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

[Joseph Wright]

On 05/12/2012 00:53, Vafa Khalighi wrote:
> The point about specials is one I
>> guess I'll look at by reading the bidi code and doing some tests.
> 
> bidi package does not patch \special. It only make changes in packages like 
> color, xcolor and hyperrref, etc. And this makes them work in a very limited 
> case. For example, if you use color package in RTL with bidi package, color 
> works correctly only if your colored text stays on one line.

OK, does sound a bit limited.

>> As you might guess, my interest here steams from some LaTeX3
>> discussions, and one issue I'm trying to understand is whether the
>> TeX--XeT approach is really one that is sensible to try to support,
>> given the fact that the Omega approach exists. 
> 
> 
> My advice: do not waste time on TeX--XeT; it's useless. I have spent four years 
> developing bidi package using TeX--XeT and I can tell you that it has many 
> bugs/limitations.

At the moment, I'm looking specifically at what we need to worry about
at a low level. For example, the current expl3 code does not take any
notice of direction, which is probably right for something like \hbox:n
(follow whatever is going on around it), but should be documented and
deliberate, not just something we've ignored. So what's important at
this stage is much more the concepts than trying to write any code,
although any thoughts on what is required for RTL support at the 'base
level' are of course welcome.

What you say fits in with what I'd already suspected: for RTL work,
we've be better only supporting one set of primitives, the Omega ones.
For pdfTeX that's not an issue: I doubt very many people use pdfTeX for
RTL. XeTeX is a bit more 'interesting': I guess the existence of bidi
means that people are using XeTeX for 'real life' RTL work, despite
limitations.
-- 
Joseph Wright