public static extern bool SetWindowRgn([In] HWnd hWnd, [Out] out HRng hRgn, [In][MarshalAs(UnmanagedType.Bool)] bool bRedraw);
public static extern RgnStatus GetWindowRgn([In] HWnd hWnd, [In] HRng hRgn);
public static extern RgnStatus GetUpdateRgn([In] HWnd hWnd, [In] HRng hRgn, [In][MarshalAs(UnmanagedType.Bool)] bool erase);