bug#67269: 30.0.50; italic face fallback does not assume italic properties

[Eli Zaretskii <eliz@gnu.org>]

> From: Po Lu <luangruo@yahoo.com>
> Cc: 67269@debbugs.gnu.org
> Date: Mon, 20 Nov 2023 20:00:36 +0800
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > If so, then it is strange that we haven't heard about this issue
> > before.
> >
> > Maybe we should do something like the below, and leave the rest to end
> > users and downstream distros.
> >
> >> > I don't understand how shr-tag-i is relevant.  I'm probably missing
> >> > something.
> >> 
> >> It combines a variable pitch face with italic, and so loses when the
> >> italic face doesn't support slant properties, even if the variable pitch
> >> one does.
> >
> > Yes, you already said that in your original message.  I thought
> > shr-tag-i provides some additional insight.
> 
> Ah, I'm sorry for the misunderstanding then.
> 
> > diff --git a/lisp/faces.el b/lisp/faces.el
> > index 7eacc40..8eaabbf 100644
> > --- a/lisp/faces.el
> > +++ b/lisp/faces.el
> > @@ -2440,7 +2440,10 @@ italic
> >    '((((supports :slant italic))
> >       :slant italic)
> >      (((supports :underline t))
> > -     :underline t)
> > +     ;; Include italic, even if it isn't supported by the default
> > +     ;; font, because this face could be merged with another face
> > +     ;; which uses font that does have an italic variant.
> > +     :underline t :slant italic)
> >      (t
> >       ;; Default to italic, even if it doesn't appear to be supported,
> >       ;; because in some cases the display engine will do its own
> > @@ -2457,7 +2460,9 @@ bold-italic
> >  (defface underline
> >    '((((supports :underline t))
> >       :underline t)
> > -    (((supports :weight bold))
> > +    ;; Include underline, for when this face is merged with another
> > +    ;; whose font does support underline.
> > +    (((supports :weight bold :underline t))
> >       :weight bold)
> >      (t :underline t))
> >    "Basic underlined face."
> 
> That's alright by me, thanks.

Thanks, installed on master, and closing the bug.