Hi,
While trying to convert some stuff from HTML to PDF (using LuaTeX) I have noticed some minor problems: unicode math characters work OK in text mode (under assumption that the font has them), but not in math mode. In pdfTeX they work OK in both cases. (That behaviour is expected, but not necessary desired.)
I know about this, and this is one of the main reason that I am still using pdftex for day to day work. I have become used to typing most of my math in unicode, and now none of it works (with luatex). But I have been too busy to actually try to understand what is happening behind the scences.
Is there any cure to it?
AFAIK, luatex has not toched on the math handling of tex yet. There are some old ideas on how TeX's math support can be improved, and with luatex that is a real possibility. I am sure that at some stage, once some aspects of the lua functionality are more stable, this will be looked into. It makes sense to finalize mkiv support only after that.
I could/should solve the problem with better handling of xml entities or with fallbacks (if φ is not present in font, use \phi etc.), but I don't know how to do either of them.
I would normally say something like \chardef`φ=\active \defφ{\phi} to solve the problem, but that doesn't work when doing XML conversion.
Actually, for a unicode aware engine it should be the other way around \def\phi{φ} That is, all definemathcommand be changed to something like \definemathcharacter[φ][font:location] and so on. But my guess is that this will need a overhaul of the math character encoding. Again, that is something which I do not understand at the moment. Aditya