refactor: moved scaling logic to `BallScalingBehavior` (#313)

packages/pinball_components/lib/src/components/ball/ball.dart

@@ -1,11 +1,11 @@
 import 'dart:async';
 import 'dart:math' as math;
-import 'dart:ui';
 
 import 'package:flame/components.dart';
 import 'package:flame_forge2d/flame_forge2d.dart';
 import 'package:flutter/widgets.dart';
 import 'package:pinball_components/pinball_components.dart';
+import 'package:pinball_components/src/components/ball/behaviors/ball_scaling_behavior.dart';
 import 'package:pinball_flame/pinball_flame.dart';
 
 /// {@template ball}
@@ -20,6 +20,7 @@ class Ball<T extends Forge2DGame> extends BodyComponent<T>
           renderBody: false,
           children: [
             _BallSpriteComponent()..tint(baseColor.withOpacity(0.5)),
+            BallScalingBehavior(),
           ],
         ) {
     // TODO(ruimiguel): while developing Ball can be launched by clicking mouse,
@@ -30,6 +31,15 @@ class Ball<T extends Forge2DGame> extends BodyComponent<T>
     layer = Layer.board;
   }
 
+  /// Creates a [Ball] without any behaviors.
+  ///
+  /// This can be used for testing [Ball]'s behaviors in isolation.
+  @visibleForTesting
+  Ball.test({required this.baseColor})
+      : super(
+          children: [_BallSpriteComponent()],
+        );
+
   /// The size of the [Ball].
   static final Vector2 size = Vector2.all(4.13);
 
@@ -81,26 +91,9 @@ class Ball<T extends Forge2DGame> extends BodyComponent<T>
   void update(double dt) {
     super.update(dt);
 
-    _rescaleSize();
     _setPositionalGravity();
   }
 
-  void _rescaleSize() {
-    final boardHeight = BoardDimensions.bounds.height;
-    const maxShrinkValue = BoardDimensions.perspectiveShrinkFactor;
-
-    final standardizedYPosition = body.position.y + (boardHeight / 2);
-
-    final scaleFactor = maxShrinkValue +
-        ((standardizedYPosition / boardHeight) * (1 - maxShrinkValue));
-
-    body.fixtures.first.shape.radius = (size.x / 2) * scaleFactor;
-
-    // TODO(alestiago): Revisit and see if there's a better way to do this.
-    final spriteComponent = firstChild<_BallSpriteComponent>();
-    spriteComponent?.scale = Vector2.all(scaleFactor);
-  }
-
   void _setPositionalGravity() {
     final defaultGravity = gameRef.world.gravity.y;
     final maxXDeviationFromCenter = BoardDimensions.bounds.width / 2;

packages/pinball_components/lib/src/components/ball/behaviors/ball_scaling_behavior.dart

@@ -0,0 +1,24 @@
+import 'package:flame/components.dart';
+import 'package:pinball_components/pinball_components.dart';
+import 'package:pinball_flame/pinball_flame.dart';
+
+/// Scales the ball's body and sprite according to its position on the board.
+class BallScalingBehavior extends Component with ParentIsA<Ball> {
+  @override
+  void update(double dt) {
+    super.update(dt);
+    final boardHeight = BoardDimensions.bounds.height;
+    const maxShrinkValue = BoardDimensions.perspectiveShrinkFactor;
+
+    final standardizedYPosition = parent.body.position.y + (boardHeight / 2);
+    final scaleFactor = maxShrinkValue +
+        ((standardizedYPosition / boardHeight) * (1 - maxShrinkValue));
+
+    parent.body.fixtures.first.shape.radius = (Ball.size.x / 2) * scaleFactor;
+
+    parent.firstChild<SpriteComponent>()!.scale.setValues(
+          scaleFactor,
+          scaleFactor,
+        );
+  }
+}

packages/pinball_components/lib/src/components/ball/behaviors/behaviors.dart

@@ -0,0 +1 @@
+export 'ball_scaling_behavior.dart';

packages/pinball_components/lib/src/components/components.dart

@@ -2,7 +2,7 @@ export 'android_animatronic.dart';
 export 'android_bumper/android_bumper.dart';
 export 'android_spaceship/android_spaceship.dart';
 export 'backboard/backboard.dart';
-export 'ball.dart';
+export 'ball/ball.dart';
 export 'baseboard.dart';
 export 'board_background_sprite_component.dart';
 export 'board_dimensions.dart';

packages/pinball_components/test/src/components/ball/ball_test.dart

@@ -6,18 +6,29 @@ import 'package:flame_test/flame_test.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:pinball_components/pinball_components.dart';
+import 'package:pinball_components/src/components/ball/behaviors/behaviors.dart';
 
