[luatex] LuaTeX + LaTeX

[Elie Roux]

Hello all,

During the last month I had a lot of email conversations about what 
seems to be a growing need: LuaTeX + LaTeX. Here is a summary of what I 
learned from these conversations, about some topics:

Basically there are two needs: adapting the LuaTeX new features to 
LaTeX, and adapting LaTeX to the LuaTeX engine.

On the first category is one main project: OT fonts.

== Open Type ==

The discussions lead to one proposal: adapting XeTeX's fontspec to 
LuaTeX. To do so there are two distinct steps:

First being able to open a OT font and being able to choose the 
functionalities we want from it.

Then adapting fontspec to the code of the fist step.

Arthur showed a base code on which we could work, and Hans said he could 
isolate some code from ConTeXt and make it generic enough for plainTeX, 
but only after the math functions are stable. I don't know if the math 
functions are stable, but Hans is your proposition still available?

Will Robertson is willing to help on this, especially on adapting 
fonspec, but first we need to work on the code to open OT fonts.

== luatex.sty ==

Heiko has already been working on adapting LaTeX to LuaTeX by writing a 
luatex.sty, integrated into TeXLive 2008. There are though several 
problems with this package: first Heiko is very busy, and almost 
unreachable. The macros defined in the package do not all start by lua, 
when they should, like the macros defined by pdfTeX (that start by pdf). 
Also the package is not stable enough to be integrated in the LaTeX format.

Integration in the LaTeX format will be totally impossible now for any 
style (even stable), because the LaTeX team works on LaTeX 3, and does 
not want to start changing things in LaTeX 2. But Kark Berry can 
integrate a style (like a style for LuaTeX) in the LaTeX format of 
TeXLive, so we don't have to worry about that.

The style misses, I think, a very important thing, which is multiple 
callbacks. As I can't really reach Heiko, I think the best solution is 
to make a separate style, and ask him to integrate it when it's done. So 
I think we can relaunch the discussions on this. We stopped the 
discussion with a sample code from Hans, asking if it would be 
interesting to continue it... now it is. So if someone wants to continue 
the code given by Hans, please do. Maybe Hans himself?

== Backward compatibility ==

If we want (and I think we do) LuaTeX to be the next "normal" engine for 
LaTeX, like pdfTeX is now, we need to ensure a total backward compatibility.

This compatibilty is broken with two major packages: inputenc and 
fontenc. The two styles are not working at all anymore.

For inputenc, the problem is the same for XeTeX, and the solution can be 
common, so we can work with Will.

For fontenc, the problem does not appear at all with XeTeX, so we'll 
have to work on a LuaTeX solution.

== (Personal) Bonus ==

And at the end of this, we may be able to modify the parallel package so 
that parallel paragraph have a perfect vertical alignment (which is 
impossible now), and that will change the life of a lot of LaTeX users, 
so everyone will go LuaTeX... But that's off-topic...

If you have any suggestion or if you want to work on one of the tasks, 
please do not hesitate!
-- 
Elie