Japanese on NixOS

Background

I’ve been studying japanese for some time and because of that I set up most of my devices to be able to also type in japanese. On all my other devices I had no trouble setting this up, but in Linux I had problems since I was using Gentoo, when I moved to NixOS I tried again but no luck. Until some days ago when I found this blog post, it’s kinda outdated, from 2018, but it gave me hope and I tried again. And it worked, with a little bit of tweaking but I can finally type in Japanese すごい.

How

I created two new files fonts.nix and japanese.nix on my system configuration and add fcitx5 & to my riverwm configuration.

This is the contents of fonts.nix, in this file I simply add some fonts to the system and set the default so fontconfig doesn’t use the wrong ones.

{pkgs, ...}: {
	fonts = {
	 packages = with pkgs; [
       carlito
       dejavu_fonts
       ipafont
       kochi-substitute
       source-code-pro
       ttf_bitstream_vera
     ];
     fontconfig = {
       defaultFonts = {
         monospace = [
           "DejaVu Sans Mono"
           "IPAGothic"
         ];
         sansSerif = [
           "DejaVu Sans"
           "IPAPGothic"
         ];
         serif = [
           "DejaVu Serif"
           "IPAPMincho"
         ];
       };
     };
   };
 }

And here is the contents of japanese.nix, in this file I set the input method to be used as fcitx5 and use mozc as IME.

{pkgs, ...}: {
    i18n.inputMethod = {
     enable = true;
     type = "fcitx5";
     fcitx5 = {
       waylandFrontend = true;
       addons = with pkgs; [
         fcitx5-mozc
         fcitx5-gtk
         fcitx5-rose-pine
       ];
     };
   };
 }

This simple configuration worked, all I had to do after the reboot was to set the mozc in the fcitx5 input list.