Re: Bidirectional text and URLs

[Eli Zaretskii <eliz@gnu.org>]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: Eli Zaretskii <eliz@gnu.org>,  larsi@gnus.org,  emacs-devel@gnu.org
> Date: Thu, 04 Dec 2014 10:53:29 -0500
> 
> The problematic case that started this thread was because strongly L2R
> characters were displayed in R2L fashion because of their context.
> And *that* is indeed a problem, because there was no obvious visual
> clue: the reversed chars were all latin chars.

We now have a primitive that can be used to detect such regions in a
buffer.  So we can implement a warning in those cases.

> So, if we want to emit a warning, it should not be when "there's some
> R2L text in an L2R context" but only when L2R characters end up layed out in
> R2L because of the context.

And likewise with R2L characters that end up displayed left to right
(although the target audience for this would be much smaller).

> I'm not familiar enough with bidi uses to know for sure whether such
> "forced wrong-way layout" is something that can occur regularly in
> normal/legitimate situations

There's no reason for it to occur regularly.  Its main purpose is to
satisfy very specific and rare circumstances, like when you need to
show R2L text in logical order (e.g., for didactic reasons), or force
punctuation characters to display in a particular visual order.