Re: Mixed "pen" and multitouch input devices

[Chase Douglas <chasedouglas@gmail.com>]

On 03/15/2012 06:52 PM, Thorsten Wissmann wrote:
> On Thu, Mar 15, 2012 at 11:29:37AM -0700, Chase Douglas wrote:
>> On 03/15/2012 10:56 AM, Thorsten Wissmann wrote:
>>> On Thu, Mar 15, 2012 at 12:27:22PM -0500, Chris Bagwell wrote:
>>>> If you want to work with other unmodified user land apps (perhaps
>>>> xf86-input-evdev for touches) then its probably easiest to split pen
>>>> and touch to separate input devices.  drivers/input/tablet/wacom_wac.c
>>>> shows some examples of that approach but that driver doesn't have to
>>>> work to hard to split in to 2 input devices because the USB device
>>>> already puts the events on separate USB  interfaces.
>>>
>>> OK. We want the device to work with the xf86-input-evdev driver. So we
>>> will split it into two devices.
>>
>> Or you could teach evdev to know how to handle mixed devices :). I think
>> that's the "better" approach over all, but it's up to you.
> 
> Thanks! We didn't thought about this. It turned out that the problem
> isn't caused by the usage of both BTN_TOOL_PEN and BTN_TOOL_FINGER.
> 
> It turned out xf86-input-evdev really discards all non-multitouch events
> (especially ABS_X and ABS_Y) events in EvdevProcessAbsoluteMotionEvent()
> in evdev.c, if the device is configured as a multitouch device. So there
> is a quick fix (or only workaround?), which processes ABS_X and ABS_Y
> events even if it is a multitouch device:
> 
> diff --git a/src/evdev.c b/src/evdev.c
> index d540b87..b857b83 100644
> --- a/src/evdev.c
> +++ b/src/evdev.c
> @@ -832,7 +832,7 @@ EvdevProcessAbsoluteMotionEvent(InputInfoPtr pInfo,
> struct input_event *ev)
>      if (ev->code >= ABS_MT_SLOT) {
>          EvdevProcessTouchEvent(pInfo, ev);
>          pEvdev->abs_queued = 1;
> -    } else if (!pEvdev->mt_mask) {
> +    } else if (!pEvdev->mt_mask || ev->code == ABS_X || ev->code ==
> ABS_Y) {
>          map = pEvdev->axis_map[ev->code];
>          valuator_mask_set(pEvdev->vals, map, value);
>          pEvdev->abs_queued = 1;
> 
> This patch already is submitted to the xorg bugtracker and can be found
> at [1].
> 
> The only remaining question is: Does it break other drivers?
> 
>     Max and Thorsten
> 
> [1] https://bugs.freedesktop.org/show_bug.cgi?id=47382

Great!

I haven't fully thought about it enough to give a reviewed-by, but it
seems sane.

I suggest sending the patch to xorg-devel@lists.x.org. That's where most
patch reviews are handled. You will likely get faster results there.

-- Chase