multi-touch-dev team mailing list archive

[Chase Douglas <chase.douglas@xxxxxxxxxxxxx>]

On Sat, 2010-10-09 at 21:07 +1000, Peter Hutterer wrote:
> On 9/10/10 20:31 , Henrik Rydberg wrote:
> > On 10/09/2010 08:04 AM, Peter Hutterer wrote:
> > I agree that the meaning of a gesture is context dependent, just like a typed
> > word means different things in different contexts. Gesture primitives, however,
> > are much more like the keys themselves.
> 
> what is a gesture primitive though? this is one of the points I have 
> troubles with: at what point does a movement of a finger become a swipe 
> (which I think is what you'd classify as primitive, right?). And isn't 
> that context-dependent too?
> Or do I misunderstand something here.

A one finger movement becomes a one finger drag iff the application
wants to receive one finger drag gestures. I don't foresee this being
useful in a standard cursor based environment, but there may be UIs
where touch positioning isn't important but single finger movements are.
We calculate extra data like velocity of drags in our gesture
recognizer, which can also be helpful to a developer.

This is an example where I see a gesture API being a helpful development
tool instead of a new feature. Sure, you could do the exact same thing
with XI, but for certain usage scenarios it may be easier to think of
touch movements as single finger drags rather than cursor movements.

To compose an answer to your question, yes, gesture primitives are
context dependent as well. But their "meaning" is very well defined. The
only question is whether an application is interested in hearing about
them. Gestures, on the other hand, have a more context-specific
"meaning" even when two different applications subscribe to the same
gesture primitives.

-- Chase