[dev-context] BiDi in ConTeXt

[Adam Lindsay]

Hi folks.

I just started thinking about further language support within ConTeXt now
that the XeTeX-ConTeXt "basics" are done. XeTeX doesn't have the same
character/line directionality control that is apparently in Omega, but it
does control Right/Left typesetting fairly well.

In particular, it makes a fairly big deal of its implementation of the
eTeX beginR/beginL extensions. They seem to work fairly well in demos
I've seen and simplistic tests I've done.

I was wondering about the bigger issues in terms of BiDi support, though.
Do people want an interface that mimics Omega's \pardir command? Or is
there a more simple/focussed/specific way?

(I imagine I don't see a single \beginR in ConTeXt's source code because
it relies heavily on proper font support, probably beyond what the TFM
system usually offers.)

Anyway, I cooked up a quick simulation of the Omega \pardir command as
used in m-gamma. It only supports \pardir TRT and \pardir TLT, but is it
a way people want to progress?

\def\pardir#1#2#3{%TRT,TLT
  \ifnum\TeXXeTstate=1\else \TeXXeTstate=1\fi % check or blindly set?
  \doifinsetelse{#2}{R,L}
   {\EveryPar{\setbox0=\lastbox %
              \csname begin#2\endcsname\box0}}
   {\message{Paragraph direction must be right or left}}
  \doifnot{#1#3}{TT}
   {\message{Typesetting lines from top to bottom only}}}

Also, is dev-context the right place for a discussion like this?
-- 
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 Adam T. Lindsay, Computing Dept.     atl at comp.lancs.ac.uk
 Lancaster University, InfoLab21        +44(0)1524/510.514
 Lancaster, LA1 4WA, UK             Fax:+44(0)1524/510.492
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