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My Dell XPS 13 (9370) came pre-installed with Ubuntu 16.04. Recently I have been experimenting with Ubuntu 18.04, installed to an external hard-drive.

Whilst using 18.04 I have noticed a fairly frequent issue where the touchpad cursor jumps after certain finger movements. After some experminetation I have managed to work out a technique for reproducing/demonstrating the issue with quite high accuracy.

The technique requires moving a finger on the touchpad fairly slowly, then lifting the finger completely off the touchpad for a seemingly-specific amount of time, then re-engaging the moving finger with the touchpad again but at a different touchpad location.

It's quite hard to describe accurately, so I've also recorded a video, showing both the cursor movement and my finger movement:

https://youtu.be/3y8i0riN_KM

As mentioned, the issue seems to be quite timing-dependant, so as you can see in the video I cannot reproduce it on every attempt. Thankfully I do manage it on my first attempt in the video though; and overall I'd say I have about 60% reproduction success rate.

I have also recorded some libinput-debug-events output when the issue happens:

event16  POINTER_MOTION   +81.50s     2.43/  4.87
event16  POINTER_MOTION   +81.51s     2.43/  4.87
event16  POINTER_MOTION   +81.52s     1.22/  3.65
event16  POINTER_MOTION   +81.52s     2.43/  3.65
event16  POINTER_MOTION   +81.53s     1.22/  2.43
event16  POINTER_MOTION   +81.54s     2.43/  2.43
event16  POINTER_MOTION   +81.54s     2.43/  2.43
event16  POINTER_MOTION   +81.55s     2.43/  2.43
event16  POINTER_MOTION   +81.56s     2.43/  2.43
event16  POINTER_MOTION   +81.56s     1.22/  1.22
event16  POINTER_MOTION   +83.35s   -392.57/-193.26
event16  POINTER_MOTION   +83.36s   -18.14/-12.09
event16  POINTER_MOTION   +83.36s    -3.65/ -2.43
event16  POINTER_MOTION   +83.37s    -3.65/ -2.43
event16  POINTER_MOTION   +83.38s    -2.43/ -1.22
event16  POINTER_MOTION   +83.38s    -2.43/ -1.22
event16  POINTER_MOTION   +83.39s    -2.43/ -1.22
event16  POINTER_MOTION   +83.40s    -2.43/ -1.22
event16  POINTER_MOTION   +83.41s    -2.43/ -1.22
event16  POINTER_MOTION   +83.41s    -1.22/ -1.22
event16  POINTER_MOTION   +83.43s    -1.22/  0.00
event16  POINTER_MOTION   +83.43s    -1.22/  0.00

The erroneous motion is quite obvious from that output, I think, although I not know why it might happen.

(I also noticed the common issue of multiple touchpads being detected by xinput, so I followed the common procedure to tell it to ignore the non-Dell pad; but that has not solved my main issue.)

As mentioned previously, this issue does not occur on the pre-installed Ubuntu 16.04.

Any suggestions on possible fixes for this, or ideas on what part of the system may be causing it, would be much appreciated.

Thanks.

thoughton
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1 Answers1

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Go to Mouse and Touchpad in Settings. Increase touchpad speed and disable Natural scrolling.

You can install gnome-tweaks.

sudo apt install gnome-tweaks

You can change default behavior. You need to change settings from Keyboard & mouse >> Mouse Click Emulations >> Area

KK Patel
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