Re: Arabic support

[Eli Zaretskii <eliz@gnu.org>]

> From: Kenichi Handa <handa@m17n.org>
> Cc: jasonr@gnu.org, emacs-bidi@gnu.org, emacs-devel@gnu.org
> Date: Thu, 02 Sep 2010 22:01:07 +0900
> 
> A not-yet-shaped LGSTRING is created by autocmp_chars
> (composite.c) from a character sequence matching with a
> regular expression PATTERN stored in a
> composition-function-table.  This pattern is
> "[\u0600-\u06FF]+" for Arabic (lisp/language/misc-lang.el),
> and a more complicated regex for Hebrew
> (lisp/language/hebrew.el).

Thanks.  So character compositions are used not only to compose
several characters into one glyph, but also to break text into
individually shaped chunks, is that right?

If so, auto-composition-mode cannot be turned off for scripts that
need this kind of "grouped shaping" without degrading the presentation
of these scripts to the point of illegibility?

> > I'm asking because it's possible that we will need to modify
> > w32uniscribe.c to reorder R2L characters before we pass them to the
> > Uniscribe ScriptShape API, to let it see the characters in the logical
> > order it expects them.  That's if it turns out that Uniscribe cannot
> > otherwise shape them correctly.
> 
> ??? Currently characters and glyphs in LGSTRING are always
> in logical order.

See my mail from yesterday, where I describe that I see in GDB that
Arabic characters in LGSTRINGs arrive to uniscribe_shape in visual
order:

  http://lists.gnu.org/archive/html/emacs-devel/2010-09/msg00029.html

That is why I asked the question in the first place.  What am I
missing?