RE: facemenu-unlisted-faces

[Drew Adams]

        Things that it might be argued are missing from the notion
        of face, to achieve the full flexibility of "semantic" markup,
        are 1) the ability to map faces in different ways to different
        appearances (or sounds or whatever) in different media,

    It would be easy to add such a mapping to ps-print if it doesn't have
    that feature already.  (Does it?)  That is the only Emacs feature which
    can output to "different media".

        2) the ability to constrain the context of application of a
        given face,

    I see no need for that.

          and 3) the ability to define and add new face attributes
        (possibly unrelated to appearance).

    That seems like creeping featurism, and is not needed for semantic
    markup.

I was thinking of the possibility of users adding their own face attributes,
for whatever purposes. I don't know if that would be difficult to handle
(implement).

It is very convenient, for example, that you can add any frame parameters
you want, and use them however you want in your own code. It would be useful
to be able to do the same with face attributes, but I don't know if that
would be difficult to implement (e.g. if existing code counts on a fixed set
of attributes).

    I see no need for "constant" faces.  If you don't want to change one,
    don't.

        I'm not suggesting we should necessarily have any kind of
        tight control here; a defconst-like treatment would probably
        be sufficient. The constantness of `defconst' amounts to little
        more than a doc admonition not to change the value, and that's
        probably enough for constant faces too.

    I would not object to that, if it would solve a real problem.  I don't
    want the complexity if the problem it would solve is purely
    theoretical.  So far no evidence has been presented that it is real.