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

Henrik Rydberg rydberg at euromail.se
Tue Jun 22 05:21:59 PDT 2010

Peter Hutterer wrote:
> 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.

Hehe, well, the example illustrates that if every new touch gets a unique
tracking id, one can use that information to determine "newness" over extended
periods of time. The straw trick does not really change that fact.


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