evdev: Attach touchscreen to X screen

[Peter Hutterer]

On Mon, May 09, 2011 at 02:40:01PM +0200, Stephan Josel wrote:
> We're trying to get a multi-touchscreen (multiple touchscreens not
> multi touch) setup working with the evdev driver in Ubuntu (Natty
> Narwhal, 11.04). Basically, the touchscreens are configured and
> working except that the mapping to the correct X screen is wrong. We
> set up 5 touchscreens in a row (Xorg ServerLayout "RightOf") with
> Xinerama enabled and their corresponding touchscreen inputdevices.
> Using xinput we are able to create a pointer for each of the
> touchscreens. The following is observed then: When touching any
> screen, the resulting movement of the pointer is only displayed on
> the first X screen (there are 5 pointers visible then on this
> screen). This is not at all the desired behavior. We would like to
> attach a touchscreen to a specific X screen.
> 
> Unfortunately, we found no way to tell the evdev driver to map a
> InputDevice to a X screen. Older versions of the driver provided an
> option "AbsoluteScreen" but the latest version hasn't anything like
> this. I know that the evtouch driver would provide a "ScreenNo"
> option, however evtouch is not available for Natty Narwhal. We also
> experimented with the Xorg coordinate transformation matrix, but
> with the result that the mouse movements where still on the first X
> screen.
> 
> So my question is:
> How do I tell the evdev driver to map an InputDevice to a specific X
> screen? Is there an option line in xorg.conf or is there any method
> via xinput?

tbh, I don't think we have anything in place right now for multiple screens.
Multiple outputs - yes (the transformation matrix) but not multiple screens.

Cheers,
  Peter