[GEM Development] Newbie questions about OpenGEM

[John Elliott]

> 
> Greetings,
> 
> I'm interested in the possibility of developing an OpenGEM application to
> do some hardware control tasks via the parallel port. Since timing
> precision is critical and my application utilizes timer interrupts for
> it's operation I'm interested in opinions on how well OpenGEM would work
> with this sort of application.

  GEM is a cooperatively-multitasking environment, so you can't put
time-critical code in the normal event loop.

  It's possible to hook the timer interrupt in GEM, but since this is also
hooked by GEM itself you have to make sure to call the original handler. The
GEM function vex_timv() will hook the timer interrupt and return the address
of the previous handler; it should be called with interrupts disabled.
 
> Also, so far I have only run OpenGEM in DOSBox where the mouse response is a
> little sluggish when clicking. Is mouse performance under non-emulated DOS
> snappy and responsive as it is under Windows?

  The thing with GEM and mouse clicks is that when you click once, GEM will
wait to see if there's another click so that it can tell if what it's got is
a double- or a single-click. Depending on what double-click time you have
configured this may take up to half a second.
 
> I'm also curious if anyone has done any work with developing with Borlands
> CLX under OpenGEM?

  Unlikely; CLX, as I understand it, is a wrapper round the Qt widget set,
and I've not heard of anyone trying to port Qt to GEM.

-- 
John Elliott