bug#49562: 27.2; Crash with specific mode-line-format in BiDi processing

[Eli Zaretskii]

> From: Martin Brüstel <martin.bruestel@tu-dresden.de>
> CC: <49562@debbugs.gnu.org>
> Date: Thu, 15 Jul 2021 11:30:27 +0200
> 
> Is there any built-in functionality to either
> 
> 1. "sanitize" a string to remove bidi formatting in a sane way, or
> 2. have `substring` functionality that can somehow deal with these
>    formatting controls, or
> 3. restore balance of a possibly broken bidi formatted string?

Not as you describe it, no.  You could remove all bidi formatting
controls with subst-char-in-string or with string-match/replace-match,
and then use bidi-string-mark-left-to-right to solve many problems
with bidirectional display of mixed RTL and LTR text.  But note that
bidi-string-mark-left-to-right doesn't exactly wrap the string in an
embedding, it does something smarter.