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

[Eli Zaretskii <eliz@gnu.org>]

> Date: Mon, 27 Mar 2017 08:49:47 -0700 (PDT)
> From: Drew Adams <drew.adams@oracle.com>
> Cc: emacs-devel@gnu.org
> 
> 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').

As I explained, the display engine, which is the part that implements
the faces, will be unable to do anything with attributes that don't
affect display.  And the implementation of the features which do need
to pay attention to such attributes is entirely unrelated to faces.
So I don't understand why you want this to be attributes of faces.

Moreover, you consistently mention the display engine as the main part
of this proposal.  But features that don't affect display cannot be
usefully built on top of the display code, because the display code is
designed to run and examine text only when and where there's likely to
be changes in buffer text that will affect the display.  By contrast,
the non display-related properties need to be processed regardless of
any changes that could affect display.  Do you see a conflict here
between the goals and the proposed design?