Port examples to the new animation API

These now use Animation and AnimationController instead of PerformanceView and
Performance.

examples/material_gallery/lib/demo/page_selector_demo.dart

@@ -12,21 +12,21 @@ final List<String> _iconNames = <String>["event", "home", "android", "alarm", "f
 class TabViewDemo extends StatelessComponent {
   Widget _buildTabIndicator(BuildContext context, String iconName) {
     final Color color = Theme.of(context).primaryColor;
-    final AnimatedColorValue _selectedColor = new AnimatedColorValue(Colors.transparent, end: color, curve: Curves.ease);
-    final AnimatedColorValue _previousColor = new AnimatedColorValue(color, end: Colors.transparent, curve: Curves.ease);
+    final ColorTween _selectedColor = new ColorTween(begin: Colors.transparent, end: color);
+    final ColorTween _previousColor = new ColorTween(begin: color, end: Colors.transparent);
     final TabBarSelectionState selection = TabBarSelection.of(context);
 
-    return new BuilderTransition(
-      performance: selection.performance,
-      variables: <AnimatedColorValue>[_selectedColor, _previousColor],
+    Animation animation = new CurvedAnimation(parent: selection.animation, curve: Curves.ease);
+    return new AnimationWatchingBuilder(
+      watchable: animation,
       builder: (BuildContext context) {
         Color background = selection.value == iconName ? _selectedColor.end : _selectedColor.begin;
         if (selection.valueIsChanging) {
           // Then the selection's performance is animating from previousValue to value.
           if (selection.value == iconName)
-            background = _selectedColor.value;
+            background = _selectedColor.evaluate(animation);
           else if (selection.previousValue == iconName)
-            background = _previousColor.value;
+            background = _previousColor.evaluate(animation);
         }
         return new Container(
           width: 12.0,

examples/widgets/progress_indicator.dart

@@ -16,7 +16,7 @@ class _ProgressIndicatorAppState extends State<ProgressIndicatorApp> {
       duration: const Duration(milliseconds: 1500)
     )..play(AnimationDirection.forward);
 
-    animation = new ACurve(
+    animation = new CurvedAnimation(
       parent: controller,
       curve: new Interval(0.0, 0.9, curve: Curves.ease),
       reverseCurve: Curves.ease

examples/widgets/smooth_resize.dart

@@ -26,29 +26,28 @@ class SmoothBlock extends StatefulComponent {
 class CardTransition extends StatelessComponent {
   CardTransition({
     this.child,
-    this.performance,
+    this.animation,
     this.x,
     this.opacity,
     this.scale
   });
 
   final Widget child;
-  final Performance performance;
-  final AnimatedValue<double> x;
-  final AnimatedValue<double> opacity;
-  final AnimatedValue<double> scale;
+  final Animation animation;
+  final Evaluatable<double> x;
+  final Evaluatable<double> opacity;
+  final Evaluatable<double> scale;
 
   Widget build(BuildContext context) {
-
-    return new BuilderTransition(
-      performance: performance,
-      variables: <AnimatedValue<double>>[x, opacity, scale],
+    return new AnimationWatchingBuilder(
+      watchable: animation,
       builder: (BuildContext context) {
+        double currentScale = scale.evaluate(animation);
         Matrix4 transform = new Matrix4.identity()
-          ..translate(x.value)
-          ..scale(scale.value, scale.value);
+          ..translate(x.evaluate(animation))
+          ..scale(currentScale, currentScale);
         return new Opacity(
-          opacity: opacity.value,
+          opacity: opacity.evaluate(animation),
           child: new Transform(
             transform: transform,
             child: child
@@ -63,22 +62,22 @@ class SmoothBlockState extends State<SmoothBlock> {
 
   double _height = 100.0;
 
-  Widget _handleEnter(PerformanceView performance, Widget child) {
+  Widget _handleEnter(Animation animation, Widget child) {
     return new CardTransition(
-      x: new AnimatedValue<double>(-200.0, end: 0.0, curve: Curves.ease),
-      opacity: new AnimatedValue<double>(0.0, end: 1.0, curve: Curves.ease),
-      scale: new AnimatedValue<double>(0.8, end: 1.0, curve: Curves.ease),
-      performance: performance,
+      x: new Tween<double>(begin: -200.0, end: 0.0),
+      opacity: new Tween<double>(begin: 0.0, end: 1.0),
+      scale: new Tween<double>(begin: 0.8, end: 1.0),
+      animation: new CurvedAnimation(parent: animation, curve: Curves.ease),
       child: child
     );
   }
 
