bug#54219: 26.3; Bidi and empty parentheses

[Eli Zaretskii]

> Date: Wed, 2 Mar 2022 05:26:37 +0000
> From:  Richard Wordingham via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> 
> ; Create a new buffer for general text, e.g. c.txt
> C-x C-f c.txt RET
> ; Enter RTL character
> insert-char 644 RET
> ; Enter rest of line
> x()y
> 
> --Problem--
> The result is that a flush-right line is produced that appears to read
> 
> y()xل
> 
> It should appear to read
> 
> x()yل

Thanks, fixed for the upcoming Emacs 28.1.

> See https://corp.unicode.org/pipermail/unicode/2022-February/009984.html
> and reply from Ken Whistler for confirmation that the observed
> behaviour is wrong.

Unfortunately, that reply didn't really help, because it didn't
analyze the BPA details, which are crucial in this case.  (If you set
bidi-inhibit-bpa non-nil, the problem goes away.)  It just provided
the final output from Ken's program, which (as any other program) can
have bugs.

> For the usage that prompted this report, several work-arounds are
> available, including defining end of line as a paragraph boundary.
> The Emacs display in that usage is also rendered baffling by Bug #27525
> 'Line wrapping of bidi paragraphs'.

Not sure what paragraph boundaries have to do with this.  Sounds like
an unrelated issue.