nixos/dms-greeter: add module

nixos/modules/module-list.nix

@@ -607,6 +607,7 @@
   ./services/development/zammad.nix
   ./services/display-managers/cosmic-greeter.nix
   ./services/display-managers/default.nix
+  ./services/display-managers/dms-greeter.nix
   ./services/display-managers/gdm.nix
   ./services/display-managers/greetd.nix
   ./services/display-managers/lemurs.nix

nixos/modules/services/display-managers/dms-greeter.nix

@@ -0,0 +1,261 @@
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
+
+let
+  inherit (lib)
+    types
+    mkEnableOption
+    mkOption
+    mkIf
+    mkDefault
+    mkPackageOption
+    literalExpression
+    getExe
+    makeBinPath
+    optionalString
+    concatMapStringsSep
+    ;
+
+  cfg = config.services.displayManager.dms-greeter;
+  cfgAutoLogin = config.services.displayManager.autoLogin;
+
+  greeterScript = pkgs.writeShellScriptBin "dms-greeter-start" ''
+    export PATH=$PATH:${
+      makeBinPath [
+        cfg.quickshell.package
+        config.programs.${cfg.compositor.name}.package
+      ]
+    }
+    exec ${cfg.package}/share/quickshell/dms/Modules/Greetd/assets/dms-greeter \
+      --command ${cfg.compositor.name} \
+      -p ${cfg.package}/share/quickshell/dms \
+      --cache-dir /var/lib/dms-greeter \
+      ${
+        optionalString (
+          cfg.compositor.customConfig != ""
+        ) "-C ${pkgs.writeText "dms-greeter-compositor-config" cfg.compositor.customConfig}"
+      } \
+      ${optionalString cfg.logs.save ">> ${cfg.logs.path} 2>&1"}
+  '';
+
+  configFilesFromHome =
+    if cfg.configHome != null then
+      [
+        "${cfg.configHome}/.config/DankMaterialShell/settings.json"
+        "${cfg.configHome}/.local/state/DankMaterialShell/session.json"
+        "${cfg.configHome}/.cache/DankMaterialShell/dms-colors.json"
+      ]
+    else
+      [ ];
+in
+{
+  options.services.displayManager.dms-greeter = {
+    enable = mkEnableOption "DankMaterialShell greeter";
+
+    package = mkPackageOption pkgs "dms-shell" { };
+
+    compositor = {
+      name = mkOption {
+        type = types.enum [
+          "niri"
+          "hyprland"
+          "sway"
+        ];
+        example = "niri";
+        description = ''
+          The Wayland compositor to run the greeter in.
+
+          The specified compositor must be enabled via its corresponding
+          `programs.<compositor>.enable` option.
+
+          Supported compositors:
+          - niri: A scrollable-tiling Wayland compositor
+          - hyprland: A dynamic tiling Wayland compositor
+          - sway: An i3-compatible Wayland compositor
+        '';
+      };
+
+      customConfig = mkOption {
+        type = types.lines;
+        default = "";
+        example = ''
+          # Niri example
+          input {
+              keyboard {
+                  xkb {
+                      layout "us"
+                  }
+              }
+          }
+        '';
+        description = ''
+          Custom compositor configuration to use for the greeter session.
+
+          This configuration is written to a file and passed to the compositor
+          when launching the greeter. The format and available options depend
+          on the selected compositor.
+
+          Leave empty to use the system's default compositor configuration.
+        '';
+      };
+    };
+
+    configFiles = mkOption {
+      type = types.listOf types.path;
+      default = [ ];
+      example = literalExpression ''
+        [
+          "/home/user/.config/DankMaterialShell/settings.json"
+          "/home/user/.local/state/DankMaterialShell/session.json"
+        ]
+      '';
+      description = ''
+        List of DankMaterialShell configuration files to copy into the greeter
+        data directory at `/var/lib/dms-greeter`.
+
+        This is useful for preserving user preferences like wallpapers, themes,
+        and other settings in the greeter screen.
+
+        ::: {.tip}
+        Use {option}`configHome` instead if your configuration files are in
