Re: Trojan Source detection/highlight in Emacs?

[Eli Zaretskii <eliz@gnu.org>]

> From: Anders Munch <ajm@flonidan.dk>
> Date: Wed, 3 Nov 2021 08:52:52 +0000
> Accept-Language: en-US
> 
> Eli Zaretskii wrote:
> > Stefan Monnier wrote: 
> >> A simple and straightforward way to do that is to highlight any 
> >> non-ASCII char, and to render all the "non printing" chars (such as 
> >> RIGHT-TO-LEFT OVERRIDE) as tofu or something like that (otherwise, the 
> >> highlighting applied to it wouldn't be visible).
> >
> > That's already available, no changes needed.
> 
> Can we get a recipe, please?

Customize the variable glyphless-char-display-control.

> I tried customising bidi-paragraph-direction, setting it to 'left-to-right, but I'm not seeing any effect, despite the docstring saying it /forces/ directionality.

The doc string says it forces the directionality of the paragraph.  If
you don't already know what that means, I suggest to read the
"Bidirectional Editing" node in the Emacs manual, it should explain
that.

> I guess it just sets a default, and explicit bidi control characters take precedence.

Not exactly, but something like that.

The paragraph direction is not relevant to this issue, since in
prog-mode descendants we already set the value to left-to-right.