-import '../../helpers/helpers.dart';
+import '../../../helpers/helpers.dart';
 
 void main() {
   TestWidgetsFlutterBinding.ensureInitialized();
   final flameTester = FlameTester(TestGame.new);
 
   group('Ball', () {
+    const baseColor = Color(0xFFFFFFFF);
+
+    test(
+      'can be instantiated',
+      () {
+        expect(Ball(baseColor: baseColor), isA<Ball>());
+        expect(Ball.test(baseColor: baseColor), isA<Ball>());
+      },
+    );
+
     flameTester.test(
       'loads correctly',
       (game) async {
-        final ball = Ball(baseColor: Colors.blue);
+        final ball = Ball(baseColor: baseColor);
         await game.ready();
         await game.ensureAdd(ball);
 
@@ -25,11 +36,20 @@ void main() {
       },
     );
 
+    flameTester.test('add a BallScalingBehavior', (game) async {
+      final ball = Ball(baseColor: baseColor);
+      await game.ensureAdd(ball);
+      expect(
+        ball.descendants().whereType<BallScalingBehavior>().length,
+        equals(1),
+      );
+    });
+
     group('body', () {
       flameTester.test(
         'is dynamic',
         (game) async {
-          final ball = Ball(baseColor: Colors.blue);
+          final ball = Ball(baseColor: baseColor);
           await game.ensureAdd(ball);
 
           expect(ball.body.bodyType, equals(BodyType.dynamic));
@@ -38,7 +58,7 @@ void main() {
 
       group('can be moved', () {
         flameTester.test('by its weight', (game) async {
-          final ball = Ball(baseColor: Colors.blue);
+          final ball = Ball(baseColor: baseColor);
           await game.ensureAdd(ball);
 
           game.update(1);
@@ -46,7 +66,7 @@ void main() {
         });
 
         flameTester.test('by applying velocity', (game) async {
-          final ball = Ball(baseColor: Colors.blue);
+          final ball = Ball(baseColor: baseColor);
           await game.ensureAdd(ball);
 
           ball.body.gravityScale = Vector2.zero();
@@ -61,7 +81,7 @@ void main() {
       flameTester.test(
         'exists',
         (game) async {
-          final ball = Ball(baseColor: Colors.blue);
+          final ball = Ball(baseColor: baseColor);
           await game.ensureAdd(ball);
 
           expect(ball.body.fixtures[0], isA<Fixture>());
@@ -71,7 +91,7 @@ void main() {
       flameTester.test(
         'is dense',
         (game) async {
-          final ball = Ball(baseColor: Colors.blue);
+          final ball = Ball(baseColor: baseColor);
           await game.ensureAdd(ball);
 
           final fixture = ball.body.fixtures[0];
@@ -82,7 +102,7 @@ void main() {
       flameTester.test(
         'shape is circular',
         (game) async {
-          final ball = Ball(baseColor: Colors.blue);
+          final ball = Ball(baseColor: baseColor);
           await game.ensureAdd(ball);
 
           final fixture = ball.body.fixtures[0];
@@ -94,7 +114,7 @@ void main() {
       flameTester.test(
         'has Layer.all as default filter maskBits',
         (game) async {
-          final ball = Ball(baseColor: Colors.blue);
+          final ball = Ball(baseColor: baseColor);
           await game.ready();
           await game.ensureAdd(ball);
           await game.ready();
@@ -108,7 +128,7 @@ void main() {
     group('stop', () {
       group("can't be moved", () {
         flameTester.test('by its weight', (game) async {
-          final ball = Ball(baseColor: Colors.blue);
+          final ball = Ball(baseColor: baseColor);
           await game.ensureAdd(ball);
           ball.stop();
 
@@ -116,19 +136,6 @@ void main() {
           expect(ball.body.position, equals(ball.initialPosition));
         });
       });
-
-      // TODO(allisonryan0002): delete or retest this if/when solution is added
-      // to prevent forces on a ball while stopped.
-
-      // flameTester.test('by applying velocity', (game) async {
-      //   final ball = Ball(baseColor: Colors.blue);
-      //   await game.ensureAdd(ball);
-      //   ball.stop();
-
-      //   ball.body.linearVelocity.setValues(10, 10);
-      //   game.update(1);
-      //   expect(ball.body.position, equals(ball.initialPosition));
-      // });
     });
 
     group('resume', () {
@@ -136,7 +143,7 @@ void main() {
         flameTester.test(
           'by its weight when previously stopped',
           (game) async {
-            final ball = Ball(baseColor: Colors.blue);
+            final ball = Ball(baseColor: baseColor);
             await game.ensureAdd(ball);
             ball.stop();
             ball.resume();
@@ -149,7 +156,7 @@ void main() {
         flameTester.test(
           'by applying velocity when previously stopped',
           (game) async {
-            final ball = Ball(baseColor: Colors.blue);
+            final ball = Ball(baseColor: baseColor);
             await game.ensureAdd(ball);
             ball.stop();
             ball.resume();
@@ -165,7 +172,7 @@ void main() {
 
