From Mathieu Marache, "we found that events where not caught when running in ON_DEMAND frame scheme : GraphicsWindow::checkEvents() always return false and GraphicsWindowQt doesn't overload it.

here is a simple fix that will return if the list is empty or not and will match the comment in checkEvents()

include/osgUtil/SceneView

@@ -55,7 +55,6 @@ class OSGUTIL_EXPORT SceneView : public osg::Object, public osg::CullSettings
             STANDARD_SETTINGS = HEADLIGHT |
                                 COMPILE_GLOBJECTS_AT_INIT |
                                 APPLY_GLOBAL_DEFAULTS |
-                                APPLY_GLOBAL_DEFAULTS |
                                 CLEAR_GLOBAL_STATESET
 
         };

include/osgViewer/GraphicsWindow

@@ -54,7 +54,7 @@ class OSGVIEWER_EXPORT GraphicsWindow : public osg::GraphicsContext, public osgG
         const osgGA::EventQueue* getEventQueue() const { return _eventQueue.get(); }
 
         /** Check events, return true if events have been received.*/
-        virtual bool checkEvents() { return false; }
+        virtual bool checkEvents() { return !(_eventQueue->empty()); }
 
         /** Set the window's position and size.*/
         void setWindowRectangle(int x, int y, int width, int height)