Fixed|UI|Client: Game UI should be behind busy transition

If possible, keep the game UI behind the busy transition. Note that
when using the UI compositor for Oculus Rift, we must have the busy
transition in the root to cover the entire view, and this will let
the game UI to be drawn before the transition is finished.

doomsday/client/src/ui/clientwindow.cpp

@@ -174,17 +174,17 @@ DENG2_OBSERVES(App,              StartupComplete)
         game->disable();
         root.add(game);
 
+        gameUI = new GameUIWidget;
+        gameUI->rule().setRect(root.viewRule());
+        gameUI->disable();
+        container().add(gameUI);
+
         // Busy widget shows progress indicator and frozen game content.
         busy = new BusyWidget;
         busy->hide(); // normally hidden
         busy->rule().setRect(root.viewRule());
         root.add(busy);
 
-        gameUI = new GameUIWidget;
-        gameUI->rule().setRect(root.viewRule());
-        gameUI->disable();
-        container().add(gameUI);
-
         // Game selection.
         gameSelMenu = new GameSelectionWidget;
         gameSelMenu->rule()
@@ -575,6 +575,13 @@ DENG2_OBSERVES(App,              StartupComplete)
         }
 
         container().add(gameUI);
+
+        if(&container() == &root)
+        {
+            // Make sure the game UI doesn't show up over the busy transition.
+            container().moveChildBefore(gameUI, *busy);
+        }
+
         container().add(gameSelMenu);
         if(sidebar) container().add(sidebar);
         container().add(notifications);