Add display event to acknowledge ID deletion

We need to make sure the client doesn't reuse an object ID until the
server has seen the destroy request.  When a client destroys an ID
the server will now respond with the display.delete_id event, which lets
the client block reuse until it receives the event.

protocol/wayland.xml

@@ -76,6 +76,10 @@
       <arg name="name" type="uint" />
     </event>
 
+    <!-- Server has deleted the id and client can now reuse it. -->
+    <event name="delete_id">
+      <arg name="id" type="uint" />
+    </event>
   </interface>
 
   <interface name="wl_callback" version="1">

src/connection.c

@@ -587,9 +587,14 @@ wl_connection_demarshal(struct wl_connection *connection,
 			closure->args[i] = object;
 
 			*object = wl_map_lookup(objects, *p);
-			if (*object == NULL && *p != 0) {
+			if (*object == WL_ZOMBIE_OBJECT) {
+				/* references object we've already
+				 * destroyed client side */
+				*object = NULL;
+			} else if (*object == NULL && *p != 0) {
 				printf("unknown object (%d), message %s(%s)\n",
 				       *p, message->name, message->signature);
+				*object = NULL;
 				errno = EINVAL;
 				goto err;
 			}

src/wayland-client.c

@@ -141,7 +141,8 @@ wl_proxy_create(struct wl_proxy *factory, const struct wl_interface *interface)
 WL_EXPORT void
 wl_proxy_destroy(struct wl_proxy *proxy)
 {
-	wl_map_remove(&proxy->display->objects, proxy->object.id);
+	wl_map_insert_at(&proxy->display->objects,
+			 proxy->object.id, WL_ZOMBIE_OBJECT);
 	free(proxy);
 }
 
@@ -239,10 +240,23 @@ display_handle_global_remove(void *data,
 		}
 }
 
+static void
+display_handle_delete_id(void *data, struct wl_display *display, uint32_t id)
+{
+	struct wl_proxy *proxy;
+
+	proxy = wl_map_lookup(&display->objects, id);
+	if (proxy != WL_ZOMBIE_OBJECT)
+		fprintf(stderr, "server sent delete_id for live object\n");
+	else
+		wl_map_remove(&display->objects, id);
+}
+
 static const struct wl_display_listener display_listener = {
 	display_handle_error,
 	display_handle_global,
 	display_handle_global_remove,
+	display_handle_delete_id
 };
 
 static int
@@ -412,7 +426,11 @@ handle_event(struct wl_display *display,
 	wl_connection_copy(display->connection, p, size);
 	proxy = wl_map_lookup(&display->objects, id);
 
-	if (proxy == NULL || proxy->object.implementation == NULL) {
+	if (proxy == WL_ZOMBIE_OBJECT) {
+		fprintf(stderr, "Message to zombie object\n");
+		wl_connection_consume(display->connection, size);
+		return;
+	} else if (proxy == NULL || proxy->object.implementation == NULL) {
 		wl_connection_consume(display->connection, size);
 		return;
 	}

src/wayland-server.c

@@ -314,6 +314,8 @@ wl_resource_destroy(struct wl_resource *resource, uint32_t time)
 {
 	struct wl_client *client = resource->client;
 
+	wl_resource_post_event(resource->client->display_resource,
+			       WL_DISPLAY_DELETE_ID, resource->object.id);
 	wl_map_insert_at(&client->objects, resource->object.id, NULL);
 	destroy_resource(resource, &time);
 }

src/wayland-util.h

@@ -44,6 +44,8 @@ extern "C" {
 	const typeof( ((type *)0)->member ) *__mptr = (ptr);	\
 	(type *)( (char *)__mptr - offsetof(type,member) );})
 
+#define WL_ZOMBIE_OBJECT ((void *) 2)
+
 struct wl_message {
 	const char *name;
 	const char *signature;