Invert mouse scroll wheel in Debian

I’ve been using the beta of MacOS X Lion for a few weeks now, and after a few days of initial annoyance I’ve grown to really like the inverted sense of the scroll wheel. I recall when I first got one, in fact, and found the direction downright confusing. This seems to have been an easy behaviour to unlearn.

My desktop box at work runs Debian, and I wanted the same behaviour there to stop me getting split-brain and dribbling a lot. There was a time when a quick change in xorg.conf to ZAxisMapping "5 4" would do this, but it’s not so the modern age of HIDs and evdevs. After a bit of messing about I figured out how to flip the scroll wheel. This will probably work for Ubuntu too.

• Open the file /usr/share/X11/xorg.conf.d/10-evdev.conf
• Look for the section with MatchIsPointer "on". It’s at the top by default.
• Add this line:

Option "ButtonMapping" "1 2 3 5 4 6 7 8"

• Add more buttons if you need them for your mouse. The section should look like:

Section "InputClass"
    Identifier "evdev pointer catchall"
    MatchIsPointer "on"
    MatchDevicePath "/dev/input/event*"
    Driver "evdev"
    Option "ButtonMapping" "1 2 3 5 4 6 7 8"
EndSection

That’s it! Just restart X.