Re: Redisplay slower in Emacs 28 than Emacs 27

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: ghe@sdf.org,  emacs-devel@gnu.org
> Date: Tue, 08 Dec 2020 16:07:29 +0100
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > What will this do when the image file on disk changes?  AFAIU, the
> > current implementation will use the new image for the tool bar on the
> > next redisplay opportunity, but this change will make us continue
> > using the cached one?
> 
> Yes.  Changing toolbar image file contents is such a rare action that
> it's not worth making Emacs recheck them on redisplay.

All we need to do is stat the file, and reload it if its time stamp or
size changed.  Why is that a problem?  If we don't do that, we are
making an incompatible change, and I don't see a reason for doing that
unconditionally.