How to enable two-finger scrolling using xinput (ThinkPad T420)

solution.txt

I can't say that this will work for everyone, but here's what I did:

First, list the input devices:

    xinput list

You should get output like this:

⎡ Virtual core pointer                          id=2    [master pointer  (3)]
⎜   ↳ Virtual core XTEST pointer                id=4    [slave  pointer  (2)]
⎜   ↳ SynPS/2 Synaptics TouchPad                id=11   [slave  pointer  (2)]
⎜   ↳ TPPS/2 IBM TrackPoint                     id=12   [slave  pointer  (2)]
⎣ Virtual core keyboard                         id=3    [master keyboard (2)]
    ↳ Virtual core XTEST keyboard               id=5    [slave  keyboard (3)]
    ↳ Power Button                              id=6    [slave  keyboard (3)]
    ↳ Video Bus                                 id=7    [slave  keyboard (3)]
    ↳ Sleep Button                              id=8    [slave  keyboard (3)]
    ↳ Integrated Camera                         id=9    [slave  keyboard (3)]
    ↳ AT Translated Set 2 keyboard              id=10   [slave  keyboard (3)]
    ↳ ThinkPad Extra Buttons                    id=13   [slave  keyboard (3)]

The correct ID is 11 - the "SynPS/2 Synaptics TouchPad". Note that number. Now do: 

    xinput list-props 11
    
(where 11 is your device number). Should result in something like this:

Device 'SynPS/2 Synaptics TouchPad':
        Device Enabled (137):   1
        Coordinate Transformation Matrix (139): 1.000000, 0.000000, 0.000000, 0.000000, 1.000000, 0.000000, 0.000000, 0.000000, 1.000000
        libinput Tapping Enabled (276): 1
        libinput Tapping Enabled Default (277): 0
        libinput Tapping Drag Enabled (278):    1
        libinput Tapping Drag Enabled Default (279):    1
        libinput Tapping Drag Lock Enabled (280):       0
        libinput Tapping Drag Lock Enabled Default (281):       0
        libinput Tapping Button Mapping Enabled (282):  1, 0
        libinput Tapping Button Mapping Default (283):  1, 0
        libinput Accel Speed (284):     0.000000
        libinput Accel Speed Default (285):     0.000000
        libinput Natural Scrolling Enabled (286):       0
        libinput Natural Scrolling Enabled Default (287):       0
        libinput Send Events Modes Available (261):     1, 1
        libinput Send Events Mode Enabled (262):        0, 0
        libinput Send Events Mode Enabled Default (263):        0, 0
        libinput Left Handed Enabled (288):     0
        libinput Left Handed Enabled Default (289):     0
        libinput Scroll Methods Available (290):        1, 1, 0
        libinput Scroll Method Enabled (291):   0, 1, 0
        libinput Scroll Method Enabled Default (292):   1, 1, 0
        libinput Disable While Typing Enabled (293):    1
        libinput Disable While Typing Enabled Default (294):    1
        Device Node (264):      "/dev/input/event5"
        Device Product ID (265):        2, 7
        libinput Drag Lock Buttons (295):       <no items>
        libinput Horizontal Scroll Enabled (296):       1

Note the number on the line with "Scroll Method Enabled". In my case, it's "291".

Now that we have those two numbers, we can enable the vertical scrolling:

    xinput set-prop 11 291 1 0 0

The last numbers are three booleans, only one of them can be set to 1 at a time, two have to be set to 0. 
The booleans are (in order): "two-finger", "edge", "button" - indicate which scroll method is 
currently enabled on this device.

So to enable two-finger scrolling, you have to set them to "1, 0, 0".

That's it. It worked for me, not 100% sure if it'll work for you.

Hi thanks for posting! I have been trying to get 2 finger scrolling working with an apple magic trackpad on a raspberry pi. I get an error when I try this method. I noticed that for my trackpad it says "libinput Scroll Methods Available (267): 0, 0, 1". So Im guesing this means two-finger scroll is not available? Any idea how to make it available?

No, sorry.

Thanks this solved my problem. I was searching for like 10 hours thank you so much. It's so good to have scrollinggggg