27 Aug 2020

I've been a very big fan of small Wacom tablets as a replacement for a mouse. I'll go through my current setup for Linux in case it can help anyone out there.

I started using a Wacom tablet for drawing but found it an excellent replacement for a mouse and moved to exclusive use when I started having symptons of RSI. The change from having the wrist on top of a mouse to having it gripping a pen made a big difference and my problems went away.

When I started using macbooks this became almost a non issue since the trackpad (on OS X) removes a lot of the stress points, in particular if you enable tap to click, tap with two fingers to right click and three finger drag.

Now I find myself on desktop PCs running Linux most of the time so I went back to using it as my main device, tweaking it to my liking. I have compiled my tweaks and hacks here, currently all is tested on a relatively old Wacom Intuos pen & touch small tablet (CTH-480).

Oh and kudos to Jason Gerecke the maintainer of the linuxwacom driver, such an essential but slightly thankless job (and Wacom for supporting him).

The basics

Luckily most distros these days detect Wacom tablets without any hassle and provide even a tool that will help you do some simple mappings.

First of all you'll need to find the ID of the device you want to modify, and you'll need to have xsetwacom installed (part of xserver-xorg-input-wacom, normally installed by default).

In my case:

xsetwacom --list devices

 Wacom Intuos PT S Finger touch    id: 13  type: TOUCH
 Wacom Intuos PT S Pad pad         id: 14  type: PAD
 Wacom Intuos PT S Pen eraser      id: 17  type: ERASER
 Wacom Intuos PT S Pen stylus      id: 16  type: STYLUS

The following commands can use the name of the device or the id number, I'll use the name to make it easier to read.

Absolute positioning

This is a must, trying to use the pen as if it was a trackpad just doesn't function in an usable way. What you want is to map a point on the tablet to a point on the screen. This allows you to fly from one corner of the screen to the other faster than a trackpad could do.

For almost all distros you can switch this on via a UI, but if you don't have it, you can do it manually, for my case:

xsetwacom --set "Wacom Intuos PT S Pen stylus" Mode Absolute
xsetwacom --set "Wacom Intuos PT S Pen eraser" Mode Absolute

Aspect ratio

There is one subtle but very big problem I have noticed as the aspect ratio of my monitors have diverged from the aspect ratio of the tablet over time.

If your tablet proportions don't match the proportions of the screen it will be impossible to draw properly, this is painfully evident on an Ultrawide screen: you'll draw a circle but it will show as an oval. The brain is able to more or less adjust to that and you may be able to manage it but it's a very frustrating experience.

For my case I have written a small script that will calculate the aspect ratio of the screen and map the tablet to it.

# if you have more than one monitor you can specify which one to use by
# adding a --display option to the xrandr call
s_w=`xrandr | grep -w connected  | awk -F'[ \+]' '{print $4}' | sed 's/x/ /' | awk '{print $1}'`
s_h=`xrandr | grep -w connected  | awk -F'[ \+]' '{print $4}' | sed 's/x/ /' | awk '{print $2}'`

ratio=`echo "${s_h}/${s_w}" | bc -l`

echo "Screen detected: ${s_w}x${s_h}"
for device in 'Wacom Intuos PT S Pen stylus' 'Wacom Intuos PT S Pen eraser' ; do
  echo ""
  echo "${device}:"
  xsetwacom set "$device" ResetArea
  area=`xsetwacom get "$device" area | awk '{print $3,$4}'`
  w=`echo ${area} | awk '{print $1}'`
  h=`echo ${area} | awk '{print $2}'`
  hn=`echo "${w}*${ratio}" | bc -l`
  hn=`printf %.0f "${hn}"`
  echo "  Area ${w}x${h} ==> ${w}x${hn}"
  xsetwacom set "$device" area 0 0 ${w} ${hn}

Fix the jitter

My hand is not particularly steady and I find that if I try to keep it still I will get tiny movements (jitter). These two parameters make it less sensitive. You can play with the values. This seems to work for my Intuos S.

