Fcitx5

Fcitx5 is a lightweight input method framework with addon support.

Setup

The following is a simple NixOS configuration that'll setup fcitx5, its GUI config tool, and two addons.

i18n.inputMethod = {
    enabled = "fcitx5";
    fcitx5.addons = with pkgs; [
        fcitx5-mozc
        fcitx5-gtk
    ];
};

Notably, NixOS automagically sets session variables that are required for fcitx5.

Troubleshooting

Add-ons Not Detected

Installing fcitx5 using environment.systemPackages can interfere with add-on detection. Make sure to only add fcitx5 to your config as shown in Setup.

Fcitx5 Doesn't Start When Using WM

As of NixOS 23.11 i18n.inputMethod.enabled no longer creates systemd services for fcitx5. Instead it relies on XDG autostart files. If using a Window Manager (WM), such as Sway, you may need to add services.xserver.desktopManager.runXdgAutostartIfNone = true; to your NixOS configuration.

See the NixOS 23.11 Release Notes for more information.

Using Wayland

Set boolean i18n.inputMethod.fcitx5.waylandFrontend to true to suppress warnings about environment variables.