Move example fn widgets into sky/framework/components

sky/examples/fn/widgets/material.dart

-part of widgets;
-
-abstract class MaterialComponent extends Component {
-
-  static const _splashesKey = const Object();
-
-  static Style _style = new Style('''
-    transform: translateX(0);
-    position: absolute;
-    top: 0;
-    left: 0;
-    right: 0;
-    bottom: 0'''
-  );
-
-  LinkedHashSet<SplashAnimation> _splashes;
-
-  MaterialComponent({ Object key }) : super(key: key);
-
-  Node build() {
-    List<Node> children = [];
-
-    if (_splashes != null) {
-      children.addAll(_splashes.map((s) => new InkSplash(s.onStyleChanged)));
-    }
-
-    return new Container(
-      style: _style,
-      children: children,
-      key: _splashesKey
-    )..events.listen('gesturescrollstart', _cancelSplashes)
-     ..events.listen('wheel', _cancelSplashes)
-     ..events.listen('pointerdown', _startSplash);
-  }
-
-  sky.ClientRect _getBoundingRect() => (getRoot() as sky.Element).getBoundingClientRect();
-
-  void _startSplash(sky.PointerEvent event) {
-    setState(() {
-      if (_splashes == null) {
-        _splashes = new LinkedHashSet<SplashAnimation>();
-      }
-
-      var splash;
-      splash = new SplashAnimation(_getBoundingRect(), event.x, event.y,
-                                   onDone: () { _splashDone(splash); });
-
-      _splashes.add(splash);
-    });
-  }
-
-  void _cancelSplashes(sky.Event event) {
-    if (_splashes == null) {
-      return;
-    }
-
-    setState(() {
-      var splashes = _splashes;
-      _splashes = null;
-      splashes.forEach((s) { s.cancel(); });
-    });
-  }
-
-  void didUnmount() {
-    _cancelSplashes(null);
-  }
-
-  void _splashDone(SplashAnimation splash) {
-    if (_splashes == null) {
-      return;
-    }
-
-    setState(() {
-      _splashes.remove(splash);
-      if (_splashes.length == 0) {
-        _splashes = null;
-      }
-    });
-  }
-}