libinput touchscreen maxTouchPoints

[Johannes Pointner]

On Wed, Jan 31, 2018 at 1:02 AM, Peter Hutterer
<peter.hutterer at who-t.net> wrote:
> On Tue, Jan 30, 2018 at 04:18:26PM +1000, Peter Hutterer wrote:
>> On Wed, Jan 24, 2018 at 10:47:10AM +0100, Johannes Pointner wrote:
>> > On Wed, Jan 24, 2018 at 10:18 AM, Peter Hutterer
>> > <peter.hutterer at who-t.net> wrote:
>> > > On Wed, Jan 24, 2018 at 10:04:52AM +0100, Johannes Pointner wrote:
>> > >> Hello,
>> > >>
>> > >> I have noticed that since we are using xf86-input-libinput all our
>> > >> touchscreens (resistive and pcap) reporting a value of 15 for
>> > >> maxTouchPoints.
>> > >> After further looking into this I saw that xf86-input-libinput sets
>> > >> this value fix to 15. I also checked if it is possible to get this
>> > >> info from libinput but I wasn't able to find a possibility.
>> > >>
>> > >> Is this intentionally?
>> > >
>> > > mostly, it's largely a matter of not exporting information that doesn't need
>> > > to be exported. at least with touchpads libinput does a few tricks and
>> > > changes the number of touches available (not yet at runtime, but who knows)
>> > > - once we start exporting this we're a lot more limited in what we can do
>> > > internally to work around broken devices.
>> > >
>> > > Main question is though: what do you need this value for?
>> > We use this value which is available through the browser
>> > (https://developer.mozilla.org/en-US/docs/Web/API/Navigator/maxTouchPoints)
>> > to determine if it is a multitouch device or not.
>> > The same goes for Qt
>> > (http://doc.qt.io/qt-5/qtouchdevice.html#maximumTouchPoints) which has
>> > a libinput backend.
>>
>> Actually, this is something we could fix in the driver by checking for
>> ABS_MT_SLOT and forcing it to 1 when missing. that wouldn't fix Qt though,
>> so it may be better to have this exported by libinput after all...
>> Need to think of the various special cases here.
>
> for reference, I filed this bug:
> https://bugs.freedesktop.org/show_bug.cgi?id=104867
>
> Cheers,
>    Peter

Hello Peter,

thx for your feedback and for creating this bug.

Regards,
Hannes