tools : can reorganize the level tree using folders

samples/core/editors/level_editor/level_editor.lua

@@ -244,7 +244,9 @@ end
 
 function Selection:clear()
 	for k, v in pairs(self._ids) do
-		LevelEditor._objects[v]:on_selected(false)
+		if LevelEditor._objects[v] ~= nil then
+			LevelEditor._objects[v]:on_selected(false)
+		end
 	end
 	self._ids = {}
 end
@@ -285,7 +287,9 @@ end
 function Selection:set(ids)
 	self:clear()
 	for k, v in pairs(ids) do
-		LevelEditor._objects[v]:on_selected(true)
+		if LevelEditor._objects[v] ~= nil then
+			LevelEditor._objects[v]:on_selected(true)
+		end		
 	end
 	self._ids = ids
 end

tools/core/guid.vala

@@ -13,23 +13,34 @@ public struct Guid
 
 	public static Guid new_guid()
 	{
-		// FIXME: Replace Rand with something better.
-		Rand rnd = new Rand();
-		uint64 a = rnd.next_int();
-		uint64 b = rnd.next_int();
-		uint64 c = rnd.next_int();
-		uint64 d = rnd.next_int();
+		Guid new_guid = { 0, 0 }; 
 
-		uint64 d1;
-		d1  = a << 32;
-		d1 |= b <<  0;
-		uint64 d2;
-		d2  = c << 32;
-		d2 |= d <<  0;
+		do
+			{
+				// FIXME: Replace Rand with something better.
+				Rand rnd = new Rand();
+				uint64 a = rnd.next_int();
+				uint64 b = rnd.next_int();
+				uint64 c = rnd.next_int();
+				uint64 d = rnd.next_int();
+
+				uint64 d1;
+				d1  = a << 32;
+				d1 |= b <<  0;
+				uint64 d2;
+				d2  = c << 32;
+				d2 |= d <<  0;
+
+				d1 = (d1 & 0xffffffffffff4fffu) | 0x4000u;
+				d2 = (d2 & 0x3fffffffffffffffu) | 0x8000000000000000u;
+
+				new_guid = { d1, d2 };
+		} 
+		while (new_guid == GUID_NONE_FOLDER 
+			|| new_guid == GUID_UNIT_FOLDER
+			|| new_guid == GUID_SOUND_FOLDER);
 
-		d1 = (d1 & 0xffffffffffff4fffu) | 0x4000u;
-		d2 = (d2 & 0x3fffffffffffffffu) | 0x8000000000000000u;
-		return { d1, d2 };
+		return new_guid;
 	}
 
 	public static Guid parse(string guid)

tools/level_editor/level.vala

@@ -2,14 +2,28 @@
  * Copyright (c) 2012-2025 Daniele Bartolini et al.
  * SPDX-License-Identifier: GPL-3.0-or-later
  */
-
 using Gee;
 
 namespace Crown
 {
 /// Manages objects in a level.
 public class Level
 {
+	public class Folder
+	{
+		public Guid id { get; set; } 
+		public string name { get; set; }
+		public Guid parent_id { get; set; }
+
+		// Constructor
+		public Folder(Guid id, string name, Guid parent_id = GUID_ZERO)
+		{
+			this.id = id;
+			this.name = name;
+			this.parent_id = parent_id;
+		}
+	}
+
 	public Project _project;
 
 	// Engine connections
@@ -31,13 +45,17 @@ public class Level
 	public double _camera_orthographic_size;
 	public double _camera_target_distance;
 	public CameraViewType _camera_view_type;
+	public Gee.ArrayList<Folder> _folders;
 
 	// Signals
 	public signal void selection_changed(Gee.ArrayList<Guid?> selection);
 	public signal void object_editor_name_changed(Guid object_id, string name);
+	public signal void level_loaded();
 
 	public Level(Database db, RuntimeInstance runtime, Project project)
 	{
+		_folders = new Gee.ArrayList<Folder>();
+
 		_project = project;
 
 		// Engine connections
@@ -89,6 +107,7 @@ public class Level
 		camera_decode();
 		GLib.Application.get_default().activate_action("camera-view", new GLib.Variant.int32(_camera_view_type));
 
+
 		_name = name;
 		_path = path;
 
@@ -103,19 +122,94 @@ public class Level
 		// FIXME: hack to keep the LevelTreeView working.
 		_db.key_changed(_id, "units");
 
