From 2df9437b391494770608bb0f1c3adec74b12a0bb Mon Sep 17 00:00:00 2001
From: Parthiv Seetharaman <parthivs@myrdd.info>
Date: Mon, 6 Oct 2025 08:42:36 -0400
Subject: [PATCH] add nixos support for greeter (#298)

* add nixos support for greeter

* fix greeter config file access

* fix wallpaper perms and allow for adding extra compositor config

* fix greeter config files ownership

* set default for compositor.extraConfig

* update option docs about copying instead of symlinking

* explain configHome in doc further

* add nixos option to redirect greeter logs

* prevent possible errors in greetd preStart
---
 Modules/Greetd/README.md |   4 +-
 flake.nix                |  18 ++++--
 nix/greeter.nix          | 127 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 142 insertions(+), 7 deletions(-)
 create mode 100644 nix/greeter.nix

diff --git a/Modules/Greetd/README.md b/Modules/Greetd/README.md
index a36867cc..095aff45 100644
--- a/Modules/Greetd/README.md
+++ b/Modules/Greetd/README.md
@@ -59,8 +59,8 @@ Enable the greeter with this in your NixOS config:
 ```nix
 programs.dankMaterialShell.greeter = {
   enable = true;
-  compositor = "niri"; # or set to hyprland
-  configHome = "/home/user"; # optionally symlinks that users DMS settings to the greeters data directory
+  compositor.name = "niri"; # or set to hyprland
+  configHome = "/home/user"; # optionally copyies that users DMS settings (and wallpaper if set) to the greeters data directory as root before greeter starts
 };
 ```
 
diff --git a/flake.nix b/flake.nix
index 31e1b78b..f453aa93 100644
--- a/flake.nix
+++ b/flake.nix
@@ -29,6 +29,11 @@
             nixpkgs.lib.genAttrs
             ["aarch64-darwin" "aarch64-linux" "x86_64-darwin" "x86_64-linux"]
             (system: fn system nixpkgs.legacyPackages.${system});
+        buildDmsPkgs = pkgs: {
+            dmsCli = dms-cli.packages.${pkgs.system}.default;
+            dgop = dgop.packages.${pkgs.system}.dgop;
+            dankMaterialShell = self.packages.${pkgs.system}.dankMaterialShell;
+        };
     in {
         formatter = forEachSystem (_: pkgs: pkgs.alejandra);
 
@@ -49,16 +54,19 @@
         });
 
         homeModules.dankMaterialShell.default = {pkgs, ...}: let
-            dmsPkgs = {
-                dmsCli = dms-cli.packages.${pkgs.system}.default;
-                dgop = dgop.packages.${pkgs.system}.dgop;
-                dankMaterialShell = self.packages.${pkgs.system}.dankMaterialShell;
-            };
+            dmsPkgs = buildDmsPkgs pkgs;
         in {
             imports = [./nix/default.nix];
             _module.args.dmsPkgs = dmsPkgs;
         };
 
