layer-shell: implement configure scheduling

This commit introduces wlr_layer_surface_v1.scheduled and implements
configure scheduling mechanism used by xdg-surface, unifying the API.

include/wlr/types/wlr_layer_shell_v1.h

@@ -77,6 +77,10 @@ struct wlr_layer_surface_v1 {
 
 	struct wlr_layer_surface_v1_state current, pending;
 
+	// Properties to be sent to the client in the next configure event.
+	struct wlr_layer_surface_v1_configure scheduled;
+	struct wl_event_source *configure_idle;
+
 	struct wl_listener surface_destroy;
 
 	struct {
@@ -115,9 +119,9 @@ struct wlr_layer_shell_v1 *wlr_layer_shell_v1_create(struct wl_display *display)
 /**
  * Notifies the layer surface to configure itself with this width/height. The
  * layer_surface will signal its map event when the surface is ready to assume
- * this size.
+ * this size. Returns the associated configure serial.
  */
-void wlr_layer_surface_v1_configure(struct wlr_layer_surface_v1 *surface,
+uint32_t wlr_layer_surface_v1_set_size(struct wlr_layer_surface_v1 *surface,
 		uint32_t width, uint32_t height);
 
 /**

types/wlr_layer_shell_v1.c

@@ -234,6 +234,10 @@ static void layer_surface_unmap(struct wlr_layer_surface_v1 *surface) {
 	}
 
 	surface->configured = surface->mapped = false;
+	if (surface->configure_idle) {
+		wl_event_source_remove(surface->configure_idle);
+		surface->configure_idle = NULL;
+	}
 }
 
 static void layer_surface_destroy(struct wlr_layer_surface_v1 *surface) {
@@ -256,43 +260,48 @@ static void layer_surface_resource_destroy(struct wl_resource *resource) {
 	}
 }
 
-static bool layer_surface_state_changed(struct wlr_layer_surface_v1 *surface,
-		uint32_t width, uint32_t height) {
-	struct wlr_layer_surface_v1_configure last_acked;
-	struct wlr_layer_surface_v1_configure *configure;
-	if (wl_list_empty(&surface->configure_list)) {
-		last_acked.width = surface->pending.actual_width;
-		last_acked.height = surface->pending.actual_height;
-		configure = &last_acked;
-	} else {
-		configure = wl_container_of(surface->configure_list.prev,
-			configure, link);
+static void surface_send_configure(void *data) {
+	struct wlr_layer_surface_v1 *surface = data;
+
+	surface->configure_idle = NULL;
+
+	struct wlr_layer_surface_v1_configure *configure =
+		calloc(1, sizeof(*configure));
+	if (configure == NULL) {
+		wl_resource_post_no_memory(surface->resource);
+		return;
 	}
 
-	bool changed = configure->width != width
-		|| configure->height != height;
-	return changed;
+	wl_list_insert(surface->configure_list.prev, &configure->link);
+	configure->serial = surface->scheduled.serial;
+	configure->width = surface->scheduled.width;
+	configure->height = surface->scheduled.height;
+
+	zwlr_layer_surface_v1_send_configure(surface->resource,
+		configure->serial, configure->width, configure->height);
 }
 
-void wlr_layer_surface_v1_configure(struct wlr_layer_surface_v1 *surface,
-		uint32_t width, uint32_t height) {
-	if (layer_surface_state_changed(surface, width, height)) {
-		struct wl_display *display =
-			wl_client_get_display(wl_resource_get_client(surface->resource));
-		struct wlr_layer_surface_v1_configure *configure =
-			calloc(1, sizeof(struct wlr_layer_surface_v1_configure));
-		if (configure == NULL) {
-			wl_client_post_no_memory(wl_resource_get_client(surface->resource));
-			return;
+static uint32_t schedule_configure(struct wlr_layer_surface_v1 *surface) {
+	struct wl_client *client = wl_resource_get_client(surface->resource);
+	struct wl_display *display = wl_client_get_display(client);
+	struct wl_event_loop *loop = wl_display_get_event_loop(display);
+
+	if (surface->configure_idle == NULL) {
+		surface->scheduled.serial = wl_display_next_serial(display);
+		surface->configure_idle = wl_event_loop_add_idle(loop,
+			surface_send_configure, surface);
+		if (surface->configure_idle == NULL) {
+			wl_client_post_no_memory(client);
 		}
-		wl_list_insert(surface->configure_list.prev, &configure->link);
-		configure->width = width;
-		configure->height = height;
-		configure->serial = wl_display_next_serial(display);
-		zwlr_layer_surface_v1_send_configure(surface->resource,
-				configure->serial, configure->width,
-				configure->height);
 	}
+	return surface->scheduled.serial;
+}
+
+uint32_t wlr_layer_surface_v1_set_size(struct wlr_layer_surface_v1 *surface,
+		uint32_t width, uint32_t height) {
+	surface->scheduled.width = width;
+	surface->scheduled.height = height;
+	return schedule_configure(surface);
 }
 
 void wlr_layer_surface_v1_destroy(struct wlr_layer_surface_v1 *surface) {