RE: link appearance and soft face properties

[Drew Adams]

    >     That way, a single (possibly user) definition of the :link
    >     attribute would automatically affect any faces that have that
    >     property. And it would also be easy (including for users) to
    >     selectively apply the :link property to face or mouse-face
    >     or both.
    >
    > I think this can be done by making these faces inherit
    > from a face named `link'.

    This is an interesting idea, but then for consistency this should be
    applied to every mouse-over attribute with follow-link property, i.e.
    not only in compilation and grep buffers, but also in info,
    dired, gnus...

Yes, that's what I meant: use a predefined (but user-customizable) `link'
face everywhere, for links.

Currently, we have no "soft" (= user-changeable) notion of what a "link" is.

In fact, even apart from a lack of customizability, we have no notion of
"link", except for that provided by the `follow-link' property (which is not
even used for all links). A link is currently defined only by whatever the
underlying code happens to do with a mouse-1 or mouse-2 click at that
position: if the code "follows a link" upon mouse click, then we can say
that a link is present.

One cannot assign "linkness" (behavior and appearance) to a portion of text.
The appearance of a link is governed by a face or mouse-face at that
position. There is no notion of a "link" object that unites function and
appearance (and allows for user modification of appearance).

Providing a link face (that inherits etc.) and using it for all links (i.e.
places where the code in fact "follows a link" upon click) would let users
customize, in a single place, how links appear. (If we provided buffer-local
faces, users would also be able to easily customize link appearance on a
per-buffer basis.)

Best: Provide "link" objects: text that has certain properties that include
both appearance and "link-following" behavior when clicked.

OK (but < Best): Provide only a "link-appearance" text property or face. We
would continue to count on an underlying association of locally coded
mouse-click-link-behavior with the text that has the `link' property or
face.