How to setup xcape in configuration.nix without home manager?

Knarkzel · July 22, 2022, 8:52pm

My setup is currently this: NixOS.

I use following for xcape, however it only works when manually running systemctl --user start xcape instead of starting automatically:

  # xcape service
  systemd.user.services.xcape = {
    restartIfChanged = true;
    description = "Combine Ctrl+Escape";
    wantedBy = ["graphical-session.target"];
    partOf = ["graphical-session.target"];
    serviceConfig = {
      Type = "forking";
      Restart = "always";
      ExecStart = ''${pkgs.xcape}/bin/xcape -e "Control_L=Escape"'';
    };
  };

gravndal · July 22, 2022, 9:24pm

What’s the output of $ systemctl --user status graphical-session.target?

If it’s inactive/hasn’t been reached, you need to configure your window manager/desktop environment to start and stop the target at the appropriate time. Here’s how I do it in my .xinitrc:

systemctl --user -q start graphical-session.target
herbstluftwm --locked
systemctl --user -q stop graphical-session.target

Knarkzel · July 22, 2022, 9:33pm

~ ❯ systemctl --user status graphical-session.target
● graphical-session.target - Current graphical user session
     Loaded: loaded (/etc/systemd/user/graphical-session.target; static)
    Drop-In: /nix/store/h9f84vyplfs1hdhdwphz7jwq6b8rnvy6-user-units/graphical-session.target.d
             └─overrides.conf
     Active: active since Fri 2022-07-22 22:39:14 CEST; 54min ago
      Until: Fri 2022-07-22 22:39:14 CEST; 54min ago
       Docs: man:systemd.special(7)

Jul 22 22:39:14 odd systemd[1176]: Reached target Current graphical user session.

Knarkzel · July 22, 2022, 9:34pm

Here’s xcape as well:

~ ❯ systemctl --user status xcape
● xcape.service - Combine Ctrl+Escape
     Loaded: loaded (/etc/systemd/user/xcape.service; enabled; vendor preset: enabled)
     Active: active (running) since Fri 2022-07-22 22:39:14 CEST; 54min ago
   Main PID: 1208 (xcape)
      Tasks: 2 (limit: 19089)
     Memory: 564.0K
        CPU: 259ms
     CGroup: /user.slice/user-1000.slice/user@1000.service/app.slice/xcape.service
             └─1208 /nix/store/2dxqy8lh3r03dxgqkg0zkr2ffja3wig9-xcape-unstable-2018-03-01/bin/xcape -e Control_L Escape

Jul 22 22:39:14 odd systemd[1176]: Starting Combine Ctrl+Escape...
Jul 22 22:39:14 odd systemd[1176]: Started Combine Ctrl+Escape.

gravndal · July 22, 2022, 9:50pm

Is the status output for xcape after you’ve manually started it? Because that certainly looks like it’s working.

Knarkzel · July 22, 2022, 9:53pm

It’s from when the system is booting. However the change doesn’t persist, for instance after sudo nixos-rebuild switch. I don’t think it works after booting either, will try.

Knarkzel · July 22, 2022, 9:55pm

Hmm, for some reason xcape starts before graphical-session.target…

~ ❯ systemctl --user status graphical-session.target
● graphical-session.target - Current graphical user session
     Loaded: loaded (/etc/systemd/user/graphical-session.target; static)
    Drop-In: /nix/store/h9f84vyplfs1hdhdwphz7jwq6b8rnvy6-user-units/graphical-session.target.d
             └─overrides.conf
     Active: active since Fri 2022-07-22 23:53:37 CEST; 14s ago
      Until: Fri 2022-07-22 23:53:37 CEST; 14s ago
       Docs: man:systemd.special(7)

Jul 22 23:53:37 odd systemd[1171]: Reached target Current graphical user session.
~ ❯ systemctl --user status xcape
● xcape.service - Combine Ctrl+Escape
     Loaded: loaded (/etc/systemd/user/xcape.service; enabled; vendor preset: enabled)
     Active: active (running) since Fri 2022-07-22 23:53:37 CEST; 18s ago
    Process: 1202 ExecStart=/nix/store/2dxqy8lh3r03dxgqkg0zkr2ffja3wig9-xcape-unstable-2018-03-01/bin/xcape -e Control_L=Escape (code=exited,>
   Main PID: 1203 (xcape)
      Tasks: 2 (limit: 19089)
     Memory: 564.0K
        CPU: 6ms
     CGroup: /user.slice/user-1000.slice/user@1000.service/app.slice/xcape.service
             └─1203 /nix/store/2dxqy8lh3r03dxgqkg0zkr2ffja3wig9-xcape-unstable-2018-03-01/bin/xcape -e Control_L Escape

Jul 22 23:53:37 odd systemd[1171]: Starting Combine Ctrl+Escape...
Jul 22 23:53:37 odd systemd[1171]: Started Combine Ctrl+Escape.

