bug#18367: 24.4.50; [PATCH] Text property `font-lock-ignore', to protect from font-lock

[Michael Heerdegen]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

> > Bug or missing feature: Prevent font-lock from changing text
> > properties on text that has property `font-lock-ignore'.  See
> > http://lists.gnu.org/archive/html/emacs-devel/2014-08/msg00540.html
>
> Could you add a short explanation for why font-lock-face is
> not sufficient?

I'm not sure about that question.  But I see a problem in cases where
packages use the 'face property without using font-lock (e.g. Helm does
this in its Completions buffer) and other packages come and invoke
font-lock in such a buffer (like e.g. rainbow-delimiters does/did in
it's globalized mode).  In such a case, all the fontification with 'face
is erased.

I guess it is an error to use 'face in any buffer that could become
subject to font-locking caused by some mode or package.  If that's the
case - if it is recommended to use font-lock-face in all these
situations, we should say in the manual that 'face is dangerous to use
in such situations:

  (info "(elisp) Special Properties")

Michael.