Several tools exist that may do this, like KMonad, Interception Tools, and keyd.
I've had complete success with
keyd under Wayland, so I describe what I did with that. I suggest reading the short the README for inspiration. The deamon can do a lot more than what's used here.
The present solution does what I want, but circumvents using the
AltGr detour. It treats
Control everywhere, except in
h ,j ,k , l, which it changes to arrow keys.
keyd from source, as that was easy. The next lines first install dependencies (including C compiler), downloads the source, builds and installs it, and enables it as service, and starts it and runs it at startup.
When done, it'll tell you where it installed what so you can delete it for uninstall. You can delete the source code after installation.
sudo apt install cmake libudev-dev
git clone https://github.com/rvaiya/keyd
make && sudo make install
sudo systemctl enable keyd && sudo systemctl start keyd
2. FIND THE NAME OF THE KEYBOARD YOU WANT TO REMAP
You should find the name of your keyboard, so we can make a remapping just for that. Run
sudo keyd -m
and press some keys. It'll show the name of the keyboard and the keys pressed. Note down the name. Mine was
AT Translated Set 2 keyboard.
3. MAKE A CONFIGURATION FILE
Wherever, make a configuration file called whatever. We'll move it later. Let's say you use
In it, put the following. The #'ed are comments that explains the behavior defined (the is updated for v2.1.1. I hope I didn't make any mistakes):
### MAIN LAYER
# Make capslock activate the second layer:
capslock = layer(movement_layer)
### SECOND LAYER (called "movement_layer")
# Define the new layer, which while active
# by default treats every key as if Control was pressed,
# (":C" means the layer should inherit the Control layer),
# and overrides this default for only h, j, k and l, which
# are mapped to directions.
h = left
j = down
k = up
l = right
# In sum, in the main default layer, everything is standard, except
# when CapsLock is pressed, then the second layer is activated.
# When the second layer is activate, everything but h, j, k, l
# acts as if Control is held---e.g., c copies and v pastes,
# which we want, as we holding down CapsLock.)
4. COPY AND RENAME THE CONFIGURATION FILE AND RESTART KEYD
Next, we copy the configuration to the right location and name it properly, namely according to the keyboard we want to remap.
sudo cp ~/my_keyboard.conf /etc/keyd/AT\ Translated\ Set\ 2\ keyboard.conf
We then restart
keyd so it loads the new configuration:
sudo systemctl restart keyd
You're now up and running :)
5. A TIP: CREATE AN ALIAS TO COPY CONFIG AND RESTART KEYD
I ended up playing a lot with the config files. I edited them in a subdirectory of my home folder, then copied them over and restarted.
To make this less of a hassle, in
~/.bash_aliases, I added
alias rekeyd='sudo cp ~/my_keyboard.conf /etc/keyd/AT\ Translated\ Set\ 2\ keyboard.conf && sudo systemctl restart keyd'