     group('boost', () {
       flameTester.test('applies an impulse to the ball', (game) async {
-        final ball = Ball(baseColor: Colors.blue);
+        final ball = Ball(baseColor: baseColor);
         await game.ensureAdd(ball);
 
         expect(ball.body.linearVelocity, equals(Vector2.zero()));
@@ -176,7 +183,7 @@ void main() {
       });
 
       flameTester.test('adds TurboChargeSpriteAnimation', (game) async {
-        final ball = Ball(baseColor: Colors.blue);
+        final ball = Ball(baseColor: baseColor);
         await game.ensureAdd(ball);
 
         await ball.boost(Vector2.all(10));
@@ -190,7 +197,7 @@ void main() {
 
       flameTester.test('removes TurboChargeSpriteAnimation after it finishes',
           (game) async {
-        final ball = Ball(baseColor: Colors.blue);
+        final ball = Ball(baseColor: baseColor);
         await game.ensureAdd(ball);
 
         await ball.boost(Vector2.all(10));

packages/pinball_components/test/src/components/ball/behaviors/ball_scaling_behavior_test.dart

@@ -0,0 +1,99 @@
+// ignore_for_file: cascade_invocations
+
+import 'dart:ui';
+
+import 'package:flame/components.dart';
+import 'package:flame_test/flame_test.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:pinball_components/pinball_components.dart';
+import 'package:pinball_components/src/components/ball/behaviors/behaviors.dart';
+
+import '../../../../helpers/helpers.dart';
+
+void main() {
+  TestWidgetsFlutterBinding.ensureInitialized();
+  final asset = Assets.images.ball.ball.keyName;
+  final flameTester = FlameTester(() => TestGame([asset]));
+
+  group('BallScalingBehavior', () {
+    const baseColor = Color(0xFFFFFFFF);
+    test('can be instantiated', () {
+      expect(
+        BallScalingBehavior(),
+        isA<BallScalingBehavior>(),
+      );
+    });
+
+    flameTester.test('can be loaded', (game) async {
+      final ball = Ball.test(baseColor: baseColor);
+      final behavior = BallScalingBehavior();
+      await ball.add(behavior);
+      await game.ensureAdd(ball);
+      expect(
+        ball.firstChild<BallScalingBehavior>(),
+        equals(behavior),
+      );
+    });
+
+    flameTester.test('can be loaded', (game) async {
+      final ball = Ball.test(baseColor: baseColor);
+      final behavior = BallScalingBehavior();
+      await ball.add(behavior);
+      await game.ensureAdd(ball);
+      expect(
+        ball.firstChild<BallScalingBehavior>(),
+        equals(behavior),
+      );
+    });
+
+    flameTester.test('scales the shape radius', (game) async {
+      final ball1 = Ball.test(baseColor: baseColor)
+        ..initialPosition = Vector2(0, 10);
+      await ball1.add(BallScalingBehavior());
+
+      final ball2 = Ball.test(baseColor: baseColor)
+        ..initialPosition = Vector2(0, -10);
+      await ball2.add(BallScalingBehavior());
+
+      await game.ensureAddAll([ball1, ball2]);
+      game.update(1);
+
+      final shape1 = ball1.body.fixtures.first.shape;
+      final shape2 = ball2.body.fixtures.first.shape;
+      expect(
+        shape1.radius,
+        greaterThan(shape2.radius),
+      );
+    });
+
+    flameTester.testGameWidget(
+      'scales the sprite',
+      setUp: (game, tester) async {
+        final ball1 = Ball.test(baseColor: baseColor)
+          ..initialPosition = Vector2(0, 10);
+        await ball1.add(BallScalingBehavior());
+
+        final ball2 = Ball.test(baseColor: baseColor)
+          ..initialPosition = Vector2(0, -10);
+        await ball2.add(BallScalingBehavior());
+
+        await game.ensureAddAll([ball1, ball2]);
+        game.update(1);
+
+        await tester.pump();
+        await game.ready();
+
+        final sprite1 = ball1.firstChild<SpriteComponent>()!;
+        final sprite2 = ball2.firstChild<SpriteComponent>()!;
+        expect(
+          sprite1.scale.x,
+          greaterThan(sprite2.scale.x),
+        );
+        expect(
+          sprite1.scale.y,
+          greaterThan(sprite2.scale.y),
+        );
+      },
+    );
+  });
+}