On 10/24/2012 11:33, Christian Costa wrote:

2012/10/24 Dmitry Timoshkov <dmitry@baikal.ru>

Christian Costa <titan.costa@gmail.com> wrote:

>  BOOL WINAPI ClientToScreen( HWND hwnd, LPPOINT lppnt )
>  {
> +    DWORD error = GetLastError();
> +
> +    if (!hwnd)
> +    {
> +        SetLastError( ERROR_INVALID_WINDOW_HANDLE );
> +        return FALSE;
> +    }
> +
> +    SetLastError( 0xdeadbeef );
>      MapWindowPoints( hwnd, 0, lppnt, 1 );
> +
> +    if (GetLastError() != 0xdeadbeef)
> +        return FALSE;
> +
> +    SetLastError(error);
>      return TRUE;
>  }

As been said before these games with saving/restoring last error value
are broken.

Last time you said wrong so what do you mean by wrong or broken?

The only way to know if MapWindowPoints fails is to set last error first and check it

after. If I don't restore the previous value, the tests will not pass. Of course I can

arrange the tests but hey. And I can check windows handle here as Alexandre said.

If error reporting from MapWindowPoints is not sufficient to use it somewhere else you can always move its guts to
a separate function and report failure as you want. By the way, it only fails on invalid window handles I guess, is that right?
If you need this behaviour you have a failing WIN_GetPtr() in this case. Messing with last error is not a solution obviously,
and I don't see where MapWindowPoints even sets it.