Re: Foreground color opacity

[Eli Zaretskii]

> From: Filippo Argiolas <filippo.argiolas@gmail.com>
> Date: Mon, 11 Sep 2023 15:09:45 +0200
> Cc: emacs-devel@gnu.org
> 
> > Why not cover the "inactive" portion with an overlay which has the
> > 'face' (or font-lock-face) property that specifies only the opacity?
> > That is IMO simpler and doesn't need to run any functions after
> > fontifications.
> >
> > (Caveat: I didn't actually try this approach, so maybe I'm missing
> > something.)
> >
> > Thanks.
> 
> That would be the perfect solution, but as far as I can tell we don't
> have an opacity face attribute, do we?

Too bad.  (The alpha parameter is what I had in mind , but I see now
that it's only supported for the entire frame, not for a single face.)

Anyway, it sounds inelegant that we need to jump through such hoops to
achieve such a simple effect.  It could even be a problem, if some
Lisp program expects to find the font-lock faces in a buffer, but
instead sees your special faces which replaced them.  E.g., don't we
have features that detect strings and comments in code by looking for
their respective font-lock faces?