bug#67794: 30.0.50; mouse-face is not respected on SVG images

[Manuel Giraud]

Eli Zaretskii <eliz@gnu.org> writes:

[...]

>> Here are the results:
>> 
>> Right after "emacs -Q": rss = 44688
>> After 'M-x +insert-stuff': rss = 54292
>> After first hover on text: rss = 54464
>> After repeated hover on/off text: rss = 54496
>
> Does it get bumped each hover-over, or does it stabilize after a few?

This I don't know.  When I write "repeated hover", it is because I hover
on and off maybe ten times just to see if there was a growing trend.

[...]

>> You're right: it does only work with SVG.  XPM are already handled with
>> mask.  I have tested and it does not work with PNG with transparent
>> background: don't know why.  Maybe instead of guard it with a "only for
>> SVG" test, we should resolve the issue for transparent PNG at a later
>> time.
>
> It would be a shame to waste cycles on PNG images as long as we don't
> solve this problem, so I'd prefer to enable this only for SVG and
> leave a FIXME comment about PNG.

Yes I'm ok with it.  I'll modify the patch.
-- 
Manuel Giraud