Re: ***SPAM*** Re: (x-display-pixel-height)

[Eli Zaretskii]

> From: Po Lu <luangruo@yahoo.com>
> Cc: emacs-devel@gnu.org
> Date: Sat, 21 May 2022 11:19:18 +0800
> 
> Po Lu <luangruo@yahoo.com> writes:
> 
> > Sounds reasonable, I'll try to work on it.  Thanks.
> 
> What you want should now be `display-monitors-changed-functions' in
> Emacs 29.

Thanks.

However, the documentation of this hook IMO falls short of being
useful to Lisp programs:

  +@defvar display-monitors-changed-functions
  +This variable is an abnormal hook run when the monitor configuration
  +changes, which can happen if a monitor is rotated, moved, added or
  +removed from a multiple-monitor setup, if the primary monitor changes,
  +or if the resolution of a monitor changes.  It is called with a single
  +argument consisting of the terminal on which the monitor configuration
  +changed.
  +@end defvar

This doesn't give any hints for how should a Lisp program get the
information about the monitor-configuration changes that triggered the
hook call, given just the terminal name.  Without knowing how to
access that information, this hook is not very useful.

I also notice that this hook was implemented for all the supported GUI
backends except w32, which is unfortunate and undocumented.