implement surface frame

The surface frame callback lets a window know when it is a good time to show the
next frame if it is animating. In particular, this callback is used by
weston-simple-shm to throttle drawing.

examples/compositor/main.c

@@ -23,6 +23,13 @@ struct sample_state {
 	struct xdg_shell_state xdg_shell;
 };
 
+/*
+ * Convert timespec to milliseconds
+ */
+static inline int64_t timespec_to_msec(const struct timespec *a) {
+	return (int64_t)a->tv_sec * 1000 + a->tv_nsec / 1000000;
+}
+
 void handle_output_frame(struct output_state *output, struct timespec *ts) {
 	struct compositor_state *state = output->compositor;
 	struct sample_state *sample = state->data;
@@ -39,6 +46,12 @@ void handle_output_frame(struct output_state *output, struct timespec *ts) {
 			wlr_texture_get_matrix(surface->texture, &matrix,
 					&wlr_output->transform_matrix, 200, 200);
 			wlr_render_with_matrix(sample->renderer, surface->texture, &matrix);
+
+			struct wlr_frame_callback *cb, *cnext;
+			wl_list_for_each_safe(cb, cnext, &surface->frame_callback_list, link) {
+				wl_callback_send_done(cb->resource, timespec_to_msec(ts));
+				wl_resource_destroy(cb->resource);
+			}
 		}
 	}
 

include/wlr/types/wlr_surface.h

@@ -3,6 +3,11 @@
 
 #include <wayland-server.h>
 
+struct wlr_frame_callback {
+	struct wl_resource *resource;
+	struct wl_list link;
+};
+
 struct wlr_surface {
 	struct wl_resource *pending_buffer;
 	bool pending_attached;
@@ -16,6 +21,8 @@ struct wlr_surface {
 		struct wl_signal destroy;
 		struct wl_signal commit;
 	} signals;
+
+	struct wl_list frame_callback_list; // wl_surface.frame
 };
 
 struct wlr_renderer;

types/wlr_surface.c

@@ -23,9 +23,36 @@ static void surface_damage(struct wl_client *client,
 	wlr_log(L_DEBUG, "TODO: surface damage");
 }
 
+static void destroy_frame_callback(struct wl_resource *resource) {
+	struct wlr_frame_callback *cb = wl_resource_get_user_data(resource);
+
+	wl_list_remove(&cb->link);
+	free(cb);
+}
+
 static void surface_frame(struct wl_client *client,
 		struct wl_resource *resource, uint32_t callback) {
-	wlr_log(L_DEBUG, "TODO: surface frame");
+	struct wlr_frame_callback *cb;
+	struct wlr_surface *surface = wl_resource_get_user_data(resource);
+
+	cb = malloc(sizeof *cb);
+	if (cb == NULL) {
+		wl_resource_post_no_memory(resource);
+		return;
+	}
+
+	cb->resource = wl_resource_create(client, &wl_callback_interface, 1,
+					  callback);
+	if (cb->resource == NULL) {
+		free(cb);
+		wl_resource_post_no_memory(resource);
+		return;
+	}
+
+	wl_resource_set_implementation(cb->resource, NULL, cb,
+				       destroy_frame_callback);
+
+	wl_list_insert(surface->frame_callback_list.prev, &cb->link);
 }
 
 static void surface_set_opaque_region(struct wl_client *client,
@@ -103,6 +130,13 @@ static void destroy_surface(struct wl_resource *resource) {
 	struct wlr_surface *surface = wl_resource_get_user_data(resource);
 	wl_signal_emit(&surface->signals.destroy, surface);
 	wlr_texture_destroy(surface->texture);
+
+
+	struct wlr_frame_callback *cb, *next;
+	wl_list_for_each_safe(cb, next, &surface->frame_callback_list, link) {
+		wl_resource_destroy(cb->resource);
+	}
+
 	free(surface);
 }
 
@@ -113,6 +147,7 @@ struct wlr_surface *wlr_surface_create(struct wl_resource *res,
 	surface->resource = res;
 	wl_signal_init(&surface->signals.commit);
 	wl_signal_init(&surface->signals.destroy);
+	wl_list_init(&surface->frame_callback_list);
 	wl_resource_set_implementation(res, &surface_interface,
 			surface, destroy_surface);