Generic Precedence Grouping for Input Devices

Peter Hutterer peter.hutterer at
Mon Jun 4 20:13:48 PDT 2012

On Mon, Jun 04, 2012 at 04:09:21PM +0200, Michal Suchanek wrote:
> Hello,
> what you seem to want is device exclusion so that input from one
> device precludes events from other devices to be processed.
> As XI has support for disabling devices this should be doable with a
> user program so long as a user program can get proximity events
> reliably.

> I don't think this should be by default enabled in X server, it's not
> something most users would expect.

in addition, proximity events is just one case and we don't have the luxury
of getting them from all devices. a tablet may not support proximity but
still interfer with touch events or, already commonplace, a keyboard may
interfere with a touchpad. the problem is that the context of which device
interferes with other devices and in what usage scenario is unknown to the X
server. this really needs to be controlled by the client side.


> Since it would not get much use not being the default implementing
> this in X would just add some dead untested code.
> I can see that in case you have one tablet and one mouse then tablet
> pen in proximity might be thought of as an indication of tablet input
> and a sign that mouse input is unwanted.
> However, note that pen can be seen in-proximity when just laying near
> the tablet, even on a pen stand. AFAIK normally you can move the
> cursor with mouse when pen is in proximity so long as pen position
> does not change (eg. on stand) which would be broken by this priority
> framework.
> I can definitely get click events by touching down the pen way outside
> the tablet area or get motion events by moving the pen somewere on the
> table nearby the tablet.

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