DWORD (APIENTRY *PDD_SURFCB_UPDATEOVERLAY)(
PDD_UPDATEOVERLAYDATA lpUpdateOverlay
);
UpdateOverlay repositions or modifies the visual attributes of an overlay surface.
UpdateOverlay returns a DDHAL_DRIVER_Xxx callback code that indicates how the driver handled the call. These return codes are defined in ddrawint.h.
UpdateOverlay shows, hides, or repositions an overlay surface on the screen. It also sets attributes of the overlay surface, such as the stretch factor or type of color key to be used. Note that Flip will be used for flipping between overlay surfaces, so performance for UpdateOverlay is not critical.