bug#57691: 29.0.50; image-tests failures

[Eli Zaretskii]

> From: Stefan Kangas <stefankangas@gmail.com>
> Date: Fri, 9 Sep 2022 05:03:00 -0400
> 
> Could you build with --enable-checking="glyphs", and see what you get
> from evaluating:
> 
>   (let ((img (create-image
>               (expand-file-name "test/data/image/black.gif"
>                                 source-directory))))
>     (cons (lookup-image img) (image-metadata img)))
> 
> It should print some output to the terminal too, which is also
> interesting.

Evaluation returns (21), and prints this on stderr:

  (image :type gif :file "d:/gnu/git/emacs/trunk/test/data/image/black.gif" 
:scale 1 :transform-smoothing t)

> For reference, I get:
> 
>   (10 delay 0.06666666666666667 extension-data (249 "\^A\0\0\^A"))

I get something similar if I disable w32-use-native-image-API (which
is ON by default in Emacs 29):

  (21 delay 0.06666666666666667 extension-data (249 "^A\0\0^A"))

So I guess the test assumes something non-portable?  If I invoke the
test with --eval "(setq w32-use-native-image-API nil)", the
image-tests-image-metadata/gif test passes.

> I'm not sure if it matters or not, but do you happen to know which
> version of giflib you're using?

If w32-use-native-image-API is nil, my Emacs uses libgif v5.1.0.  By
default, libgif is not used at all; instead, Emacs uses MS-Windows
native APIs in the system library gdiplus.dll to display GIF images.

> > F image-tests-load-image/svg-invalid
> >     (ert-test-failed
> >      ((should
> >        (string-search "XML parse error"
> >                   (buffer-string)))
> >       :form
> >       (string-search "XML parse error" "For information about GNU Emacs and 
> > the GNU system, type C-h C-a.\nType C-c C-c to view the image as 
> > text\nError parsing SVG image: Error domain 1 code 4 on line 1 column 1 of 
> > data: Start tag expected, '<' not found [3 times]\n")
> >       :value nil))
> 
> This looks like some version of librsvg giving a different error
> message.  Does the attached patch fix this for you?

Yes, thanks.

> Also, out of interest, do you know which version of librsvg you're
> using?

2.40.1.