bug#45224: 28.0.50; eww and GIFS (cpu usage shoots through the roof)

[Lars Ingebrigtsen <larsi@gnus.org>]

(Please keep the debbugs address in the Cc headers -- otherwise your
mails won't reach the Emacs bug tracker.)

Madhavan Krishnan <krishnanmadhavan000@gmail.com> writes:

>>> In any case, Emacs should be stopping animations that take too much CPU.
>>> Do you get the "Stopping animation; animation possibly too big"
>>> messages?
>>
>> Nope, I was hardly able to scroll to the end of the page, at any rate my
>> cpu fan kicked in and I killed the entire session.
>
> My bad, I miss spoke yes the message does show "Stopping animation;
> animation possibly too big" (when you scroll the buffer message is gone)
> but the cpu usage is still not down (untill the buffer is killed
> manually)

I see Emacs gradually killing more and more of the animations until
Emacs has reached a usable state again, but it takes a while.  Perhaps
it should be more aggressive in stopping the animations...

Anyway, that's a side issue -- this should really be fixed by making the
GIF animations faster.  I'm not sure whether there's been any work done
on that -- it's been mentioned a few times, but possibly nobody has done
the work?

If I remember correctly, the current code will decode the entire GIF
file for each frame, which is pretty pessimal.  The ImageMagick version
of the animation code keeps a special cache to avoid doing all those
decodings, so perhaps that code can be reused...