bug#74104: 31.0.50; 'custom-set-faces' overrides face when no theme is loaded

[Eli Zaretskii <eliz@gnu.org>]

> From: Protesilaos Stavrou <info@protesilaos.com>
> Cc: 74104@debbugs.gnu.org
> Date: Thu, 31 Oct 2024 07:35:34 +0200
> 
> > From: Eli Zaretskii <eliz@gnu.org>
> > Date: Wed, 30 Oct 2024 17:39:30 +0200
> >
> >> From: Protesilaos Stavrou <info@protesilaos.com>
> >> Date: Wed, 30 Oct 2024 12:14:40 +0200
> >> 
> >> Dear maintainers,
> >> 
> >> When a theme is already enabled, 'custom-set-faces' has the effect of
> >> adding face attributes on top of the existing ones. Those that were
> >> present are not removed: they are blended with the new ones.
> >> 
> >> This, however, is not happening when no theme is loaded. In that
> >> scenario, 'custom-set-faces' removes all the underlying face attributes
> >> and keeps only those specified in the function call. I think this is a
> >> mistake.
> >
> > custom-set-faces is used to set up customized faces in the user's init
> > files: they are the forms written by Custom when the user decides to
> > save the face customizations for future sessions.  So I don't think
> > this is a mistake, and I don't see how we can change this without
> > catastrophic effects on everyone's init files.
> 
> Indeed, I do not want to break anybody's setup or even make far-reaching
> changes just for this. Do you think the difference in behaviour when a
> theme is loaded versus when it is not is the intended design?

Yes, I think so.