bug#55322: 28.1; :base-uri not working for svg images on mac

[Howard Melman]

> On May 8, 2022, at 11:32 PM, Po Lu <luangruo@yahoo.com> wrote:
> 
> What happens if you set a breakpoint in GDB on this piece of code in
> image.c?
> 
>  /* Set base_uri for properly handling referenced images (via 'href').
>     Can be explicitly specified using `:base_uri' image property.
>     See rsvg bug 596114 - "image refs are relative to curdir, not .svg file"
>     <https://gitlab.gnome.org/GNOME/librsvg/issues/33>. */
>  if (filename)
>    rsvg_handle_set_base_uri (rsvg_handle, filename);
> 
> Is it triggered?  And if so, what is the value of `filename'?

I'm hoping someone else can try this.  It's been a long time since I've 
used gdb, I don't have it installed now, and don't have emacs c source 
installed as I don't build my own emacs.

> It's not useful to compare the code in Carbon Emacs with the code in
> Emacs.app.  They use completely different code paths to handle the
> `base-uri' attribute.

I understand.  I'm a macport user, first saw the issue there, and then
recreated it on Emacs.app.  I know the paths are different, they both
fail here, I didn't know why and reported them as distinctly as I could.

That did turn out to be useful because @mituharu reported that 
compiling the macport w/ librsvg works.
https://github.com/minad/osm/issues/23#issuecomment-1121032499

Howard