screencast: use the pipewire callback process to start screencast

We can trigger that with pw_stream_trigger_process when we are the
driver of the stream. Additionally this let's us run passivly with the
consumer driving the stream.

include/pipewire_screencast.h

@@ -6,6 +6,8 @@
 #define XDPW_PWR_BUFFERS 1
 #define XDPW_PWR_ALIGN 16
 
+void xdpw_pwr_trigger_process(struct xdpw_screencast_instance *cast);
+bool xdpw_pwr_is_driving(struct xdpw_screencast_instance *cast);
 void xdpw_pwr_dequeue_buffer(struct xdpw_screencast_instance *cast);
 void xdpw_pwr_enqueue_buffer(struct xdpw_screencast_instance *cast);
 void pwr_update_stream_param(struct xdpw_screencast_instance *cast);

src/screencast/pipewire_screencast.c

@@ -44,6 +44,14 @@ static struct spa_pod *build_format(struct spa_pod_builder *b, enum spa_video_fo
 	return spa_pod_builder_pop(b, &f[0]);
 }
 
+static void pwr_handle_stream_process(void *data) {
+	struct xdpw_screencast_instance *cast = data;
+
+	logprint(TRACE, "pipewire: stream process");
+
+	xdpw_wlr_frame_start(cast);
+}
+
 static void pwr_handle_stream_state_changed(void *data,
 		enum pw_stream_state old, enum pw_stream_state state, const char *error) {
 	struct xdpw_screencast_instance *cast = data;
@@ -174,8 +182,17 @@ static const struct pw_stream_events pwr_stream_events = {
 	.param_changed = pwr_handle_stream_param_changed,
 	.add_buffer = pwr_handle_stream_add_buffer,
 	.remove_buffer = pwr_handle_stream_remove_buffer,
+	.process = pwr_handle_stream_process,
 };
 
+void xdpw_pwr_trigger_process(struct xdpw_screencast_instance *cast) {
+	pw_stream_trigger_process(cast->stream);
+}
+
+bool xdpw_pwr_is_driving(struct xdpw_screencast_instance *cast) {
+	return pw_stream_is_driving(cast->stream);
+}
+
 void xdpw_pwr_dequeue_buffer(struct xdpw_screencast_instance *cast) {
 	logprint(TRACE, "pipewire: dequeueing buffer");
 

src/screencast/wlr_screencast.c

@@ -53,17 +53,17 @@ void xdpw_wlr_frame_finish(struct xdpw_screencast_instance *cast) {
 		return ;
 	}
 
-	if (cast->pwr_stream_state) {
+	if (cast->pwr_stream_state && xdpw_pwr_is_driving(cast)) {
 		if (cast->frame_state == XDPW_FRAME_STATE_SUCCESS) {
 			uint64_t delay_ns = fps_limit_measure_end(&cast->fps_limit, cast->framerate);
 			if (delay_ns > 0) {
 				xdpw_add_timer(cast->ctx->state, delay_ns,
-					(xdpw_event_loop_timer_func_t) xdpw_wlr_frame_start, cast);
+					(xdpw_event_loop_timer_func_t) xdpw_pwr_trigger_process, cast);
 			} else {
-				xdpw_wlr_frame_start(cast);
+				xdpw_pwr_trigger_process(cast);
 			}
 		} else {
-			xdpw_wlr_frame_start(cast);
+			xdpw_pwr_trigger_process(cast);
 		}
 	}
 }