[RFC] Multitouch support, step one

[Daniel Stone]

Hi,

On Mon, Mar 15, 2010 at 04:56:05PM +1000, Peter Hutterer wrote:
> Core requires us to always send x/y

Er, I don't think it does _always_ require it.

> hence for core emulation we should
> always include _some_ coordinates that are easily translated. While the
> server does caching of absolute values, I think it would be worthwile to
> always have an x/y coordinate _independent of the touchpoints_ in the event.
> The driver can decide which x/y coordinates are chosen if the first
> touchpoint becomes invalid.

Why not just use the first touchpoint for x/y, and when it goes away, no
more core x/y is sent? Principle of least surprise and all that.

> Hence, the example with 4 valuators above becomes a device with 6 valuators
> instead. x/y and the two coordinate pairs as mentioned above. If extra data
> is provided by the kernel driver, these pairs are simple extended into
> tuples of values, appropriately labeled.

Yep.

This all looks fine, really, and doesn't require terribly much work.
Multi-focus multi-touch is a bit further off, but hey, none of us can
even particularly describe how it should work, so I don't think it's
such a pressing issue. :)

Cheers,
Daniel
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