bug#47895: 28.0.50; Emacs should only animate images that are visible

[Lars Ingebrigtsen]

Eli Zaretskii <eliz@gnu.org> writes:

> I'd be interested to see a backtrace for such animation of an image
> that is not on display.  In general, since animation is triggered (I
> think) when the image is being prepared for redisplay, what you
> describe shouldn't be happening.  If it dies indeed happen, I have a
> couple of guesses how that could be triggered, but it would be nice to
> see evidence.

I unfortunately don't have the time to debug right now, but it's easy
enough to reproduce:

(progn
  (eww "https://lars.ingebrigtsen.no/wp-content/uploads/2018/03/candid.gif";)
  (bury-buffer))

This will leave you with an Emacs that uses at least 99% CPU, even if
the eww buffer isn't even displayed.  (At least on this Debian/bullseye
system, starting from -Q.)

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no