bug#71741: 30.0.60; Wrong type argument: number-or-marker-p after C-x C-+ in eww

[Eli Zaretskii <eliz@gnu.org>]

> Cc: Po Lu <luangruo@yahoo.com>
> Date: Sun, 23 Jun 2024 17:32:36 -0700
> From: Jim Porter <jporterbugs@gmail.com>
> 
> > I can reproduce this bug.  Copying in Po Lu.
> 
> I was just looking at image scaling in an unrelated bug, so I had 
> already swapped in all the necessary mental context for this. Here's a 
> patch.
> 
> The second part fixes a closely-related issue: the scaling didn't work 
> for sliced images (you can get a sliced image by zooming it: put point 
> on the image and press "z").
> 
> Fixing that required fixing a bug in 'get-display-property': it only 
> returned the CAR of the display property value. To maintain backwards 
> compatibility, I changed it so that it still returns the CAR if there's 
> only one element, but it now returns the whole list if there are 
> multiple elements. I don't love this, and maybe we should always return 
> a list, but I'll leave that decision to others (for what it's worth, 
> 'get-display-property' is new in Emacs 29, so there hopefully aren't too 
> many uses of it out in the wild yet).
> 
> I think the first patch is definitely worth merging to Emacs 30, but the 
> second I'm neutral on. Maybe we should fix 'get-display-property' now?

I think changes in get-display-property and in find_display_property
must wait for Emacs 31.  They are used in too many places to be a safe
change for the release branch.

The first patch is okay for the release branch, assuming Po Lu agrees
with it.

Thanks.