-  Widget _handleExit(PerformanceView performance, Widget child) {
+  Widget _handleExit(Animation animation, Widget child) {
     return new CardTransition(
-      x: new AnimatedValue<double>(0.0, end: 200.0, curve: Curves.ease),
-      opacity: new AnimatedValue<double>(1.0, end: 0.0, curve: Curves.ease),
-      scale: new AnimatedValue<double>(1.0, end: 0.8, curve: Curves.ease),
-      performance: performance,
+      x: new Tween<double>(begin: 0.0, end: 200.0),
+      opacity: new Tween<double>(begin: 1.0, end: 0.0),
+      scale: new Tween<double>(begin: 1.0, end: 0.8),
+      animation: new CurvedAnimation(parent: animation, curve: Curves.ease),
       child: child
     );
   }

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

@@ -92,7 +92,7 @@ abstract class ProxyWatchableMixin implements Watchable {
 abstract class Evaluatable<T> {
   const Evaluatable();
 
-  T evaluate(double t);
+  T evaluate(Animation animation);
 
   WatchableValue<T> watch(Animation parent) {
     return new WatchableValue<T>(parent: parent, evaluatable: this);
@@ -105,7 +105,7 @@ class WatchableValue<T> extends Watchable with ProxyWatchableMixin {
   final Animation parent;
   final Evaluatable<T> evaluatable;
 
-  T get value => evaluatable.evaluate(parent.progress);
+  T get value => evaluatable.evaluate(parent);
 }
 
 abstract class Animation extends Watchable {
@@ -261,9 +261,8 @@ class _RepeatingSimulation extends Simulation {
   bool isDone(double timeInSeconds) => false;
 }
 
-// TODO(abarth): Rename Curve to UnitTransform and ACurve to Curve.
-class ACurve extends Animation with ProxyWatchableMixin {
-  ACurve({ this.parent, this.curve, this.reverseCurve }) {
+class CurvedAnimation extends Animation with ProxyWatchableMixin {
+  CurvedAnimation({ this.parent, this.curve, this.reverseCurve }) {
     assert(parent != null);
     assert(curve != null);
     parent.addStatusListener(_handleStatusChanged);
@@ -317,9 +316,7 @@ class ACurve extends Animation with ProxyWatchableMixin {
 }
 
 class Tween<T extends dynamic> extends Evaluatable<T> {
-  Tween({ this.begin, this.end }) {
-    assert(begin != null);
-  }
+  Tween({ this.begin, this.end });
 
   /// The value this variable has at the beginning of the animation.
   T begin;
@@ -330,9 +327,10 @@ class Tween<T extends dynamic> extends Evaluatable<T> {
   /// Returns the value this variable has at the given animation clock value.
   T lerp(double t) => begin + (end - begin) * t;
 
-  T evaluate(double t) {
+  T evaluate(Animation animation) {
     if (end == null)
       return begin;
+    double t = animation.progress;
     if (t == 0.0)
       return begin;
     if (t == 1.0)

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

@@ -415,10 +415,10 @@ class TabBarSelection<T> extends StatefulComponent {
 
 class TabBarSelectionState<T> extends State<TabBarSelection<T>> {
 
-  PerformanceView get performance => _performance.view;
+  Animation get animation => _controller.view;
   // Both the TabBar and TabBarView classes access _performance because they
   // alternately drive selection progress between tabs.
-  final _performance = new Performance(duration: _kTabBarScroll, progress: 1.0);
+  final AnimationController _controller = new AnimationController(duration: _kTabBarScroll, progress: 1.0);
   final Map<T, int> _valueToIndex = new Map<T, int>();
 
   void _initValueToIndex() {
@@ -442,7 +442,7 @@ class TabBarSelectionState<T> extends State<TabBarSelection<T>> {
   }
 
   void dispose() {
-    _performance.stop();
+    _controller.stop();
     PageStorage.of(context)?.writeState(context, _value);
     super.dispose();
   }
@@ -481,21 +481,21 @@ class TabBarSelectionState<T> extends State<TabBarSelection<T>> {
     // the previous and current selection index.
 
     double progress;
-    if (_performance.status == PerformanceStatus.completed)
+    if (_controller.status == PerformanceStatus.completed)
       progress = 0.0;
     else if (_previousValue == values.first)
-      progress = _performance.progress;
+      progress = _controller.progress;
     else if (_previousValue == values.last)
-      progress = 1.0 - _performance.progress;
+      progress = 1.0 - _controller.progress;
     else if (previousIndex < index)
-      progress = (_performance.progress - 0.5) * 2.0;
+      progress = (_controller.progress - 0.5) * 2.0;
     else
-      progress = 1.0 - _performance.progress * 2.0;
+      progress = 1.0 - _controller.progress * 2.0;
 
