feat(nixos): add support for sddm (#168)

modules/nixos/sddm.nix

@@ -0,0 +1,51 @@
+{ lib
+, pkgs
+, config
+, ...
+}:
+let
+  cfg = config.services.displayManager.sddm.catppuccin;
+  enable = cfg.enable && config.services.displayManager.sddm.enable;
+
+  inherit (lib) mkIf ctp types mkOption;
+in
+{
+  options.services.displayManager.sddm.catppuccin =
+    ctp.mkCatppuccinOpt "sddm"
+    // {
+      font = mkOption {
+        type = types.str;
+        default = "Noto Sans";
+        description = "Font to use for the login screen";
+      };
+
+      fontSize = mkOption {
+        type = types.str;
+        default = "9";
+        description = "Font size to use for the login screen";
+      };
+
+      background = mkOption {
+        type = with types; (either path str);
+        default = "";
+        description = "Background image to use for the login screen";
+      };
+
+      loginBackground = mkOption {
+        type = types.bool;
+        default = true;
+        description = "Add an additonal background layer to the login panel";
+      };
+    };
+
+  config = mkIf enable {
+    services.displayManager.sddm.theme = "catppuccin-${cfg.flavour}";
+
+    environment.systemPackages = [
+      (pkgs.catppuccin-sddm.override {
+        flavor = cfg.flavour;
+        inherit (cfg) font fontSize background loginBackground;
+      })
+    ];
+  };
+}

test.nix

@@ -13,7 +13,6 @@ let
           hash = "sha256-qZjMlZFTzJotOYjURRQMsiOdR2XGGba8XzXwx4+v9tk=";
         };
       };
-
     };
   };
 
@@ -32,6 +31,11 @@ testers.runNixOSTest {
 
     boot.loader.grub = enable;
 
+    services = {
+      displayManager.sddm = enable;
+      xserver.enable = true; # required for sddm
+    };
+
     console = enable;
 
     programs.dconf = enable; # required for gtk