touchscreens in multiscreen setups

Matthieu Herrb matthieu.herrb at
Thu Dec 17 23:32:20 PST 2009

On Thu, Dec 17, 2009 at 09:27:07PM -0800, Keith Packard wrote:
> On Fri, 18 Dec 2009 15:04:48 +1000, Peter Hutterer <peter.hutterer at> wrote:
> > there's two parts to it:
> > - xf86InputSetScreen seems broken, this should be fixed in the server.
> >   though it's probably optimised for the Xinerama scenario, I think it
> >   should be possible to set it up for randr output or CRTC tracking in a
> >   similar manner.
> It would need to be tied to an output, not a crtc. And, what we'd need
> to do is let the input device know which output it is associated with,
> and then provide a helper function to translate coordinates relative to
> that output. That could deal with output transforms as well. I don't see
> how xf86XInputSetScreen has much to do with this though, other than
> having that be used as a hint to go lookup the output property in the
> config file?

For touchscreens you want to tie it to the particular output it's 
physically bound to in (almost) all cases. And in multi-head setups
you need another pointer for heads without associated touchscreens.

Tablets may be a bit different: you may want to use it as the only
input device, covering all the screen. (Although the geometry will
probably be awfully distorded). Other people, like graphic designers
will prefer to have the tablet restricted to the output bound to the
head where their main canvas is displayed and use a second input
driver to drive the 2nd head where the menus with all tools are

>From the configuration point of view, in most cases the underlaying
driver knows if it's a touchscreen or a tablet and can choose a
reasonable default, but the configuration should be modifiable on the
Matthieu Herrb

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