Stephan,

> > The input semaphore is only useful if in fact the VM event 
> > processing loop is running in a separate thread. In this case,
> > it can signal the input semaphore to announce that events are available.
> 
> What do you think about having two threads? Do you see platform
> compatibility problems there?

Yes, definitely. On most platforms. The different Unix versions have no
common understanding of the semantics of threads (although I think pthreads
are pretty widely available now) and I don't think that there's a lot of
thread support on pre MacOS/X. On Windows I have my doubts about to what
extent this will really work a good old Win95.

Cheers,
  - Andreas