nixos-config/nixos/components/gui/kmonad.nix

{ config, pkgs, lib, ... }:
{

  options.components.gui.kmonad.enable = lib.mkOption {
    type = lib.types.bool;
    default = config.components.gui.enable;
  };

  config = lib.mkIf (config.components.gui.kmonad.enable) {

    # only needed if you have an UHK
    hardware.keyboard.uhk.enable = true;
    environment.systemPackages = [ pkgs.unstable.uhk-agent ];
    users.users.mainUser.extraGroups = [ "input" ];

    services.xserver = {
      layout = "us";
      xkbOptions = "compose:ralt";
    };

    services.kmonad = {
      enable = true;
      keyboards =
        let
          keyboard = device: leftOfSpace: {
            device = device;
            extraGroups = [ "video" ];
            defcfg = {
              enable = true;
              fallthrough = true;
              allowCommands = true;
            };
            config = ''
              (defsrc
                grv  1    2    3    4    5    6    7    8    9    0    -    =    bspc
                tab  q    w    e    r    t    y    u    i    o    p    [    ]    \
                caps a    s    d    f    g    h    j    k    l    ;    '    ret
                lsft z    x    c    v    b    n    m    ,    .    /    rsft
                ${lib.concatStringsSep " " leftOfSpace}           spc            ralt rmet cmp  rctl
              )

              (defalias sym (layer-toggle symbols))

              (deflayer qwerty
                grv  1    2    3    4    5    6    7    8    9    0    -    =    bspc
                tab  q    w    e    r    t    y    u    i    o    p    [    ]    \
                esc  a    s    d    f    g    h    j    k    l    ;    '    ret
                lsft z    x    c    v    b    n    m    ,    .    /    rsft
                lctl lalt lmet           spc            @sym rmet cmp  rctrl
              )

              (deflayer symbols
                _    ½    ²    ³    ⁴    ⁵    ⁶    ⁷    ⁸    ⁹    ∞    _    _    _
                _    _    _    €    _    ™    _    ü    _    ö    _    _    _    _
                caps ä    ß    _    _    _    _    _    _    _    _    _    _
                _    _    _    ¢    _    _    _    _    _    _    _    _
                _    _    _              _              _    _    _    _)
            '';
          };

        in
        {
          nativ = keyboard "/dev/input/by-path/platform-i8042-serio-0-event-kbd" [ "lctl" "lmet" "lalt" ];
          dasKeyboard = keyboard "/dev/input/by-id/usb-Metadot_-_Das_Keyboard_Das_Keyboard-event-kbd" [ "lctl" "lmet" "lalt" ];
          uhk = keyboard "/dev/input/by-id/usb-Ultimate_Gadget_Laboratories_UHK_60_v2-if01-event-kbd" [ "lctl" "lalt" "lmet" ];
        };
    };
  };
}