bug#44236: [PATCH] xdisp: Apply nobreak-char-display also to NARROW NO-BREAK SPACE U+202F

[Eli Zaretskii <eliz@gnu.org>]

> Date: Mon, 26 Oct 2020 12:13:48 +0100
> From: Neil Roberts via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> 
> U+202F is like the normal non-breaking space character except that it
> is slightly narrower. In the French language, this character is
> supposed to be used before most punctation marks such as question
> marks and quote characters. For people using the BÉPO keyboard layout,
> this character is typed with just shift+space, so it’s quite easy to
> accidentally type it. For that reason it would be nice if it was
> displayed differently like the regular non-breaking space. This patch
> makes that change.

Thanks.

But what is the purpose of showing this character like we do with
NBSP?  We do that with NBSP because otherwise it will be easy to
interpret NBSP as a SPC: they have the same width and appearance on
display.  By contrast, U+202F NARROW NO-BREAK SPACE is much thinner,
and cannot be mistaken to be SPC.

OTOH, if we make U+202F stand out, then why not others, for example
U+2007? or U+2060? or U+2002? or U+2003? or U+2009 etc.

IOW, we need to decide on the rationale for displaying these
specially, and then we can decide which ones should have this applied.