Add AnimatedContainer

This widget is used in Material and Drawer. We don't currently support
animating towards null, but we can add that in a future patch.

packages/flutter/lib/src/rendering/box.dart

@@ -178,6 +178,60 @@ class BoxConstraints extends Constraints {
            (minHeight <= size.height) && (size.height <= math.max(minHeight, maxHeight));
   }
 
+  BoxConstraints operator*(double other) {
+    return new BoxConstraints(
+      minWidth: minWidth * other,
+      maxWidth: maxWidth * other,
+      minHeight: minHeight * other,
+      maxHeight: maxHeight * other
+    );
+  }
+
+  BoxConstraints operator/(double other) {
+    return new BoxConstraints(
+      minWidth: minWidth / other,
+      maxWidth: maxWidth / other,
+      minHeight: minHeight / other,
+      maxHeight: maxHeight / other
+    );
+  }
+
+  BoxConstraints operator~/(double other) {
+    return new BoxConstraints(
+      minWidth: (minWidth ~/ other).toDouble(),
+      maxWidth: (maxWidth ~/ other).toDouble(),
+      minHeight: (minHeight ~/ other).toDouble(),
+      maxHeight: (maxHeight ~/ other).toDouble()
+    );
+  }
+
+  BoxConstraints operator%(double other) {
+    return new BoxConstraints(
+      minWidth: minWidth % other,
+      maxWidth: maxWidth % other,
+      minHeight: minHeight % other,
+      maxHeight: maxHeight % other
+    );
+  }
+
+  /// Linearly interpolate between two BoxConstraints
+  ///
+  /// If either is null, this function interpolates from [BoxConstraints.zero].
+  static BoxConstraints lerp(BoxConstraints a, BoxConstraints b, double t) {
+    if (a == null && b == null)
+      return null;
+    if (a == null)
+      return b * t;
+    if (b == null)
+      return a * (1.0 - t);
+    return new BoxConstraints(
+      minWidth: sky.lerpDouble(a.minWidth, b.minWidth, t),
+      maxWidth: sky.lerpDouble(a.maxWidth, b.maxWidth, t),
+      minHeight: sky.lerpDouble(a.minHeight, b.minHeight, t),
+      maxHeight: sky.lerpDouble(a.maxHeight, b.maxHeight, t)
+    );
+  }
+
   bool operator ==(other) {
     if (identical(this, other))
       return true;

