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RE: facemenu-unlisted-faces

From: Drew Adams
Subject: RE: facemenu-unlisted-faces
Date: Sat, 8 Jul 2006 22:45:11 -0700

    > Understanding the concept of "face" includes understanding
    > that a face is changeable, and that is not true of text properties.

    You're apparently using some bizarro definition of the term "text
    property", because the text properties most of us use are indeed

    Maybe you're talking about the practice of using face-attribute lists
    instead of named faces??

Sorry I'm not getting this across. I'll try one more time. It's really not
that important, so hit delete if you're tired of this.

I can use the number 4 or not use it, but it remains the number 4 - it is
not changeable. I can apply  the :bold attribute to text or not, but it
remains the unchangeable :bold attribute; if applied, it always imposes
boldness. That is different from use of a face whose name happens to be
`bold', even if the face looks bold. Whether applied to text or not, the
`bold' face is not a constant, and its name "bold" doesn't necessarily stand
for how it looks.

I tried to say that I was not speaking necessarily of Emacs text properties,
or face attributes, or font properties, or styles, but of all of those, on
the one hand, and faces on the other. And I was not making a difference in
terms of implementation but in terms of user (conceptual) model.

Consider some text that has a :foreground face attribute with a value of
"Red" applied to it as a text property. The value of :foreground that is
applied to that particular text can certainly be changed (e.g. to "Green"),
and the :foreground attribute can be removed from the text altogether. But
the color "Red" can't be changed; it's a constant. It's not just a name
associated with the color, whose association can be changed. And the meaning
of :foreground cannot be changed; it always means the foreground color,
regardless of its value. Likewise, for face attribute :underline: it can be
applied to text or removed, but it always means underlining. Likewise :bold
always means boldness.

On the other hand, a face that happens to be named `underline', and that
has, right now, an appearance of underlining, is not such a constant.
Applying the attribute :underline will always underline, but applying the
face `underline' will not (not necessarily). The definition and appearance
of a face named `bold' can change; the definition and appearance of
attribute :bold cannot.

Users unused to Emacs don't know or care about faces. They can and will
eventually use them, and that's good. But they don't _need_ to understand
the notion of a face to be able to apply constant
"properties"/"styles"/"attributes" (however such things are defined) to
text. That's the model to use for the Text Properties menu, with the sole
exception of `Face...', where Emacs faces are applied.

Let users think simply in terms of applying boldness, underlining, redness,
and so on, where each of these properties (again, however it might be
implemented) is thought of as as constant.

To my mind, we can treat fixed pitchness the same way. Even if "applying"
fixed pitchness really means changing the font family, or even if it really
means applying a `fixed-pitch' face, or whatever, things should work simply
enough that the user need not be aware of that, that s?he can think of
applying fixed pitchness the same way s?he thinks of applying underlining.
IOW, think of it as a constant property that you are applying to the text.

Finally, I don't really care about fixed pitchness. I don't care whether we
provide it along with Bold and the others, as if it were a constant property
you can paint text with (even if it is not, in terms of implementation), or
whether we force users to use face `fixed-pitch' and be aware that they are
doing that. I simply meant to point out that what Richard said was not
necessarily true:

  "For 'fixed pitch', I think that can only be considered as a face."

Fixed pitch _can_ be treated like any of the other constant "properties",
_if we want_. If you prefer to treat it as an exception, as the only face in
the menu (aside from face access via `Faces...'), so be it. My only point
about it was that we do not _have_ to present fixed pitchness to the user as
a face. (Personally, I'd prefer to remove it from the Text Properties menu,
and treat it only in the font menu, as a font-family change - which it is.)

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