Don't crash on accesses to stale window-backed apps

The JS code could still be holding on to a reference to a window-backed app
after all windows have vanished. (For example, the dash queues an idle to
refetch apps and display them.) Avoid dying with an error message if we
attempt to activate or otherwise manipulate such a window.

https://bugzilla.gnome.org/show_bug.cgi?id=674799

diff --git a/src/shell-app.c b/src/shell-app.c
index 4f1fe10f7446e52289afeb9bd675970620453d5d..afc45cb65836c75a042436db400e72696a1d429a 100644 (file)
--- a/src/shell-app.c
+++ b/src/shell-app.c
@@ -156,16 +156,20 @@ static MetaWindow *
 window_backed_app_get_window (ShellApp     *app)
 {
   g_assert (app->info == NULL);
-  g_assert (app->running_state);
-  g_assert (app->running_state->windows);
-  return app->running_state->windows->data;
+  if (app->running_state)
+    {
+      g_assert (app->running_state->windows);
+      return app->running_state->windows->data;
+    }
+  else
+    return NULL;
 }
 
 static ClutterActor *
 window_backed_app_get_icon (ShellApp *app,
                             int       size)
 {
-  MetaWindow *window;
+  MetaWindow *window = NULL;
   ClutterActor *actor;
   gint scale;
   ShellGlobal *global;
@@ -181,14 +185,16 @@ window_backed_app_get_icon (ShellApp *app,
    * window-backend apps, it's possible we get a request for the icon.
    * Avoid asserting here and just return an empty image.
    */
-  if (app->running_state == NULL)
+  if (app->running_state != NULL)
+    window = window_backed_app_get_window (app);
+
+  if (window == NULL)
     {
       actor = clutter_texture_new ();
       g_object_set (actor, "opacity", 0, "width", (float) size, "height", (float) size, NULL);
       return actor;
     }
 
-  window = window_backed_app_get_window (app);
   actor = st_texture_cache_bind_cairo_surface_property (st_texture_cache_get_default (),
                                                         G_OBJECT (window),
                                                         "icon");
@@ -232,9 +238,10 @@ shell_app_get_name (ShellApp *app)
   else
     {
       MetaWindow *window = window_backed_app_get_window (app);
-      const char *name;
+      const char *name = NULL;
 
-      name = meta_window_get_wm_class (window);
+      if (window)
+        name = meta_window_get_wm_class (window);
       if (!name)
         name = C_("program", "Unknown");
       return name;
@@ -1154,7 +1161,13 @@ shell_app_launch (ShellApp     *app,
   if (app->info == NULL)
     {
       MetaWindow *window = window_backed_app_get_window (app);
-      meta_window_activate (window, timestamp);
+      /* We don't use an error return if there no longer any windows, because the
+       * user attempting to activate a stale window backed app isn't something
+       * we would expect the caller to meaningfully handle or display an error
+       * message to the user.
+       */
+      if (window)
+        meta_window_activate (window, timestamp);
       return TRUE;
     }