bug#68006: 30.0.50; Image-mode speed

[Eli Zaretskii]

> From: Manuel Giraud <manuel@ledu-giraud.fr>
> Cc: stefankangas@gmail.com,  68006@debbugs.gnu.org
> Date: Fri, 05 Jan 2024 15:35:42 +0100
> 
> I also imagine it would be mostly in C.  But looking at the code, I
> think I have overlooked something: lookup_image is what currently does
> most of the work (with caching) and this is in called in many places in
> "xdisp.c".  Of course, I think we should keep that... but then how could
> we design this new cache?

For example, lookup_image could look in both the existing and this new
cache.