Introduce an optional CLI argument for the max FPS

The default value is 0, meaning unlimited FPS; this also disables the
measuring and logging of the average FPS.

include/fps_limit.h

@@ -10,6 +10,6 @@ struct fps_limit_state {
 	uint32_t fps_measurement_frame_count;
 };
 
-void fps_limit_apply(struct fps_limit_state* state);
+void fps_limit_apply(struct fps_limit_state* state, double max_fps);
 
 #endif

include/screencast_common.h

@@ -61,6 +61,7 @@ struct xdpw_screencast_context {
 
 	// cli options
 	const char *output_name;
+	double max_fps;
 
 	// sessions
 	struct wl_list screencast_instances;
@@ -95,6 +96,7 @@ struct xdpw_screencast_instance {
 	bool quit;
 
 	// fps limit
+	double max_fps; // 0 means no limit
 	struct fps_limit_state fps_limit;
 };
 

include/xdpw.h

@@ -41,7 +41,7 @@ enum {
 };
 
 int xdpw_screenshot_init(struct xdpw_state *state);
-int xdpw_screencast_init(struct xdpw_state *state, const char *output_name);
+int xdpw_screencast_init(struct xdpw_state *state, const char *output_name, double max_fps);
 
 struct xdpw_request *xdpw_request_create(sd_bus *bus, const char *object_path);
 void xdpw_request_destroy(struct xdpw_request *req);

src/core/main.c

@@ -25,6 +25,7 @@ static int xdpw_usage(FILE* stream, int rc) {
 		"    -o, --output=<name>              Select output to capture.\n"
 		"                                     metadata (performs no conversion).\n"
 		"    -r, --replace                    Replace a running instance.\n"
+		"    -f, --max-fps=<fps>              Set the FPS limit (default 0, no limit).\n"
 		"    -h, --help                       Get help (this text).\n"
 		"\n";
 
@@ -42,12 +43,14 @@ int main(int argc, char *argv[]) {
 	const char* output_name = NULL;
 	enum LOGLEVEL loglevel = ERROR;
 	bool replace = false;
+	double max_fps = 0;
 
-	static const char* shortopts = "l:o:rh";
+	static const char* shortopts = "l:o:f:rh";
 	static const struct option longopts[] = {
 		{ "loglevel", required_argument, NULL, 'l' },
 		{ "output", required_argument, NULL, 'o' },
 		{ "replace", no_argument, NULL, 'r' },
+		{ "max-fps", required_argument, NULL, 'f' },
 		{ "help", no_argument, NULL, 'h' },
 		{ NULL, 0, NULL, 0 }
 	};
@@ -67,6 +70,9 @@ int main(int argc, char *argv[]) {
 		case 'r':
 			replace = true;
 			break;
+		case 'f':
+			max_fps = atof(optarg);
+			break;
 		case 'h':
 			return xdpw_usage(stdout, EXIT_SUCCESS);
 		default:
@@ -116,7 +122,7 @@ int main(int argc, char *argv[]) {
 	wl_list_init(&state.xdpw_sessions);
 
 	xdpw_screenshot_init(&state);
-	ret = xdpw_screencast_init(&state, output_name);
+	ret = xdpw_screencast_init(&state, output_name, max_fps);
 	if (ret < 0) {
 		logprint(ERROR, "xdpw: failed to initialize screencast");
 		goto error;

src/screencast/fps_limit.c

@@ -5,14 +5,13 @@
 #include <unistd.h>
 
 #define FPS_MEASURE_PERIOD_SEC 5.0
-#define TARGET_FPS 10.0
 
 void measure_fps(struct fps_limit_state* state, uint64_t now_us);
 
 void fps_limit_apply(struct fps_limit_state* state, double max_fps) {
 	if (max_fps <= 0.0) 
 		return;
-
+		
 	uint64_t now_us = gettime_us();
 
 	if (state->last_time_us == 0) {
@@ -23,7 +22,7 @@ void fps_limit_apply(struct fps_limit_state* state, double max_fps) {
 
 		measure_fps(state, now_us);
 
-		uint64_t target_us = (1.0 / TARGET_FPS) * 1e6;
+		uint64_t target_us = (1.0 / max_fps) * 1e6;
 		int64_t delay_us = target_us - elapsed_us;
 		if (delay_us > 0) {
 			logprint(TRACE, "fps_limit: elapsed time since the end of last sleep: %u, sleeping for %u (microseconds)", elapsed_us, delay_us);

src/screencast/screencast.c

@@ -22,6 +22,7 @@ void xdpw_screencast_instance_init(struct xdpw_screencast_context *ctx,
 		struct xdpw_screencast_instance *cast, struct xdpw_wlr_output *out, bool with_cursor) {
 	cast->ctx = ctx;
 	cast->target_output = out;
+	cast->max_fps = ctx->max_fps;
 	cast->framerate = out->framerate;
 	cast->with_cursor = with_cursor;
 	cast->refcount = 1;
@@ -434,12 +435,13 @@ static const sd_bus_vtable screencast_vtable[] = {
 	SD_BUS_VTABLE_END
 };
 
-int xdpw_screencast_init(struct xdpw_state *state, const char *output_name) {
+int xdpw_screencast_init(struct xdpw_state *state, const char *output_name, double max_fps) {
 	sd_bus_slot *slot = NULL;
 
 	state->screencast = (struct xdpw_screencast_context) { 0 };
 	state->screencast.state = state;
 	state->screencast.output_name = output_name;
+	state->screencast.max_fps = max_fps;
 
 	int err;
 	err = xdpw_pwr_core_connect(state);

src/screencast/wlr_screencast.c

@@ -135,7 +135,7 @@ static void wlr_frame_buffer_done(void *data,
 
 	logprint(TRACE, "wlroots: buffer_done event handler");
 
-	fps_limit_apply(&cast->fps_limit);
+	fps_limit_apply(&cast->fps_limit, cast->max_fps);
 
 	zwlr_screencopy_frame_v1_copy_with_damage(frame, cast->simple_frame.buffer);
 	logprint(TRACE, "wlroots: frame copied");