Re: Redisplay slower in Emacs 28 than Emacs 27

[Eli Zaretskii <eliz@gnu.org>]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: ghe@sdf.org,  emacs-devel@gnu.org
> Date: Tue, 08 Dec 2020 17:34:37 +0100
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > 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?
> 
> Yes.  (For the toolbars; the other lookups aren't cached.)
> 
> > So if now this will not happen automatically, we should at least
> > document that and provide a function to do that manually.
> 
> It only seems like something a developer would encounter, I think?

We don't know that.  For all I know there could be some 3rd party
package there playing fancy games with the tool-bar button that relies
on the current behavior.  After all, we've been behaving like that
since Emacs 21.

If no one needs that function, it will never be used.  But I think the
function should be quite simple, so adding it is a net win.  If we
document it, it will avoid a potential outcry.