multi-touch-dev team mailing list archive

[Chase Douglas <chase.douglas@xxxxxxxxxxxxx>]

On Sat, 2010-10-09 at 13:49 +0200, Henrik Rydberg wrote:
> On 10/09/2010 01:07 PM, Peter Hutterer wrote:
> >>> Plus, the roundtrip issue of sending events to the recogniser who sends some of
> >>> them back before you can send them to the clients.
> >>
> >>
> >> Right, provided the recognition is placed on the client side.
> > 
> > wait, what? I'm not sure I read this comment correctly.
> 
> 
> Hehe. Point being that no particular problem is being solved by moving
> context-independent gesture recognition to the client side.

If I've read the rest of this thread correctly, it feels like Henrik is
advocating for splitting the gesture stack into a recognizer in X and an
instantiator on the client side. The issue I see here is that you still
need the context that only exists client side in order to perform
gesture recognition.

Take the case of what looks like a three finger pinch where two fingers
are over one object in a window and the third is over another object.
Imagine the two-fingered object is a scrollable region, and the
single-fingered object is a toolbar button above the scrollable region.
Now, you move the two fingers up to scroll. This looks like a three
finger pinch, but it's really a two finger drag. The recognizer would
have to enumerate all the possibilities of gestures depending on which
fingers are part of a possible gesture, and this becomes exponentially
difficult as the number of fingers increases. Thus, we can only perform
recognition after we know which fingers are part of a gesture, and we
can only do that with the knowledge available on the client side.

-- Chase