bug#13476: 24.3.50; Reverting scroll-bar face customization has no effect

[Eli Zaretskii <eliz@gnu.org>]

> From: Mauro Aranda <maurooaranda@gmail.com>
> Cc: luangruo@yahoo.com, 13476@debbugs.gnu.org, stephen.berman@gmx.net
> Date: Mon, 28 Feb 2022 11:04:13 -0300
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> >> From: Mauro Aranda <maurooaranda@gmail.com>
> >> Cc: eliz@gnu.org,  13476@debbugs.gnu.org,  stephen.berman@gmx.net
> >> Date: Mon, 28 Feb 2022 09:59:15 -0300
> >> 
> >> > --- a/lisp/faces.el
> >> > +++ b/lisp/faces.el
> >> > @@ -1743,7 +1743,14 @@ The following sources are applied in this order:
> >> >          (and tail (face-spec-set-2 face frame
> >> >                                     (list :extend (cadr tail))))))
> >> >      (setq face-attrs (face-spec-choose (get face 'face-override-spec) frame))
> >> > -    (face-spec-set-2 face frame face-attrs)))
> >> > +    (face-spec-set-2 face frame face-attrs)
> >> > +    (when (and (fboundp 'set-frame-parameter) ; This isn't available
> >> > +                                              ; during loadup.
> >> > +               (eq face 'scroll-bar))
> >> > +      ;; Set the `scroll-bar-foreground' and `scroll-bar-background'
> >> > +      ;; frame parameters.  (bug#13476)
> >> > +      (set-frame-parameter frame 'scroll-bar-foreground (face-foreground face))
> >> > +      (set-frame-parameter frame 'scroll-bar-background (face-background face)))))
> >
> > Why do we need this special treatment of the scroll-bar face?
> 
> I haven't read the code yet so I can't really answer to your question.  What
> I know is what I said on
> https://debbugs.gnu.org/cgi/bugreport.cgi?bug=13476#8
> 
> Customizing and then resetting to the standard scroll-bar face failed
> because the 'scroll-bar-foreground parameter wasn't updated after
> resetting the attributes via face-spec-reset-face.

I don't understand why we need to set the frame parameter when the
customize the face to begin with, I guess.