Multi{pointer,touch} & Userspace

Jim Gettys jg at
Tue Nov 4 08:42:39 PST 2008

On Tue, 2008-11-04 at 10:20 +0000, John Tapsell wrote:
> >> The transformation into screen coordinates is of little issue. Ideally, you'd
> >> want applications using multi-touch stuff to be aware of the events anyway,
> >> in which case you'd just use the device coordinate space.
> > What if, for example, you have a camera-based input device with a
> > fisheye lens? I can't imagine that every frontend should do the radial
> > undistortion itself..
> True, but an app might want that information.  For example to correct
> for chromatic aberration.  It's always useful to be able to get the
> raw data if wanted, while having access to the transformed data 'by
> default'.

Exactly.  Which is why I'd like an extensible format, that can be
extended in ways I had not foreseen (e.g. the fisheye example).

Events are going to be able to be complex objects; yet most applications
won't have (at least built in) the ability to deal with these objects;
we're going to see (potentially multiple) stages of interpretation.
                         - Jim

Jim Gettys <jg at>
One Laptop Per Child

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