Added the SizeEffect and a general ComponentEffect (#1122)

* Added the `SizeEffect` and a general `ComponentEffect`

* Added changelog entry

* Format throw

* Fix analyze issue

* Fix Transform2DEffect test

* Apply suggestions from code review

Co-authored-by: Luan Nico <luanpotter27@gmail.com>

* Fix missing example parenthesis

* Fix according to comments

Co-authored-by: Luan Nico <luanpotter27@gmail.com>

examples/lib/stories/effects/effects.dart

@@ -9,6 +9,7 @@ import 'move_effect_example.dart';
 import 'old_move_effect_example.dart';
 import 'old_rotate_effect_example.dart';
 import 'old_scale_effect_example.dart';
+import 'old_size_effect_example.dart';
 import 'opacity_effect_example.dart';
 import 'remove_effect_example.dart';
 import 'rotate_effect_example.dart';
@@ -20,9 +21,9 @@ void addEffectsStories(Dashbook dashbook) {
   dashbook.storiesOf('Effects')
     ..add(
       'Size Effect',
-      (_) => GameWidget(game: SizeEffectExample()),
+      (_) => GameWidget(game: OldSizeEffectExample()),
       codeLink: baseLink('effects/size_effect_example.dart'),
-      info: SizeEffectExample.description,
+      info: OldSizeEffectExample.description,
     )
     ..add(
       'Scale Effect',
@@ -83,6 +84,12 @@ void addEffectsStories(Dashbook dashbook) {
       codeLink: baseLink('effects/rotate_effect_example.dart'),
       info: RotateEffectExample.description,
     )
+    ..add(
+      'Size Effect (v2)',
+      (_) => GameWidget(game: SizeEffectExample()),
+      codeLink: baseLink('effects/size_effect_example.dart'),
+      info: SizeEffectExample.description,
+    )
     ..add(
       'Scale Effect (v2)',
       (_) => GameWidget(game: ScaleEffectExample()),

examples/lib/stories/effects/old_size_effect_example.dart

@@ -0,0 +1,47 @@
+import 'package:flame/components.dart';
+import 'package:flame/effects.dart';
+import 'package:flame/extensions.dart';
+import 'package:flame/game.dart';
+import 'package:flame/input.dart';
+import 'package:flame/palette.dart';
+import 'package:flutter/material.dart';
+
+import '../../commons/square_component.dart';
+
+class OldSizeEffectExample extends FlameGame with TapDetector {
+  static const String description = '''
+    The `SizeEffect` changes the size of the component, but the sizes of its
+    children will stay the same.
+    In this example, you can tap the screen and the component will size up or
+    down, depending on its current state.
+  ''';
+
+  late SquareComponent square;
+  bool grow = true;
+
+  @override
+  Future<void> onLoad() async {
+    await super.onLoad();
+    square = SquareComponent(
+      position: Vector2.all(200),
+      paint: BasicPalette.white.paint()..style = PaintingStyle.stroke,
+    );
+    final childSquare = SquareComponent(position: Vector2.all(70), size: 20);
+    square.add(childSquare);
+    add(square);
+  }
+
+  @override
+  void onTap() {
+    final s = grow ? 300.0 : 100.0;
+
+    grow = !grow;
+    square.add(
+      SizeEffect(
+        size: Vector2.all(s),
+        speed: 250.0,
+        curve: Curves.bounceInOut,
+      ),
+    );
+  }
+}

examples/lib/stories/effects/size_effect_example.dart

@@ -1,9 +1,10 @@
 import 'package:flame/components.dart';
-import 'package:flame/effects.dart';
 import 'package:flame/extensions.dart';
 import 'package:flame/game.dart';
 import 'package:flame/input.dart';
 import 'package:flame/palette.dart';
+import 'package:flame/src/effects2/size_effect.dart'; // ignore: implementation_imports
+import 'package:flame/src/effects2/standard_effect_controller.dart'; // ignore: implementation_imports
 import 'package:flutter/material.dart';
 
