Setting up i3 on Thinkpads running NixOS

The first step of the #Make Tech Simple Again project is to go back to i3. Why i3, and not GNOME? Because I have come to believe that i3’s workflow encourages focus & simplicity (more on this later). This note is just a historical record of what I did to get i3 working on both of my machines.

First, consult the NixOS wiki for basic instructions on seting up i3 on a #NixOS machine. This note will focus on the various little things that must be configured for an acceptable user experience on Thinkpads, mainly P71 and Thinkpad X1 Carbon.

Declarative i3 config

i3 will autogenerate the config file when you first login. You will want to put this in your Nix configuration. Move the generated config file (in ~/.config/i3/config) to your Nix repository, and use configFile = ./i3.conf under windowManager.i3¹ in order to declaratively specify it.

HiDPI displays

If any of your screens have 4k+ resolution, you’ll want to change the pixel density (DPI) so that text and UI elements don’t appear too tiny. One way to do this is to specify the DPI in the .Xresources file, which can be declaratively done using home-manager:

home.file = {
  ".Xresources".text = ''
    Xft.dpi: 196
  '';
};

You will also have to instruct X to merge these resources using xrdb on startup. When configuring i3 using configuration.nix (not home-manager) configuration, you can do this as follows:

windowManager.i3.extraSessionCommands = ''
  ${pkgs.xorg.xrdb}/bin/xrdb -merge ~/.Xresources
''

Cursor size will still be tiny, which can be fixed using home-manager configuration:

  # High DPI cursor fix
  # https://github.com/NixOS/nixpkgs/issues/34603
  xsession.pointerCursor = {
    name = "Vanilla-DMZ";
    package = pkgs.vanilla-dmz;
    size = 128;
  };

Automatic screen lock

Various solutions exist, but one way to configure automatic screen locking is to use the xautolock program. nixpkgs provides a systemd service for it:

# Auto-lock
xautolock = {
  enable = true;
  time = 5; # mins

  # Suspend after sometime
  killtime = 20; # mins
  killer = "/run/current-system/systemd/bin/systemctl suspend";
};

Disable autosuspend if you experience the System freeze on wake-up with Thunderbolt bug. You can manually suspend by running systemctl suspend.

Monitor plug and play

Unlike GNOME, in i3 you will explicitly have to configure external screens when docking or undocking the laptop. While arandr can be used to do this manually, it is better to use a service like autorandr to automatically switch configuration when docking state changes.

# Monitor plug n play
# https://github.com/phillipberndt/autorandr/blob/v1.0/README.md#how-to-use
services.autorandr = {
  enable = true;
};

Read the link for initial setup; in particular you will have to use autorandr --save for each docked state to tell autorandr what screen configuration to automatically switch to.

Trackpad & trackpoint configuration

Having used to macOS, I prefer “natural scrolling” direction. On HiDPI displays (such as the 4k of X1C7 and 5k of LG Ultrafine 5k), you will also want to increase the acceleration speed of both trackpoint and trackpad. Both of this can be achieved by configuring libinput:

services.xserver.libinput = {
  enable = true;
  # macOS like behaviour
  naturalScrolling = true;
  # Increase touchpad/trackpoint speed. 1.0 is maximum speed.
  # Changing this value won't take effect until X restart.
  accelSpeed = "0.5";
};

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