IDirectDrawSurface2::UpdateOverlayDisplay
HRESULT UpdateOverlayDisplay(DWORD dwFlags);
Repaints the rectangles in the dirty rectangle list of all active overlays. This clears the dirty rectangle list. This method is for software emulation only—it does nothing if the hardware supports overlays.
·Returns DD_OK if successful, or one of the following error values otherwise:
dwFlags
Type of update to perform. One of the following flags:
Updates the overlay display using the list of dirty rectangles previously constructed for this destination. This clears the dirty rectangle list.
Ignores the dirty rectangle list and updates the overlay display completely. This clears the dirty rectangle list.