libinput touchscreen maxTouchPoints

[Johannes Pointner]

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.
>
> Cheers,
>    Peter