Add a basic InkWell implementation

sky/examples/raw/ink_well.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:sky' as sky;
-import 'package:sky/framework/app.dart';
-import 'package:sky/framework/rendering/box.dart';
-import 'package:sky/framework/rendering/object.dart';
-import 'package:sky/framework/animation/animated_value.dart';
-import 'package:sky/framework/animation/curves.dart';
-
-const double _kInitialSize = 0.0;
-const double _kTargetSize = 100.0;
-const double _kSplashDuration = 500.0;
-const int _kInitialOpacity = 0x80;
-
-class InkSplash {
-  final InkWell inkWell;
-  final sky.Paint _paint = new sky.Paint();
-  final sky.Point position;
-  AnimatedValue radius;
-
-  InkSplash({ this.position, this.inkWell }) {
-    radius = new AnimatedValue(_kInitialSize, onChange: _handleRadiusChange);
-    radius.animateTo(_kTargetSize, _kSplashDuration, curve: easeOut);
-  }
-
-  void _handleRadiusChange() {
-    if (radius.value == _kTargetSize)
-      inkWell._splashes.remove(this);
-    inkWell.markNeedsPaint();
-  }
-
-  void paint(RenderObjectDisplayList canvas) {
-    int opacity = (_kInitialOpacity * (1.0 - (radius.value / _kTargetSize))).floor();
-    _paint.color = new sky.Color(opacity << 24);
-    canvas.drawCircle(position.x, position.y, radius.value, _paint);
-  }
-}
-
-class InkWell extends RenderBox {
-  final List<InkSplash> _splashes = new List<InkSplash>();
-
-  void handleEvent(sky.Event event) {
-    switch (event.type) {
-      case 'pointerdown':
-        _splashes.add(new InkSplash(position: new sky.Point(event.x, event.y),
-                                    inkWell: this));
-        break;
-    }
-    markNeedsPaint();
-  }
-
-  void performLayout() {
-    size = constraints.constrain(sky.Size.infinite);
-  }
-
-  void paint(RenderObjectDisplayList canvas) {
-    canvas.drawRect(new sky.Rect.fromLTRB(0.0, 0.0, size.width, size.height),
-                    new sky.Paint()..color = const sky.Color(0xFFCCCCCC));
-    for (InkSplash splash in _splashes)
-      splash.paint(canvas);
-  }
-}
-
-AppView app;
-
-void main() {
-  app = new AppView(new InkWell());
-}