Semi Implentet ExcludeUpdateRgn from user32.dll

int

STDCALL

ExcludeUpdateRgn(

  HDC hDC,

  HWND hWnd)

{

    HRGN update_rgn = CreateRectRgn( 0, 0, 0, 0 );

    INT ret = GetUpdateRgn( hWnd, update_rgn, FALSE );

    if (ret != ERROR)

    {

        POINT pt;

        GetDCOrgEx( hDC, &pt );

        MapWindowPoints( 0, hWnd, &pt, 1 );

        OffsetRgn( update_rgn, -pt.x, -pt.y );

        ret = ExtSelectClipRgn( hDC, update_rgn, RGN_DIFF );

        DeleteObject( update_rgn );

    }

    return ret;

}