Re: XRaiseWindow for activating windows in multiwindow mode

[Jon TURNEY <jon.turney@dronecode.org.uk>]

On 13/08/2011 19:39, Oliver Schmidt wrote:
> as reported in
>
>    http://www.cygwin.com/ml/cygwin-xfree/2005-06/msg00072.html
>
> windows are not raised from the Cygwin X Server in multiwindow
> mode, if a program wants to programmatically activate a window.
>
> I played around and figured out that the problem can be solved by
> invoking the windows function SetForegroundWindow if a top level
> window is to be restacked and has no previous sibling.
>
> I enclose the patch in this email. It works fine for me, but
> I'm not sure if it has any side effects for other configurations
> or usage patterns.

Thanks for looking into this, and for the patch.

There definitely are some problems in this area, but I'm not sure this is the 
'correct' fix, though.

The code as it stands is the product of some ... erm ... historical compromises.

If I am reading the code correctly, it looks like currently no attempt is made 
to synchronize changes in the X window Z-order (e.g. made by XRaiseWindow()) 
to the native Windows window Z-order, and the comment in [1] seems to bear 
this out.  The code which perhaps would do this is in the disabled branch of 
the #if/#else/#endif in winRestackWindowMultiWindow()

The relevant thread seems to be [2] and the relevant change seems to be [3], 
but I can't reconstruct the reasoning behind it.

As discussed in the thread [2] various scenarios, e.g. AOT windows, native 
windows interleaved with X windows in the native Z order, Windows with 
focus-follows-mouse enabled via TweakUI all need testing after trying to fix 
this, to ensure you haven't regressed them.

[1] http://sourceware.org/ml/cygwin-xfree/2004-12/msg00074.html
[2] http://sourceware.org/ml/cygwin-xfree/2004-03/msg00540.html
[3] 
http://cgit.freedesktop.org/xorg/xserver/commit/?h=CYGWIN&id=40bb4441ac7c87cfa0c62e8553c7e53b9fe4d765

> It would be nice if this feature could be integrated into future
> versions of the Cygwin X Server.
>
> Best regards,
> Oliver
>
>
> diff --git a/hw/xwin/winmultiwindowwindow.c b/hw/xwin/winmultiwindowwindow.c
> index 956a9a5..22390b3 100644
> --- a/hw/xwin/winmultiwindowwindow.c
> +++ b/hw/xwin/winmultiwindowwindow.c
> @@ -465,6 +465,7 @@ winRestackWindowMultiWindow (WindowPtr pWin, WindowPtr pOldNextSib)
>     HWND			hInsertAfter;
>     HWND                  hWnd = NULL;
>   #endif
> +  static Bool fRestacking = FALSE; /* Avoid recusive calls to this function */

I'd like this patch more if you said why recursive calls can occur, and why 
they must be avoided.

>     ScreenPtr		pScreen = pWin->drawable.pScreen;
>     winScreenPriv(pScreen);
>
> @@ -472,10 +473,27 @@ winRestackWindowMultiWindow (WindowPtr pWin, WindowPtr pOldNextSib)
>     winTrace ("winRestackMultiWindow - %08x\n", pWin);
>   #endif
>
> +  if (fRestacking)
> +    {
> +      /* It is a recusive call so immediately exit */
> +#if CYGWINDOWING_DEBUG
> +      ErrorF ("winRestackWindowMultiWindow - "
> +	      "exit because fRestacking == TRUE\n");
> +#endif
> +      return;
> +    }
> +  fRestacking = TRUE;
> +
>      WIN_UNWRAP(RestackWindow);
>      if (pScreen->RestackWindow)
>        (*pScreen->RestackWindow)(pWin, pOldNextSib);
>      WIN_WRAP(RestackWindow, winRestackWindowMultiWindow);
> +
> +  if (isToplevelWindow(pWin)&&  pWin->prevSib == NULL)
> +    {
> +      winWindowPriv(pWin);
> +      SetForegroundWindow(pWinPriv->hWnd);
> +    }
>
>   #if 1
>     /*
> @@ -538,6 +556,8 @@ winRestackWindowMultiWindow (WindowPtr pWin, WindowPtr pOldNextSib)
>   		0, 0,
>   		uFlags);
>   #endif
> +
> +  fRestacking = FALSE;
>   }
>
>   static void

-- 
Jon TURNEY
Volunteer Cygwin/X X Server maintainer

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