X Gesture Extension protocol - draft proposal v1

[Chase Douglas]

On Tue, 2010-08-17 at 08:31 +0200, Florian Echtler wrote:
> On Mon, 2010-08-16 at 22:27 +0200, Simon Thum wrote:
> > Am 16.08.2010 21:41, schrieb Chase Douglas:
> > > Also, we think that there's a case to be made for environmental gestures
> > > that should override gestures recognized by clients. This is provided by
> > > the mutual exclusion flag when selecting for events. Again, this
> > > wouldn't be possible without integrating it into the X propagation
> > > mechanism.
> > I like it, if only because it resembles what I described on the list
> > earlier that year :) The protocol's probably tricky to get race-free,
> > but surely worth it. I'll have a more thorough look at it this week.
> > I'm cc'ing florian in case he's still working on the issue.
> 
> Here's the old discussion:
> http://lists.x.org/archives/xorg-devel/2010-March/006388.html
> 
> Thanks for mentioning, Simon - I'm very excited to see this, it's really
> quite similar to my own work. 
> 
> Douglas, allow me to point you to my thesis from last year at
> http://mediatum2.ub.tum.de/node?id=796958 
> Chapter 3 in particular deals with very similar issues, I'd be happy if
> you could give it a quick glance and tell me about your opinion. Or did
> you already read it? The similiarities, as I said, are quite
> striking :-)
> 
> There also is a cross-platform implementation of my concepts available at
> http://tisch.sf.net/ and https://launchpad.net/~floe/+archive/libtisch .
> 
> One thing I would suggest as a future extension is something along the
> lines of less monolithic gestures, i.e. compose them out of still smaller
> primitives such as number of fingers, held time, pressure, distance change,
> angle change etc. etc.

Florian,

I haven't seen your research before, so I just read through it. It's
pretty uncanny how similar our thoughts are about the design. I hope
that means we are both on the right track!

As for gesture composition, I think the gestures you and I have outlined
(move, rotate, pinch, tap) should cover all uses. Can you explain in
more detail what you mean by composing gestures out of still smaller
primitives?

It sounds to me like you might be talking about defining boundaries for
gesture recognition initiation, as in a rotation will be recognized
after x degrees. If so, I think splitting the gesture engine out from X
and making it a separate client helps facilitate research of this, as
people can play with other engine designs and parameters. If we find
that initiation parameters should be settable by each application, we
could extend the protocol for it. I'm hesitant to do so now without
evidence that we need it though.

Thanks,

-- Chase