 import '../../commons/square_component.dart';
@@ -36,11 +37,14 @@ class SizeEffectExample extends FlameGame with TapDetector {
     final s = grow ? 300.0 : 100.0;
 
     grow = !grow;
+
     square.add(
-      SizeEffect(
-        size: Vector2.all(s),
-        speed: 250.0,
-        curve: Curves.bounceInOut,
+      SizeEffect.to(
+        Vector2.all(s),
+        StandardEffectController(
+          duration: 1.5,
+          curve: Curves.bounceInOut,
+        ),
       ),
     );
   }

packages/flame/CHANGELOG.md

@@ -38,6 +38,7 @@
  - Rename `HasTappableComponents` to `HasTappables`
  - Rename `HasDraggableComponents` to `HasDraggables`
  - Rename `HasHoverableComponents` to `HasHoverableis`
+ - Added `SizeEffect` backed by the new effects engine
  - Added `ScaleEffect` backed by the new effects engine
  - Update `OrderedSet` to 4.1.0
  - Update `OrderedSet` to 5.0.0

packages/flame/lib/src/effects2/component_effect.dart

@@ -0,0 +1,44 @@
+import 'package:flutter/cupertino.dart';
+
+import '../../components.dart';
+import 'effect.dart';
+import 'effect_controller.dart';
+
+/// Base class for effects that target a [Component] of type [T].
+///
+/// A general abstraction for creating effects targeting [Component]s, currently
+/// only used by `SizeEffect` and `Transform2DEffect`.
+abstract class ComponentEffect<T extends Component> extends Effect {
+  ComponentEffect(EffectController controller) : super(controller);
+
+  late T target;
+
+  /// The effect's `progress` variable as it was the last time that the
+  /// `apply()` method was called. Mostly used by the derived classes.
+  double get previousProgress => _lastProgress;
+  double _lastProgress = 0;
+
+  @override
+  void onMount() {
+    super.onMount();
+    assert(parent != null);
+    if (parent is T) {
+      target = parent! as T;
+    } else {
+      throw UnsupportedError('Can only apply this effect to $T');
+    }
+  }
+
+  // In the derived class, call `super.apply()` last.
+  @mustCallSuper
+  @override
+  void apply(double progress) {
+    _lastProgress = progress;
+  }
+
+  @override
+  void reset() {
+    super.reset();
+    _lastProgress = 0;
+  }
+}

packages/flame/lib/src/effects2/size_effect.dart

@@ -0,0 +1,54 @@
+import '../../components.dart';
+import '../../extensions.dart';
+import 'component_effect.dart';
+import 'effect_controller.dart';
+
+/// Change the size of a component over time.
+///
+/// This effect applies incremental changes to the component's size, and
+/// requires that any other effect or update logic applied to the same component
+/// also used incremental updates.
+class SizeEffect extends ComponentEffect<PositionComponent> {
+  /// This constructor will create an effect that sets the size in relation to
+  /// the [PositionComponent]'s  current size, for example if the [offset] is
+  /// set to `Vector2(10, -10)` and the size of the affected component is
+  /// `Vector2(100, 100)` at the start of the affected the effect will peak when
+  /// the size is `Vector2(110, 90)`, if there is nothing else affecting the
+  /// size at the same time.
+  SizeEffect.by(Vector2 offset, EffectController controller)
+      : _offset = offset.clone(),
+        super(controller);
+
+  /// This constructor will create an effect that sets the size to the absolute
+  /// size that is defined by [targetSize].
+  /// For example if the [targetSize] is set to `Vector2(200, 200)` and the size
+  /// of the affected component is `Vector2(100, 100)` at the start of the
+  /// affected the effect will peak when the size is `Vector2(200, 100)`, if
+  /// there is nothing else affecting the size at the same time.
+  factory SizeEffect.to(Vector2 targetSize, EffectController controller) =>
+      _SizeToEffect(targetSize, controller);
+
+  Vector2 _offset;
+
+  @override
+  void apply(double progress) {
+    final dProgress = progress - previousProgress;
+    target.size += _offset * dProgress;
+    target.size.clampScalar(0, double.infinity);
+    super.apply(progress);
+  }
+}
+
+/// Implementation class for [SizeEffect.to]
+class _SizeToEffect extends SizeEffect {
+  final Vector2 _targetSize;
+
+  _SizeToEffect(Vector2 targetSize, EffectController controller)
+      : _targetSize = targetSize.clone(),
+        super.by(Vector2.zero(), controller);
+
+  @override
+  void onStart() {
+    _offset = _targetSize - target.size;
+  }
+}

