Fixed|UI|libdeng2|Stereo 3D: Allow enabling UI composition during bus…

…y mode

Fixes an issue where the display would remain black after launching
straight into a map with -g and -warp options.

Also, during libdeng2 Widget tree notification, handle the situation
when a widget is removed from the tree after a notification method
has been called on it.

doomsday/client/src/ui/clientwindow.cpp

@@ -469,9 +469,6 @@ DENG2_OBSERVES(App,              StartupComplete)
             return Continue;
         }
 
-        // Offscreen composition is only needed in Oculus Rift mode.
-        enableCompositor(VR::mode() == VR::MODE_OCULUS_RIFT);
-
         // The canvas needs to be recreated when the GL format has changed
         // (e.g., multisampling).
         if(needRecreateCanvas)
@@ -767,6 +764,9 @@ void ClientWindow::draw()
     // Don't run the main loop until after the paint event has been dealt with.
     ClientApp::app().loop().pause();
 
+    // Offscreen composition is only needed in Oculus Rift mode.
+    d->enableCompositor(VR::mode() == VR::MODE_OCULUS_RIFT);
+
     if(d->performDeferredTasks() == Instance::AbortFrame)
     {
         // Shouldn't draw right now.

doomsday/libdeng2/src/widgets/widget.cpp

@@ -396,12 +396,20 @@ Widget::NotifyArgs::Result Widget::notifyTree(NotifyArgs const &args)
         {
             // The list of children was modified; let's update the current
             // index accordingly.
-            idx = d->children.indexOf(i);
+            int newIdx = d->children.indexOf(i);
 
-            // The current widget cannot be removed.
-            DENG2_ASSERT(idx >= 0);
-
-            i = d->children.at(idx);
+            // The current widget remains in the tree.
+            if(newIdx >= 0)
+            {
+                idx = newIdx;
+                i = d->children.at(newIdx);
+            }
+            else
+            {
+                // The current widget is gone. Continue with the same index.
+                idx--;
+                continue;
+            }
         }
 
         // Continue down the tree by notifying any children of this widget.