Dtyjlui

There is a problem with my laptop — jumping cursor. I think the hardware is the source of the problem. Maybe toucpad is just very inaccurate when getting finger coordinates and touching events.

On Ubuntu 14.04 I just set vertical and horizontal hysteresis and high and low finger pressure to make touchpad feel smooth and nice. When I installed 18.04 I found that I can't adjust my touchpad any more (except a few options that are not too helpful in my case).

So, can anybody of you, guys, help me with getting back that beautiful synaptics driver?

I had the same problem and basically solved it by following Ryko's advice.

sudo apt install xserver-xorg-input-synaptics

... did the trick. I didn't uninstall libinput like Pilot6 said and libinput is still happily handling my keyboard, etc.

You can do it by

sudo apt remove xserver-xorg-input-libinput

sudo apt install xserver-xorg-input-synaptics

But in most cases libinput is better than synaptics. Anyway it's your choice still.

The problem is not necessarily the missing Synaptics drivers, it is more the fact that the libinput driver settings are purposefully left generic so that the user or hardware OEM can adjust them as desired.

Rather than simply uninstalling libinput and installing Synaptics, you can still add Synaptics but to keep everything working you need to provide an "override" by removing/updating references to libinput specifically in relation to your touchpad ONLY and adding in a rule for Synaptics.

A major part of the problem is that there doesn't appear to be any proper GUI tool and few of the hardware OEMs (Dell/HP/Lenovo/etc) provide customized configs optimized to their hardware outside the possible exception of their own preinstalled Ubuntu versions (Dell provides this option at least). I haven't grabbed the latest Dell Ubuntu image and unpacked it to see if they supply any customizations, but it wouldn't surprise me if they did. If not I definitely think it is something they should see about adding, since the XPS13/XPS15 and their business brothers the Precision 55x0 models are amazingly fast running Ubuntu compared to Windows.

This article by Dell has a good start on how to potentially fix the issue (and doesn't necessarily only apply to their systems or their touchpads), https://www.dell.com/support/article/us/en/19/sln308258/precision-xps-ubuntu-general-touchpad-mouse-issue-fix?lang=en

can you give instructions on how to do the override? 

The synaptics config file can be copied to /etc/X11/xorg.conf.d and given a higher number than the /usr/share/X11/xorg.conf.d synaptics.conf default. Then the synaptics touchpad driver overrides the libinput touchpad driver by having a higher priority.

There is an option that could be added to libinput.conf to prevent the libinput touchpad driver from being considered. After "MatchIsTouchpad" add:

Option "Ignore" "true"

Check with xinput:

xinput list

xinput --list-props "whatever touchpad from above list"

That will show either the libinput or the synaptics properties if the touchpad is using libinput or synaptics respectively. The synaptics touchpad driver should show output something like this:

Device 'ELAN1300:00 04F3:3057 Touchpad':

Device Enabled (152):   1

Coordinate Transformation Matrix (154): 1.000000, 0.000000, 0.000000, 0.000000, 1.000000, 0.000000, 0.000000, 0.000000, 1.000000

Device Accel Profile (280): 1

Device Accel Constant Deceleration (281):   1.000000

Device Accel Adaptive Deceleration (282):   1.000000

Device Accel Velocity Scaling (283):    1.000000

Synaptics Edges (284):  0, 3208, 0, 2210

Synaptics Finger (285): 1, 70, 0

Synaptics Tap Time (286):   180

Synaptics Tap Move (287):   171

Synaptics Tap Durations (288):  180, 180, 100

Synaptics ClickPad (289):   1

Synaptics Middle Button Timeout (290):  0

Synaptics Two-Finger Pressure (291):    282

Synaptics Two-Finger Width (292):   7

Synaptics Scrolling Distance (293): 154, 77

Synaptics Edge Scrolling (294): 0, 0, 0

Synaptics Two-Finger Scrolling (295):   1, 0

Synaptics Move Speed (296): 1.000000, 1.000000, 0.000000, 0.000000

Synaptics Off (297):    0

Synaptics Locked Drags (298):   0

Synaptics Locked Drags Timeout (299):   5000

Synaptics Tap Action (300): 0, 0, 0, 0, 0, 0, 0

Synaptics Click Action (301):   1, 3, 2

Synaptics Circular Scrolling (302): 0

Synaptics Circular Scrolling Distance (303):    0.100000

Synaptics Circular Scrolling Trigger (304): 0

Synaptics Circular Pad (305):   0

Synaptics Palm Detection (306): 1

Synaptics Palm Dimensions (307):    10, 200

Synaptics Coasting Speed (308): 20.000000, 50.000000

Synaptics Pressure Motion (309):    30, 160

Synaptics Pressure Motion Factor (310): 1.000000, 1.000000

Synaptics Grab Event Device (311):  1

Synaptics Gestures (312):   1

Synaptics Capabilities (313):   1, 0, 0, 1, 1, 0, 0

Synaptics Pad Resolution (314): 32, 31

Synaptics Area (315):   0, 0, 0, 0

Synaptics Soft Button Areas (316):  1604, 0, 1800, 0, 0, 0, 0, 0

Synaptics Noise Cancellation (317): 50, 50

Device Product ID (276):    1267, 12375

Device Node (275):  "/dev/input/event15"

The synaptics touchpad driver allows for adjusting many settings when the libinput driver just turns a few things on or off and so is not useful for my touchpad.