xinput > core poiner?

[Roman Seidl]

I have a tablet and i want to use an external monitor that covers just a 
part of the screen. This is no problem concering xrandr as i can set a 
scale and a position. The problem is with the pen. The pen core pointer 
is automatically postioned the right way - even in this situation.

But no transformation matrix whatsoever is set in the xinput settings 
for the device. Sound nice BUT i
  want to use direct xinput for using xournal. So i would like to modify 
the Transformation matrix. If i do so the xinput can be set to be in 
line with the monitors - but then the core pointer is wrong.

How is the xinput transformed into postions on screen for the core 
pointer? Is there any way to get infos on the transformation that takes 
place? Is it possible to modify it?