+        standard XDG locations.
+        :::
+      '';
+    };
+
+    configHome = mkOption {
+      type = types.nullOr types.str;
+      default = null;
+      example = "/home/alice";
+      description = ''
+        Path to a user's home directory from which to copy DankMaterialShell
+        configuration files.
+
+        When set, the following files will be automatically copied to the greeter:
+        - `~/.config/DankMaterialShell/settings.json`
+        - `~/.local/state/DankMaterialShell/session.json`
+        - `~/.cache/DankMaterialShell/dms-colors.json`
+
+        If your configuration files are in non-standard locations, use the
+        {option}`configFiles` option instead.
+      '';
+    };
+
+    quickshell = {
+      package = mkPackageOption pkgs "quickshell" { };
+    };
+
+    logs = {
+      save = mkEnableOption "saving logs from the DMS greeter to a file";
+
+      path = mkOption {
+        type = types.path;
+        default = "/tmp/dms-greeter.log";
+        example = "/var/log/dms-greeter.log";
+        description = ''
+          File path where DMS greeter logs will be saved.
+
+          This is useful for debugging greeter issues. Logs will include
+          output from both the greeter and the compositor.
+        '';
+      };
+    };
+  };
+
+  config = mkIf cfg.enable {
+    assertions = [
+      {
+        assertion = config.programs.${cfg.compositor.name}.enable or false;
+        message = ''
+          DankMaterialShell greeter: The compositor "${cfg.compositor.name}" is not enabled.
+
+          Please enable the compositor via:
+            programs.${cfg.compositor.name}.enable = true;
+        '';
+      }
+    ];
+
+    services.greetd = {
+      enable = true;
+      settings = {
+        default_session = {
+          user = "dms-greeter";
+          command = getExe greeterScript;
+        };
+        initial_session = mkIf (cfgAutoLogin.enable && (cfgAutoLogin.user != null)) {
+          inherit (cfgAutoLogin) user command;
+        };
+      };
+    };
+
+    environment.systemPackages = [ cfg.package ];
+
+    fonts.packages = with pkgs; [
+      fira-code
+      inter
+      material-symbols
+    ];
+
+    systemd.tmpfiles.settings."10-dms-greeter"."/var/lib/dms-greeter".d = {
+      user = "dms-greeter";
+      group = "dms-greeter";
+      mode = "0750";
+    };
+
+    systemd.services.greetd.preStart =
+      let
+        allConfigFiles = cfg.configFiles ++ configFilesFromHome;
+      in
+      ''
+        set -euo pipefail
+
+        cd /var/lib/dms-greeter || exit 1
+
+        ${concatMapStringsSep "\n" (f: ''
+          if [[ -f "${f}" ]]; then
+            cp "${f}" . || true
+          fi
+        '') allConfigFiles}
+
+        # Handle session.json wallpaper path
+        if [[ -f session.json ]]; then
+          if wallpaper=$(${getExe pkgs.jq} -r '.wallpaperPath' session.json 2>/dev/null); then
+            if [[ -f "$wallpaper" ]]; then
+              cp "$wallpaper" wallpaper.jpg || true
+              mv session.json session.orig.json
+              ${getExe pkgs.jq} '.wallpaperPath = "/var/lib/dms-greeter/wallpaper.jpg"' \
+                session.orig.json > session.json || true
+            fi
+          fi
+        fi
+
+        # Rename colors file if it exists
+        [[ -f dms-colors.json ]] && mv dms-colors.json colors.json || true
+
+        # Fix ownership of all files
+        chown -R "dms-greeter:dms-greeter" . || true
+      '';
+
+    users.groups.dms-greeter = { };
+    users.users.dms-greeter = {
+      description = "DankMaterialShell greeter user";
+      isSystemUser = true;
+      home = "/var/lib/dms-greeter";
+      homeMode = "0750";
+      createHome = true;
+      group = "dms-greeter";
+      extraGroups = [ "video" ];
+    };
+
+    security.pam.services.dms-greeter = { };
+
+    hardware.graphics.enable = mkDefault true;
+    services.libinput.enable = mkDefault true;
+  };
+
+  meta.maintainers = with lib.maintainers; [ luckshiba ];
+}