Ytdyklly

Since I upgraded to 17.10, touchpad tap sensitivity is too low, and frequently misses my taps. I know that the system has figured out that my Lenovo Yoga 2 has a Synaptics touchpad:

$ sudo evtest

No device specified, trying to scan all of /dev/input/event*

Available devices:

...

/dev/input/event6:  Synaptics TM2714-001

...

But xinput doesn’t think it’s anything Synaptics-specific:

$ xinput list

⎡ Virtual core pointer                          id=2    [master pointer  (3)]

⎜   ↳ Virtual core XTEST pointer                id=4    [slave  pointer  (2)]

⎜   ↳ xwayland-pointer:13                       id=6    [slave  pointer  (2)]

⎜   ↳ xwayland-relative-pointer:13              id=7    [slave  pointer  (2)]

⎜   ↳ xwayland-touch:13                         id=9    [slave  pointer  (2)]

⎣ Virtual core keyboard                         id=3    [master keyboard (2)]

    ↳ Virtual core XTEST keyboard               id=5    [slave  keyboard (3)]

    ↳ xwayland-keyboard:13                      id=8    [slave  keyboard (3)]



$ xinput list-props "xwayland-touch:13"

Device 'xwayland-touch:13':

    Device Enabled (119):   1

    Coordinate Transformation Matrix (121): 1.000000, 0.000000, 0.000000, 0.000000, 1.000000, 0.000000, 0.000000, 0.000000, 1.000000

    Device Accel Profile (244): 0

    Device Accel Constant Deceleration (245):   1.000000

    Device Accel Adaptive Deceleration (246):   1.000000

    Device Accel Velocity Scaling (247):    10.000000

and synclient agrees:

$ synclient

Couldn't find synaptics properties. No synaptics driver loaded?

libinput does know it’s a Synaptics:

$ sudo libinput list-devices

...

Device:           Synaptics TM2714-001

Kernel:           /dev/input/event6

Group:            8

Seat:             seat0, default

Size:             87x57mm

Capabilities:     pointer 

Tap-to-click:     disabled

Tap-and-drag:     enabled

Tap drag lock:    disabled

Left-handed:      disabled

Nat.scrolling:    disabled

Middle emulation: disabled

Calibration:      n/a

Scroll methods:   *two-finger edge 

Click methods:    *button-areas clickfinger 

Disable-w-typing: enabled

Accel profiles:   none

Rotation:         n/a

...

though I don’t see anything like the old X11 finger pressure properties. (libinput measure-touchpad-tap, interestingly, collects data about time rather than pressure.)

How can I improve the sensitivity to taps?

Use the libinput measure touchpad-pressure tool provided by libinput. This tool will search for your touchpad device and print some pressure statistics, including whether a touch is/was considered logically down.

sudo libinput measure touchpad-pressure

By default, this tool uses the udev hwdb entries for the pressure range. To narrow down on the best values for your device, specify the 'logically down' and 'logically up' pressure thresholds with the `--touch-thresholds argument:

sudo libinput measure touchpad-pressure --touch-thresholds=10:8 --palm-threshold=20

Interact with the touchpad and check if the output of this tool matches your expectations.

Once the thresholds are decided on (e.g. 10 and 8), they can be enabled with the following hwdb file:

cat /etc/udev/hwdb.d/99-touchpad-pressure.hwdb

libinput:name:*SynPS/2 Synaptics TouchPad:dmi:*svnHewlett-Packard:*pnHPCompaq6910p*

LIBINPUT_ATTR_PRESSURE_RANGE=10:8

The first line is the match line and should be adjusted for the device name (see evemu-record's output) and for the local system, based on the information in /sys/class/dmi/id/modalias. The modalias should be shortened to the specific system's information, usually system vendor (svn) and product name (pn).

Once in place, you need to run the following to commands, adjusted for your device's event node:

sudo udevadm hwdb --update

sudo udevadm test /sys/class/input/eventX

If the pressure range property shows up correctly, restart X or the Wayland compositor and libinput should now use the correct pressure thresholds. The Helper tools can be used to verify the correct functionality first without the need for a restart.

Once the pressure ranges are deemed correct, report a bug to get the pressure ranges into the repository.

Note: Not a single word typed by me, this is all a quote.

Source: https://wayland.freedesktop.org/libinput/doc/latest/touchpad_pressure.html#touchpad_pressure_hwdb