Re: Making a non-ASCII space character visible

[Eli Zaretskii <eliz@gnu.org>]

> From: Will Parsons <varro@nodomain.invalid>
> Date: Sat, 16 Jun 2018 16:15:59 -0400
> 
> 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".  (This message occurs even
> if I try to change one of the display characters of an existing entry
> in the list and apply.)

Whitespace Display Mappings only has effect if you turn on
whitespace-mode.  The special display of u+00A0 does not require
whitespace-mode, it is implemented directly in the display engine.
Maybe we should extend that built-in treatment to the other
"space-like" characters.

> Feeling desperate, I copied the existing value of
> whitespace-display-mappings directly into my custom.el file, and
> manually added a new entry for A007 (8199) on the model of the
> existing entry for 00A0 (160), but this seems to have no effect on the
> display.

Did you also turn on whitespace-mode?