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

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:sky/animation.dart';
+import 'package:sky/src/widgets/basic.dart';
+import 'package:sky/src/widgets/framework.dart';
+
+import 'package:vector_math/vector_math_64.dart';
+
+class AnimatedBoxConstraintsValue extends AnimatedValue<BoxConstraints> {
+  AnimatedBoxConstraintsValue(BoxConstraints begin, { BoxConstraints end, Curve curve: linear })
+    : super(begin, end: end, curve: curve);
+
+  BoxConstraints lerp(double t) => BoxConstraints.lerp(begin, end, t);
+}
+
+class AnimatedBoxDecorationValue extends AnimatedValue<BoxDecoration> {
+  AnimatedBoxDecorationValue(BoxDecoration begin, { BoxDecoration end, Curve curve: linear })
+    : super(begin, end: end, curve: curve);
+
+  BoxDecoration lerp(double t) => BoxDecoration.lerp(begin, end, t);
+}
+
+class AnimatedEdgeDimsValue extends AnimatedValue<EdgeDims> {
+  AnimatedEdgeDimsValue(EdgeDims begin, { EdgeDims end, Curve curve: linear })
+    : super(begin, end: end, curve: curve);
+
+  EdgeDims lerp(double t) => EdgeDims.lerp(begin, end, t);
+}
+
+class AnimatedMatrix4Value extends AnimatedValue<Matrix4> {
+  AnimatedMatrix4Value(Matrix4 begin, { Matrix4 end, Curve curve: linear })
+    : super(begin, end: end, curve: curve);
+
+  Matrix4 lerp(double t) {
+    // TODO(mpcomplete): Animate the full matrix. Will animating the cells
+    // separately work?
+    Vector3 beginT = begin.getTranslation();
+    Vector3 endT = end.getTranslation();
+    Vector3 lerpT = beginT*(1.0-t) + endT*t;
+    return new Matrix4.identity()..translate(lerpT);
+  }
+}
+
+class AnimatedContainer extends StatefulComponent {
+  AnimatedContainer({
+    Key key,
+    this.child,
+    this.constraints,
+    this.decoration,
+    this.foregroundDecoration,
+    this.margin,
+    this.padding,
+    this.transform,
+    this.width,
+    this.height,
+    this.curve: linear,
+    this.duration
+  }) : super(key: key) {
+    assert(margin == null || margin.isNonNegative);
+    assert(padding == null || padding.isNonNegative);
+    assert(curve != null);
+    assert(duration != null);
+  }
+
+  final Widget child;
+  final BoxConstraints constraints;
+  final BoxDecoration decoration;
+  final BoxDecoration foregroundDecoration;
+  final EdgeDims margin;
+  final EdgeDims padding;
+  final Matrix4 transform;
+  final double width;
+  final double height;
+
+  final Curve curve;
+  final Duration duration;
+
+  AnimatedContainerState createState() => new AnimatedContainerState();
+}
+
+class AnimatedContainerState extends State<AnimatedContainer> {
+  AnimatedBoxConstraintsValue _constraints;
+  AnimatedBoxDecorationValue _decoration;
+  AnimatedBoxDecorationValue _foregroundDecoration;
+  AnimatedEdgeDimsValue _margin;
+  AnimatedEdgeDimsValue _padding;
+  AnimatedMatrix4Value _transform;
+  AnimatedValue<double> _width;
+  AnimatedValue<double> _height;
+
+  AnimationPerformance _performance;
+
+  void initState() {
+    super.initState();
+    _performance = new AnimationPerformance(duration: config.duration)
+      ..timing = new AnimationTiming(curve: config.curve)
+      ..addListener(_updateAllVariables);
+    _configAllVariables();
+  }
+
+  void didUpdateConfig(AnimatedContainer oldConfig) {
+    _performance
+      ..duration = config.duration
+      ..timing.curve = config.curve;
+    if (_configAllVariables()) {
+      _performance.progress = 0.0;
+      _performance.play();
+    }
+  }
+
+  void dispose() {
+    _performance.stop();
+    super.dispose();
+  }
+
+  void _updateVariable(AnimatedVariable variable) {
+    if (variable != null)
+      _performance.updateVariable(variable);
+  }
+
+  void _updateAllVariables() {
+    setState(() {
+      _updateVariable(_constraints);
+      _updateVariable(_constraints);
+      _updateVariable(_decoration);
+      _updateVariable(_foregroundDecoration);
+      _updateVariable(_margin);
+      _updateVariable(_padding);
+      _updateVariable(_transform);
+      _updateVariable(_width);
+      _updateVariable(_height);
+    });
+  }
+
+  bool _configVariable(AnimatedValue variable, dynamic targetValue) {
+    dynamic currentValue = variable.value;
+    variable.end = targetValue;
+    variable.begin = currentValue;
+    return currentValue != targetValue;
+  }
+
+  bool _configAllVariables() {
+    bool needsAnimation = false;
+    if (config.constraints != null) {
+      _constraints ??= new AnimatedBoxConstraintsValue(config.constraints);
+      if (_configVariable(_constraints, config.constraints))
+        needsAnimation = true;
+    } else {
+      _constraints = null;
+    }
+
+    if (config.decoration != null) {
+      _decoration ??= new AnimatedBoxDecorationValue(config.decoration);
+      if (_configVariable(_decoration, config.decoration))
+        needsAnimation = true;
+    } else {
+      _decoration = null;
+    }
+
+    if (config.foregroundDecoration != null) {
+      _foregroundDecoration ??= new AnimatedBoxDecorationValue(config.foregroundDecoration);
+      if (_configVariable(_foregroundDecoration, config.foregroundDecoration))
+        needsAnimation = true;
+    } else {
+      _foregroundDecoration = null;
+    }
+
+    if (config.margin != null) {
+      _margin ??= new AnimatedEdgeDimsValue(config.margin);
+      if (_configVariable(_margin, config.margin))
+        needsAnimation = true;
+    } else {
+      _margin = null;
+    }
+
+    if (config.padding != null) {
+      _padding ??= new AnimatedEdgeDimsValue(config.padding);
+      if (_configVariable(_padding, config.padding))
+        needsAnimation = true;
+    } else {
+      _padding = null;
+    }
+
+    if (config.transform != null) {
+      _transform ??= new AnimatedMatrix4Value(config.transform);
+      if (_configVariable(_transform, config.transform))
+        needsAnimation = true;
+    } else {
+      _transform = null;
+    }
+
+    if (config.width != null) {
+      _width ??= new AnimatedValue<double>(config.width);
+      if (_configVariable(_width, config.width))
+        needsAnimation = true;
+    } else {
+      _width = null;
+    }
+
+    if (config.height != null) {
+      _height ??= new AnimatedValue<double>(config.height);
+      if (_configVariable(_height, config.height))
+        needsAnimation = true;
+    } else {
+      _height = null;
+    }
+
+    return needsAnimation;
+  }
+
+  Widget build(BuildContext context) {
+    return new Container(
+      child: config.child,
+      constraints: _constraints?.value,
+      decoration: _decoration?.value,
+      foregroundDecoration: _foregroundDecoration?.value,
+      margin: _margin?.value,
+      padding: _padding?.value,
+      transform: _transform?.value,
+      width: _width?.value,
+      height: _height?.value
+    );
+  }
+}

