Re: No pinch events with Dell laptops and Alps

[Peter Hutterer <peter.hutterer@who-t.net>]

On Tue, Aug 18, 2020 at 03:13:45PM +0200, Paul Menzel wrote:
> Dear Peter,
> 
> 
> Am 17.07.20 um 01:22 schrieb Peter Hutterer:
> > On Thu, Jul 16, 2020 at 03:19:32PM +0200, Paul Menzel wrote:
> 
> > > On the Dell Latitude E7250 and Dell Precision 3340 I fail to get three
> > > finger pinch events generated needed for GNOME Shell gestures [1].
> > > 
> > > Debian Sid/unstable with Linux 5.7.6 is running on these systems.
> > > 
> > >      [    1.602394] input: AlpsPS/2 ALPS GlidePoint as
> > > /devices/platform/i8042/serio1/input/input2
> > > 
> > > I am only able to create swipe events. (Four finger swipe works to switch
> > > workspaces.)
> > > 
> > > ```
> > > $ sudo libinput debug-events
> > > […]
> > > -event1   DEVICE_ADDED     AlpsPS/2 ALPS GlidePoint          seat0 default
> > > group10 cap:pg  size 98x51mm tap(dl off) left scroll-nat scroll-2fg-edge
> > > dwt-on
> > > -event2   DEVICE_ADDED     DELL Wireless hotkeys             seat0 default
> > > group11 cap:k
> > > event1  - AlpsPS/2 ALPS GlidePoint: kernel bug: Wrong slot count (4),
> > > reducing to 2
> > > -event1   GESTURE_SWIPE_BEGIN +1.549s	3
> > >   event1   GESTURE_SWIPE_UPDATE +1.549s	3 -0.36/ 0.26 (-2.59/ 1.85
> > > unaccelerated)
> > > […]
> > > ```
> > > 
> > > Does the hardware and driver support that?
> > 
> > The device is an Alps GlidePoint which are usually INPUT_PROP_SEMI_MT. On
> > those devices, we don't support 3fg pinch gestures because we don't get
> > enough data to make the gestures reliable. There is no specific quirk for
> > your device otherwise, afaict.
> 
> Thank you for your reply, and the explanation.
> 
> Four finger gestures seem to work. At least in GNOME Shell workspaces can be
> switched with that.
> 
> > If it's not semi-mt then it's too hard to say without more data, I'll need
> > at least the output from libinput record to figure out why (that recording
> > will contain the libinput version which also matters).
> 
> Sorry for omitting that. It’s 1.16.1 now. I uploaded the logs [2].

thanks. based on the log, it's not a semi-mt touchpad and has 5 slots. So gestures
should work in theory, let's move this to a libinput bug please and continue
there: https://gitlab.freedesktop.org/libinput/libinput/issues

Cheers,
   Peter