         homeModules.dankMaterialShell.niri = import ./nix/niri.nix;
+
+        nixosModules.greeter = {pkgs, ...}: let
+            dmsPkgs = buildDmsPkgs pkgs;
+        in {
+            imports = [./nix/greeter.nix];
+            _module.args.dmsPkgs = dmsPkgs;
+        };
     };
 }
diff --git a/nix/greeter.nix b/nix/greeter.nix
new file mode 100644
index 00000000..13c76383
--- /dev/null
+++ b/nix/greeter.nix
@@ -0,0 +1,127 @@
+{
+    lib,
+    config,
+    pkgs,
+    dmsPkgs,
+    ...
+}: let
+    inherit (lib) types;
+    cfg = config.programs.dankMaterialShell.greeter;
+
+    user = config.services.greetd.settings.default_session.user;
+
+    buildCompositorConfig = conf: pkgs.writeText "dmsgreeter-compositor-config" ''
+        ${(lib.replaceString "_DMS_PATH_" "${dmsPkgs.dankMaterialShell}/etc/xdg/quickshell/dms" (lib.fileContents conf))}
+        ${cfg.compositor.extraConfig}
+    '';
+
+    sessionCommands = {
+        niri = ''
+            export PATH=$PATH:${lib.makeBinPath [ config.programs.niri.package ]}
+            niri -c ${buildCompositorConfig ../Modules/Greetd/assets/dms-niri.kdl} \
+        '';
+        hyprland = ''
+            export PATH=$PATH:${lib.makeBinPath [ config.programs.hyprland.package ]}
+            hyprland -c ${buildCompositorConfig ../Modules/Greetd/assets/dms-niri.kdl} \
+        '';
+    };
+
+    greeterScript = pkgs.writeShellScriptBin "dms-greeter" ''
+        export QT_QPA_PLATFORM=wayland
+        export XDG_SESSION_TYPE=wayland
+        export QT_WAYLAND_DISABLE_WINDOWDECORATION=1
+        export EGL_PLATFORM=gbm
+        export DMS_GREET_CFG_DIR="/var/lib/dmsgreeter/"
+        export PATH=$PATH:${lib.makeBinPath [ cfg.quickshell.package ]}
+        ${sessionCommands.${cfg.compositor.name}} ${lib.optionalString cfg.logs.save "> ${cfg.logs.path} 2>&1"}
+    '';
+in {
+    options.programs.dankMaterialShell.greeter = {
+        enable = lib.mkEnableOption "DankMaterialShell greeter";
+        compositor.name = lib.mkOption {
+            type = types.enum ["niri" "hyprland"];
+            description = "Compositor to run greeter in";
+        };
+        compositor.extraConfig = lib.mkOption {
+            type = types.lines;
+            default = "";
+            description = "Exra compositor config to include";
+        };
+        configFiles = lib.mkOption {
+            type = types.listOf types.path;
+            default = [];
+            description = "Config files to copy into data directory";
+            example = [
+                "/home/user/.config/DankMaterialShell/settings.json"
+            ];
+        };
+        configHome = lib.mkOption {
+            type = types.nullOr types.str;
+            default = null;
+            example = "/home/user";
+            description = ''
+                User home directory to copy configurations for greeter
+                If DMS config files are in non-standard locations then use the configFiles option instead
+            '';
+        };
+        quickshell = {
+            package = lib.mkPackageOption pkgs "quickshell" {};
+        };
+        logs.save = lib.mkEnableOption "saving logs from DMS greeter to file";
+        logs.path = lib.mkOption {
+            type = types.path;
+            default = "/tmp/dms-greeter.log";
+            description = ''
+                File path to save DMS greeter logs to
+            '';
+        };
+    };
+    config = lib.mkIf cfg.enable {
+        assertions = [
+            {
+                assertion = (config.users.users.${user} or { }) != { };
+                message = ''
+                    dmsgreeter: user set for greetd default_session ${user} does not exist. Please create it before referencing it.
+                '';
+            }
+        ];
+        services.greetd = {
+            enable = lib.mkDefault true;
+            settings.default_session.command = lib.mkDefault (lib.getExe greeterScript);
+        };
+        fonts.packages = with pkgs; [
+            fira-code
+            inter
+            material-symbols
+        ];
+        systemd.tmpfiles.settings."10-dmsgreeter" = {
+            "/var/lib/dmsgreeter".d = {
+                user = user;
+                group = if config.users.users.${user}.group != ""
+                    then config.users.users.${user}.group else "greeter";
+                mode = "0755";
+            };
+        };
+        systemd.services.greetd.preStart = ''
+            cd /var/lib/dmsgreeter
+            ${lib.concatStringsSep "\n" (lib.map (f: ''
+                if [ -f "${f}" ]; then
+                    cp "${f}" .
+                fi
+            '') cfg.configFiles)}
+
+            if [ -f session.json ]; then
+                if cp "$(${lib.getExe pkgs.jq} -r '.wallpaperPath' session.json)" wallpaper.jpg; then
+                    mv session.json session.orig.json
+                    ${lib.getExe pkgs.jq} '.wallpaperPath = "/var/lib/dmsgreeter/wallpaper.jpg"' session.orig.json > session.json
+                fi
+            fi
+            chown ${user}: *
+        '';
+        programs.dankMaterialShell.greeter.configFiles = lib.mkIf (cfg.configHome != null) [
+            "${cfg.configHome}/.config/DankMaterialShell/settings.json"
+            "${cfg.configHome}/.local/state/DankMaterialShell/session.json"
+            "${cfg.configHome}/.cache/quickshell/dankshell/dms-colors.json"
+        ];
+    };
+}