multi-touch-dev team mailing list archive

[Henrik Rydberg <rydberg@xxxxxxxxxxx>]

On 10/08/2010 03:32 PM, Chase Douglas wrote:
[...]

>> In the sense that a multi-finger drag never terminates, this is true. By not
>> listening to the drag gestures, the MT events can be let through to the client.
> 
> I'm beginning to think we need a separate gesture primitive: touch. For
> example, take the Unity window movement gesture (note this is different
> than what's been published in the original UI docs, it changed near
> release). The user initiates the gesture with three fingers, but must
> remove a finger to enter window movement mode. We don't currently have a
> good primitive for this, the closest thing we can do is subscribe to all
> three finger gesture events so that we pick up the three finger touch.


Interesting idea, let me think about that a bit.

> If we add a gesture primitive called "touch" that is active any time the
> accompanying number of fingers is touching the screen, then we can use
> it for state transitions like above and add the timeouts for initiation
> to all the current gesture types. 


I do not think we want to commit so deeply to a certain gesture policy. These
problems really seem to arise because we want to resolve a global problem
(gestures) using a local solution (touch grabs). Any other suggestions out there?

>>> I think the proper grab semantics for the purposes of system-wide
>>> gestures is for the WM to have a passive grab on MT devices. This grab
>>> would be activated when a touch begins, and deactivated when a touch
>>> ends. However, each grab would be per-touch, and the WM could choose to
>>> "replay" events for any given touch to other clients. Replaying events
>>> essentially means the client relinquishes the grab for that touch, and
>>> all further events from that touch will not be grabbed as well.
>>
>>
>> The passive grab notion fits well into reformulating what we can do today, but
>> it still leaves more to wish for in terms of touches outside of the window.
>> Imagine the situation where you have the index finger down on a substrate,
>> moving it around, reading a map. Now you want to zoom out, so you put down the
>> thumb to pinch. The thumb finger is outside the window at first, then moved
>> inside as it approaches the index finger. This feels like a very natural gesture
>> to me, but it does not fit into our current thinking of passive grabs.
> 
> I understand what you are going for, but I worry about ambiguity. The
> second touch that occurs outside the window might be intended for a
> different window. Maybe it's a different user altogether?


Here is a question for you: is the division of touches into logical groups, like
hands, a context-dependent problem?


> I wonder how often one would need to zoom like this, and not have the
> area to do so with the current method? Do you have any examples where
> this zooming paradigm is necessary?


Necessity is more or less defined by what we do here, so I believe the question
tries to avoid the problem. :-)


> Aside from necessity, I'm not sure how intuitive this zooming paradigm
> would be, since most people are used to zooming in the current fashion
> only. Maybe I'm wrong, but I've not used any UIs that allowed zooming as
> you propose.


Honestly, I have not yet seen a single touch interface that really utilizes
multitouch.

Cheers,
Henrik