feat(users): configure sessions in GDM

hosts/fennecBox/configuration.nix

@@ -113,14 +113,6 @@
     "nix-command"
   ];
 
-  # Enable the GNOME Desktop Environment.
-  services.displayManager.gdm.enable = true;
-  services.desktopManager.gnome.enable = true;
-  programs.hyprland = {
-    enable = true;
-    withUWSM = true;
-    systemd.setPath.enable = true;
-  };
   services.userborn.enable = true;
 
   # Configure keymap in X11

users/Sk7Str1p3/about.json

@@ -5,6 +5,7 @@
 	],
 	"shell": "nushell",
 	"realName": "ENC[AES256_GCM,data:KBIRbQWsz6n1nAZ2rtGfCdSoQiTrRchpqA==,iv:mD0Rx4GHSJcQhPCa4fxZgYgqYkwzaRQVe50I+bgML04=,tag:ZcrOoRAVOoUKPktL5Dpi/g==,type:str]",
+	"session": "co:niri",
 	"sops": {
 		"age": [
 			{
@@ -12,8 +13,8 @@
 				"enc": "-----BEGIN AGE ENCRYPTED FILE-----\nYWdlLWVuY3J5cHRpb24ub3JnL3YxCi0+IFgyNTUxOSB2Skp6cGdweFBaZUM2eXRC\nTHExSmtCZU53OXZWZDl3VFFMb1FSdFhkaUhnCnhiSUNQSkZZQ2htTTVxd1Nleitq\nSVV4WmFrdXNUVVU5L0RONHpMUlB2UDgKLS0tIE9UTC9qeEQ0MFlSUFhwdW9NeXYw\nelVGZ0ZYUzFoVXdibmpjTyt1ZHYxaTgKnD3m3Ceq0OT27s2OAWF+gLh5f6Xv3cpp\n28Q3JLG+FpYlBaszOdsWInouCf50tYItWHhQU3gmkhrJsA9gljOAOw==\n-----END AGE ENCRYPTED FILE-----\n"
 			}
 		],
-		"lastmodified": "2026-05-02T21:33:32Z",
-		"mac": "ENC[AES256_GCM,data:sqPuXb7Dnr9jOULMIeILhQUbj0WUdE+aQrRiyMok0GlfKDRoIM0SIxG8gKBnnZbzbd5wBu4Hf+HzbBj4RfkfAOQDXMdqR95teSIj4l1a8is/VOllLY/5iC1zTg2ShKsq2VbQJ2c9EG6QYKZABp504+XG0urGIrNgrnqyMwT3/sY=,iv:fwhLVEShUiLNolcg1LBesWupVlh4oCHtyXfFsjqYRqQ=,tag:sKbwSa7nhrRdtzV30FDOQw==,type:str]",
+		"lastmodified": "2026-05-07T15:31:42Z",
+		"mac": "ENC[AES256_GCM,data:ouXlr7xwQj05RtKc1VKByybKSuXtLk9UXxnE7JSofmVdXzPc7k4atejrWyrWa6weJonpPMldnuyXBiy2RzIHLF8nyvbyCik8o5r4pJ7LlgCHvxM5B2itN/nWCR8Ave9ijBrMk1HQLE4wodUstehnigwkmfMn6phsQEnWY9vYV2c=,iv:vX1/zN+RUDvJnrnMC/KFDKRkWJdFNd12MdH32Y4nNlY=,tag:3aP34p6oaAX8luIUc7eilA==,type:str]",
 		"encrypted_regex": "^realName$",
 		"version": "3.12.1"
 	}

users/default.nix

@@ -7,6 +7,11 @@
   - `realName`: User's real name  (optionally)
   - `extraGroups`: groups (optionally)
   - `shell`: User's shell
+  - `session`: User's default graphical session (optionally)
+
+  Session must have format of "{type}:{session}" where type is one of `co` (short for "compositor") and `de` (short for "desktop environment").
+  This `type` is actually important, because it depends where nix will search corresponding option for enabling your session.
+  If `co`, it will search it in `programs.*`, and if `de`, in `services.desktopManager.*`
 
   User's face (optionally)
     - if any, should be located at users/{user}/face.png
@@ -69,4 +74,52 @@
       }) cfg.usersList
     )
   };
+
+  # Configure DM and users' default sessions
+  services.displayManager.gdm.enable = true;
+  systemd.tmpfiles.settings."20-gdm-default-session" = lib.mkMerge (
+    map (user: {
+      "/run/tmpfiles/var/lib/AccountsService/users/${user}".f = {
+        argument = "${lib.generators.toINI { } {
+          User = {
+            Session = builtins.toString (
+              builtins.tail (
+                lib.splitString ":" (builtins.fromJSON (builtins.readFile ./${user}/about.json)).session
+              )
+            );
+            SystemAccount = false;
           }
+          // (
+            let
+              pic = ./${user}/face.png;
+            in
+            if builtins.pathExists pic then { Icon = "${pic}"; } else { }
+          );
+        }}";
+      };
+      "/var/lib/AccountsService/users/${user}"."L+" = {
+        argument = "/run/tmpfiles/var/lib/AccountsService/users/${user}";
+      };
+    }) cfg.usersList
+  );
+}
+// (lib.foldl (acc: elem: acc // elem) { } (
+  map (
+    user:
+    let
+      __session = lib.splitString ":" (builtins.fromJSON (builtins.readFile ./${user}/about.json))
+      .session;
+      sessionType = (builtins.head __session);
+      session = builtins.toString (builtins.tail __session);
+    in
+    assert sessionType == "co" || sessionType == "de";
+    if sessionType == "co" then
+      {
+        programs.${session}.enable = true;
+      }
+    else if sessionType == "de" then
+      { services.desktopManager.${session}.enable = true; }
+    else
+      { }
+  ) cfg.usersList
+))