How to determine device responsible for CorePointer event from withinclient?

[Troy Yee]

I've spent a great deal of time trying to google the answer to this
without any luck... I hope someone on the list can take the time to
point me in the right direction.

I'm using X.org server 6.8.2.  It is configured with dual monitors, each
with a touchscreen (single X-Display with two screens). The touchscreens
are configured to produce Core Pointer events.  There are also mouse and
trackball devices configured similarly.

For some X-client applications, having the touchscreen behave like the
mouse is exactly what is desired.  But I also have X-client applications
that should ignore touchscreen input but not mouse input.  Some X-client
applications also want to selectively ignore touchscreen input and to be
able to distinguish mouse motion from touchscreen motion.

I had hoped that the event handler would be able to determine the device
from which an event originated but I have not found a way to do this
yet.  Can anyone point me in a direction that will allow for this
selective client behaviour?

        
Any pointers greatly appreciated,

Troy.