[dev-context] Re: BiDi in ConTeXt

Adam Lindsay atl at comp.lancs.ac.uk
Fri Nov 12 00:39:11 CET 2004

Idris Samawi Hamid said this at Thu, 11 Nov 2004 14:37:58 -0700:

>Hi Adam, & thnx for cc'ing me.

(Well, only natural: I was looking thru m-gamma to see how things were
being used, and it had your name all over it.)

>> 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.
>I've been out of the loop on all things TeX for a while now (demands of my 
>profession and other matters). I have a couple of general questions:
>1. What exactly is the aim and purpose of XeTeX?

XeTeX is an updating of GXTeX. It is an amalgamation of eTeX with Unicode
and Apple's advanced typography APIs, and is therefore Mac OS X only.
Once cross-platform-ness is sacrificed, there are a lot of interesting
benefits. Font installation issues drop to nearly zero--it has access to
all fonts on the system--and Apple ships the systems with a fairly
impressive array of intelligent fonts. The native Unicode support unlocks
a lot of ConTeXt's stored multilingual potential, too.

>2. Since its apparently based on eTeX, and since bidi seems to be of 
>interest, why not integrate it with the Aleph project, also eTeX-based 
>(with an eye towards ConTeXt), and which already has the bidi stuff 
>implemented rather well?

I doubt it's headed that way, but Jonathan Kew, the developer, may well
be swayed by certain of Omega's paragraph/text directionality constructs.
I don't know it well enough, but William Adams seems to have a hand in
the Omega pie, and is represented in the XeTeX community.

>> 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?
>If the idea is a kind of BiDi-Light (just paragraph and text), then 
>implementing a subset of Aleph's functionality (such as \pardir and 
>textdir) seems like a good way to go.
>> (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.)
>which is where we will need Aleph and Bidi-Full

The (too hidden) implication from me was that XeTeX does offer automatic
text directionality, driven by the script and/or Unicode page. Noticing
Hebrew in a default font, I tried spelling Aleph-Dalet-Mem in the middle
of a roman paragraph, and it naturally (no markup needed) came out MDA.
(Hans, incidentally, is a little disturbed by this sort of cleverness.)

>Is Giuseppe aware of all of this (I assume he's on dev-context)?

Actually, looking at the distro list, it looks like he isn't! hi!
 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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