> And, on a vaguely related topic, is it possible to use threads with programs
> that also use OCamlTK?  I know Tk is not threadsafe, but if only one thread
> is calling Tk functions, then perhaps it's still OK?  

Yes, it should be ok. But this also includes the Tk event loop, and thus
all callbacks. Also, there is the issue of using Thread primitives within
a callback (e.g. having the callback on a button triggering a condition).
In bytecode threads, this will probably not work.
Jun and I discussed these issues a long time ago, and Jun implemented
a modified version of the CamlTK core where the event loop would be handled
in Caml instead of C, so as to be compatible with threads, to some extent
(all other Tk calls still need to be in a critical section).
I don't think we ever distributed this version, and I'm not even sure it
would work on Windows, but you might want to check with Jun.

--f