bug#38187: 27.0.50; No mouse-wheel scaling on images

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: Eli Zaretskii <eliz@gnu.org>,  stefan@marxist.se,  38187@debbugs.gnu.org
> Date: Fri, 22 Nov 2019 00:10:48 +0100
> 
> Juri Linkov <juri@linkov.net> writes:
> 
> >   /* If the number of cached images has grown unusually large,
> >      decrease the cache eviction delay (Bug#6230).  */
> >
> > Does this mean the number of cached images was not large enough?
> 
> I've successfully (ahem) made Linux kill Emacs by looping over images
> (out of memory killer), so I don't think whatever it does is well-tuned.
> I haven't looked at the code now, but doesn't it just count images/time
> and not take image size into account?  I may be misremembering.

You are misremembering.  The code counts _redisplay_ cycles, and
clears the image cache when that exceeds 101.  Any additional cache
clearing can only come from Lisp that calls clear-image-cache
explicitly.  What exactly clearing the cache does depends on the value
of image-cache-eviction-delay and on how many images are in the
frame's image cache.