packages/flame/lib/src/effects2/transform2d_effect.dart

@@ -1,8 +1,6 @@
-import 'package:flutter/cupertino.dart';
-
 import '../components/position_component.dart';
 import '../game/transform2d.dart';
-import 'effect.dart';
+import 'component_effect.dart';
 import 'effect_controller.dart';
 
 /// Base class for effects that target a [Transform2D] property.
@@ -14,41 +12,14 @@ import 'effect_controller.dart';
 /// Currently this class only supports being attached to [PositionComponent]s,
 /// but in the future it will be extended to work with any [Transform2D]-based
 /// classes.
-abstract class Transform2DEffect extends Effect {
+abstract class Transform2DEffect extends ComponentEffect<PositionComponent> {
   Transform2DEffect(EffectController controller) : super(controller);
 
-  late Transform2D target;
-
-  /// The effect's `progress` variable as it was the last time that the
-  /// `apply()` method was called. Mostly used by the derived classes.
-  double get previousProgress => _lastProgress;
-  double _lastProgress = 0;
+  late Transform2D transform;
 
   @override
   void onMount() {
     super.onMount();
-    assert(parent != null);
-    if (parent is PositionComponent) {
-      target = (parent! as PositionComponent).transform;
-    }
-    // TODO(st-pasha): add Camera support once it uses Transform2D
-    else {
-      throw UnsupportedError(
-        'Can only apply a Transform2DEffect to a PositionComponent class',
-      );
-    }
-  }
-
-  // In the derived class, call `super.apply()` last.
-  @mustCallSuper
-  @override
-  void apply(double progress) {
-    _lastProgress = progress;
-  }
-
-  @override
-  void reset() {
-    super.reset();
-    _lastProgress = 0;
+    transform = target.transform;
   }
 }

