Enabling multitouch in input-evdev

Peter Hutterer peter.hutterer at who-t.net
Tue Jan 19 16:59:20 PST 2010

On Tue, Jan 19, 2010 at 07:24:10PM +0100, Benjamin Tissoires wrote:
> >right, you could have an 0/1 axis for this type of things, that's about the
> >best approach. there's also the chance of using a button but that's more
> >likely to be misinterpreted.
> >the correct approach is that you only send those axes with a value, thus
> >explicitly specifying the on/off. This is possible with XI2 but the input
> >driver APIs aren't in place for that (no need so far).
> >
> You mean that in XI2, we (the driver) can choose which axes are send
> at each event ?

yes and no. XI2 is a protocol specification describing the server/client
communication. XI2 caters for holes in the valuator range (e.g. events with
valuators 1, 5, 6, 8) but as I said, the input driver API isn't up for that
yet. this requires some work in the server and the driver to start using the
new APIs.


> >same again, you can change the number of axes in XI2, it's just that the
> >input driver APIs are missing that feature so far.
> great ! I'll have to play with it.
> Currently, I'm waiting a little before patching evdev with the
> "one-blob with all touches", because I think that Carsten was right
> when he told that a touch may not be just an x and a y. It can also
> have many valuators. It would be a mess to send 10*(nb_valuators+1)
> at each event. (+1 due to the state of the touch: idle, start,
> etc...)

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