2012/3/19 Chase Douglas <chasedouglas@xxxxxxxxx>:
> On 03/18/2012 11:39 PM, Henrik Rydberg wrote:
>>> The proper way to send events through evdev when there are two different
>>> "tools" (pen and touch) is to use BTN_TOOL_*. In your example above, it
>>> would be:
>>>
>>> # finger touch (Note lack of tool, it's assumed to be finger)
>>> ABS_MT_SLOT 0
>>> ABS_MT_TRACKING_ID 42
>>> ABS_MT_POSITION_X finger_x
>>> ABS_MT_POSITION_Y finger_y
>>> SYN_MT_REPORT
>>> ABS_X finger_x
>>> ABS_Y finger_y
>>> SYN_REPORT
>>> # finger release
>>> ABS_MT_SLOT 0
>>> ABS_MT_TRACKING_ID -1
>>> SYN_REPORT
>>> # pen motion
>>> BTN_TOOL_PEN 1
>>> ABS_X pen_x
>>> ABS_Y pen_y
>>> SYN_REPORT
>>> # finger touch begin
>>> ABS_MT_SLOT 0
>>> ABS_MT_TRACKING_ID 42
>>> ABS_MT_POSITION_X finger_x
>>> ABS_MT_POSITION_Y finger_y
>>> SYN_MT_REPORT
>>> BTN_TOOL_PEN 0
>>> ABS_X finger_x
>>> ABS_Y finger_y
>>> SYN_REPORT
>>> etc.
>>>
>>> Then, xf86-input-evdev ignores ABS_{X,Y} events when there is no
>>> BTN_TOOL_* active.
>>
>> On the subject how pen and touch could work going forward, the MT
>> protocol is prepared to deal with tool type per slot. It makes a lot
>> of sense to move away from the above example, towards a fully parallel
>> representation of pen and touch data. Today's multitouch interfaces
>> are really tremendously restrictive; I am looking forward to the day
>> when one does not need to worry about touching or resting on a surface
>> in order to operate it.
>>
>> In short, why not make xf86-input-evdev aware of MT_TOOL_TYPE?
>
> There's no reason it can't be made aware. The question is whether you
> want to create separate X input devices, or annotate events with the
> tool type. No one has really bothered looking into it outside of wacom
> devices, but my understanding is that wacom is a big special cased
> situation due to historical reasons anyway.
>
> If we merely annotate events by setting valuator values, that's a
> trivial change that may even be already supported out of the box.
> Splitting the evdev device into multiple X input devices is also
> possible, since xf86-input-wacom does it, but would require a large
> refactoring of xf86-input-evdev.
>
FWIW, non-wacom pen+touch devices should work with current
xf86-input-wacom if they use above events. You will get split devices
as long as you modify xorg.conf.d to route this input. MT events will
be treated roughly like xf86-input-synaptics would treat DOUBLETAP
though (internal 1 and 2 finger gesture support only).
My plan is to take your xf86-input-evdev/synaptics X Input 2.2 work
and merge it into xf86-input-wacom soon to benefit from those
improvements. In addition to Wacom MT hardware, I try to occasionally
test xf86-input-wacom with a hid-multitouch touchscreen to verify it
isn't needlessly wacom specific.
Having said that, I think its good to improve multi-tool support in
xf86-input-evdev in parallel to the multi-touch improvements. In
addition, xf86-input-evdev would be a much better base to start
experimenting with annotating events.
Chris
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