[luatex] Info on direction primitives/implementation

[Joseph Wright]

Hello all,

I'm currently taking a look at the approaches used for RTL typesetting
in pdfTeX/XeTeX/LuaTeX. In pdfTeX/XeTeX, the TeX--XeT approach is used
and this is documented in the e-TeX manual (as far as I know, neither
engine does anything other than adopt the e-TeX code). On the other
hand, LuaTeX uses the Omega approach, or at least some of the same
interfaces. However, reading the LuaTeX manual I've not got a clear
picture of the detail. Is there some documentation on the way RTL (etc.)
is implemented in LuaTeX? (I've also failed to find an Omega manual to
see if there might be any help there. But even if I could, I'm guessing
the code may have been modified.)
-- 
Joseph Wright