Support TexturePacker image atlases

test/runtime/resources/game_resource_manager_test.dart

@@ -1,6 +1,7 @@
 import 'dart:async' as async;
 import 'dart:io';
 import 'dart:typed_data';
+import 'dart:ui' show Rect;
 
 import 'package:flame_lua_runtime/runtime/diagnostics/runtime_diagnostics.dart';
 import 'package:flame_lua_runtime/runtime/packages/game_package.dart';
@@ -61,6 +62,19 @@ void main() {
       },
     );
 
+    test('loads TexturePacker atlas frames for image resources', () async {
+      final resources = GameResourceManager();
+      final package = await _createTextureAtlasPackage('texture_atlas');
+
+      await resources.mount(package);
+
+      final idle = resources.textureFrame('ui', 'button_idle.png');
+      final pressed = resources.textureFrame('ui', 'button_pressed.png');
+      expect(idle?.rect, Rect.fromLTWH(2, 3, 40, 20));
+      expect(pressed?.rect, Rect.fromLTWH(44, 3, 40, 20));
+      expect(resources.textureFrame('ui', 'missing.png'), isNull);
+    });
+
     test('exports image debug json and evicts failed records', () async {
       final resources = GameResourceManager();
       final package = await _createPackage('debug_json');
@@ -332,6 +346,83 @@ Future<GamePackage> _createPackage(
   );
 }
 
+Future<GamePackage> _createTextureAtlasPackage(String name) async {
+  final root = await Directory.systemTemp.createTemp('resource_${name}_');
+  Directory('${root.path}/assets').createSync(recursive: true);
+  File('${root.path}/assets/ui.png').writeAsBytesSync(_pngBytes);
+  File('${root.path}/assets/ui.json').writeAsStringSync('''
+{
+  "frames": {
+    "button_idle.png": {
+      "frame": { "x": 2, "y": 3, "w": 40, "h": 20 },
+      "rotated": false,
+      "trimmed": false
+    }
+  }
+}
+''');
+
+  addTearDown(() {
+    if (root.existsSync()) {
+      root.deleteSync(recursive: true);
+    }
+  });
+
+  final hashAtlas = RuntimeTextureAtlas.fromJsonString(
+    File('${root.path}/assets/ui.json').readAsStringSync(),
+  );
+  expect(hashAtlas.frames['button_idle.png']?.rect, Rect.fromLTWH(2, 3, 40, 20));
+  final arrayAtlas = RuntimeTextureAtlas.fromJsonString('''
+{
+  "frames": [
+    {
+      "filename": "button_pressed.png",
+      "frame": { "x": 44, "y": 3, "w": 40, "h": 20 },
+      "rotated": false,
+      "trimmed": false
+    }
+  ]
+}
+''');
+  final mergedAtlas = '''
+{
+  "frames": {
+    "button_idle.png": {
+      "frame": { "x": 2, "y": 3, "w": 40, "h": 20 },
+      "rotated": false,
+      "trimmed": false
+    },
+    "button_pressed.png": {
+      "frame": { "x": ${arrayAtlas.frames['button_pressed.png']!.x}, "y": 3, "w": 40, "h": 20 },
+      "rotated": false,
+      "trimmed": false
+    }
+  }
+}
+''';
+  File('${root.path}/assets/ui.json').writeAsStringSync(mergedAtlas);
+
+  return GamePackage.file(
+    rootPath: root.path,
+    manifest: GamePackageManifest(
+      gameId: 'test',
+      name: 'Test',
+      version: '0.1.0',
+      runtimeApiVersion: 1,
+      entry: 'scripts/main.lua',
+      assetsBase: 'assets',
+      resources: const {
+        'ui': GameResource(
+          type: GameResourceType.image,
+          path: 'assets/ui.png',
+          atlas: 'assets/ui.json',
+          preload: GameResourcePreload.lazy,
+        ),
+      },
+    ),
+  );
+}
+
 Future<GamePackage> _createMultiImagePackage(String name) async {
   final root = await Directory.systemTemp.createTemp('resource_${name}_');
   Directory('${root.path}/assets').createSync(recursive: true);