Add a basic radial reaction to the switch

We still need to tune the various parameters, but this patch is a start.

packages/flutter/example/widgets/big_switch.dart

@@ -2,8 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import 'package:sky/widgets/basic.dart';
-import 'package:sky/widgets/switch.dart';
+import 'package:sky/widgets.dart';
 import 'package:sky/theme/colors.dart';
 import 'package:vector_math/vector_math.dart';
 
@@ -21,7 +20,7 @@ class BigSwitchApp extends App {
     scale.scale(5.0, 5.0);
     return new Container(
         child: new Switch(value: _value, onChanged: _handleOnChanged),
-        padding: new EdgeDims.all(5.0),
+        padding: new EdgeDims.all(20.0),
         transform: scale,
         decoration: new BoxDecoration(
           backgroundColor: Teal[600]

packages/flutter/lib/base/hit_test.dart

@@ -10,6 +10,14 @@ enum EventDisposition {
   consumed,
 }
 
+EventDisposition combineEventDispositions(EventDisposition left, EventDisposition right) {
+  if (left == EventDisposition.consumed || right == EventDisposition.consumed)
+    return EventDisposition.consumed;
+  if (left == EventDisposition.processed || right == EventDisposition.processed)
+    return EventDisposition.processed;
+  return EventDisposition.ignored;
+}
+
 abstract class HitTestTarget {
   EventDisposition handleEvent(sky.Event event, HitTestEntry entry);
 }

packages/flutter/lib/painting/radial_reaction.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 'dart:async';
+import 'dart:sky' as sky;
+import 'dart:sky' show Point, Offset, Color, Paint;
+
+import 'package:sky/animation/animated_value.dart';
+import 'package:sky/animation/animation_performance.dart';
+import 'package:sky/animation/curves.dart';
+
+const Duration _kShowDuration = const Duration(milliseconds: 300);
+const Duration _kHideDuration = const Duration(milliseconds: 200);
+const Color _kOuterColor = const Color(0xFFFFFFFF);
+const Color _kInnerColor = const Color(0xFFFFFFFF);
+const double _kMaxOpacity = 0.2;
+
+int _roundOpacity(double opacity) {
+  return (255 * opacity).round();
+}
+
+class RadialReaction {
+  RadialReaction({
+    this.center,
+    this.radius,
+    Point startPosition
+  }) {
+    _outerOpacity = new AnimatedValue<double>(0.0, end: _kMaxOpacity, curve: easeOut);
+    _innerCenter = new AnimatedValue<Point>(startPosition, end: center, curve: easeOut);
+    _innerRadius = new AnimatedValue<double>(0.0, end: radius, curve: easeOut);
+    _showPerformance = new AnimationPerformance()
+      ..addVariable(_outerOpacity)
+      ..addVariable(_innerCenter)
+      ..addVariable(_innerRadius)
+      ..duration = _kShowDuration;
+
+    _fade = new AnimatedValue(1.0, end: 0.0, curve: easeIn);
+    _hidePerformance = new AnimationPerformance()
+      ..addVariable(_fade)
+      ..duration =_kHideDuration;
+  }
+
+  final Point center;
+  final double radius;
+
+  AnimationPerformance _showPerformance;
+  AnimatedValue<double> _outerOpacity;
+  AnimatedValue<Point> _innerCenter;
+  AnimatedValue<double> _innerRadius;
+
+  Future _showComplete;
+
+  AnimationPerformance _hidePerformance;
+  AnimatedValue<double> _fade;
+
+  void show() {
+    _showComplete = _showPerformance.forward();
+  }
+
+  Future hide() async {
+    await _showComplete;
+    await _hidePerformance.forward();
+  }
+
+  void addListener(Function listener) {
+    _showPerformance.addListener(listener);
+    _hidePerformance.addListener(listener);
+  }
+
+  final Paint _outerPaint = new Paint();
+  final Paint _innerPaint = new Paint();
+
+  void paint(sky.Canvas canvas, Offset offset) {
+    _outerPaint.color = _kOuterColor.withAlpha(_roundOpacity(_outerOpacity.value * _fade.value));
+    canvas.drawCircle(center + offset, radius, _outerPaint);
+
+    _innerPaint.color = _kInnerColor.withAlpha(_roundOpacity(_kMaxOpacity  * _fade.value));
+    canvas.drawCircle(_innerCenter.value + offset, _innerRadius.value, _innerPaint);
+  }
+}

packages/flutter/lib/widgets/basic.dart

@@ -19,7 +19,7 @@ import 'package:sky/rendering/stack.dart';
 import 'package:sky/widgets/default_text_style.dart';
 import 'package:sky/widgets/framework.dart';
 
