by Zubair Abid
This is a log of sorts of the first time I tried to setup home row mods on my computer using interception-tools. The attempt was unsuccessful, due to the stock dual function keys plugin not being optimised for the mod.
The first two sections are essentially information (fluff?) on what home row mods are, so skip to process for the main content.
I want to be comfortable using my keyboard to navigate about my computer. So far: i3, vim keybindings everywhere that is sane, relearning how to type from scratch, and a little script that converts my Caps Lock key to a combined Escape and Control have helped. I’ve also ordered an ergo split keyboard but we do not talk of that yet.
Currently, my CapsLock as Control/Escape is achieved using interception-tools, which allows me to take advantage of the feature even when the X Server is not running, such as when using a TTY, or if I were to setup Wayland. Interception tools’ Gitlab contains several plugins, including the one I have earlier used – caps2esc – and another one that caught my eye called “dual function keys”.
Incidentally, I have since replaced caps2esc entirely with dual function keys.
This article explains it best,
but to summarise: Ctrl, Shift, Alt, and Super (Sys/Gui/Winkey),
referred to henceforth as “modifiers”, are brought up to
the home row (the row with asdf and jkl; that your fingers rest on while
typing). More specifically, the aforementioned keys: a, s, d, f, and
j, k, l, ;, are also given “secondary functions” when held down instead
of just pressed. So “tapping” a (pressing it down for less than a specified
time, often 200ms or so to provide an example) registers on the computer as ‘a’,
but holding it returns Alt (or any other key – how you configure it is up to
you). Accordingly, the four modifiers are assigned some combination of a, s,
d, and f. This is mirrored to the other side on j, k, l, ; to ensure
that all keys are available at all times.
It has (in my limited testing) significant ergonomic
benefits. However, this configuration is usually done using keyboard firmware
known as QMK, which does not run on many cheap mass-produced boards – like the
ones I have (for now).
Which is where the plugin called “dual function keys” catches the eye. Theoretically, we should be able to use it to setup dual-functionality on the necessary keys on any Linux machine independent of the display server in use. And that is true – but there are quirks. This is an attempt at documenting and logging those quirks, and my attempts at overcoming them.
Install interception-tools and dual function keys.
Instructions are on the README; if you’re on arch then
sudo pacman -Syu interception-tools interception-dual-function-keys
will work.
Fundamentally, all one needs to do is add this job in
/etc/interception/udevmon.yaml:
- JOB: "intercept -g $DEVNODE | dual-function-keys -c path_to_config.yml | uinput -d $DEVNODE"
DEVICE:
EVENTS:
EV_KEY: [<keys_being_used>]
Note: I am not sure how important the EV_KEY is, but I don’t need to fill
it in to make it work…
Then, the next step would be to write the config file itself, which would follow the broad formulae of:
TIMING:
- TAP_MILLISEC: 200
- DOUBLE_TAP_MILLISEC: 0
MAPPINGS:
- KEY: KEY_A
TAP: KEY_A
HOLD: KEY_LEFTALT
- KEY: KEY_S
TAP: KEY_S
HOLD: KEY_LEFTMETA
- KEY: KEY_D
TAP: KEY_D
HOLD: KEY_LEFTSHIFT
- KEY: KEY_F
TAP: KEY_F
HOLD: KEY_LEFTCTRL
- KEY: KEY_J
TAP: KEY_J
HOLD: KEY_RIGHTCTRL
- KEY: KEY_K
TAP: KEY_K
HOLD: KEY_RIGHTSHIFT
- KEY: KEY_L
TAP: KEY_L
HOLD: KEY_RIGHTMETA
- KEY: KEY_SEMICOLON
TAP: KEY_SEMICOLON
HOLD: KEY_RIGHTALT
- KEY: KEY_CAPSLOCK
There are some quirks here I want to discuss first.
The location of the udev rule:
This is possibly a udevmon thing that I need to get familiar with, but what
I know as of now:
So I have on previous occasions used
/etc/udevmon.yaml to configure interception. The documentation specifies
both /etc/interception/udevmon.yaml and a variety of subfolders such as
/etc/interception/dual-function-keys/<name>.yaml and others. There is
also a /etc/interception/udevmon.d/ in which the files can possibly go.
However, nothing but /etc/interception/udevmon.yaml worked,
for some reason.
A single config file needs to contain all your configurations:
This one messed with me for a bit. But you can’t have two rules in
/etc/interception/udevmon.yaml like
- JOB: ... homerowmods.yaml ...
- JOB: ... caps2esc.yaml ...
Only the first job will run.
If you want to have both home row mods and caps/esc replacement, then all your configurations have to be under the same config file. This again, is possibly a udev thing I’m not too familiar with.
Also, I want to point out a stupid mistake I made that I hope you will not: I (initially) named my config file “config.yml”, while the reference to the file in udev was “config.yaml”. Please don’t do this.
Performance is suboptimal. Without the “Ignore Mod Tap Interrupt” configuration option (among others) specified in the aforementioned article, it is very easy to
Super + e instead, which changes a layout
option in i3.The issue is simple: when typing quickly, it is common to “slide” across letters – start typing the next letter while the previous one is still pressed down. Essentially,
Current:
<-- <200ms -->
<-- <200ms -->
keyboard: l↓ e↓ l↑ e↑
computer sees: Super↓ e↓ Super↑ e↑
This is suboptimal, and under ideal conditions, the behaviour would be similar to:
Desired:
<------ <200ms ------>
<------- <200ms ------->
keyboard: l↓ e↓ l↑ e↑
computer sees: Super↓ Super↑ l↓ e↓ l↑ e↑
Or better yet (maybe), (Better) Desired:
<---- <200ms ---->
<----- <200ms ----->
keyboard: l↓ e↓ l↑ e↑
computer sees: l↓ e↓ l↑ e↑
Unfortunately, configuring the plugin for home-row mods is not very straightforward – one can check the open issue on the matter. The plan currently is to spend the next post exploring how an optimal mod-tap would work, along with comparisons with a QMK keyboard (a Soyuz I built a couple of days back that will suffice for experimentation).
tags: linux - emacs pinky - keyboards - setup - ergonomics - configuration