[XeTeX] Unicode math, was fontspec 1.5 (& Lucida Math)

[Will Robertson]

William F. Adams wrote regarding creating an XeTeX math font from 
Fourier:

> The .vf issue is kind of tedious --- one would have to stitch all the 
> characters together from the discrete fonts --- but technically no 
> huhu.

It hasn't been explicitly stated, but -if- such a task were undertaken, 
it would be foolishness *not* to do it in Unicode.

The STIX fonts should be rearing their head in the near future (on a 
TeX/LaTeX time scale), so it would be great if we could demonstrate how 
much easier it is to use them in XeTeX than pdfeTeX.

I've spent a small amount of time investigating the use of 
symbols/greek letters within unicode fonts for maths seeing what is 
possible with LaTeX's
    \DeclareMathSymbol{<symbol>}{<type>}{<font>}{<"slot">}
command, but it's hard-coded (understandably) to only accept 256 
positions within a font.

Something along the lines of Ross Moore's extension to 
\DeclareTextCommand to allow for unicode characters (in 
utf8accents.sty) is required, along with some sort of extended mathchar 
support of which I'm not too sure of the details.

And then a whopping great file that lists every unicode math character 
and gives it a name.

Just some musings to start the day.
Will