Infinite and alternating effects

docs/examples/effects/simple/lib/main_move.dart

@@ -4,7 +4,7 @@ import 'package:flame/gestures.dart';
 import 'package:flame/effects/effects.dart';
 import 'package:flame/position.dart';
 
-import './square.dart';
+import 'square.dart';
 
 class MyGame extends BaseGame with TapDetector {
   Square square;

docs/examples/effects/simple/lib/main_scale.dart

@@ -4,7 +4,7 @@ import 'package:flame/gestures.dart';
 import 'package:flame/anchor.dart';
 import 'package:flame/effects/effects.dart';
 
-import './square.dart';
+import 'square.dart';
 
 class MyGame extends BaseGame with TapDetector {
   Square square;

docs/examples/effects/simple/pubspec.yaml

@@ -1,4 +1,4 @@
-name: effects
+name: effects2
 description: A Flame game showcasing the use of the effects api
 
 version: 1.0.0+1
@@ -10,4 +10,4 @@ dependencies:
   flutter:
     sdk: flutter
   flame:
-    path: ../../../
+    path: ../../../..

lib/components/component.dart

@@ -157,6 +157,14 @@ abstract class PositionComponent extends Component {
     _effects.add(effect..component = this);
   }
 
+  void removeEffect(PositionComponentEffect effect) {
+    effect.dispose();
+  }
+
+  void clearEffects() {
+    _effects.forEach(removeEffect);
+  }
+
   @mustCallSuper
   @override
   void update(double dt) {

lib/effects/effects.dart

@@ -1,10 +1,41 @@
+import 'dart:math';
 import '../components/component.dart';
 
 export './move_effect.dart';
 export './scale_effect.dart';
 
 abstract class PositionComponentEffect {
-  void update(double dt);
-  bool hasFinished();
-  PositionComponent component;
+  bool _isDisposed = false;
+  bool get isDisposed => _isDisposed;
+
+  /// If the animation should first follow the initial curve and then follow the
+  /// curve backwards
+  bool isAlternating;
+  bool isInfinite;
+  double percentage;
+  double travelTime;
+  double _curveTime = 0.0;
+  int _curveDirection = 1;
+
+  PositionComponentEffect(this.isInfinite, this.isAlternating);
+
+  void update(double dt) {
+    _curveTime += dt * _curveDirection;
+    if (isAlternating) {
+      _curveDirection = isMax() ? -1 : (isMin() ? 1 : _curveDirection);
+    } else if (isInfinite && isMax()){
+      percentage = 0.0;
+    }
+    percentage = min(1.0, max(0.0, _curveTime / travelTime));
+  }
+
+  void dispose() => _isDisposed = true;
+
+  PositionComponent component;
+
+  bool hasFinished() =>
+      (!isInfinite && !isAlternating && isMax()) ||
+          (!isInfinite && isAlternating && isMin()) || isDisposed;
+  bool isMax() => percentage == null ? false : percentage == 1.0;
+  bool isMin() => percentage == null ? false : percentage == 0.0;
 }

lib/effects/move_effect.dart

@@ -7,15 +7,13 @@ import './effects.dart';
 import '../position.dart';
 
 double _direction(double p, double d) => (p - d).sign;
-double _size(double a, double b) => (a - b).abs();
+double _distance(double a, double b) => (a - b).abs();
 
 class MoveEffect extends PositionComponentEffect {
   Position destination;
   double speed;
   Curve curve;
 
-  double _travelTime;
-
   double _xOriginal;
   double _xDistance;
   double _xDirection;
@@ -24,13 +22,13 @@ class MoveEffect extends PositionComponentEffect {
   double _yDistance;
   double _yDirection;
 
-  double _elapsedTime = 0.0;
-
   MoveEffect({
     @required this.destination,
     @required this.speed,
     this.curve,
-  });
+    isInfinite = false,
+    isAlternating = false
+  }) : super(isInfinite, isAlternating);
 
   @override
   set component(_comp) {
@@ -39,34 +37,25 @@ class MoveEffect extends PositionComponentEffect {
     _xOriginal = component.x;
     _yOriginal = component.y;
 
-    _xDistance = _size(destination.x, component.x);
-    _yDistance = _size(destination.y, component.y);
+    _xDistance = _distance(destination.x, component.x);
+    _yDistance = _distance(destination.y, component.y);
 
     _xDirection = _direction(destination.x, component.x);
     _yDirection = _direction(destination.y, component.y);
 
-    _travelTime = max(
-      _xDistance / speed,
-      _yDistance / speed,
-    );
+    final totalDistance = sqrt(pow(_xDistance, 2) + pow(_yDistance, 2));
+    travelTime = totalDistance / speed;
   }
 
   @override
   void update(double dt) {
+    super.update(dt);
+
     if (!hasFinished()) {
-      final double percent = min(1.0, _elapsedTime / _travelTime);
-      final double c = curve?.transform(percent) ?? 1.0;
+      final double c = curve?.transform(percentage) ?? 1.0;
 
       component.x = _xOriginal + _xDistance * c * _xDirection;
       component.y = _yOriginal + _yDistance * c * _yDirection;
-    } else {
-      component.x = destination.x;
-      component.y = destination.y;
     }
-
-    _elapsedTime += dt;
   }
-
-  @override
-  bool hasFinished() => _elapsedTime >= _travelTime;
 }

lib/effects/scale_effect.dart

@@ -15,9 +15,6 @@ class ScaleEffect extends PositionComponentEffect {
   double speed;
   Curve curve;
 
-  double _scaleTime;
-  double _elapsedTime = 0.0;
-
   Size _original;
   Size _diff;
   final Position _dir = Position.empty();
@@ -26,7 +23,9 @@ class ScaleEffect extends PositionComponentEffect {
     @required this.size,
     @required this.speed,
     this.curve,
-  });
+    isInfinite = false,
+    isAlternating = false
+  }) : super(isInfinite, isAlternating);
 
   @override
   set component(_comp) {
@@ -41,28 +40,18 @@ class ScaleEffect extends PositionComponentEffect {
     _dir.x = _direction(size.width, _original.width);
     _dir.y = _direction(size.height, _original.height);
 
-    _scaleTime = max(
-      _diff.width / speed,
-      _diff.height / speed,
-    );
+    final scaleDistance = sqrt(pow(_diff.width, 2) + pow(_diff.height, 2));
+    travelTime = scaleDistance / speed;
   }
 
   @override
   void update(double dt) {
+    super.update(dt);
     if (!hasFinished()) {
-      final double percent = min(1.0, _elapsedTime / _scaleTime);
-      final double c = curve?.transform(percent) ?? 1.0;
+      final double c = curve?.transform(percentage) ?? 1.0;
 
       component.width = _original.width + _diff.width * c * _dir.x;
       component.height = _original.height + _diff.height * c * _dir.y;
-    } else {
-      component.width = size.width;
-      component.height = size.height;
     }
-
-    _elapsedTime += dt;
   }
-
-  @override
-  bool hasFinished() => _elapsedTime >= _scaleTime;
 }