Knarkzel · July 22, 2022, 9:56pm

Process seems to start but it has no effect. Restarting makes it work again. Then after some time it stops working. Don’t know why.

gravndal · July 22, 2022, 10:00pm

Yeah, when I was using xcape I found it was fairly finicky in general, the workaround I used at the time was having my window manager restart it when reloading it’s configuration.

If you don’t mind side-stepping the issue, I would recommend switching to interception-tools and the dual-function-keys plugin. It wraps evdev, so will work anywhere, be it X11, wayland, or the linux TTY.

Knarkzel · July 22, 2022, 10:03pm

Do you have an example of using either of those in NixOS? As long as I have control + escape it doesn’t matter

gravndal · July 22, 2022, 10:09pm

I was just writing that up actually:

  services.interception-tools =
    let
      dfkConfig = pkgs.writeText "dual-function-keys.yaml" ''
        MAPPINGS:
          - KEY: KEY_CAPSLOCK
            TAP: KEY_ESC
            HOLD: KEY_LEFTCTRL
      '';
    in
    {
      enable = true;
      plugins = lib.mkForce [
        pkgs.interception-tools-plugins.dual-function-keys
      ];
      udevmonConfig = ''
        - JOB: "${pkgs.interception-tools}/bin/intercept -g $DEVNODE | ${pkgs.interception-tools-plugins.dual-function-keys}/bin/dual-function-keys -c ${dfkConfig} | ${pkgs.interception-tools}/bin/uinput -d $DEVNODE"
          DEVICE:
            NAME: "USB Keyboard"
            EVENTS:
              EV_KEY: [[KEY_CAPSLOCK, KEY_ESC, KEY_LEFTCTRL]]
      '';
    };

This puts left control and escape on capslock.

To get the device name you can use sudo uinput -p -d /dev/input/by-id/foo. Or just drop it, as it’s technically not required, it just limits interception tools from wrapping any compatible device (which can include things you wouldn’t really expect).

Knarkzel · July 22, 2022, 11:17pm

Added this configuration here: configuration.nix, and control seems to work but not escape.

Knarkzel · July 22, 2022, 11:18pm

Hmm wait, services.xserver.xkbOptions might be interferring.

Knarkzel · July 22, 2022, 11:21pm

Now my caps lock is acting as backspace. Don’t know why this is the case.

EDIT:
Finally got it working here, thanks for the help!

~knarkzel/nixos: Caps + Escape finally working - sourcehut git

I used xinput to find the proper NAME:

gravndal · July 22, 2022, 11:22pm

That’s the default colemak behaviour.

Is $ systemctl status interception-tools showing you something like:

CGroup: /system.slice/interception-tools.service
        ├─3021901 /nix/store/ch2272gvqhzwrjxzcf6ldg39b61nrlfw-interception-tools-0.6.8/bin/udevmon -c /nix/store/v16yzikjkz6w3a8qgjfirgks39x63hdl-udevmon.yaml
        ├─3021967 sh -c "/nix/store/ch2272gvqhzwrjxzcf6ldg39b61nrlfw-interception-tools-0.6.8/bin/intercept -g \$DEVNODE | /nix/store/5vyziafj0x0jk8y89mlkaxnwi3wlf6c0-dual-function
        ├─3021970 /nix/store/ch2272gvqhzwrjxzcf6ldg39b61nrlfw-interception-tools-0.6.8/bin/intercept -g /dev/input/event1
        ├─3021971 /nix/store/5vyziafj0x0jk8y89mlkaxnwi3wlf6c0-dual-function-keys-1.4.0/bin/dual-function-keys -c /nix/store/bnlgww1gn5gqfk448f5964dx6m8bfv4q-dual-function-keys.yaml
        └─3021972 /nix/store/ch2272gvqhzwrjxzcf6ldg39b61nrlfw-interception-tools-0.6.8/bin/uinput -d /dev/input/event1

Knarkzel · July 22, 2022, 11:23pm

     CGroup: /system.slice/interception-tools.service
             └─5889 /nix/store/ch2272gvqhzwrjxzcf6ldg39b61nrlfw-interception-tools-0.6.8/bin/udevmon -c /nix/store/fx4g2aqvn9fb4bl7khvjhrfpfa>

gravndal · July 22, 2022, 11:27pm

Then it hasen’t found a device with a matching device name and EV_KEYs.

The system control in the device name is a bit suspicious, try dropping the name and see what happens.