feat: Add Transform2D.setFrom and Transform2D.clone (#1495)

examples/lib/stories/input/joystick_advanced_example.dart

@@ -11,7 +11,7 @@ import 'package:flutter/material.dart';
 import 'joystick_player.dart';
 
 class JoystickAdvancedExample extends FlameGame
-    with HasDraggables, HasTappables {
+    with HasDraggables, HasTappables, HasCollisionDetection {
   static const String description = '''
     In this example we showcase how to use the joystick by creating 
     `SpriteComponent`s that serve as the joystick's knob and background.
@@ -35,6 +35,7 @@ class JoystickAdvancedExample extends FlameGame
       columns: 6,
       rows: 1,
     );
+    add(ScreenHitbox());
     joystick = JoystickComponent(
       knob: SpriteComponent(
         sprite: sheet.getSpriteById(1),

examples/lib/stories/input/joystick_player.dart

@@ -1,29 +1,45 @@
+import 'package:flame/collisions.dart';
 import 'package:flame/components.dart';
+import 'package:flame/game.dart';
 
-class JoystickPlayer extends SpriteComponent with HasGameRef {
+class JoystickPlayer extends SpriteComponent
+    with HasGameRef, CollisionCallbacks {
   /// Pixels/s
   double maxSpeed = 300.0;
+  late final Vector2 _lastSize = size.clone();
+  late final Transform2D _lastTransform = transform.clone();
 
   final JoystickComponent joystick;
 
   JoystickPlayer(this.joystick)
-      : super(
+      : super(size: Vector2.all(100.0), anchor: Anchor.center);
-          size: Vector2.all(100.0),
-        ) {
-    anchor = Anchor.center;
-  }
 
   @override
   Future<void> onLoad() async {
     sprite = await gameRef.loadSprite('layers/player.png');
     position = gameRef.size / 2;
+    add(RectangleHitbox()..debugMode = true);
   }
 
   @override
   void update(double dt) {
-    if (!joystick.delta.isZero()) {
+    if (!joystick.delta.isZero() && activeCollisions.isEmpty) {
+      _lastSize.setFrom(size);
+      _lastTransform.setFrom(transform);
       position.add(joystick.relativeDelta * maxSpeed * dt);
       angle = joystick.delta.screenAngle();
     }
   }
+
+  @override
+  void onCollisionStart(Set<Vector2> _, PositionComponent __) {
+    super.onCollisionStart(_, __);
+    transform.setFrom(_lastTransform);
+    size.setFrom(_lastSize);
+  }
+
+  @override
+  void onCollisionEnd(PositionComponent __) {
+    super.onCollisionEnd(__);
+  }
 }

packages/flame/lib/src/game/transform2d.dart

@@ -1,6 +1,8 @@
 import 'dart:math' as math;
+
 import 'package:flutter/foundation.dart';
 import 'package:vector_math/vector_math_64.dart';
+
 import 'notifying_vector2.dart';
 
 /// This class describes a generic 2D transform, which is a combination of
@@ -53,6 +55,17 @@ class Transform2D extends ChangeNotifier {
     ..scale = other.scale
     ..offset = other.offset;
 
+  /// Clone of this.
+  Transform2D clone() => Transform2D.copy(this);
+
+  /// Set this to the values of the [other] [Transform2D].
+  void setFrom(Transform2D other) {
+    angle = other.angle;
+    position = other.position;
+    scale = other.scale;
+    offset = other.offset;
+  }
+
   /// Check whether this transform is equal to [other], up to the given
   /// [tolerance]. Setting tolerance to zero will check for exact equality.
   /// Transforms are considered equal if their rotation angles are the same