Remove AnimatedSimulation

This patch folds the functionality from AnimatedSimulation into Timeline.

packages/flutter/lib/animation.dart

@@ -7,7 +7,6 @@
 /// This library depends only on core Dart libraries and the `newton` package.
 library animation;
 
-export 'src/animation/animated_simulation.dart';
 export 'src/animation/animated_value.dart';
 export 'src/animation/animation_performance.dart';
 export 'src/animation/clamped_simulation.dart';
@@ -15,4 +14,5 @@ export 'src/animation/curves.dart';
 export 'src/animation/forces.dart';
 export 'src/animation/scheduler.dart';
 export 'src/animation/scroll_behavior.dart';
-export 'src/animation/timeline.dart';
+export 'src/animation/simulation_stepper.dart';
+export 'src/animation/ticker.dart';

packages/flutter/lib/src/animation/animation_performance.dart

@@ -6,7 +6,7 @@ import 'dart:async';
 
 import 'package:sky/src/animation/animated_value.dart';
 import 'package:sky/src/animation/forces.dart';
-import 'package:sky/src/animation/timeline.dart';
+import 'package:sky/src/animation/simulation_stepper.dart';
 
 /// The status of an animation
 enum AnimationStatus {
@@ -53,7 +53,7 @@ abstract class WatchableAnimationPerformance {
 /// progression.
 class AnimationPerformance implements WatchableAnimationPerformance {
   AnimationPerformance({ this.duration, double progress }) {
-    _timeline = new Timeline(_tick);
+    _timeline = new SimulationStepper(_tick);
     if (progress != null)
       _timeline.value = progress.clamp(0.0, 1.0);
   }
@@ -66,7 +66,7 @@ class AnimationPerformance implements WatchableAnimationPerformance {
   /// The length of time this performance should last
   Duration duration;
 
-  Timeline _timeline;
+  SimulationStepper _timeline;
   Direction _direction;
 
   /// The direction used to select the current curve
@@ -159,7 +159,7 @@ class AnimationPerformance implements WatchableAnimationPerformance {
     if (force == null)
       force = kDefaultSpringForce;
     _direction = velocity < 0.0 ? Direction.reverse : Direction.forward;
-    return _timeline.fling(force.release(progress, velocity));
+    return _timeline.animateWith(force.release(progress, velocity));
   }
 
   final List<AnimationPerformanceListener> _listeners = new List<AnimationPerformanceListener>();

packages/flutter/lib/src/animation/timeline.dart → packages/flutter/lib/src/animation/simulation_stepper.dart

@@ -5,23 +5,26 @@
 import 'dart:async';
 
 import 'package:newton/newton.dart';
-import 'package:sky/src/animation/curves.dart';
 import 'package:sky/src/animation/animated_value.dart';
-import 'package:sky/src/animation/animated_simulation.dart';
+import 'package:sky/src/animation/curves.dart';
+import 'package:sky/src/animation/ticker.dart';
 
-/// A simulation that linearly varies from [begin] to [end] over [duration]
+/// A simulation that varies from [begin] to [end] over [duration] using [curve]
+///
+/// This class is an adaptor between the Simulation interface and the
+/// AnimatedValue interface.
 class _TweenSimulation extends Simulation {
-  final double _durationInSeconds;
-  final AnimatedValue<double> _tween;
-
   _TweenSimulation(double begin, double end, Duration duration, Curve curve)
-    : _durationInSeconds = duration.inMicroseconds / Duration.MICROSECONDS_PER_SECOND,
+    : _durationInSeconds = duration.inMicroseconds.toDouble() / Duration.MICROSECONDS_PER_SECOND,
       _tween = new AnimatedValue<double>(begin, end: end, curve: curve) {
     assert(_durationInSeconds > 0.0);
     assert(begin != null);
     assert(end != null);
   }
 
+  final double _durationInSeconds;
+  final AnimatedValue<double> _tween;
+
   double x(double timeInSeconds) {
     assert(timeInSeconds >= 0.0);
     final double t = (timeInSeconds / _durationInSeconds).clamp(0.0, 1.0);
@@ -34,24 +37,30 @@ class _TweenSimulation extends Simulation {
   bool isDone(double timeInSeconds) => timeInSeconds > _durationInSeconds;
 }
 
-/// A timeline for an animation
-class Timeline {
-  Timeline(Function onTick) {
-    _animation = new AnimatedSimulation(onTick);
+typedef TimelineCallback(double value);
+
+/// Steps a simulation one per frame
+class SimulationStepper {
+  SimulationStepper(TimelineCallback onTick) : _onTick = onTick {
+    _ticker = new Ticker(_tick);
   }
 
-  AnimatedSimulation _animation;
+  final TimelineCallback _onTick;
+  Ticker _ticker;
+  Simulation _simulation;
 
   /// The current value of the timeline
-  double get value => _animation.value;
+  double get value => _value;
+  double _value = 0.0;
   void set value(double newValue) {
     assert(newValue != null);
     assert(!isAnimating);
-    _animation.value = newValue;
+    _value = newValue;
+    _onTick(_value);
   }
 
   /// Whether the timeline is currently animating
-  bool get isAnimating => _animation.isAnimating;
+  bool get isAnimating => _ticker.isTicking;
 
