Re: region-based face-remapping

[Dmitry Gutov]

On 05/01/2024 10:50, Eli Zaretskii wrote:
> > Date: Fri, 5 Jan 2024 05:49:24 +0200
> > Cc:jdtsmith@gmail.com,emacs-devel@gnu.org
> > From: Dmitry Gutov<dmitry@gutov.dev>
> >
> > On 04/01/2024 09:05, Eli Zaretskii wrote:
> > >     . one of the subroutines of face_at_buffer_position calls some Lisp
> > >       hook
> > >     . that Lisp hook calls code that calls face-font (or some other
> > >       primitive which takes face-remapping-alist into account)
> > Could you give an example of a Lisp hook which might be called from
> > face_at_buffer_position's subroutines?
> Why is having a specific example important?
>
> Are you saying that there can never be such an example?

Yes, it would seem odd to me for face_at_buffer_position to call any hooks.

But if it did, I would consider whether any of the hooks being called 
would allow substituting the face with a different one (making it a 
different way to solve the present feature request). This sounds like a 
way to slow things down by an order of a magnitude, though, so it 
probably will not happen.

> With the
> current tendency of moving stuff to Lisp and adding hooks to C code,
> we clearly cannot convince ourselves such a hook will never happen in
> the future, even if it doesn't exist in this particular moment in
> time.

Even if it moved to Lisp, it won't necessarily add any hooks.