How to configure the DEFT Pro trackball on Linux

This is my Xorg configuration for the Elecom DEFT Pro trackball on Manjaro.

Create this configuration file:

/usr/share/X11/xorg.conf.d/99-trackball.conf
            
          

The important part is ButtonMapping. In the first mapping, button 10 is remapped to 1, so Fn1 acts as the left button. Button 11 is remapped to 2, so Fn2 acts as the middle button.

Section "InputClass"
        # DEFT PRO Buttons:
        #    1: Left button
        #    2: Middle button (wheel click)
        #    3: Right button
        #    4: Wheel scroll up
        #    5: Wheel scroll down
        #    6: Wheel tilt left
        #    7: Wheel tilt right
        #    8: Back button
        #    9: Forward button
        #   10: Fn1 (button on the left of the ball)
        #   11: Fn2 (button on right most)
        #   12: Fn3 (button on the above of the slide switch)
        Identifier      "Elecom DEFT Pro Trackball"
        MatchProduct    "DEFT Pro TrackBall"
    Driver          "libinput"
        Option          "ScrollMethod" "button"
        Option          "ScrollButton" "9"
        Option        "MiddleEmulation" "on"
        Option          "ButtonMapping" "1 2 3 4 5 6 7 8 9 1 2 12"
EndSection
            
          

I also use a second version with scroll-button lock. This makes the forward button toggle scroll mode while the ball handles scrolling.

Section "InputClass"
# DEFT PRO Buttons:
# 1: Left button
# 2: Middle button (wheel click)
# 3: Right button
# 4: Wheel scroll up
# 5: Wheel scroll down
# 6: Wheel tilt left
# 7: Wheel tilt right
# 8: Back button
# 9: Forward button
# 10: Fn1 (button on the left of the ball)
# 11: Fn2 (button on right most)
# 12: Fn3 (button on the above of the slide switch)
Identifier "Elecom DEFT Pro Trackball"
MatchProduct "DEFT Pro TrackBall"
Driver "libinput"
Option "ScrollMethod" "button"
Option "ScrollButton" "9"
Option "ScrollButtonLock" "true"
Option "MiddleEmulation" "on"
Option "ButtonMapping" "1 2 3 4 5 6 7 8 12 1 2 9"
EndSection