On 6/23/2024 4:24 PM, Stefan Kangas wrote:
> epg@pretzelnet.org writes:
> 
>> To reproduce:
>> - emacs -Q
>> - M-x eww RET gnu.org RET C-x C-+
>>
>> Expected:
>> Text is scaled up without error.
>>
>> Actual:
>> Text is scaled up, but with an error:
>>
>> run-hooks: Wrong type argument: number-or-marker-p, default
> 
> 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?