merge emacs-bidi into the main tree

[Alex Schroeder <alex at emacswiki dot org>]

Some people have been waiting for a long time for a bidi-enabled Emacs
-- at least I have been waiting for more than a year.  The strange
thing is that we have a working implementation:  emacs-bidi is
available from www.m17n.org, and has been since Emacs 20.3 or earlier.

There are a few imperfections, or so I hear, but when I -- as a
non-Arabic-speaker -- saw the Arabic glyphs rendered correctly on IRC
(using ERC, the Emacs IRC client) -- I was surprised!  Yes, there may
be problems with the existing solution, but at least there *is* a
solution.

I would therefore like to see the existing emacs-bidi implementation
merged with our CVS version.

Back at in the days when Gerd was maintainer, I heard he had issues
with the emacs-bidi implementation and didn't want to use it.  Perhaps
performance was bad.  Perhaps he thought changes to the redisplay code
would be necessary, and he felt that these changes had to wait.
Perhaps you could not turn bidi off at the time.

Well, for somebody like me who just wants to learn Arabic, copy Arabic
song titles from old tapes onto his website, or read the occasional
Arabic greeting on IRC, the current solution is good enough.  And I
don't feel we should wait any longer.  We have waited long enough.

If the reasons for rejecting the current emacs-bidi are still valid,
let's list them and discuss them again.  In the mean time a few people
like Jan D and Kim Storm have had quite some exposure to the redisplay
code, so perhaps we do have the necessary know-how now to fix the
remaining issues.  That would be wonderful.  Eli has already done
some work in this area, so if prefered, people could start asking him
for some directions.

If the reasons for rejecting the current emacs-bidi are weak,
however, I think we should weight them against the long time we've
been waiting.

And last but not least, consider what I found here
(http://www.arabeyes.org/project.php?proj=VIM):

    About: VIM-6 already has a number of the required Arabization
    features developed (unicode support, a hack to support
    right-to-left (RTL) write ability, etc). What is lacking is
    shaping code as well as a firm font/keymap definition.

    Status: Completed

    Notes

    * The various common keyboard used out there (Arabic has 5
      keyboard mappings :-)

    * Shaping code ought to be modularized so that we could
      potentially release it stand-alone to other projects for
      inclusion - thoughts?

    * Bidi support is not really included (rightleft is not Bidi),
      what to do about this (long term question - not a show-stopper)?

    * Any thoughts from Bram about non-fixed width fonts?

See what I mean?  The people from arabeyes.org ("The Arabic Unix
Project") don't consider imperfect right-to-left implementation and
lacking shaping code to be a show-stopper.  Why should we?

If you are new to bidi issues, take a look at
http://www.emacswiki.org/cgi-bin/wiki.pl/CategoryBiDi
for an introduction.

Alex.
-- 
http://www.emacswiki.org/alex/
I was on holidays from 2003-07-01 to 2003-07-29
and have a lot of catching up to do.