Re: region-based face-remapping

[Eli Zaretskii <eliz@gnu.org>]

> 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?  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.  Assumptions that certain things "cannot happen" between points
A and B in display code already led to tricky bugs that needed tricky
solutions.  Thus, I don't want to design a new feature on such shaky
assumptions.