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

[Manuel Giraud]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Manuel Giraud <manuel@ledu-giraud.fr>
>> Cc: Eli Zaretskii <eliz@gnu.org>,  gerd.moellmann@gmail.com,
>>   67794@debbugs.gnu.org
>> Date: Tue, 19 Dec 2023 13:45:03 +0100
>> 
>> > I believe that we need to do some final set-up for the image under
>> > X/GTK/whatever and it looks as though this is all that's needed:
>> >
>> >      id = lookup_image (f, s->img->spec, hlinfo->mouse_face_face_id);
>> >      s->img = IMAGE_FROM_ID (f, id);
>> >      prepare_image_for_display (f, s->img); <------
>> >
>> > Under X we need to send the image to the X server, and under Cairo it
>> > does some other stuff. That's what prepare_image_for_display does. It
>> > does nothing under NS, so the image worked fine under GNUstep.
>> 
>> Thank you Alan!  That does the trick.  So here is an updated version of
>> the patch that works with XRender (i'll test with cairo).
>
> With this change, if you move the mouse pointer on and off the image
> several times, what happens to the Emacs memory footprint?
> Specifically, how many times is memory allocated for the SVG image,
> and if it's allocated each time, does it ever get deallocated?

I didn't measure this memory footprint but AFAIU lookup_image uses the
image cache so an image is allocated once (for one foreground/background
combination).  And I think that there is an eviction timeout in the
image cache, no?
-- 
Manuel Giraud