Thoughts on an xinput extension?

[Jason Miller]

I was frustrated by the fact that since the pointer-grab is global, you can't
inject pointer events with e.g. xdotool from button maps.

I hacked-up a demo that allows grabbing via xinput, which only grabs a specific
device which means pointer events can still be sent to the window.

My current syntax is only tested in the guile format; it allows specifying an
xinput device by name as a modifier and looks like:

("d:ELECOM ELECOM TrackBall Mouse" "b:9")

Which will map to button 9 of the first xinput device named "d:ELECOM ELECOM 
TrackBall Mouse" 

Is this something that interests anyone?  If so I can make a more polished 
patch.

Still TBD:

1. I haven't looked at the non-guile parser at all; would introducing spaces in
modifier names cause a grammar ambiguity?  If not we would need a way of
quoting xinput device names, since spaces are relatively common.

2. Should this be just for pointers?  As implemented it currently pointer-only
as I haven't had any issues with injecting keystrokes from keygrabs.  Maybe in
corner-cases from chording it can happen?  Anyone run into keyboard issues with
grabs affecting your ability to send keystrokes?  If we do allow keyboards as
well, then the syntax will need tweaking as many programmable mice may register
both a pointer and a keyboard with the same name.
(maybe p:<devname> and k:<devname> ?)

-Jason