Re: Redisplay slower in Emacs 28 than Emacs 27

[Eli Zaretskii]

> Date: Mon, 07 Dec 2020 16:46:27 +0000
> cc: emacs-devel@gnu.org
> From: Gregory Heytings via "Emacs development discussions." 
> <emacs-devel@gnu.org>
> 
> >> No, with the tests were ran with emacs -Q.  I forgot to mention this, 
> >> it was too obvious to me.
> >
> > But "emacs -Q" does show images in the tool bar.  :-) (Very small ones, 
> > though.)
> 
> Yes, and as you probably understood, by "does not load any image" I meant 
> "in a buffer"... ;-)

You asked why Emacs messes with the image cache although there are no
images in the buffer, and the answer is probably that Emacs doesn't
mess with images in the buffer, it messes with images elsewhere on
display.  Depending on whether your build uses GTK, this could happen
each time Emacs scrolls the window, because it then examines the tool
bar in order to decide whether it needs to be redrawn.