GNU bug report logs - #75936
monitor width reporting

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Message #29 received at 75936 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Po Lu <luangruo <at> yahoo.com>
Cc: rudalics <at> gmx.at, david <at> ngdr.net, 75936 <at> debbugs.gnu.org
Subject: Re: bug#75936: monitor width reporting
Date: Sun, 02 Feb 2025 09:25:11 +0200

> From: Po Lu <luangruo <at> yahoo.com>
> Cc: "david" <david <at> ngdr.net>,  rudalics <at> gmx.at,  75936 <at> debbugs.gnu.org
> Date: Sun, 02 Feb 2025 14:59:29 +0800
> 
> Eli Zaretskii <eliz <at> gnu.org> writes:
> 
> >> At the very least, the build information should indicate the difference.
> >
> > Agreed.  Po Lu, do we have some indication of whether XRandR was used
> > in the recorded features that report-emacs-bug shows?  If not, can we
> > add that?
> 
> No, but it's an exceedingly simple oversight that can be addressed thus:
> 
> diff --git a/configure.ac b/configure.ac
> index 9db1f07d7fc..55a4be1a0ee 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -7481,7 +7481,7 @@ AC_DEFUN
>   HARFBUZZ IMAGEMAGICK JPEG LCMS2 LIBOTF LIBSELINUX LIBSYSTEMD LIBXML2 \
>   M17N_FLT MODULES NATIVE_COMP NOTIFY NS OLDXMENU PDUMPER PGTK PNG RSVG SECCOMP \
>   SOUND SQLITE3 THREADS TIFF TOOLKIT_SCROLL_BARS TREE_SITTER \
> - UNEXEC WEBP X11 XAW3D XDBE XFT XIM XINPUT2 XPM XWIDGETS X_TOOLKIT \
> + UNEXEC WEBP X11 XAW3D XDBE XFT XIM XINPUT2 XPM XRANDR XWIDGETS X_TOOLKIT \
>   ZLIB; do
>  
>      case $opt in

Thanks.  And the same with XINERAMA, I presume?

> I cannot imagine why this was not installed at the outset, because all
> optional features are meant to be enumerated here...

The documentation portion of the changeset which added support for
XRandR and Xinerama is lacking in more than one way, unfortunately.
E.g., the NEWS item didn't even mention these two X features, which
are prerequisites for multiple-monitor support.

> > Po Lu, is the following correct?
> >
> >  . accurate information about multiple monitors is available only if
> >    Emacs was built with XRandR or Xinerama, and was not built with the
> >    GTK toolkit
> 
> "or Emacs was built with the GTK toolkit, in both cases provided that
> the X server also supports XRandR or Xinerama."

So GTK also supports this internally?  Where's the code for that?
xfns.c defines monitor attributes only "#ifndef USE_GTK", AFAICT.
What did I miss?

> >  . if the 'source' field of the value returned by
> >    display-monitor-attributes-list is "fallback", it means neither
> >    XRandR nor Xinerama are used, and the monitor information is for
> >    the "combined screen", as if all the physical monitors formed a
> >    single combined monitor; the results could be inaccurate if the
> >    system has more than a single physical monitor connected
> 
> Otherwise, this is correct.  I would clarify that "the attributes
> returned in this case represent the dimensions of the X server screen".

OK, will do.

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