RE: Idea: Be able to use text properties as face attributes

[Drew Adams <drew.adams@oracle.com>]

> > In my view, the effect of a applying a face whose spec
> > contains non-face properties to some text would not
> > change the text properties of that text (other than its
> > `face', `font-lock-face', or `mouse-face' property).
> > It would change only the rendered _effect_, i.e., what
> > the display engine does.
> 
> I don't understand what that means, for most text properties, since
> they don't affect the visual appearance of the text in any way.  Which
> properties, except 'invisible', did you have in mind?  I'm confused.

It's about the effect of a text property, regardless of
what the effect is or where in the Emacs base code that
effect is applied.  It's not about only text properties
that visually affect the display of the text they are
applied to.

I mentioned "rendered" and "display engine" only as a
shortcut, and because I am not familiar with the actual
code that implements the various effects.

It's not important (to my general description of the
feature) which code in fact makes text that has a `keymap'
property behave as if the keymap at that place were the
keymap that is the value of that text property.

There are lots of text properties, and as you say, many
have nothing really to do with how the text they are
applied to "appears".  They do have some relation to
that text, and there is some effect of their being
present.  And some Emacs code manages that effect.

The idea of the feature is that a face property that
contains text properties as (pseudo) face attributes
would produce the same effect as applying those text
properties to the text.  But those text properties
would not in fact be applied to the text - they would
remain encapsulated in the value of the applied face
property (`face', `font-lock-face', or `mouse-face').