Add FPS profiling (set DEBUG_FPS when running tint2)

src/tint.c

@@ -79,6 +79,8 @@ XSettingsClient *xsettings_client = NULL;
 timeout *detect_compositor_timer = NULL;
 int detect_compositor_timer_counter = 0;
 
+gboolean debug_fps = FALSE;
+
 void detect_compositor(void *arg)
 {
 	if (server.composite_manager) {
@@ -376,6 +378,7 @@ void init(int argc, char *argv[])
 
 	debug_geometry = getenv("DEBUG_GEOMETRY") != NULL;
 	debug_gradients = getenv("DEBUG_GRADIENTS") != NULL;
+	debug_fps = getenv("DEBUG_FPS") != NULL;
 }
 
 static int sigchild_pipe_valid = FALSE;
@@ -1560,8 +1563,14 @@ start:
 	int ufd = uevent_init();
 	int hidden_dnd = 0;
 
+	double ts_event_read = 0;
+	double ts_event_processed = 0;
+	double ts_render_finished = 0;
+	double ts_flush_finished = 0;
 	while (1) {
 		if (panel_refresh) {
+			if (debug_fps)
+				ts_event_processed = get_time();
 			if (systray_profile)
 				fprintf(stderr,
 				        BLUE "[%f] %s:%d redrawing panel" RESET "\n",
@@ -1635,7 +1644,23 @@ start:
 					          0);
 				}
 			}
+			if (debug_fps)
+				ts_render_finished = get_time();
 			XFlush(server.display);
+			if (debug_fps) {
+				ts_flush_finished = get_time();
+				double period = ts_flush_finished - ts_event_read;
+				double fps = 1.0 / period;
+				double proc_ratio = (ts_event_processed - ts_event_read) / period;
+				double render_ratio = (ts_render_finished - ts_event_processed) / period;
+				double flush_ratio = (ts_flush_finished - ts_render_finished) / period;
+				fprintf(stderr,
+				        BLUE "fps = %.1f : processing %.1f%%, rendering %.1f%%, flushing %.1f%%" RESET "\n",
+				        fps,
+				        proc_ratio * 100,
+				        render_ratio * 100,
+				        flush_ratio * 100);
+			}
 		}
 
 		// Create a File Description Set containing x11_fd
@@ -1686,6 +1711,8 @@ start:
 			if (XPending(server.display) > 0) {
 				XEvent e;
 				XNextEvent(server.display, &e);
+				if (debug_fps)
+					ts_event_read = get_time();
 #if HAVE_SN
 				if (startup_notifications)
 					sn_display_process_event(server.sn_display, &e);