Re: Buffer-local faces

[Miles Bader]

On Mon, May 03, 2004 at 06:20:46PM -0400, Richard Stallman wrote:
>        Each element is of the form:
>         (FACE . NEW-FACE)
>        or
>         (FACE NEW-FACE MERGE-FACE...),
>        which causes NEW-FACE to be used where FACE normally would.
>        If present, MERGE-FACE... are merged during display with NEW-FACE.
> 
> Wouldn't it be cleaner just to have one kind of element,
> (FACE REPLACEMENT-FACES...)

I think so, but I'm not entirely sure if it's possible; perhaps it is.

The question is whether there are places that want remapping, but don't
operate in terms of face-ids -- e.g., they use `lisp-faces' (lisp vectors),
or face names.  Face-ids can represent merged faces, but the other
representations can not, so my original thought while implementing this was
that I'd need to support the concept of a `simple remapping' that merely
returned one face name/vector for another.

However that may actually not be necessary.  I still have to go through the
corner cases I think.

A related questions is whether the remapping should be visible to lisp code
using face functions.  For instance, does (face-attribute 'default :family)
1. return the remapped family, or 2. return the family of the `underlying'
default face?

My current patch does the former, but now I'm leaning towards making it the
latter, and having remapping be a pure display operation -- it just seems
simpler to deal with.  Lisp code that's interested in such matters can look
at the variable to see what's up.

-Miles
-- 
`Cars give people wonderful freedom and increase their opportunities.
 But they also destroy the environment, to an extent so drastic that
 they kill all social life' (from _A Pattern Language_)