Re: Redisplay slower in Emacs 28 than Emacs 27

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: ghe@sdf.org,  emacs-devel@gnu.org
> Date: Tue, 08 Dec 2020 15:06:44 +0100
> 
> But before doing that, we should probably decide, once and for all,
> whether the cache should be on spec equality or identity...
> 
> And if we really go with identity (which we do now, but...  wrognly), we
> could go one step further, and just look at the identity of the spec
> itself, instead of looking at the identity of the contents.
> 
> That is, use
> 
>       && EQ (img->spec, spec)
> 
> instead of
> 
>       && equal_lists (img->spec, spec)

I think using EQ might break something, given that we've been using
Fequal for a long time.

> Or, if we decide to revert to a more permissive cache again, we could
> just go back to using
> 
>       && !NILP (Fequal (img->spec, spec))

We could do that, yeah.  But most of the members of an image spec are
symbols and suchlikes, so maybe we could use EQ for almost all of
them, except for strings?