Re: Unicode confusables and reordering characters considered harmful

[Eli Zaretskii <eliz@gnu.org>]

> Date: Wed, 03 Nov 2021 16:01:20 +0000
> From: Gregory Heytings <gregory@heytings.org>
> cc: stefan@marxist.se, emacs-devel@gnu.org, cpitclaudel@gmail.com, 
>     monnier@iro.umontreal.ca
> 
> > It could, but I don't think we should install such features.
> 
> Why not?

Because it doesn't pass my quality-control tests.

> Is this not simply an improved (and built-in) version of your 
> initial suggestion to use glyphless-char-display?

glyphless-char-display already exists and is built-in.  People who
want to have these characters stand out for some reason can use it,
that's why it is open to customization.  What you propose is "yet
another mechanism similar to glyphless-char-display", and I don't see
why we should have this for a small group of characters.  We already
have a small mess because display-tables and glyphless-char-display
produce a race; I certainly don't think we should introduce yet
another, third mechanism for a similar purpose.

I could consider adding an additional METHOD to those we already
support there, if someone thinks the existing ones are insufficient.
Not sure if this is needed, but it at least makes some sense, assuming
the proposal would be reasonable and not limited to a small group of
codepoints.

> Except that glyphless-char-display is global (whereas
> buffer-display-table is buffer-local), and that a tofu is not as
> visible as a character highlighted with the font-lock-warning-face.

Patches to allow glyphless display to be controlled on a buffer-local
basis would be welcome, I think this would be a good enhancement.