[XeTeX] [luatex] Info on direction primitives/implementation

[Khaled Hosny]

On Tue, Dec 04, 2012 at 04:49:58PM +0000, Joseph Wright wrote:
> On 04/12/2012 15:55, Khaled Hosny wrote:
> > IMO TeXXeT and all its incarnation has always been a hack to get RTL
> > with the least modification as possible. Two main limitations I'm
> > concerned about are the broken handling of specials (you can not get
> > coloring or hyperlinks in RTL text without macro hacks with limited
> > functionality) and lack of RTL math. On the other hand Omega's
> > directionality code is more sophisticated and requires less adaptations
> > at macro side (check the size of bidi package on how things can go wild
> > with TeX--XeT), and it should allow for proper vertical typesetting in
> > XeTeX as bonus.
> 
> I'd picked up the math mode point (although I'm not 100% sure on how
> this works out with numerals, which don't always seem to be reversed
> compared to the latin script order). The point about specials is one I
> guess I'll look at by reading the bidi code and doing some tests.

This document summarises different approaches to typesetting Arabic
mathematics (the only language I know where math is typeset right to
left):

http://www.w3.org/TR/arabic-math/

But basically, any sequence of digits is not reversed, but everything
else in a formula is reversed.

> >> A slightly wider question which this leads me to: do I take it that
> >> getting some (minor) additions to XeTeX might be possible? There was
> >> some discussion last week about a few pdfTeX primitives that might be
> >> useful.
> > 
> > Patches are always welcomed of course :) Right now work is mainly on
> > layout side (replacing the abandoned ICU LayoutEngine with HarfBuzz,
> > there is even a chance of replacing ATS/ATSU with Core Text, and old
> > SilGraphite with Graphite2 engine) and further polishing of OpenType
> > math.
> 
> Jonathan K. will tell you that my ability to write XeTeX patches is very
> limited :-) I was thinking much less complicated than layout engines
> (which all sounds very good!). I'll see what makes sense and perhaps be
> in contact again.

Great.

Regards,
 Khaled