Re: Trojan Source detection/highlight in Emacs?

[Eli Zaretskii <eliz@gnu.org>]

> From: Anders Munch <ajm@flonidan.dk>
> Date: Wed, 3 Nov 2021 15:17:32 +0000
> 
> Eli Zaretskii wrote:
> > Anders Munch <ajm@flonidan.dk> wrote:
> >> Can we get a recipe, please?
> >
> > Customize the variable glyphless-char-display-control.
> 
> Thanks for the pointer, that would be the 'format-control' group?

Yes.

> I see it set to "Display as thin space".

Yes.

> But that's only half the story. The other half of how bidi control characters display is the effect that they have on surrounding text. 
> glyphless-char-display-control does not affect that.

That you cannot change easily, and you shouldn't try.  Emacs
implements the Unicode Bidirectional Algorithm when it produces
character glyphs for display, and that includes reordering them into
the so-called "visual" order.

> I went looking for a bidi off switch precisely because I'm aware that the Unicode bidi rules are complicated, or at least confusing when put into practice, and for those of us that don't read RTL languages, it might be better to switch it off completely than to try to understand it.
> 
> bidi-paragraph-direction was the only candidate to a bidi off switch that I could find.
> If that's not what it is, then where is the master switch to turn bidi processing off?

There is no such switch in Emacs.  Bidi reordering is always turned
on.  (And don't believe people who will tell you about
bidi-display-reordering: that variable doesn't disable the reordering
completely, exists only for my own debugging, and if turned off, will
cause the display code work unreliably in some situations.)