bug#9366: Display geometry change hook

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Date: Sat, 19 Sep 2020 17:28:48 +0200
> Cc: 9366@debbugs.gnu.org
> 
> > +#ifdef HAVE_XRANDR
> > +    /* xrandr extension may or may not be present on a display =>
> > +       can't check for it as a constant C "case" arg, hence "if" here  */
> > +    if (dpyinfo->xrandr_present &&
> > +        (event.type == (dpyinfo->xrandr_event_base + 
> > RRScreenChangeNotify)))
> > +      {
> > +        /* FIXME: is XRRUpdateConfiguration actually called by the 
> > toolkit/gtk+?
> 
> But looking through the code, it doesn't seem like Emacs has grown this
> capability over the years?  But I may be looking in the wrong places.
> 
> In any case, it sounds useful?  I haven't tried applying the patch,
> though, so I don't know how much work that would be to bring it up to
> date.
> 
> Anybody got any opinions here?

Do we really have to do this on such a low level?  Why cannot we call
such a hook from change_frame_size, which would allow us to do that in
platform-independent manner?

Martin, am I missing something here?