Re: Elisp manual: Note that created faces cannot be removed.

[Eli Zaretskii <eliz@gnu.org>]

> Date: Mon, 22 Jul 2019 10:02:09 +0000
> Cc: emacs-devel@gnu.org, Noam Postavsky <npostavs@gmail.com>
> From: Alan Mackenzie <acm@muc.de>
> 
> Sorry to go on about this (trivial) point, but I'm not happy about my
> proposed text any more.  With the mechanism pointed out by Noam, it
> clearly _is_ possible to undefine a face, but it's unsafe.
> 
> So, using "undefine" rather than "remove" (suggested to me by private
> email), and inserting the word "safely", I now propose this:
> 
> diff --git a/doc/lispref/display.texi b/doc/lispref/display.texi
> index 276d60b21a..4ae0bba723 100644
> --- a/doc/lispref/display.texi
> +++ b/doc/lispref/display.texi
> @@ -2476,6 +2476,10 @@ Defining Faces
>  usual procedure is to define a face with @code{defface}, and then use
>  its name directly.
> 
> +@cindex face (non-removability of)
> +Note that once you have defined a face (usually with @code{defface}),
> +you cannot later undefine this face safely, except by restarting Emacs.

That's fine with me, but unlike you, I don't really see a difference:
for the reader of the ELisp manual "cannot undefine safely" and
"cannot remove" are identical for all practical purposes.  Moreover,
"undefine a face" is not really well-defined.