nested: Add double-buffered state semantics to the nested example

The buffer and frame callback state on the surfaces in the nested
compositor example are now double-buffered so that they only take
effect when the commit request is received. This doesn't really make
much difference for the current state that the example has but it will
be useful when more state is added in later patches.

clients/nested.c

@@ -86,6 +86,16 @@ struct nested_surface {
 	GLuint texture;
 	struct wl_list link;
 	cairo_surface_t *cairo_surface;
+
+	struct {
+		/* wl_surface.attach */
+		int newly_attached;
+		struct nested_buffer *buffer;
+		struct wl_listener buffer_destroy_listener;
+
+		/* wl_surface.frame */
+		struct wl_list frame_callback_list;
+	} pending;
 };
 
 struct nested_frame_callback {
@@ -353,6 +363,11 @@ static void
 destroy_surface(struct wl_resource *resource)
 {
 	struct nested_surface *surface = wl_resource_get_user_data(resource);
+	struct nested_frame_callback *cb, *next;
+
+	wl_list_for_each_safe(cb, next,
+			      &surface->pending.frame_callback_list, link)
+		wl_resource_destroy(cb->resource);
 
 	nested_buffer_reference(&surface->buffer_ref, NULL);
 
@@ -374,45 +389,75 @@ surface_attach(struct wl_client *client,
 {
 	struct nested_surface *surface = wl_resource_get_user_data(resource);
 	struct nested *nested = surface->nested;
-	EGLint format, width, height;
+	struct nested_buffer *buffer = NULL;
-	cairo_device_t *device;
-	struct nested_buffer *buffer =
-		nested_buffer_from_resource(buffer_resource);
 
-	nested_buffer_reference(&surface->buffer_ref, buffer);
+	if (buffer_resource) {
+		int format;
 
 		if (!query_buffer(nested->egl_display, (void *) buffer_resource,
 				  EGL_TEXTURE_FORMAT, &format)) {
-		fprintf(stderr, "attaching non-egl wl_buffer\n");
+			wl_resource_post_error(buffer_resource,
+					       WL_DISPLAY_ERROR_INVALID_OBJECT,
+					       "attaching non-egl wl_buffer");
 			return;
 		}
 
-	if (surface->image != EGL_NO_IMAGE_KHR)
-		destroy_image(nested->egl_display, surface->image);
-	if (surface->cairo_surface)
-		cairo_surface_destroy(surface->cairo_surface);
-
 		switch (format) {
 		case EGL_TEXTURE_RGB:
 		case EGL_TEXTURE_RGBA:
 			break;
 		default:
-		fprintf(stderr, "unhandled format: %x\n", format);
+			wl_resource_post_error(buffer_resource,
+					       WL_DISPLAY_ERROR_INVALID_OBJECT,
+					       "invalid format");
 			return;
 		}
 
+		buffer = nested_buffer_from_resource(buffer_resource);
+		if (buffer == NULL) {
+			wl_client_post_no_memory(client);
+			return;
+		}
+	}
+
+	if (surface->pending.buffer)
+		wl_list_remove(&surface->pending.buffer_destroy_listener.link);
+
+	surface->pending.buffer = buffer;
+	surface->pending.newly_attached = 1;
+	if (buffer) {
+		wl_signal_add(&buffer->destroy_signal,
+			      &surface->pending.buffer_destroy_listener);
+	}
+}
+
+static void
+nested_surface_attach(struct nested_surface *surface,
+		      struct nested_buffer *buffer)
+{
+	struct nested *nested = surface->nested;
+	EGLint width, height;
+	cairo_device_t *device;
+
+	nested_buffer_reference(&surface->buffer_ref, buffer);
+
+	if (surface->image != EGL_NO_IMAGE_KHR)
+		destroy_image(nested->egl_display, surface->image);
+	if (surface->cairo_surface)
+		cairo_surface_destroy(surface->cairo_surface);
+
 	surface->image = create_image(nested->egl_display, NULL,
-				      EGL_WAYLAND_BUFFER_WL, buffer_resource,
+				      EGL_WAYLAND_BUFFER_WL, buffer->resource,
 				      NULL);
 	if (surface->image == EGL_NO_IMAGE_KHR) {
 		fprintf(stderr, "failed to create img\n");
 		return;
 	}
 
-	query_buffer(nested->egl_display,
+	query_buffer(nested->egl_display, (void *) buffer->resource,
-		     (void *) buffer_resource, EGL_WIDTH, &width);
+		     EGL_WIDTH, &width);
-	query_buffer(nested->egl_display,
+	query_buffer(nested->egl_display, (void *) buffer->resource,
-		     (void *) buffer_resource, EGL_HEIGHT, &height);
+		     EGL_HEIGHT, &height);
 
 	device = display_get_cairo_device(nested->display);
 	surface->cairo_surface = 
@@ -420,8 +465,6 @@ surface_attach(struct wl_client *client,
 						    CAIRO_CONTENT_COLOR_ALPHA,
 						    surface->texture,
 						    width, height);
-
-	window_schedule_redraw(nested->window);
 }
 
 static void
@@ -446,7 +489,6 @@ surface_frame(struct wl_client *client,
 {
 	struct nested_frame_callback *callback;
 	struct nested_surface *surface = wl_resource_get_user_data(resource);
-	struct nested *nested = surface->nested;
 
 	callback = malloc(sizeof *callback);
 	if (callback == NULL) {
@@ -459,7 +501,8 @@ surface_frame(struct wl_client *client,
 	wl_resource_set_implementation(callback->resource, NULL, callback,
 				       destroy_frame_callback);
 
-	wl_list_insert(nested->frame_callback_list.prev, &callback->link);
+	wl_list_insert(surface->pending.frame_callback_list.prev,
+		       &callback->link);
 }
 
 static void
@@ -481,6 +524,25 @@ surface_set_input_region(struct wl_client *client,
 static void
 surface_commit(struct wl_client *client, struct wl_resource *resource)
 {
+	struct nested_surface *surface = wl_resource_get_user_data(resource);
+	struct nested *nested = surface->nested;
+
+	/* wl_surface.attach */
+	if (surface->pending.newly_attached)
+		nested_surface_attach(surface, surface->pending.buffer);
+
+	if (surface->pending.buffer) {
+		wl_list_remove(&surface->pending.buffer_destroy_listener.link);
+		surface->pending.buffer = NULL;
+	}
+	surface->pending.newly_attached = 0;
+
+	/* wl_surface.frame */
+	wl_list_insert_list(&nested->frame_callback_list,
+			    &surface->pending.frame_callback_list);
+	wl_list_init(&surface->pending.frame_callback_list);
+
+	window_schedule_redraw(nested->window);
 }
 
 static void
@@ -501,6 +563,16 @@ static const struct wl_surface_interface surface_interface = {
 	surface_set_buffer_transform
 };
 
+static void
+surface_handle_pending_buffer_destroy(struct wl_listener *listener, void *data)
+{
+	struct nested_surface *surface =
+		container_of(listener, struct nested_surface,
+			     pending.buffer_destroy_listener);
+
+	surface->pending.buffer = NULL;
+}
+
 static void
 compositor_create_surface(struct wl_client *client,
 			  struct wl_resource *resource, uint32_t id)
@@ -516,6 +588,10 @@ compositor_create_surface(struct wl_client *client,
 
 	surface->nested = nested;
 
+	wl_list_init(&surface->pending.frame_callback_list);
+	surface->pending.buffer_destroy_listener.notify =
+		surface_handle_pending_buffer_destroy;
+
 	display_acquire_window_surface(nested->display,
 				       nested->window, NULL);