bug#27525: 25.1; Line wrapping of bidi paragraphs

[Eli Zaretskii <eliz@gnu.org>]

> From: Itai Berli <itai.berli@gmail.com>
> Date: Wed, 19 Jul 2017 11:50:54 +0300
> 
> Eli, in different bug report, namely 27526, I recently wrote the following remark:
> 
> > the line-wrapping bug is still a major annoyance, at best, and until it is fixed, Emacs cannot claim to be
> Unicode compliant.
> 
> to which you replied:
> 
> > I disagree, as I already said many times.
> 
> You do agree, though, that Emacs does not conform to the Unicode Bidirectional Algorithm as specified in the
> Unicode Standard Annex #9.

I maintain that Emacs deviates from the UBA in a relatively minor way,
in an aspect that is only tangentially related to reordering
bidirectional text for display, and that raises its head in situations
that are relatively rare in practice, and in many of those rare cases
can be easily worked around by breaking long lines.

> So the only thing you disagree with me is that non-conformance to the Unicode Bidirectional Algorithm is
> tantamount to non-conformance to the Unicode Standard.

Not only, see above.

> Well, this disagreement is easily settled by reading
> article C12 'Bidirectional Text' of section 3.2 'Conformance Requirements' of the Unicode Standard:

No, it is not settled; see above.

And I don't really understand what is the purpose of your insistence
on the formal definition of this deviation.  It certainly won't help
fixing this issue any time soon, not unless someone steps forward to
do the job, which IMO is quite large.  All it does is cause me to
think, for the first time in many years, whether I indeed had to
invest all that huge amount of time and energy in single-handedly
coding, testing, and debugging the bidirectional text support for
Emacs, which even today, 10 years later, still shines among all the
bidi-aware editors out there, certainly among those of the Free
Software variety.  Even the fribidi library didn't yet catch up with
Unicode 6.3 and later.

If after all that all I get is this badgering about a minor issue
whose solution needs a thorough rewrite of the related code, then I
wish I never wasted those efforts working on a feature which I naïvely
assumed will be tremendously useful to many, and that in fact causes
only negative reactions from the few who use it.