smoke: Don't commit an xdg_surface with a NULL buffer

Committing to an xdg_surface with a NULL buffer is currently illegal in
the mutter implementation, so this simply causes the client to error and
exit.

It seems the reason the client did this was so it could add its own
frame callback, but toytoolkit actually provides accurate everything we
need. Just use its functions instead to get the time and schedule a
redraw.

Reviewed-by: Bryce Harrington <b.harrington@samsung.com>
Reviewed-by: Giulio Camuffo <giuliocamuffo@gmail.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>

clients/smoke.c

@@ -39,7 +39,6 @@ struct smoke {
 	struct widget *widget;
 	int width, height;
 	int current;
-	uint32_t time;
 	struct { float *d, *u, *v; } b[2];
 };
 
@@ -170,28 +169,11 @@ static void render(struct smoke *smoke, cairo_surface_t *surface)
 	}
 }
 
-static void
-frame_callback(void *data, struct wl_callback *callback, uint32_t time)
-{
-	struct smoke *smoke = data;
-
-	window_schedule_redraw(smoke->window);
-	smoke->time = time;
-
-	if (callback)
-		wl_callback_destroy(callback);
-}
-
-static const struct wl_callback_listener listener = {
-	frame_callback,
-};
-
 static void
 redraw_handler(struct widget *widget, void *data)
 {
 	struct smoke *smoke = data;
-	uint32_t time = smoke->time;
+	uint32_t time = widget_get_last_time(smoke->widget);
-	struct wl_callback *callback;
 	cairo_surface_t *surface;
 
 	diffuse(smoke, time / 30, smoke->b[0].u, smoke->b[1].u);
@@ -222,9 +204,7 @@ redraw_handler(struct widget *widget, void *data)
 
 	cairo_surface_destroy(surface);
 
-	callback = wl_surface_frame(window_get_wl_surface(smoke->window));
+	widget_schedule_redraw(smoke->widget);
-	wl_callback_add_listener(callback, &listener, smoke);
-	wl_surface_commit(window_get_wl_surface(smoke->window));
 }
 
 static void