sync->videoFrameWait) {
 			return;
 		}
+		if (m_delayTimer.elapsed() >= 1000 / m_window->screen()->refreshRate()) {
+			return;
+		}
 		if (!m_drawTimer.isActive()) {
 			m_drawTimer.start(1);
 		}
@@ -654,30 +651,23 @@ void PainterGL::draw() {
 	}
 	dequeue();
 	bool forceRedraw = !m_videoProxy;
-	if (sync->audioWait || sync->videoFrameWait) {
-		while (delay + m_delayTimer.nsecsElapsed() + OVERHEAD_NSEC < targetNsec) {
-			QThread::usleep(200);
+	if (!m_delayTimer.isValid()) {
+		m_delayTimer.start();
+	} else {
+		if (sync->audioWait || sync->videoFrameWait) {
+			while (m_delayTimer.nsecsElapsed() + OVERHEAD_NSEC < 1000000000 / sync->fpsTarget) {
+				QThread::usleep(500);
+			}
+			forceRedraw = sync->videoFrameWait;
+		}
+		if (!forceRedraw) {
+			forceRedraw = m_delayTimer.nsecsElapsed() + OVERHEAD_NSEC >= 1000000000 / m_window->screen()->refreshRate();
 		}
-		forceRedraw = sync->videoFrameWait;
-	}
-	if (!forceRedraw) {
-		forceRedraw = delay + m_delayTimer.nsecsElapsed() + OVERHEAD_NSEC >= refreshNsec;
 	}
 	mCoreSyncWaitFrameEnd(sync);
 
 	if (forceRedraw) {
-		delay += m_delayTimer.nsecsElapsed();
 		m_delayTimer.restart();
-
-		delay -= targetNsec;
-		m_timerResidue = (m_timerResidue + delay) / 2;
-
-		if (m_timerResidue > refreshNsec) {
-			if (!m_drawTimer.isActive()) {
-				m_drawTimer.start(1);
-			}
-		}
-
 		performDraw();
 		m_backend->swap(m_backend);
 	}
@@ -689,16 +679,11 @@ void PainterGL::forceDraw() {
 		if (m_delayTimer.elapsed() < 1000 / m_window->screen()->refreshRate()) {
 			return;
 		}
-		resetTiming();
+		m_delayTimer.restart();
 	}
 	m_backend->swap(m_backend);
 }
 
-void PainterGL::resetTiming() {
-	m_delayTimer.restart();
-	m_timerResidue = 0;
-}
-
 void PainterGL::stop() {
 	m_started = false;
 	QMetaObject::invokeMethod(this, "doStop", Qt::BlockingQueuedConnection);
@@ -736,7 +721,6 @@ void PainterGL::pause() {
 
 void PainterGL::unpause() {
 	m_active = true;
-	resetTiming();
 }
 
 void PainterGL::performDraw() {
diff --git a/src/platform/qt/DisplayGL.h b/src/platform/qt/DisplayGL.h
index 5b12feae0..47f94157d 100644
--- a/src/platform/qt/DisplayGL.h
+++ b/src/platform/qt/DisplayGL.h
@@ -176,9 +176,8 @@ private:
 	void performDraw();
 	void dequeue();
 	void dequeueAll(bool keep = false);
-	void resetTiming();
 
-	std::array<std::array<uint32_t, 0x100000>, 8> m_buffers;
+	std::array<std::array<uint32_t, 0x100000>, 3> m_buffers;
 	QList<uint32_t*> m_free;
 	QQueue<uint32_t*> m_queue;
 	uint32_t* m_buffer = nullptr;
@@ -195,7 +194,6 @@ private:
 	bool m_active = false;
 	bool m_started = false;
 	QTimer m_drawTimer;
-	qint64 m_timerResidue;
 	std::shared_ptr<CoreController> m_context;
 	CoreController::Interrupter m_interrupter;
 	bool m_supportsShaders;