Re: Making a non-ASCII space character visible

[Eli Zaretskii <eliz@gnu.org>]

> From: Michael Heerdegen <michael_heerdegen@web.de>
> Date: Sun, 17 Jun 2018 07:07:30 +0200
> Cc: help-gnu-emacs@gnu.org
> 
> Will Parsons <varro@nodomain.invalid> writes:
> 
> > I have a desire to use the Unicode character A007 (FIGURE SPACE) in a
> > document and to be able to distinguish it visually from a regular ASCII
> > space.  This seems to be already done in the case of 00A0 (NO-BREAK
> > SPACE) which appears as an underscore with a distinctive face.
> >
> > It *looks* like I should be able to do this via the customization
> > option "Whitespace Display Mappings", but no matter what I do,
> > attempting to "Apply" the changes results in an error message, "This
> > field should contain a single character".
> 
> Seems you tried to insert a printed representation of the character?
> AFAIK you must insert the character.  You can achieve this with M-:
> (insert ?\x2007) for example.  Yes, that's not so nice.

??? How does that differ from "C-x 8 RET 2007 RET"?  The latter is the
standard way of inserting characters in Emacs.

If you did succeed to customize that variable, can you show a step by
step recipe?