@@ -60,7 +60,7 @@ GBAConfigLoad(&context->config);
 		GBAConfigLoadDefaults(&context->config, &opts);
 	}
 
-	context->gba->sync = 0;
+	context->gba->sync = &context->sync;
 	return true;
 }
 
@@ -190,6 +190,11 @@
 	int frameCounter = context->gba->video.frameCounter;
 	while (frameCounter == context->gba->video.frameCounter) {
 		ARMRunLoop(context->cpu);
+	}
+	if (context->sync.videoFrameSkip < 0) {
+		int frameskip = 0;
+		GBAConfigGetIntValue(&context->config, "frameskip", &frameskip);
+		context->sync.videoFrameSkip = frameskip;
 	}
 }
 

@@ -9,6 +9,7 @@
 #include "util/common.h"
 
 #include "gba/context/config.h"
+#include "gba/context/sync.h"
 #include "gba/input.h"
 
 struct GBAContext {
@@ -23,6 +24,7 @@ struct ARMComponent* components[GBA_COMPONENT_MAX];
 	struct GBAConfig config;
 	struct GBAOptions opts;
 	struct GBAInputMap inputMap;
+	struct GBASync sync;
 };
 
 bool GBAContextInit(struct GBAContext* context, const char* port);

@@ -17,6 +17,24 @@ .background = &runner->background.d
 	};
 	GUIMenuItemListInit(&menu.items, 0);
 	*GUIMenuItemListAppend(&menu.items) = (struct GUIMenuItem) {
+		.title = "Frameskip",
+		.data = "frameskip",
+		.submenu = 0,
+		.state = 0,
+		.validStates = (const char*[]) {
+			"0", "1", "2", "3", "4", "5", "6", "7", "8", "9", 0
+		}
+	};
+	*GUIMenuItemListAppend(&menu.items) = (struct GUIMenuItem) {
+		.title = "Show framerate",
+		.data = "fpsCounter",
+		.submenu = 0,
+		.state = false,
+		.validStates = (const char*[]) {
+			"Off", "On", 0
+		}
+	};
+	*GUIMenuItemListAppend(&menu.items) = (struct GUIMenuItem) {
 		.title = "Use BIOS if found",
 		.data = "useBios",
 		.submenu = 0,

@@ -108,6 +108,10 @@ runner->luminanceSource.luxLevel = 0;
 	runner->context.gba->luminanceSource = &runner->luminanceSource.d;
 	runner->background.d.draw = _drawBackground;
 	runner->background.p = runner;
+	runner->fps = 0;
+	runner->lastFpsCheck = 0;
+	runner->totalDelta = 0;
+	CircleBufferInit(&runner->fpsBuffer, FPS_BUFFER_SIZE * sizeof(uint32_t));
 	if (runner->setup) {
 		runner->setup(runner);
 	}
@@ -120,6 +124,7 @@ }
 	if (runner->context.config.port) {
 		GBAConfigSave(&runner->context.config);
 	}
+	CircleBufferDeinit(&runner->fpsBuffer);
 	GBAContextDeinit(&runner->context);
 }
 
@@ -212,8 +217,16 @@ GBAContextStart(&runner->context);
 		if (runner->gameLoaded) {
 			runner->gameLoaded(runner);
 		}
+
 		bool running = true;
 		while (running) {
+			CircleBufferClear(&runner->fpsBuffer);
+			runner->totalDelta = 0;
+			runner->fps = 0;
+			struct timeval tv;
+			gettimeofday(&tv, 0);
+			runner->lastFpsCheck = 1000000LL * tv.tv_sec + tv.tv_usec;
+
 			while (true) {
 				uint32_t guiKeys;
 				GUIPollInput(&runner->params, &guiKeys, 0);
@@ -239,9 +252,37 @@ runner->prepareForFrame(runner);
 				}
 				GBAContextFrame(&runner->context, keys);
 				if (runner->drawFrame) {
+					int drawFps = false;
+					GBAConfigGetIntValue(&runner->context.config, "fpsCounter", &drawFps);
+
 					runner->params.drawStart();
 					runner->drawFrame(runner, false);
+					if (drawFps) {
+						GUIFontPrintf(runner->params.font, 0, GUIFontHeight(runner->params.font), GUI_TEXT_LEFT, 0x7FFFFFFF, "%.2f fps", runner->fps);
+					}
 					runner->params.drawEnd();
+
+					if (runner->context.gba->video.frameCounter % FPS_GRANULARITY == 0) {
+						if (drawFps) {
+							struct timeval tv;
+							gettimeofday(&tv, 0);
+							uint64_t t = 1000000LL * tv.tv_sec + tv.tv_usec;
+							uint64_t delta = t - runner->lastFpsCheck;
+							runner->lastFpsCheck = t;
+							if (delta > 0x7FFFFFFFLL) {
+								CircleBufferClear(&runner->fpsBuffer);
+								runner->fps = 0;
+							}
+							if (CircleBufferSize(&runner->fpsBuffer) == CircleBufferCapacity(&runner->fpsBuffer)) {
+								int32_t last;
+								CircleBufferRead32(&runner->fpsBuffer, &last);
+								runner->totalDelta -= last;
+							}
+							CircleBufferWrite32(&runner->fpsBuffer, delta);
+							runner->totalDelta += delta;
+							runner->fps = (CircleBufferSize(&runner->fpsBuffer) * FPS_GRANULARITY * 1000000.0f) / (runner->totalDelta * sizeof(uint32_t));
+						}
+					}
 				}
 			}
 

@@ -7,6 +7,7 @@ #ifndef GUI_RUNNER_H
 #define GUI_RUNNER_H
 
 #include "gba/context/context.h"
+#include "util/circle-buffer.h"
 #include "util/gui.h"
 
 enum GBAGUIInput {
@@ -37,6 +38,11 @@ struct GBAGUIRunnerLux luminanceSource;
 
 	struct GUIMenuItem* configExtra;
 	size_t nConfigExtra;
+
+	float fps;
+	int64_t lastFpsCheck;
+	int32_t totalDelta;
+	struct CircleBuffer fpsBuffer;
 
 	void (*setup)(struct GBAGUIRunner*);
 	void (*teardown)(struct GBAGUIRunner*);