XI2 relative motion events documentation

[Chase Douglas]

On Thu, 2010-10-14 at 23:54 -0500, Rendaw wrote:
> Hello,
> http://www.x.org/wiki/XI2 lists "Support for relative motion events" as 
> a feature of XI2.  I've googled around quite a bit but I haven't been 
> able to find any more information on this.  The spec doesn't seem to 
> list anything related to it either.  The closest I've been able to find 
> is valuators, but for the (my) master mouse, none seem to be relative.
> 
> I imagined, from reading that webpage, that I could get relative motion 
> events for all cursor devices.  Is this, or something similar, 
> possible?  Are there any webpages or resources that document this?

I'm somewhat new the X input, so I'm hoping someone will catch me if I
say something stupid :).

Master pointer device events are always in absolute screen coordinates.
However, the slave device events, which may or may not be tied to any
given master device, are in device coordinates. If a device is relative,
slave device events will be relative.

You should be able to test this out with "xinput test-xi2".

-- Chase