# Interception plugin for vimproved input

My hideous (but working and performant) C++ code to remap the keys on any input device that emits keys.

## tl;dr;

* space cadet: Maps space into modifier key when held for long that transforms hjkl (vim homerow) into arrows, number row into F-keys and a bit more. Space still emits SPACE key when tapped without holding.
* caps2esc: Makes CAPS key send ESC when tapped and CTRL when held.

## Requirements
Basically any OS that works with `libevdev` (linux with kernel newer than 2.6.36), no matter what desktop environment, or even if any DE is used (yes, it works the same in X server instead of `xmodmap`, but also in plain terminal, without graphical environment).

## Running
Use it with a job specification for `udevmon` (from [Interception Tools](https://gitlab.com/interception/linux/tools)). I install the binary to `/opt/interception/interception-vimproved` and use it like the following on Arch linux on Thinkpad x1c gen7.

```yaml
- JOB: "intercept -g $DEVNODE | /opt/interception/interception-vimproved | uinput -d $DEVNODE"
  DEVICE:
    EVENTS:
      EV_KEY:
        [
          KEY_SPACE,

          KEY_1,
          KEY_2,
          KEY_3,
          KEY_4,
          KEY_5,
          KEY_6,
          KEY_7,
          KEY_8,
          KEY_9,
          KEY_0,
          KEY_MINUS,
          KEY_EQUAL,
          KEY_F1,
          KEY_F2,
          KEY_F3,
          KEY_F4,
          KEY_F5,
          KEY_F6,
          KEY_F7,
          KEY_F8,
          KEY_F9,
          KEY_F10,
          KEY_F11,
          KEY_F12,

          KEY_B,
          KEY_BACKSPACE,

          KEY_E,
          KEY_ESC,

          KEY_D,
          KEY_DELETE,

          KEY_Y,
          KEY_U,
          KEY_I,
          KEY_O,
          KEY_HOME,
          KEY_PAGEDOWN,
          KEY_PAGEUP,
          KEY_END,

          KEY_H,
          KEY_J,
          KEY_K,
          KEY_L,
          KEY_LEFT,
          KEY_DOWN,
          KEY_UP,
          KEY_RIGHT,

          KEY_M,
          KEY_COMMA,
          KEY_DOT,
          KEY_MUTE,
          KEY_VOLUMEDOWN,
          KEY_VOLUMEUP,

          KEY_CAPSLOCK,
          KEY_LEFTCTRL,
        ]
```

Alternatively, you can run it with `udevmon` straight, just make sure to be negatively nice (`nice -n -20 udevmon -c /etc/udevmon.yml`) so your input is always available.

### Testing
In case you want to edit the source code, kill the `udevmon` daemon, and manually try the following to avoid getting stuck with broken input. Trust me, you can get yourself in a dead end situation easily.

```bash
# sleep buys you some time to focus away from terminal to your playground
sleep 1 && timeout 10 udevmon -c /etc/udevmon.yml
```


## Why make this
1. I have problems switching back and forth between my external keyboard and laptop keyboard. I customized my external keyboard with QMK to reduce my pinky strain and improve usability, but when I switch back to laptop keyboard, it's all lost, plus I have to fight my muscle memory.
2. I used to use X.Org server with xinput, where I had an [xkbcomp based solution with xcape and xmodmap](https://github.com/maricn/dotfiles/blob/master/.xinitrc-keyboard-remap). However, since moving to wayland, that solution doesn't work anymore, and I needed to move to `libevdev` based solution.
3. Enter [Interception Tools](https://gitlab.com/interception/linux/tools). It advertises itself as "a minimal composable infrastructure on top of libudev and libevdev". It, on one side, intercepts events from devices and writes them raw to `stdout`, and on the other side, it receives events from `stdin` and writes them to virtual input device.
4. This plugin sits piped between Interception Tool's `intercept` and `uinput` (`intercept | interception-vimproved | uinput`). It interprets input from `intercept` and maps it to desired events which are then passed to `uinput` for emitting.

* Other solutions I tried didn't behave as expected and produced unexpected artefacts.
* In this solution, the use of sleeps is eliminated, there's no buffers for input and the interaction with output is minimized to reduce extra costs of writing to it often.

## Related work

* [Interception Tools](https://gitlab.com/interception/linux/tools)
* [space2meta](https://gitlab.com/interception/linux/plugins/space2meta)
* [dual-function-keys](https://gitlab.com/interception/linux/plugins/dual-function-keys)
* [interception-k2k](https://github.com/zsugabubus/interception-k2k)