Remap a key combination to another combination, e.g. AltGr+C -> Ctrl+C, under Wayland

Question

TL;DR

Under Wayland, can I somehow bind AltGr + C to Ctrl + C?

Details

I basically want to ask this question, but for GNOME on Wayland. This means that answers involving AutoKey and xbindkeys wont work, as neither works under Wayland.

Background

I would like to remap some keys to ultimately make better use of CapsLock.

My plan is to map CapsLock to AltGr, and then follow this to obtain vim-like keybindings. On Wayland, this remapping can be done through XKB files (see the link).

However, I would also like to use CapsLock for copy/pasting. Currently, I have it mapped to Ctrl (using XKB files). This makes CapsLock + C work smoothly throughout the system, and I would like to preserve this.

So: With CapsLock mapped to AltGr, I would like Capslock (= AltGr) + C to act as Ctrl + C.

My question

Under Wayland, can I somehow bind AltGr + C to Ctrl + C?

(Without just rebinding AltGr to Ctrl, as that would defeat the purpose)

An alternative example with Q

In the XKB file for latin /usr/share/X11/xkb/symbols/latin, the following behavior is defined for my Q key:

key <AD01>  { [ q, Q, at, Greek_OMEGA ] };

This states that the key has four possible outputs:

1. Pressed alone, it produces q.
2. Pressed with Shift, it produces Q.
3. Pressed with AltGr, it produces @.
4. Pressed with AltGr + Shift, it produces Ω.

Essentially what I would like to achieve is that when Q is pressed with AltGr, it does not produce @ but Ctrl + Q.

Answer 1

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 CapsLock as Control everywhere, except in h ,j ,k , l, which it changes to arrow keys.

1. INSTALLATION

I build 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
cd 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 can skip this step and remap the default keyboard, see below on default.conf

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.

Tip: keyd -m is useful find the name of keys by pressing them. keyd -l lists the key names you can map to.

3. MAKE A CONFIGURATION FILE

Wherever, make a configuration file called whatever. We'll move it later. Let's say you use ~/my_keyboard.conf.

In it, put the following. The #'ed are comments that explains the behavior defined:

[ids]

*

[main]
### 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.

[movement_layer:C]

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 are 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

Note: default.conf. You can also copy your config file to /etc/keyd/default.conf to make it apply to all keyboards. But if you mess up and remap your Enter key, you cannot plugin another keyboard to undo the changes...

We then restart keyd so it loads the new configuration:

sudo systemctl restart keyd

You're now up and running :)

5. 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 keyd.

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'