bug#56182: 28.1; Display of SVG file with transparent background is incorrect

[Corwin Brust]

On Mon, Sep 11, 2023 at 2:10 PM Alan Third <alan@idiocy.org> wrote:
>
> I found it easy to check by setting the theme to "light blue" and
> loading etc/images/down.svg. The correct result should have a black
> triangle on a blue background, but incorrect is a black triangle on a
> yellow background.
>

Compile: yes.  Fixes the problem: unsure.

I did not have difficulty building the emacs-29 branch with this patch
applied. Unfortunately, I could not confirm (or disprove) the success
of the patch because I received (under -Q) "Invalid Image
Specification" trying to load etc/images/down.svg.  Here's a
screenshot:

https://bru.st/i/emacs-29.1.50.1_i9DY4oaggq.png

I then confirmed I get this same from a recent (upatched:
ca95e45f7e828aebdf2736c9c7b2d64f9621214e) build from the development
branch.  Others I grabbed at random also give this error now, so I'm
confident it's nothing to do with down.svg.  An unpatched emacs-28
build could display SVGs, I remember that 29.1 can but didn't check.
Is it possible there's a recent regression breaking SVG image display
more generally (perhaps merged up, already)?

Are there things you can think of which I might be doing incorrectly?
I can't think of them.

This was a perfectly clean clone, checkout at emacs-29, patch applied
cleanly, I noticed only the below couple of warnings in the build log,
but perhaps I've missed something so the full output from
autogen+configure and from make are attached.

w32heap.c:853:14: warning: 'm' may be used uninitialized [-Wmaybe-uninitialized]
mml1991.el:140:16: Warning: the function `mm-disable-multibyte' might
not be defined at runtime.

I'm assuming bisection may be appreciated but I'll wait for
confirmation before trying.  In theory, I have an excellent setup for
this but I haven't tried it in anger yet.

Should I open a seperate bug report?

> --
> Alan Third

emacs-29-configure.log
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emacs-29-make.log
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