From a51066820a4930fb3d63d410c8a1c7d2bce1ebac Mon Sep 17 00:00:00 2001
From: Jeffrey Pfau <jeffrey@endrift.com>
Date: Mon, 1 Jun 2015 23:55:44 -0700
Subject: [PATCH] Qt: Replace pause-after-frame mutex with an atomic

---
 CHANGES                            |  1 +
 src/platform/qt/GameController.cpp | 13 +++++--------
 src/platform/qt/GameController.h   |  5 ++---
 3 files changed, 8 insertions(+), 11 deletions(-)

diff --git a/CHANGES b/CHANGES
index ae0e96536..4a2de53ac 100644
--- a/CHANGES
+++ b/CHANGES
@@ -55,6 +55,7 @@ Misc:
  - Qt: Fix windows being resizable when they shouldn't have been
  - Qt: Only hide cursor in full screen
  - Perf: Ability to load savestates immediately on launch
+ - Qt: Replace pause-after-frame mutex with an atomic
 
 0.2.1: (2015-05-13)
 Bugfixes:
diff --git a/src/platform/qt/GameController.cpp b/src/platform/qt/GameController.cpp
index 042007183..0adf18c01 100644
--- a/src/platform/qt/GameController.cpp
+++ b/src/platform/qt/GameController.cpp
@@ -40,6 +40,7 @@ GameController::GameController(QObject* parent)
 	, m_gameOpen(false)
 	, m_audioThread(new QThread(this))
 	, m_audioProcessor(AudioProcessor::create())
+	, m_pauseAfterFrame(false)
 	, m_videoSync(VIDEO_SYNC)
 	, m_audioSync(AUDIO_SYNC)
 	, m_fpsTarget(-1)
@@ -114,13 +115,10 @@ GameController::GameController(QObject* parent)
 
 	m_threadContext.frameCallback = [] (GBAThread* context) {
 		GameController* controller = static_cast<GameController*>(context->userData);
-		controller->m_pauseMutex.lock();
-		if (controller->m_pauseAfterFrame) {
+		if (controller->m_pauseAfterFrame.testAndSetAcquire(true, false)) {
 			GBAThreadPauseFromThread(context);
-			controller->m_pauseAfterFrame = false;
 			controller->gamePaused(&controller->m_threadContext);
 		}
-		controller->m_pauseMutex.unlock();
 		if (GBASyncDrawingFrame(&controller->m_threadContext.sync)) {
 			controller->frameAvailable(controller->m_drawContext);
 		} else {
@@ -422,10 +420,9 @@ void GameController::frameAdvance() {
 	if (m_rewindTimer.isActive()) {
 		return;
 	}
-	m_pauseMutex.lock();
-	m_pauseAfterFrame = true;
-	setPaused(false);
-	m_pauseMutex.unlock();
+	if (m_pauseAfterFrame.testAndSetRelaxed(false, true)) {
+		setPaused(false);
+	}
 }
 
 void GameController::setRewind(bool enable, int capacity, int interval) {
diff --git a/src/platform/qt/GameController.h b/src/platform/qt/GameController.h
index 176898d15..6848c6fd2 100644
--- a/src/platform/qt/GameController.h
+++ b/src/platform/qt/GameController.h
@@ -6,10 +6,10 @@
 #ifndef QGBA_GAME_CONTROLLER
 #define QGBA_GAME_CONTROLLER
 
+#include <QAtomicInt>
 #include <QFile>
 #include <QImage>
 #include <QObject>
-#include <QMutex>
 #include <QString>
 #include <QTimer>
 
@@ -177,8 +177,7 @@ private:
 	QThread* m_audioThread;
 	AudioProcessor* m_audioProcessor;
 
-	QMutex m_pauseMutex;
-	bool m_pauseAfterFrame;
+	QAtomicInt m_pauseAfterFrame;
 
 	bool m_videoSync;
 	bool m_audioSync;