HRESULT Unlock(LPVOID lpSurfaceData);
Notifies DirectDraw that the direct surface manipulations are complete.
·Returns DD_OK if successful, or one of the following error values otherwise:
lpSurfaceData
Address of a pointer returned by the IDirectDrawSurface2::Lock method. Because it is possible to call IDirectDrawSurface2::Lock multiple times for the same surface with different destination rectangles, this pointer links the calls to the IDirectDrawSurface2::Lock and IDirectDrawSurface2::Unlock methods.