-    _performance
+    _controller
       ..progress = progress
       ..forward().then((_) {
-        if (_performance.progress == 1.0) {
+        if (_controller.progress == 1.0) {
           if (config.onChanged != null)
             config.onChanged(_value);
           _valueIsChanging = false;
@@ -507,14 +507,14 @@ class TabBarSelectionState<T> extends State<TabBarSelection<T>> {
 
   void registerPerformanceListener(TabBarSelectionPerformanceListener listener) {
     _performanceListeners.add(listener);
-    _performance
+    _controller
       ..addStatusListener(listener.handleStatusChange)
       ..addListener(listener.handleProgressChange);
   }
 
   void unregisterPerformanceListener(TabBarSelectionPerformanceListener listener) {
     _performanceListeners.remove(listener);
-    _performance
+    _controller
       ..removeStatusListener(listener.handleStatusChange)
       ..removeListener(listener.handleProgressChange);
   }
@@ -590,17 +590,11 @@ class _TabBarState<T> extends ScrollableState<TabBar<T>> implements TabBarSelect
 
     if (_valueIsChanging && status == PerformanceStatus.completed) {
       _valueIsChanging = false;
-      double progress = 0.5;
-      if (_selection.index == 0)
-        progress = 0.0;
-      else if (_selection.index == config.labels.length - 1)
-        progress = 1.0;
+      _indicatorTween
+        ..begin = _tabIndicatorRect(math.max(0, _selection.index - 1))
+        ..end = _tabIndicatorRect(math.min(config.labels.length - 1, _selection.index + 1));
       setState(() {
-        _indicatorRect
-          ..begin = _tabIndicatorRect(math.max(0, _selection.index - 1))
-          ..end = _tabIndicatorRect(math.min(config.labels.length - 1, _selection.index + 1))
-          ..curve = null
-          ..setProgress(progress, AnimationDirection.forward);
+        _indicatorRect = _tabIndicatorRect(_selection.index);
       });
     }
   }
@@ -612,23 +606,32 @@ class _TabBarState<T> extends ScrollableState<TabBar<T>> implements TabBarSelect
     if (!_valueIsChanging && _selection.valueIsChanging) {
       if (config.isScrollable)
         scrollTo(_centeredTabScrollOffset(_selection.index), duration: _kTabBarScroll);
-      _indicatorRect
-        ..begin = _indicatorRect.value ?? _tabIndicatorRect(_selection.previousIndex)
-        ..end = _tabIndicatorRect(_selection.index)
-        ..curve = Curves.ease;
+      _indicatorTween
+        ..begin = _indicatorRect ?? _tabIndicatorRect(_selection.previousIndex)
+        ..end = _tabIndicatorRect(_selection.index);
       _valueIsChanging = true;
     }
-    Rect oldRect = _indicatorRect.value;
-    _indicatorRect.setProgress(_selection.performance.progress, AnimationDirection.forward);
-    Rect newRect = _indicatorRect.value;
-    if (oldRect != newRect)
+    Rect oldRect = _indicatorRect;
+    double t = _selection.animation.progress;
+    if (_valueIsChanging) {
+      // When _valueIsChanging is true, we're animating based on a ticker and
+      // want to curve the animation. When _valueIsChanging is false, we're
+      // animating based on a pointer event and want linear feedback. It's
+      // possible we should move this curve into the selection animation.
+      t = Curves.ease.transform(t);
+    }
+    // TODO(abarth): If we've never gone through handleStatusChange before, we
+    // might not have set up our _indicatorTween yet.
+    _indicatorRect = _indicatorTween.lerp(t);
+    if (oldRect != _indicatorRect)
       setState(() { });
   }
 
   Size _viewportSize = Size.zero;
   Size _tabBarSize;
   List<double> _tabWidths;
-  AnimatedRectValue _indicatorRect = new AnimatedRectValue(null);
+  Rect _indicatorRect;
+  RectTween _indicatorTween = new RectTween();
 
   Rect _tabRect(int tabIndex) {
     assert(_tabBarSize != null);
@@ -673,9 +676,9 @@ class _TabBarState<T> extends ScrollableState<TabBar<T>> implements TabBarSelect
       labelColor = isSelectedTab ? selectedColor : color;
       if (_selection.valueIsChanging) {
         if (isSelectedTab)
-          labelColor = Color.lerp(color, selectedColor, _selection.performance.progress);
+          labelColor = Color.lerp(color, selectedColor, _selection.animation.progress);
         else if (isPreviouslySelectedTab)
-          labelColor = Color.lerp(selectedColor, color, _selection.performance.progress);
+          labelColor = Color.lerp(selectedColor, color, _selection.animation.progress);
       }
     }
     return new _Tab(
@@ -749,7 +752,7 @@ class _TabBarState<T> extends ScrollableState<TabBar<T>> implements TabBarSelect
           children: tabs,
           selectedIndex: _selection?.index,
           indicatorColor: indicatorColor,
-          indicatorRect: _indicatorRect.value,
+          indicatorRect: _indicatorRect,
           textAndIcons: textAndIcons,
           isScrollable: config.isScrollable,
           onLayoutChanged: _layoutChanged
@@ -873,14 +876,14 @@ class _TabBarViewState extends PageableListState<TabBarView> implements TabBarSe
       return;
     // The TabBar is driving the TabBarSelection performance.
 
