home-manager/modules/misc/fontconfig.nix

# This module is heavily inspired by the corresponding NixOS module. See
#
#   https://github.com/NixOS/nixpkgs/blob/23.11/nixos/modules/config/fonts/fontconfig.nix

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

let

  cfg = config.fonts.fontconfig;

  profileDirectory = config.home.profileDirectory;

in {
  meta.maintainers = [ lib.maintainers.rycee ];

  imports = [
    (lib.mkRenamedOptionModule [ "fonts" "fontconfig" "enableProfileFonts" ] [
      "fonts"
      "fontconfig"
      "enable"
    ])
  ];

  options = {
    fonts.fontconfig = {
      enable = lib.mkOption {
        type = lib.types.bool;
        default = false;
        description = ''
          Whether to enable fontconfig configuration. This will, for
          example, allow fontconfig to discover fonts and
          configurations installed through
          {var}`home.packages` and
          {command}`nix-env`.
        '';
      };

      defaultFonts = {
        monospace = lib.mkOption {
          type = with lib.types; listOf str;
          default = [ ];
          description = ''
            Per-user default monospace font(s). Multiple fonts may be listed in
            case multiple languages must be supported.
          '';
        };

        sansSerif = lib.mkOption {
          type = with lib.types; listOf str;
          default = [ ];
          description = ''
            Per-user default sans serif font(s). Multiple fonts may be listed
            in case multiple languages must be supported.
          '';
        };

        serif = lib.mkOption {
          type = with lib.types; listOf str;
          default = [ ];
          description = ''
            Per-user default serif font(s). Multiple fonts may be listed in
            case multiple languages must be supported.
          '';
        };

        emoji = lib.mkOption {
          type = with lib.types; listOf str;
          default = [ ];
          description = ''
            Per-user default emoji font(s). Multiple fonts may be listed in
            case a font does not support all emoji.

            Note that fontconfig matches color emoji fonts preferentially,
            so if you want to use a black and white font while having
            a color font installed (eg. Noto Color Emoji installed alongside
            Noto Emoji), fontconfig will still choose the color font even
            when it is later in the list.
          '';
        };
      };
    };
  };

  config = lib.mkIf cfg.enable {
    home.packages = [
      # Make sure that buildEnv creates a real directory path so that we avoid
      # trying to write to a read-only location.
      (pkgs.runCommandLocal "dummy-fc-dir1" { } "mkdir -p $out/lib/fontconfig")
      (pkgs.runCommandLocal "dummy-fc-dir2" { } "mkdir -p $out/lib/fontconfig")
    ];

    home.extraProfileCommands = ''
      if [[ -d $out/lib/X11/fonts || -d $out/share/fonts ]]; then
        export FONTCONFIG_FILE="$(pwd)/fonts.conf"

        cat > $FONTCONFIG_FILE << EOF
      <?xml version='1.0'?>
      <!DOCTYPE fontconfig SYSTEM 'fonts.dtd'>
      <fontconfig>
        <dir>$out/lib/X11/fonts</dir>
        <dir>$out/share/fonts</dir>
        <cachedir>$out/lib/fontconfig/cache</cachedir>
      </fontconfig>
      EOF

        ${lib.getBin pkgs.fontconfig}/bin/fc-cache -f
        rm -f $out/lib/fontconfig/cache/CACHEDIR.TAG
        rmdir --ignore-fail-on-non-empty -p $out/lib/fontconfig/cache

        rm "$FONTCONFIG_FILE"
        unset FONTCONFIG_FILE
      fi

      # Remove the fontconfig directory if no files were available.
      if [[ -d $out/lib/fontconfig ]] ; then
        rmdir --ignore-fail-on-non-empty -p $out/lib/fontconfig
      fi
    '';

    xdg.configFile = let
      mkFontconfigConf = conf: ''
        <?xml version='1.0'?>

        <!-- Generated by Home Manager. -->

        <!DOCTYPE fontconfig SYSTEM 'urn:fontconfig:fonts.dtd'>
        <fontconfig>
        ${conf}
        </fontconfig>
      '';
    in {
      "fontconfig/conf.d/10-hm-fonts.conf".text = mkFontconfigConf ''
        <description>Add fonts in the Nix user profile</description>

        <include ignore_missing="yes">${config.home.path}/etc/fonts/conf.d</include>
        <include ignore_missing="yes">${config.home.path}/etc/fonts/fonts.conf</include>

        <dir>${config.home.path}/lib/X11/fonts</dir>
        <dir>${config.home.path}/share/fonts</dir>
        <dir>${profileDirectory}/lib/X11/fonts</dir>
        <dir>${profileDirectory}/share/fonts</dir>

        <cachedir>${config.home.path}/lib/fontconfig/cache</cachedir>
      '';

      "fontconfig/conf.d/52-hm-default-fonts.conf".text = let
        genDefault = fonts: name:
          lib.optionalString (fonts != [ ]) ''
            <alias binding="same">
              <family>${name}</family>
              <prefer>
              ${
                lib.concatStringsSep "" (map (font: ''
                  <family>${font}</family>
                '') fonts)
              }
              </prefer>
            </alias>
          '';
      in mkFontconfigConf ''
        <!-- Default fonts -->
        ${genDefault cfg.defaultFonts.sansSerif "sans-serif"}
        ${genDefault cfg.defaultFonts.serif "serif"}
        ${genDefault cfg.defaultFonts.monospace "monospace"}
        ${genDefault cfg.defaultFonts.emoji "emoji"}
      '';
    };
  };
}