From 00dd5bdaa81e97f46474f527443e8cf07f6e1ae9 Mon Sep 17 00:00:00 2001
From: Jeffrey Pfau <jeffrey@endrift.com>
Date: Wed, 24 Apr 2013 02:43:55 -0700
Subject: [PATCH] Dual condition-variable non-hacky waiting-on-frame

---
 src/gba/renderers/video-software.c | 12 ++++++++----
 src/gba/renderers/video-software.h |  3 ++-
 src/main.c                         | 16 +++++++++++++---
 3 files changed, 23 insertions(+), 8 deletions(-)

diff --git a/src/gba/renderers/video-software.c b/src/gba/renderers/video-software.c
index bba7f3698..1e17e3195 100644
--- a/src/gba/renderers/video-software.c
+++ b/src/gba/renderers/video-software.c
@@ -46,7 +46,8 @@ void GBAVideoSoftwareRendererCreate(struct GBAVideoSoftwareRenderer* renderer) {
 		pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
 		renderer->mutex = mutex;
 		pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
-		renderer->cond = cond;
+		renderer->upCond = cond;
+		renderer->downCond = cond;
 	}
 }
 
@@ -93,14 +94,16 @@ static void GBAVideoSoftwareRendererInit(struct GBAVideoRenderer* renderer) {
 	}
 
 	pthread_mutex_init(&softwareRenderer->mutex, 0);
-	pthread_cond_init(&softwareRenderer->cond, 0);
+	pthread_cond_init(&softwareRenderer->upCond, 0);
+	pthread_cond_init(&softwareRenderer->downCond, 0);
 }
 
 static void GBAVideoSoftwareRendererDeinit(struct GBAVideoRenderer* renderer) {
 	struct GBAVideoSoftwareRenderer* softwareRenderer = (struct GBAVideoSoftwareRenderer*) renderer;
 
 	pthread_mutex_destroy(&softwareRenderer->mutex);
-	pthread_cond_destroy(&softwareRenderer->cond);
+	pthread_cond_destroy(&softwareRenderer->upCond);
+	pthread_cond_destroy(&softwareRenderer->downCond);
 }
 
 static uint16_t GBAVideoSoftwareRendererWriteVideoRegister(struct GBAVideoRenderer* renderer, uint32_t address, uint16_t value) {
@@ -210,8 +213,9 @@ static void GBAVideoSoftwareRendererFinishFrame(struct GBAVideoRenderer* rendere
 
 	pthread_mutex_lock(&softwareRenderer->mutex);
 	renderer->framesPending++;
+	pthread_cond_broadcast(&softwareRenderer->upCond);
 	if (!renderer->turbo) {
-		pthread_cond_wait(&softwareRenderer->cond, &softwareRenderer->mutex);
+		pthread_cond_wait(&softwareRenderer->downCond, &softwareRenderer->mutex);
 	}
 	pthread_mutex_unlock(&softwareRenderer->mutex);
 }
diff --git a/src/gba/renderers/video-software.h b/src/gba/renderers/video-software.h
index 866ebc4d6..6ce21f3f9 100644
--- a/src/gba/renderers/video-software.h
+++ b/src/gba/renderers/video-software.h
@@ -71,7 +71,8 @@ struct GBAVideoSoftwareRenderer {
 	uint16_t* row;
 
 	pthread_mutex_t mutex;
-	pthread_cond_t cond;
+	pthread_cond_t upCond;
+	pthread_cond_t downCond;
 };
 
 void GBAVideoSoftwareRendererCreate(struct GBAVideoSoftwareRenderer* renderer);
diff --git a/src/main.c b/src/main.c
index 3e5e28a35..2ae792e83 100644
--- a/src/main.c
+++ b/src/main.c
@@ -9,6 +9,7 @@
 #include <fcntl.h>
 #include <errno.h>
 #include <signal.h>
+#include <sys/time.h>
 #include <unistd.h>
 
 struct GLSoftwareRenderer {
@@ -118,12 +119,21 @@ static void _GBASDLRunloop(struct GBAThread* context, struct GLSoftwareRenderer*
 
 			SDL_GL_SwapBuffers();
 			pthread_mutex_lock(&renderer->d.mutex);
-			pthread_cond_broadcast(&renderer->d.cond);
+			pthread_cond_broadcast(&renderer->d.downCond);
 			pthread_mutex_unlock(&renderer->d.mutex);
 		} else {
+			while (!renderer->d.d.framesPending) {
+				struct timeval tv;
+				struct timespec ts;
+				gettimeofday(&tv, 0);
+				ts.tv_sec = tv.tv_sec;
+				ts.tv_nsec = tv.tv_usec * 1000 + 800000;
+				int err = pthread_cond_timedwait(&renderer->d.upCond, &renderer->d.mutex, &ts);
+				if (err == ETIMEDOUT) {
+					break;
+				}
+			}
 			pthread_mutex_unlock(&renderer->d.mutex);
-			// We have no frame, let's just wait a sec to see if we get one.
-			usleep(500);
 		}
 		while (SDL_PollEvent(&event)) {
 			switch (event.type) {