Simulating a graphics tablet?

[Dan Kegel]

I'm looking into how to write an automated test case for
the graphics tablet handling in an application (Wine).
To do this, I would need a robotic arm to move a stylus
around on a real graphics tablet --- or a simulated graphics
tablet with an API for simulating moving the stylus around.

It would be nice to be able to control what the simulated
driver reported back (e.g. number of axes, etc.) to X.

Offhand, I think doing this conveniently is difficult; the
closest thing to it would be to have the test app write its
own little xorg.conf and spawn a (nonprivileged) Xvfb that
reads an xorg.conf and loads the simulated graphics tablet
driver.  I suppose Xvfb doesn't read config files, so
this would be something new.

How far off track am I?  Is there an easier way?

Thanks,
Dan