bug#47074: Replace XPM icons with Unicode codepoints in customize/widgets

[Eli Zaretskii]

> From: Stefan Kangas <stefan@marxist.se>
> Date: Sat, 13 Mar 2021 04:35:43 -0600
> Cc: alan@idiocy.org, 47074@debbugs.gnu.org
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> >> IIUC, it would show the :on and :off text on such configurations,
> >> i.e. "[X]" and "[ ]".
> >
> > That'd be a regression, no?
> 
> Are there any systems we care about where librsvg is not available?  Do
> we think it is important to support these graphical icons on those
> systems?  If the answer is yes to both of these questions, then I guess
> we should count it as a regression.

Since librsvg is an _optional_ dependency, IMO the answer is YES by
definition, right?

> > Can we arrange for the old XPM files to be used if SVG is not
> > available?
> 
> Perhaps fixing this it is as easy as moving/copying the old XPM files to
> ui/<newnames>.xpm, but I'd need to test it as I didn't study the code
> very closely.

Yes, I think copying the XPM file would be okay.

Alternatively, we could move and rename the new SVG files.  They are
in a separate directory just because of the license?  If so, I don't
think that's a string enough reason to segregate them, we could just
mention in the README in etc/images that these files (with an explicit
list) are from so-and-so place under such-and-such license.