xsetwacom --set "Wacom Intuos PT S Pen stylus" Suppress 10
xsetwacom --set "Wacom Intuos PT S Pen stylus" RawSample 9
xsetwacom --set "Wacom Intuos PT S Pen eraser" RawSample 9
xsetwacom --set "Wacom Intuos PT S Pen eraser" Suppress 10

Mapping of the tablet buttons

There are some buttons on the tablet. I find the most useful thing to do is to map them to mouse buttons so that I can click more precisely. I find hovering over a selection and using the other hand to press the buttons makes me more precise. You can also map them to any key or combination of keys.

# the pad of my tablet has 4 buttons
# the mapping is a bit weird because Xinput reserves some buttons
# https://github.com/linuxwacom/xf86-input-wacom/wiki/Tablet-Configuration-1%3A-xsetwacom-and-xorg.conf
#  [ button 3 ]               [ button 9 ]
#  [ button 1 ]               [ button 8 ]
xsetwacom set "Wacom Intuos PT S Pad pad" Button 9 "key +ctrl z -ctrl"  # undo
xsetwacom set "Wacom Intuos PT S Pad pad" Button 8 2  # middle button
xsetwacom set "Wacom Intuos PT S Pad pad" button 1 1  # mouse click
xsetwacom set "Wacom Intuos PT S Pad pad" button 3 2  # middle button

You can use trial and error to find which buttons correspond to which numbers. Note the mapping for the 'undo' functionality, it's equivalent to saying "press control, while holding it press z, then release control"

Mapping of pen buttons

You can map the buttons on the pen itself to various functions.

For years one feature I missed was the ability to scroll just using the pen. The way this works is I press on the button on the side of the pen (which is very ergonomic) and then press with the pen on the tablet and move up and down. Works like a charm as a relaxed way of scrolling. This is called "pan scroll", I have seen it called "drag to scroll" too and has worked in Linux for a couple of years now and it's implemented as a button mapping.

# pan scroll (press lower button + click and drag to scroll)
xsetwacom --set "Wacom Intuos PT S Pen stylus" button 2 "pan"
xsetwacom --set "Wacom Intuos PT S Pen stylus" "PanScrollThreshold" 200

I leave the other buttons as they are, which is the tip of the button acts as a 'left click' and the second button on the side acts as a right click. This particular pen can also be used as an eraser - so you can change the eraser mapping too. Defaults work fine for me.

Touch and multi-touch (fusuma)

Without doing anything you get functional trackpad functionality on Wacom touch models. For mine you get standard movement, tap to click, tap with two fingers to right click and what I can best describe as "tap + release + tap again and move" to select or drag, plus scrolling by using two fingers up and down the tablet. Some distributions enable also going forwards and backwards in browsers by sliding both fingers left or right, while the most common case seems to enable scrolling left and right.

There's a few multi touch frameworks you can use to extend what's possible. I'm currently using fusuma, I simply followed the instructions to set it up and then launch it as part of my window manager startup. It can do a lot more than what I need so my configuration is very simple:

$ cat ~/.config/fusuma/config.yml
      sendkey: "LEFTALT+RIGHT" # History forward
      sendkey: "LEFTALT+LEFT" # History back
      sendkey: "LEFTMETA" # Activity
      sendkey: "LEFTALT+LEFTMETA+LEFT"
    command: "xdotool keydown ctrl click 4 keyup ctrl" # Zoom in
    command: "xdotool keydown ctrl click 5 keyup ctrl" # Zoom out

Basically I use four fingers to move between workspaces (I have mapped those keys in my window manager to switch workspaces) and three fingers to go back/forwards in browsers. I have pinch configured but it's not very practical to be honest.

Here you can really play with whatever fits best with your preferences and window manager. Note that you can issue extended complicated commands via xdotool in a similar way to what linuxwacom can already do by itself.

That's it. This is what works for me so far, feel free to ping me if you get stuck setting up something.

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