-export 'package:sky/base/hit_test.dart' show EventDisposition;
+export 'package:sky/base/hit_test.dart' show EventDisposition, combineEventDispositions;
 export 'package:sky/rendering/box.dart' show BackgroundImage, BoxConstraints, BoxDecoration, Border, BorderSide, EdgeDims;
 export 'package:sky/rendering/flex.dart' show FlexDirection, FlexJustifyContent, FlexAlignItems;
 export 'package:sky/rendering/object.dart' show Point, Offset, Size, Rect, Color, Paint, Path;

packages/flutter/lib/widgets/framework.dart

@@ -13,7 +13,7 @@ import 'package:sky/rendering/box.dart';
 import 'package:sky/rendering/object.dart';
 import 'package:sky/rendering/sky_binding.dart';
 
-export 'package:sky/base/hit_test.dart' show EventDisposition;
+export 'package:sky/base/hit_test.dart' show EventDisposition, combineEventDispositions;
 export 'package:sky/rendering/box.dart' show BoxConstraints, BoxDecoration, Border, BorderSide, EdgeDims;
 export 'package:sky/rendering/flex.dart' show FlexDirection;
 export 'package:sky/rendering/object.dart' show Point, Offset, Size, Rect, Color, Paint, Path;

packages/flutter/lib/widgets/switch.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 'dart:async';
 import 'dart:sky' as sky;
 
+import 'package:sky/painting/radial_reaction.dart';
 import 'package:sky/painting/shadows.dart';
 import 'package:sky/rendering/box.dart';
 import 'package:sky/rendering/object.dart';
@@ -26,6 +28,7 @@ const double _kTrackWidth =
     _kSwitchWidth - (_kThumbRadius - _kTrackRadius) * 2.0;
 const Duration _kCheckDuration = const Duration(milliseconds: 200);
 const Size _kSwitchSize = const Size(_kSwitchWidth + 2.0, _kSwitchHeight + 2.0);
+const double _kReactionRadius = _kSwitchWidth / 2.0;
 
 class Switch extends Component {
   Switch({Key key, this.value, this.onChanged}) : super(key: key);
@@ -72,13 +75,48 @@ class _RenderSwitch extends RenderToggleable {
 
   Color _thumbColor;
   Color get thumbColor => _thumbColor;
-
   void set thumbColor(Color value) {
     if (value == _thumbColor) return;
     _thumbColor = value;
     markNeedsPaint();
   }
 
+  RadialReaction _radialReaction;
+
+  EventDisposition handleEvent(sky.Event event, BoxHitTestEntry entry) {
+    if (event is sky.PointerEvent) {
+      if (event.type == 'pointerdown') {
+        _showRadialReaction(entry.localPosition);
+        return combineEventDispositions(EventDisposition.processed,
+                                        super.handleEvent(event, entry));
+      }
+      if (event.type == 'pointerup') {
+        _hideRadialReaction();
+        return combineEventDispositions(EventDisposition.processed,
+                                        super.handleEvent(event, entry));
+      }
+    }
+    return super.handleEvent(event, entry);
+  }
+
+  void _showRadialReaction(Point startLocation) {
+    if (_radialReaction != null)
+      return;
+    _radialReaction = new RadialReaction(
+      center: new Point(_kSwitchSize.width / 2.0, _kSwitchSize.height / 2.0),
+      radius: _kReactionRadius,
+      startPosition: startLocation)
+      ..addListener(markNeedsPaint)
+      ..show();
+  }
+
+  Future _hideRadialReaction() async {
+    if (_radialReaction == null)
+      return;
+    await _radialReaction.hide();
+    _radialReaction = null;
+  }
+
   void paint(PaintingCanvas canvas, Offset offset) {
     sky.Color thumbColor = _kThumbOffColor;
     sky.Color trackColor = _kTrackOffColor;
@@ -97,6 +135,9 @@ class _RenderSwitch extends RenderToggleable {
       ..setRectXY(rect, _kTrackRadius, _kTrackRadius);
     canvas.drawRRect(rrect, paint);
 
+    if (_radialReaction != null)
+      _radialReaction.paint(canvas, offset);
+
     // Draw the raised thumb with a shadow
     paint.color = thumbColor;
     var builder = new ShadowDrawLooperBuilder();