feat: Added transform to Rect (#1360)

packages/flame/lib/src/extensions/rect.dart

@@ -3,6 +3,7 @@ import 'dart:math' as math;
 import 'dart:ui';
 
 import '../../geometry.dart';
+import 'matrix4.dart';
 import 'offset.dart';
 import 'size.dart';
 import 'vector2.dart';
@@ -52,6 +53,31 @@ extension RectExtension on Rect {
     ];
   }
 
+  /// Transform Rect using the transformation defined by [matrix].
+  ///
+  /// **Note:** Rotation matrices will increase the size of the [Rect] but they
+  /// will not rotate it as [Rect] does not have any rotational values.
+  ///
+  /// **Note:** Only non-negative scale transforms are allowed, if a negative
+  /// scale is applied it will return a zero-based [Rect].
+  ///
+  /// **Note:** The transformation will always happen from the center of the
+  /// `Rect`.
+  Rect transform(Matrix4 matrix) {
+    // For performance reasons we are using the same logic from
+    // `Matrix4.transform2` but without the extra overhead of creating vectors.
+    return Rect.fromLTRB(
+      (topLeft.dx * matrix.m11) + (topLeft.dy * matrix.m21) + matrix.m41,
+      (topLeft.dx * matrix.m12) + (topLeft.dy * matrix.m22) + matrix.m42,
+      (bottomRight.dx * matrix.m11) +
+          (bottomRight.dy * matrix.m21) +
+          matrix.m41,
+      (bottomRight.dx * matrix.m12) +
+          (bottomRight.dy * matrix.m22) +
+          matrix.m42,
+    );
+  }
+
   /// Creates bounds in from of a [Rect] from a list of [Vector2]
   static Rect fromBounds(List<Vector2> pts) {
     final minX = pts.map((e) => e.x).reduce(min);

packages/flame/test/extensions/rect_test.dart

@@ -1,6 +1,7 @@
 import 'dart:math' as math;
 
 import 'package:flame/extensions.dart';
+import 'package:flame_test/flame_test.dart';
 import 'package:test/test.dart';
 
 void main() {
@@ -36,5 +37,14 @@ void main() {
       expect(r2.position.x, r1.left);
       expect(r2.position.y, r1.top);
     });
+
+    test('test transform', () {
+      final matrix4 = Matrix4.translation(Vector3(10, 10, 0));
+      const input = Rect.fromLTWH(0, 0, 10, 10);
+      final result = input.transform(matrix4);
+
+      expect(result.topLeft.toVector2(), closeToVector(10, 10));
+      expect(result.bottomRight.toVector2(), closeToVector(20, 20));
+    });
   });
 }