packages/flame/test/effects2/size_effect_test.dart

@@ -0,0 +1,160 @@
+import 'dart:math';
+
+import 'package:flame/components.dart';
+import 'package:flame/game.dart';
+import 'package:flame/src/effects2/size_effect.dart';
+import 'package:flame/src/effects2/standard_effect_controller.dart';
+import 'package:flame_test/flame_test.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  group('SizeEffect', () {
+    flameGame.test('relative', (game) {
+      final component = PositionComponent();
+      game.ensureAdd(component);
+
+      component.size = Vector2.all(1.0);
+      component.add(
+        SizeEffect.by(Vector2.all(1.0), StandardEffectController(duration: 1)),
+      );
+      game.update(0);
+      expectVector2(component.size, Vector2.all(1.0));
+      expect(component.children.length, 1);
+
+      game.update(0.5);
+      expectVector2(component.size, Vector2.all(1.5));
+
+      game.update(0.5);
+      expectVector2(component.size, Vector2.all(2.0));
+      game.update(0);
+      expect(component.children.length, 0);
+      expectVector2(component.size, Vector2.all(2.0));
+    });
+
+    flameGame.test('absolute', (game) {
+      final component = PositionComponent();
+      game.ensureAdd(component);
+
+      component.size = Vector2.all(1.0);
+      component.add(
+        SizeEffect.to(Vector2.all(3.0), StandardEffectController(duration: 1)),
+      );
+      game.update(0);
+      expectVector2(component.size, Vector2.all(1.0));
+      expect(component.children.length, 1);
+
+      game.update(0.5);
+      expectVector2(component.size, Vector2.all(2.0));
+
+      game.update(0.5);
+      expectVector2(component.size, Vector2.all(3.0));
+      game.update(0);
+      expect(component.children.length, 0);
+      expectVector2(component.size, Vector2.all(3.0));
+    });
+
+    flameGame.test('reset relative', (game) {
+      final component = PositionComponent();
+      game.ensureAdd(component);
+
+      final effect = SizeEffect.by(
+        Vector2.all(1.0),
+        StandardEffectController(duration: 1),
+      );
+      component.add(effect..removeOnFinish = false);
+      final expectedSize = Vector2.zero();
+      for (var i = 0; i < 5; i++) {
+        expectVector2(component.size, expectedSize);
+        // After each reset the object will be sized up by Vector2(1, 1)
+        // relative to its size at the start of the effect.
+        effect.reset();
+        game.update(1);
+        expectedSize.add(Vector2.all(1.0));
+        expectVector2(component.size, expectedSize);
+      }
+    });
+
+    flameGame.test('reset absolute', (game) {
+      final component = PositionComponent();
+      game.ensureAdd(component);
+
+      final effect = SizeEffect.to(
+        Vector2.all(1.0),
+        StandardEffectController(duration: 1),
+      );
+      component.add(effect..removeOnFinish = false);
+      for (var i = 0; i < 5; i++) {
+        component.size = Vector2.all(1 + 4.0 * i);
+        // After each reset the object will be sized to the value of
+        // `Vector2(1, 1)`, regardless of its initial orientation.
+        effect.reset();
+        game.update(1);
+        expectVector2(component.size, Vector2.all(1.0));
+      }
+    });
+
+    flameGame.test('size composition', (game) {
+      final component = PositionComponent();
+      game.ensureAdd(component);
+
+      component.add(
+        SizeEffect.by(Vector2.all(5), StandardEffectController(duration: 10)),
+      );
+      component.add(
+        SizeEffect.by(
+          Vector2.all(0.5),
+          StandardEffectController(
+            duration: 1,
+            reverseDuration: 1,
+            repeatCount: 5,
+          ),
+        ),
+      );
+
+      game.update(1);
+      expectVector2(
+        component.size,
+        Vector2.all(1),
+        epsilon: 1e-15,
+      ); // 5*1/10 + 0.5*1
+      game.update(1);
+      expectVector2(
+        component.size,
+        Vector2.all(1),
+        epsilon: 1e-15,
+      ); // 5*2/10 + 0.5*1 - 0.5*1
+      for (var i = 0; i < 10; i++) {
+        game.update(1);
+      }
+      expectVector2(component.size, Vector2.all(5), epsilon: 1e-15);
+      expect(component.children.length, 0);
+    });
+
+    testRandom('a very long size change', (Random rng) {
+      final game = FlameGame()..onGameResize(Vector2(1, 1));
+      final component = PositionComponent();
+      game.ensureAdd(component);
+
+      final effect = SizeEffect.by(
+        Vector2.all(1.0),
+        StandardEffectController(
+          duration: 1,
+          reverseDuration: 1,
+          infinite: true,
+        ),
+      );
+      component.add(effect);
+
+      var totalTime = 0.0;
+      while (totalTime < 999.9) {
+        final dt = rng.nextDouble() * 0.02;
+        totalTime += dt;
+        game.update(dt);
+      }
+      game.update(1000 - totalTime);
+      // Typically, `component.size` could accumulate numeric discrepancy on the
+      // order of 1e-11 .. 1e-12 by now.
+      expectVector2(component.size, Vector2.zero(), epsilon: 1e-10);
+    });
+  });
+}

packages/flame/test/effects2/transform2d_effect_test.dart

@@ -14,14 +14,14 @@ void main() {
     flameGame.test(
       'onMount',
       (game) {
-        final obj = PositionComponent();
-        game.add(obj);
+        final component = PositionComponent();
+        game.add(component);
         game.update(0);
 
         final effect = _MyEffect(StandardEffectController(duration: 1));
-        obj.add(effect);
+        component.add(effect);
         game.update(0);
-        expect(effect.target, obj.transform);
+        expect(effect.transform, component.transform);
 
         final effect2 = _MyEffect(StandardEffectController(duration: 1));
         expect(