From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Henrik Rydberg" <rydberg@euromail.se>
Subject: Re: Mixed "pen" and multitouch input devices
Date: Mon, 19 Mar 2012 07:39:15 +0100
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To: Chase Douglas <chasedouglas@gmail.com>
Cc: Thorsten Wissmann <re06huxa@stud.informatik.uni-erlangen.de>, Chris Bagwell <chris@cnpbagwell.com>, linux-input@vger.kernel.org, Maximilian =?iso-8859-1?Q?Kr=FCger?= <maxfragg@gmail.com>, i4passt@lists.informatik.uni-erlangen.de

> 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?

Thanks,
Henrik