+		load_folders();
+
+		level_loaded();
+
 		return 0;
 	}
+	public void load_folders() {
+		_folders.clear();
+
+		HashSet<Guid?> folder_ids = _db.get_property_set(_id, "folders", new HashSet<Guid?>());
+		bool needToSave = false;
+
+		foreach (var root_info in get_root_folder_info()) {
+			needToSave |= ensure_root_folder(folder_ids, root_info.guid, root_info.name, root_info.object_type);
+		}
 
+		if (_path != null && needToSave) {
+			_db.save(_path, _id);
+		}
+
+		foreach (Guid folder_id in folder_ids) {
+			_folders.add(load_or_create_folder(folder_id));
+		}
+	}
+
+	private bool ensure_root_folder(HashSet<Guid?> folder_ids, Guid folder_id, string name, string type) {
+		if (!folder_ids.contains(folder_id)) {
+			if (_path != null) {
+				add_folder(folder_id, name, type, GUID_ZERO);
+			}
+			folder_ids.add(folder_id);
+			return true;
+		}
+		return false;
+	}
+
+	private Folder load_or_create_folder(Guid folder_id) {
+		if (_db.has_object(folder_id)) {
+			return new Folder(
+				folder_id,
+				_db.get_property_string(folder_id, "editor.name"),
+				_db.get_property_guid(folder_id, "parent_folder")
+			);
+		} else {
+			foreach (var root_info in get_root_folder_info()) {
+				if (folder_id == root_info.guid) {
+					// TODO AVOID THIS TO PREVENT "NEED TO SAVE TRIGGER" , but for now its needed to fix crash at Value? item_type = view_i.db.get_property(guid, "_type"); from on_drag_data_get_internal
+					_db.create(folder_id,root_info.object_type);
+					_db.set_property(folder_id, "editor.name", root_info.name);
+					_db.set_property(folder_id, "parent_folder", GUID_ZERO);
+					_db.set_property(folder_id, "_type", root_info.object_type);
+					return new Folder(folder_id, root_info.name, GUID_ZERO);
+				}
+			}
+			print("ERROR: Unknown Folder ID - %s", folder_id.to_string());
+			return null;
+		}
+	}
+
 	public void save(string name)
 	{
 		string path = Path.build_filename(_project.source_dir(), name + ".level");
 
+		save_folders();
+
 		camera_encode();
 		_db.save(path, _id);
 		_path = path;
 		_name = name;
 	}
 
+    public void save_folders()
+    {
+        foreach (Folder folder in _folders) {
+            _db.set_property_string(folder.id, "editor.name", folder.name);
+            _db.set_property_guid(folder.id, "parent_folder", folder.parent_id);
+            _db.add_to_set(_id, "folders", folder.id);
+        }
+    }
+	public void add_folder(Guid id, string name, string type, Guid parent_id = GUID_ZERO)
+	{
+		_db.create(id, type);
+		_db.set_property_string(id, "editor.name", name);
+		_db.set_property_guid(id, "parent_folder", parent_id);
+		_db.add_to_set(_id, "folders", id);
+		_folders.add(new Folder(id, name, parent_id));
+	}
+
 	public void spawn_empty_unit()
 	{
 		Guid id = Guid.new_guid();
@@ -176,14 +270,16 @@ public class Level
 		selection_set(ids);
 	}
 
-	public void on_unit_spawned(Guid id, string? name, Vector3 pos, Quaternion rot, Vector3 scl)
-	{
-		Unit unit = Unit(_db, id);
-		unit.create(name, pos, rot, scl);
-
-		_db.set_property_string(id, "editor.name", "unit_%04u".printf(_num_units++));
-		_db.add_to_set(_id, "units", id);
-	}
+    public void on_unit_spawned(Guid id, string? name, Vector3 pos, Quaternion rot, Vector3 scl)
+    {
+        Unit unit = Unit(_db, id);
+        unit.create(name, pos, rot, scl);
+
+        _db.set_property_string(id, "editor.name", "unit_%04u".printf(_num_units++));
+        _db.add_to_set(_id, "units", id);
+
+		_db.set_property_guid(id, "parent_folder", GUID_UNIT_FOLDER);
+    }
 
 	public void on_sound_spawned(Guid id, string name, Vector3 pos, Quaternion rot, Vector3 scl, double range, double volume, bool loop)
 	{
@@ -192,6 +288,8 @@ public class Level
 
 		_db.set_property_string    (id, "editor.name", "sound_%04u".printf(_num_sounds++));
 		_db.add_to_set(_id, "sounds", id);
+
+		_db.set_property_guid(id, "parent_folder", GUID_SOUND_FOLDER);
 	}
 
 	public void on_move_objects(Guid?[] ids, Vector3[] positions, Quaternion[] rotations, Vector3[] scales)