-    final Performance performance = _selection.performance;
+    final Animation animation = _selection.animation;
 
-    if (performance.status == PerformanceStatus.completed) {
+    if (animation.status == PerformanceStatus.completed) {
       _updateItemsAndScrollBehavior();
       return;
     }
 
-    if (performance.status != PerformanceStatus.forward)
+    if (animation.status != PerformanceStatus.forward)
       return;
 
     final int selectedIndex = _selection.index;
@@ -895,9 +898,9 @@ class _TabBarViewState extends PageableListState<TabBarView> implements TabBarSe
     }
 
     if (_scrollDirection == AnimationDirection.forward)
-      scrollTo(performance.progress);
+      scrollTo(animation.progress);
     else
-      scrollTo(1.0 - performance.progress);
+      scrollTo(1.0 - animation.progress);
   }
 
   void dispatchOnScroll() {
@@ -905,12 +908,12 @@ class _TabBarViewState extends PageableListState<TabBarView> implements TabBarSe
       return;
     // This class is driving the TabBarSelection's performance.
 
-    final Performance performance = _selection._performance;
+    final AnimationController controller = _selection._controller;
 
     if (_selection.index == 0 || _selection.index == _tabCount - 1)
-      performance.progress = scrollOffset;
+      controller.progress = scrollOffset;
     else
-      performance.progress = scrollOffset / 2.0;
+      controller.progress = scrollOffset / 2.0;
   }
 
   Future fling(Offset scrollVelocity) {

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

@@ -70,30 +70,30 @@ class _SmoothlyResizingOverflowBoxState extends State<SmoothlyResizingOverflowBo
 class _Entry {
   _Entry({
     this.child,
-    this.enterPerformance,
+    this.enterController,
     this.enterTransition
   });
 
   final Widget child;
-  final Performance enterPerformance;
+  final AnimationController enterController;
   final Widget enterTransition;
 
   Size childSize = Size.zero;
 
-  Performance exitPerformance;
+  AnimationController exitController;
   Widget exitTransition;
 
   Widget get currentTransition => exitTransition ?? enterTransition;
 
   void dispose() {
-    enterPerformance?.stop();
-    exitPerformance?.stop();
+    enterController?.stop();
+    exitController?.stop();
   }
 }
 
-typedef Widget TransitionBuilderCallback(PerformanceView performance, Widget child);
+typedef Widget TransitionBuilderCallback(Animation animation, Widget child);
 
-Widget _identityTransition(PerformanceView performance, Widget child) => child;
+Widget _identityTransition(Animation animation, Widget child) => child;
 
 class EnterExitTransition extends StatefulComponent {
   EnterExitTransition({
@@ -129,11 +129,11 @@ class _EnterExitTransitionState extends State<EnterExitTransition> {
   }
 
   _Entry _createEnterTransition() {
-    Performance enterPerformance = new Performance(duration: config.duration)..play();
+    AnimationController enterController = new AnimationController(duration: config.duration)..forward();
     return new _Entry(
       child: config.child,
-      enterPerformance: enterPerformance,
-      enterTransition: config.onEnter(enterPerformance, new KeyedSubtree(
+      enterController: enterController,
+      enterTransition: config.onEnter(enterController, new KeyedSubtree(
         key: new GlobalKey(),
         child: config.child
       ))
@@ -141,11 +141,11 @@ class _EnterExitTransitionState extends State<EnterExitTransition> {
   }
 
   Future _createExitTransition(_Entry entry) async {
-    Performance exitPerformance = new Performance(duration: config.duration);
+    AnimationController exitController = new AnimationController(duration: config.duration);
     entry
-      ..exitPerformance = exitPerformance
-      ..exitTransition = config.onExit(exitPerformance, entry.enterTransition);
-    await exitPerformance.play();
+      ..exitController = exitController
+      ..exitTransition = config.onExit(exitController, entry.enterTransition);
+    await exitController.forward();
     if (!mounted)
       return;
     setState(() {