Hello everyone. First of all, sorry if my English is bad, I'm from Italy.
I use Arch Linux x64, so I have the latest version of Plasma Desktop.

Arch Linux is a rolling release distro, so it adopted libinput as default library for pointing devices, even if old synaptics library was better and more customizable.
Anyway using libinput (latest version 1.6.0 and xf86-input-libinput 0.23.0) I found a proper configuration for my touchpad setting acceleration speed option at -0.5 in a custom xorg config file. This option accepts values between -1 and +1, the default is 0 and it's too faster.

Code: Select all

Section "InputClass"
    Identifier                          "Touchpad"
    Driver                              "libinput"
    MatchIsTouchpad                     "on"
    Option      "AccelSpeed"            "-0.5"
EndSection


The problem is Plasma Desktop. When I start the system and get into sddm, I detect the right speed of the pointer, which means the option has been set properly.
But whenever I start any user Plasma session, the pointer is too fast and "xinput list-props" command reports that acceleration speed has been reset to 0.
So I tried to change it from system settings. The acceleration option is regulated by a controller on an horizontal bar. The controller is on the left side and its value is 0, so I cannot move it to the left and cannot set -0.5 value.

In substance, Plasma can only set values above 0 but I need -0.5. This is a bug because libinput can expect also values below 0.
I tried also to manually configure touchpadrc file in config home directory setting -0.5 value, but when I restart the session the option is reset to 0, while if I set 0.5 or another value above 0, the option is set properly and I can see it from xinput command.

So, how can I prevent Plasma from changing my xorg configuration at start?

Nobody?
Meanwhile I found this: https://bugs.kde.org/show_bug.cgi?id=357749.
Submitted one year ago and not fixed yet. What are you waiting for?