Re: faces `compilation-info' and `compilation-line-number'

[John Yates <john@yates-sheets.org>]

 On Thu, Feb 3, 2011 in "Eliminating a couple of independent face
definitions"  Stephen J. Turnbull wrote:

> The basic problem is that faces are not colors.  Faces are not fonts.
> (Where have I heard this before? ;-)  A face is a semantic component,
> intended to express meaning.  Common meanings should have a common
> expression.

Somewhat incoherently I attempted to introduce another perspective.
On reflection my mistake seems to have been to take issue with
Stephen's definition of a face.  What I had wanted to show is that
users often customize faces for reasons other than semantic
consistency.  That they use faces as a poor man's substitute for the
theming capability present in many GUI frameworks.

This new thread hinges not on aligning semantics but on which elements
in a given setting merit more or less visual emphasis.  That was
exactly the perspective I tried to capture in my earlier posting.

I have come to think that what emacs lacks is a palette framework.  I
imagine the palette framework as a partial order of degrees of
emphasis.  For lack of a better term I will call the members of this
partial order roles.  This ordering relationship would be captured in
the role names.  Thus we might have

garish
strident-2
strident-1a, strident-1b
emphasis-2
emphasis-1a, emphasis-1c, emphasis-1c
normal
deemphasis-1a , deemphasis-1b
deemphasis-2

(High lighting probably belongs in this list by I am not sure exactly where.)

Emacs would provide style guidance for the palette roles.  E.g. garish
applies to a limited span (a word or token, not the better part of a
line); strident-1a/b are appropriate for entire lines.

An actual palette is realized by associating with each role:
- a basic foreground/background color pair
- a font modification rule. Examples: base, bold else base, italic
else underline else base

Notice that a palette is less than a face because it is not associated
with a font or font family.  Applying a palette to a font family would
result in a basic set of faces (e.g. palette-garish,
palette-strident-2, palette-normal, etc).  These faces could then form
the basis for a set of derived faces that would introduce a base set
of semantic notions.

/john