AppBase::OnUpdateFrame

virtual void OnUpdateFrame(bool needRepaint);

OnUpdateFrame is called in a loop to advance and update frame rendering. The frequency of calls is controlled by SetFrameTime. This function may be called more frequently due to updated UI. 

needRepaint specifies when the UI must be repainted due to OS event, it is always set to 'true' on the first frame. On subsequent frames, applications can choose to avoid rendering if no animation update is required.