Issues with trackball button scroll.

Connecting a trackball that used to work on previous Gnome versions (Wayland as well), I realized today that button scrolling didn't work.

Here are the settings I have always used on wayland with that trackball:

• gsettings set org.gnome.desktop.peripherals.trackball scroll-wheel-emulation-button 9

After spending some time on IRC, I rebooted the machine several times. Then I decided to try to plug/unplug the trackball after gnome started and now the button scroll works.

The weird thing is that if I try to set it during my session to 8 or 0 to disable, it continues to work with button 9. I tried to change the setting (to 8 and 0) and unplug/plug the trackball, and the new setting take effect.

I checked and the terminal I ran the gsettings command in uses the same DBUS session as gnome-shell, and when I tried to do a gsettings monitor on some settings, I was able to see in the terminal the changes I made in the GUI.

There is definitively something strange here.

To reproduce:

• Start Gnome
• Notice scrolling is not working
• Unplug/plug the trackball
• Scrolling is working
• Change settings for the scroll button
• No effect scroll still works with the same button
• Unplug/plug the trackball
• New setting take effect

It used to work properly with Gnome 3.34.

Here are the infos about the trackball if needed: libinput:

Device:           Logitech USB Trackball
Kernel:           /dev/input/event6
Group:            6
Seat:             seat0, default
Capabilities:     pointer 
Tap-to-click:     n/a
Tap-and-drag:     n/a
Tap drag lock:    n/a
Left-handed:      disabled
Nat.scrolling:    disabled
Middle emulation: n/a
Calibration:      n/a````
Scroll methods:   button
Click methods:    none
Disable-w-typing: n/a
Accel profiles:   flat *adaptive
Rotation:         0.0

lsusb:

Bus 001 Device 011: ID 046d:c408 Logitech, Inc. Marble Mouse (4-button)

Versions:

Distribution: Arch Linux (up to date as of today) Gnome: 3.36.0 Wayland: 1.18.0 Libinput: 1.15.3