XInput 2.1 valuator values when resuming from SlaveSwitch

[Peter Hutterer]

On Tue, Mar 12, 2013 at 12:53:33PM -0700, Paul Vojta wrote:
> Dear all:
> 
> I've been working on adding "smooth scrolling" to xdvi (after a long
> hiatus), and I'm encountering some glitches when switching pointer devices.
> 
> Specifically, when a slave is being switched back on, the scroll valuators
> are always reported as having value 0 in the classes field of the
> XIDeviceChanged event.
> 
> When using the evdev driver, however, the valuator values are the same
> as when the device was last used, and so this causes a large scroll
> glitch when resuming using the device.  (When using the synaptics driver,
> the values are always reset, so there is no problem in that case.)
> (I'm only checking the vertical scroll valuator so far, but I expect
> that the same would be true for the horizontal scroll valuator.)

unfortunately, that is the correct behaviour
http://who-t.blogspot.com.au/2012/06/xi-21-protocol-design-issues.html

the reset should not happen in synaptics, that's likely a bug in the driver.

Cheers,
   Peter

> I'm using version 1.12.4 of the server (Debian version 2:1.12.4-4),
> version 2.7.0 of evdev (Debian version 1:2.7.0-1+b1), and
> version 1.6.2 of the synaptics driver (Debian version 1.6.2-2).
> The hardware is x86_64.
> 
> Comments, anyone?
> 
> In particular, is it correct to assume that the classes field of the
> XIDeviceChanged event should contain the correct value for the valuator,
> and that the behavior with evdev is buggy?