[PATCH evdev 0/3] Preliminary support of multitouch (rev4)

[Peter Hutterer]

On Fri, Jun 18, 2010 at 09:41:01AM +0200, Henrik Rydberg wrote:
> Peter Hutterer wrote:
> [...]
> >> On the other hand, some devices carry a tiny be of extra information
> >> through the specific contact id's, and they are not strictly the lowest
> >> set of numbers needed to express the contacts that are active or have
> >> been activated since the last period of inactivity.  From what I've
> >> heard the magic mouse (again) is one such example.  I haven't actually
> >> poked around enough to see it.
> > 
> > do you have any info on what this extra information could be?
> 
> You sit at a coffee table, coated with the finest multitouch film there is. You
> put down the tea cup and leave for the restroom, taking the btwallet with you.
> As everybody knows, once the btwallet is off the table, you are logged out. You
> come back, log in. Did anyone drink from your cup?

Interesting example but I can't quite map it to the technical
implementation. We don't have a notion of "logged out", at our level the
tea cup would continue to produce touch points (or not, if lifted off).
Even someone drinking out of it with a straw is covered by the change in
pressure.

"did anyone drink" is IMO too contextual that we can deal with it at our
level. we can only say "yes, the cup was lifted off" or "the cup is lighter
now". 

still not quite sure what that information could be.

Cheers,
  Peter