multi-touch-dev team mailing list archive

[Peter Hutterer <peter.hutterer@xxxxxxxxx>]

On Tue, Oct 05, 2010 at 11:16:20PM +0100, Mark Shuttleworth wrote:
>  On 05/10/10 19:13, Ping Cheng wrote:
> > Peter said: "With the new approach the recognition happens purely
> > client-side and is done by a library or a daemon. This allows for
> > multiple different gesture recognisers be active at the same time, a
> > scenario that is quite likely to happen (I do envision GTK, Qt,
> > Mozilla, etc. all wanting their own system). Whether that's a good
> > thing for the UI is another matter, consistency for gestures is
> > important and especially Ping Cheng was not happy at the prospect of
> > having multiple, possibly inconsistent, systems. We need to find some
> > common ground here between desktop environments and toolkits."
> 
> This smacks of the old X inability to make a decision and commit to a
> direction. 

[citation needed]

> We can be very clear about this: Ubuntu won't support
> multiple simultaneous competing gesture engines. We're already in
> conversations with Qt et al to ensure they can work with utouch, and
> we'll enhance the interface to allow apps to leyer their own
> interpretation on the raw data. But there will be a single gesture
> engine, and it will see the data before anything else does.

gesture recognition won't be in the X server, that was the main outcome of
the discussions we had at the MT workshop and at XDS. The server will give
the client raw touch data, how it is interpreted is up to the client.

Anything past that is implementation detail and whether you allow for one or
more recognisers is up to the clients. If you can manage to make them use
one single recognition engine, fine. In fact, that's probably the best
outcome since it likely provides the best consistency, at least for common
gestures. But I predict that sooner or later, we'll see a second and third
engine emerge, maybe for an app that needs really specialised gestures.

> We can be very clear about this: Ubuntu won't support
> multiple simultaneous competing gesture engines.

How does this work out if an application decides to interpret raw touch data
into gestures by itself? That would be a competing gesture engine then.

Cheers,
  Peter