IDirectDrawSurface2::AddOverlayDirtyRect
HRESULT AddOverlayDirtyRect(LPRECT lpRect);
Builds the list of the rectangles that need to be updated the next time the IDirectDrawSurface2::UpdateOverlayDisplay method is called.
·Returns DD_OK if successful, or one of the following error values otherwise:
lpRect
Address of the RECT structure that needs to be updated.
This method is used for the software implementation. It is not needed if the overlay support is provided by the hardware.