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 16:19:39 +0100
> 
> > Yes.  Changing toolbar image file contents is such a rare action that
> > it's not worth making Emacs recheck them on redisplay.
> 
> Sorry, thinko -- what this new cache does is cache the image locations,
> not the contents.  So if you add a new search.xpm somewhere in the load
> path, the toolbar will continue using the previously found location.
> 
> If you change the image on file, there's no change from how this worked
> in Emacs 27 -- Emacs will not show the new image, because it never
> checks whether an image file is newer than what's in the image cache.
> 
> So before as now, you have to clear the image cache in that case.

But before one could put a new image file in a different place on
image-load-path, and it would be used automatically instead of the old
one?  So if now this will not happen automatically, we should at least
document that and provide a function to do that manually.