Re: region-based face-remapping

[Eli Zaretskii <eliz@gnu.org>]

> Date: Wed, 3 Jan 2024 14:40:49 +0200
> Cc: emacs-devel@gnu.org
> From: Dmitry Gutov <dmitry@gutov.dev>
> 
> On 03/01/2024 14:31, Eli Zaretskii wrote:
> > The workhorse we use now for obtaining face information is the
> > function face_at_buffer_position, which calls the various face-merging
> > routines.  Those merging routines and their subroutines consider
> > face-remapping-alist as part of face merging process outlined above.
> > I don't see how we can avoid passing the buffer position to them if
> > face-remapping depends on buffer position.
> 
> Perhaps face_at_buffer_position would first look up the overlay/text 
> property 'face-remapping-alist, then merge its value with the variable 
> face-remapping-alist (using plain 'append', for example), and pass on 
> the resulting value to the face-merging routines?

Then any code running while face_at_buffer_position does its job will
see a tweaked value of face-remapping-alist, which is not necessarily
TRT, since it is not guaranteed that the buffer position being
examined by face_at_buffer_position is relevant to the rest of the
code.