The One with the Thoughts of Frans

I didn’t spot it in the Debian changelog, but apparently the latest libinput10 update on Debian/stretch (unstable) broke my EmulateWheel option. Because the scroll ring on my trackball is broken, it’s all I’ve got. It’s also rather nice on trackballs without any kind of scrolling functionality at all, such as the Logitech Trackman Marble.

Let’s start by examining my current xorg.conf:

$ cat /etc/X11/xorg.conf 
Section "InputClass"
	Identifier	"Kensington Trackball"
	MatchProduct	"Kensington Expert Mouse"
	Option		"SendCoreEvents" "True"
	Option		"ButtonMapping" "0 1 2 4 5 6 7 3"
	Option		"EmulateWheel" "True"
	Option		"EmulateWheelButton" "1"
EndSection

Scanning man libinput doesn’t list any entries for those options anymore, but it does contain the following:

Option "ScrollButton" "int"

Designates a button as scroll button. If the ScrollMethod is button and the button is logically held down, x/y axis movement is converted into scroll events.

Option "ScrollMethod" "string"

Enables a scroll method. Permitted values are none, twofinger, edge, button. Not all devices support all options. If an option is unsupported, the default scroll option for this device is used.

Note how this would allow you to disable two-finger scroll on e.g. our Wacom drawing tablet if you don’t like it. (But I do!) In any case, adjusting my xorg.conf accordingly:

Section "InputClass"
        Identifier      "Kensington Trackball"
        MatchProduct    "Kensington Expert Mouse"
        Option          "SendCoreEvents" "True"
        Option          "ButtonMapping" "0 1 2 4 5 6 7 3"
        Option          "ScrollMethod" "button"
        Option          "ScrollButton" "1"
EndSection

Works like a charm. Better yet, it now also scrolls horizontally. Which can be disabled with Option "HorizontalScrolling" "false" if you so desire. All’s well that ends well.