compositor.c: hidden panel windows aren't top (#802)

Top windows are tracked for the purpose of evaluating whether to
unredirect the top window.  Prior to this change, systray icon windows
could be considered top windows, even in the presence of a fullscreen
window.  When this occurs, the fullscreen window will never be
unredirected, since it is not the top window.

When a window is fullscreen, we already hide the panel, including all
systray icons.  This change ensures that we do not consider such hidden
panel windows to ever be top windows.

Author: jknockel

src/compositor/compositor.c

@@ -1189,6 +1189,13 @@ get_top_visible_window_actor (MetaCompositor *compositor)
 
       if (!window->visible_to_compositor)
         continue;
+      if (meta_window_get_client_pid (window) == getpid ())
+        {
+          if (!clutter_actor_get_paint_visibility (CLUTTER_ACTOR (window_actor)))
+            continue;
+          if (clutter_actor_get_paint_opacity (CLUTTER_ACTOR (window_actor)) == 0)
+            continue;
+        }
 
       meta_window_get_buffer_rect (window, &buffer_rect);
       meta_display_get_size (priv->display,