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

@@ -22,6 +22,7 @@ export 'package:sky/rendering.dart' show
     FlexAlignItems,
     FlexDirection,
     FlexJustifyContent,
+    Matrix4,
     Offset,
     Paint,
     Path,
@@ -392,11 +393,11 @@ class Container extends StatelessComponent {
     this.constraints,
     this.decoration,
     this.foregroundDecoration,
-    this.width,
-    this.height,
     this.margin,
     this.padding,
-    this.transform
+    this.transform,
+    this.width,
+    this.height
   }) : super(key: key) {
     assert(margin == null || margin.isNonNegative);
     assert(padding == null || padding.isNonNegative);
@@ -940,4 +941,4 @@ class KeyedSubtree extends StatelessComponent {
   final Widget child;
 
   Widget build(BuildContext context) => child;
-}
\ No newline at end of file
+}

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

@@ -6,6 +6,7 @@ import 'dart:async';
 
 import 'package:sky/animation.dart';
 import 'package:sky/material.dart';
+import 'package:sky/src/widgets/animated_container.dart';
 import 'package:sky/src/widgets/framework.dart';
 import 'package:sky/src/widgets/basic.dart';
 import 'package:sky/src/widgets/gesture_detector.dart';
@@ -102,9 +103,9 @@ class DrawerState extends State<Drawer> {
     Widget content = new SlideTransition(
       performance: _performance.view,
       position: new AnimatedValue<Point>(_kClosedPosition, end: _kOpenPosition),
-      // TODO(abarth): Use AnimatedContainer
-      child: new Container(
-        // behavior: implicitlyAnimate(const Duration(milliseconds: 200)),
+      child: new AnimatedContainer(
+        curve: ease,
+        duration: const Duration(milliseconds: 200),
         decoration: new BoxDecoration(
           backgroundColor: Theme.of(context).canvasColor,
           boxShadow: shadows[config.level]),

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

@@ -2,8 +2,10 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'package:sky/animation.dart';
 import 'package:sky/painting.dart';
 import 'package:sky/material.dart';
+import 'package:sky/src/widgets/animated_container.dart';
 import 'package:sky/src/widgets/basic.dart';
 import 'package:sky/src/widgets/framework.dart';
 import 'package:sky/src/widgets/theme.dart';
@@ -61,10 +63,11 @@ class Material extends StatelessComponent {
         );
       }
     }
-    // TODO(abarth): This should use AnimatedContainer.
     return new DefaultTextStyle(
       style: Theme.of(context).text.body1,
-      child: new Container(
+      child: new AnimatedContainer(
+        curve: ease,
+        duration: const Duration(milliseconds: 200),
         decoration: new BoxDecoration(
           backgroundColor: getBackgroundColor(context),
           borderRadius: edges[type],

packages/flutter/lib/widgets.dart

@@ -6,6 +6,7 @@
 library widgets;
 
 export 'src/widgets/animated_component.dart';
+export 'src/widgets/animated_container.dart';
 export 'src/widgets/app.dart';
 export 'src/widgets/basic.dart';
 export 'src/widgets/binding.dart';

packages/unit/test/widget/animated_container_test.dart

+import 'package:sky/rendering.dart';
+import 'package:sky/widgets.dart';
+import 'package:test/test.dart';
+
+import 'widget_tester.dart';
+
+void main() {
+  test('AnimatedContainer control test', () {
+    testWidgets((WidgetTester tester) {
+      GlobalKey key = new GlobalKey();
+
+      BoxDecoration decorationA = new BoxDecoration(
+        backgroundColor: new Color(0xFF00FF00)
+      );
+
+      BoxDecoration decorationB = new BoxDecoration(
+        backgroundColor: new Color(0xFF0000FF)
+      );
+
+      tester.pumpWidget(
+        new AnimatedContainer(
+          key: key,
+          duration: const Duration(milliseconds: 200),
+          decoration: decorationA
+        )
+      );
+
+      RenderDecoratedBox box = key.currentState.context.findRenderObject();
+      expect(box.decoration.backgroundColor, equals(decorationA.backgroundColor));
+
+      tester.pumpWidget(
+        new AnimatedContainer(
+          key: key,
+          duration: const Duration(milliseconds: 200),
+          decoration: decorationB
+        )
+      );
+
+      expect(key.currentState.context.findRenderObject(), equals(box));
+      expect(box.decoration.backgroundColor, equals(decorationA.backgroundColor));
+
+      tester.pump(const Duration(seconds: 1));
+
+      expect(box.decoration.backgroundColor, equals(decorationB.backgroundColor));
+
+    });
+  });
+}