   /// Animate value of the timeline to the given target over the given duration
   ///
@@ -59,18 +68,38 @@ class Timeline {
   /// typically when the timeline arives at the target value.
   Future animateTo(double target, { Duration duration, Curve curve: linear }) {
     assert(duration > Duration.ZERO);
-    assert(!_animation.isAnimating);
-    return _animation.start(new _TweenSimulation(value, target, duration, curve));
+    assert(!isAnimating);
+    return _start(new _TweenSimulation(value, target, duration, curve));
+  }
+
+  /// Gives the given simulation control over the timeline
+  Future animateWith(Simulation simulation) {
+    stop();
+    return _start(simulation);
+  }
+
+  /// Start ticking the given simulation once per frame
+  ///
+  /// Returns a future that resolves when the simulation stops ticking.
+  Future _start(Simulation simulation) {
+    assert(simulation != null);
+    assert(!isAnimating);
+    _simulation = simulation;
+    _value = simulation.x(0.0);
+    return _ticker.start();
   }
 
   /// Stop animating the timeline
   void stop() {
-    _animation.stop();
+    _simulation = null;
+    _ticker.stop();
   }
 
-  /// Gives the given simulation control over the timeline
-  Future fling(Simulation simulation) {
-    stop();
-    return _animation.start(simulation);
+  void _tick(Duration elapsed) {
+    double elapsedInSeconds = elapsed.inMicroseconds.toDouble() / Duration.MICROSECONDS_PER_SECOND;
+    _value = _simulation.x(elapsedInSeconds);
+    if (_simulation.isDone(elapsedInSeconds))
+      stop();
+    _onTick(_value);
   }
 }

packages/flutter/lib/src/animation/animated_simulation.dart → packages/flutter/lib/src/animation/ticker.dart

@@ -4,17 +4,16 @@
 
 import 'dart:async';
 
-import 'package:newton/newton.dart';
 import 'package:sky/src/animation/scheduler.dart';
 
-typedef _TickerCallback(Duration elapsed);
+typedef TickerCallback(Duration elapsed);
 
 /// Calls its callback once per animation frame
 class Ticker {
   /// Constructs a ticker that will call onTick once per frame while running
-  Ticker(_TickerCallback onTick) : _onTick = onTick;
+  Ticker(TickerCallback onTick) : _onTick = onTick;
 
-  final _TickerCallback _onTick;
+  final TickerCallback _onTick;
 
   Completer _completer;
   int _animationId;
@@ -45,7 +44,7 @@ class Ticker {
       _animationId = null;
     }
 
-    // We take the _completer into a local variable so that !isTicking
+    // We take the _completer into a local variable so that isTicking is false
     // when we actually complete the future (isTicking uses _completer
     // to determine its state).
     Completer localCompleter = _completer;
@@ -78,57 +77,3 @@ class Ticker {
     _animationId = scheduler.requestAnimationFrame(_tick);
   }
 }
-
-/// Ticks a simulation once per frame
-class AnimatedSimulation {
-
-  AnimatedSimulation(Function onTick) : _onTick = onTick {
-    _ticker = new Ticker(_tick);
-  }
-
-  final Function _onTick;
-  Ticker _ticker;
-
-  Simulation _simulation;
-
-  double _value = 0.0;
-  /// The current value of the simulation
-  double get value => _value;
-  void set value(double newValue) {
-    assert(!_ticker.isTicking);
-    _value = newValue;
-    _onTick(_value);
-  }
-
-  /// Start ticking the given simulation once per frame
-  ///
-  /// Returns a future that resolves when the simulation stops ticking.
-  Future start(Simulation simulation) {
-    assert(simulation != null);
-    assert(!_ticker.isTicking);
-    _simulation = simulation;
-    _value = simulation.x(0.0);
-    return _ticker.start();
-  }
-
-  /// Stop ticking the current simulation
-  void stop() {
-    _simulation = null;
-    _ticker.stop();
-  }
-
-  /// Whether this object is currently ticking a simulation
-  bool get isAnimating => _ticker.isTicking;
-
-  void _tick(Duration elapsed) {
-
-    double elapsedInSeconds =  elapsed.inMicroseconds.toDouble() / Duration.MICROSECONDS_PER_SECOND;
-    _value = _simulation.x(elapsedInSeconds);
-
-    if (_simulation.isDone(elapsedInSeconds))
-      stop();
-
-    _onTick(_value);
-  }
-
-}

packages/flutter/lib/src/widgets/scrollable.dart

@@ -51,10 +51,10 @@ abstract class ScrollableState<T extends Scrollable> extends State<T> {
     super.initState();
     if (config.initialScrollOffset is double)
       _scrollOffset = config.initialScrollOffset;
-    _animation = new Timeline(_setScrollOffset);
+    _animation = new SimulationStepper(_setScrollOffset);
   }
 
-  Timeline _animation;
+  SimulationStepper _animation;
 
   double _scrollOffset = 0.0;
   double get scrollOffset => _scrollOffset;
@@ -151,7 +151,7 @@ abstract class ScrollableState<T extends Scrollable> extends State<T> {
       _createSnapSimulation(velocity) ?? _createFlingSimulation(velocity ?? 0.0);
     if (simulation == null)
       return new Future.value();
-    return _animation.fling(simulation);
+    return _animation.animateWith(simulation);
   }
 
   void dispose() {

packages/flutter/lib/src/widgets/tabs.dart

@@ -13,7 +13,6 @@ import 'package:sky/painting.dart';
 import 'package:sky/rendering.dart';
 import 'package:sky/src/widgets/basic.dart';
 import 'package:sky/src/widgets/framework.dart';
-import 'package:sky/src/widgets/gesture_detector.dart';
 import 'package:sky/src/widgets/icon.dart';
 import 'package:sky/src/widgets/ink_well.dart';
 import 'package:sky/src/widgets/scrollable.dart';