bug#64759: Broken faces

[Eli Zaretskii]

> From: Juri Linkov <juri@linkov.net>
> Cc: maurooaranda@gmail.com,  64759@debbugs.gnu.org
> Date: Tue, 25 Jul 2023 20:04:16 +0300
> 
> >> The semantics of nil could be the same as '((t nil)).
> >
> > And what is the semantics of '((t nil)) ?  What attributes will the
> > face have when realized?
> 
> No attributes.  This is the standard value used by empty faces.

What does this mean?  For example, what would be the foreground color?
what would be the font? etc.

I'm not familiar with "empty face" notion.  A face always has
attributes when it is fully realized, otherwise Emacs will be unable
to use it.

> >> Do you agree that currently the value '((t nil))
> >> should be used for faces without default face attributes?
> >
> > Yes, I think so.  If no better face to inherit from is available in
> > each such case, that is.
> 
> This means these faces should have by default '((t nil)):
> semantic-decoration-on-includes, shr-h4, shr-h5, shr-h6,
> nxml-text, nxml-delimiter, nxml-element-colon, makefile-shell
> as before?

Only if "no better face to inherit from is available" in all of those
cases.  Which I'm not sure is true.  If you are sure, please tell why
the faces I put there are not better ideas.