Merge remote-tracking branch 'upstream/master'

examples/address_book/lib/main.dart

@@ -53,14 +53,12 @@ class AddressBookHome extends StatelessComponent {
     );
   }
 
-  static final GlobalKey nameKey = new GlobalKey();
-  static final GlobalKey phoneKey = new GlobalKey();
-  static final GlobalKey emailKey = new GlobalKey();
-  static final GlobalKey addressKey = new GlobalKey();
-  static final GlobalKey ringtoneKey = new GlobalKey();
-  static final GlobalKey noteKey = new GlobalKey();
-  static final GlobalKey fillKey = new GlobalKey();
-  static final GlobalKey emoticonKey = new GlobalKey();
+  static final GlobalKey nameKey = new GlobalKey(label: 'name field');
+  static final GlobalKey phoneKey = new GlobalKey(label: 'phone field');
+  static final GlobalKey emailKey = new GlobalKey(label: 'email field');
+  static final GlobalKey addressKey = new GlobalKey(label: 'address field');
+  static final GlobalKey ringtoneKey = new GlobalKey(label: 'ringtone field');
+  static final GlobalKey noteKey = new GlobalKey(label: 'note field');
 
   Widget buildBody(BuildContext context) {
     return new Material(
@@ -83,7 +81,7 @@ class AddressBookHome extends StatelessComponent {
 
   Widget build(BuildContext context) {
     return new Scaffold(
-      toolbar: buildToolBar(context),
+      toolBar: buildToolBar(context),
       body: buildBody(context),
       floatingActionButton: buildFloatingActionButton(context)
     );

examples/demo_launcher/lib/main.dart

@@ -192,7 +192,7 @@ final ThemeData _theme = new ThemeData(
 class DemoHome extends StatelessComponent {
   Widget build(BuildContext context) {
     return new Scaffold(
-      toolbar: new ToolBar(center: new Text('Sky Demos')),
+      toolBar: new ToolBar(center: new Text('Sky Demos')),
       body: new Material(
         type: MaterialType.canvas,
         child: new DemoList()

examples/fitness/lib/feed.dart

@@ -58,11 +58,9 @@ class FeedFragment extends StatefulComponent {
 }
 
 class FeedFragmentState extends State<FeedFragment> {
+  final GlobalKey<PlaceholderState> _snackBarPlaceholderKey = new GlobalKey<PlaceholderState>();
   FitnessMode _fitnessMode = FitnessMode.feed;
 
-  PerformanceStatus _snackBarStatus = PerformanceStatus.dismissed;
-  bool _isShowingSnackBar = false;
-
   void _handleFitnessModeChange(FitnessMode value) {
     setState(() {
       _fitnessMode = value;
@@ -119,15 +117,17 @@ class FeedFragmentState extends State<FeedFragment> {
     );
   }
 
-  FitnessItem _undoItem;
-
   void _handleItemDismissed(FitnessItem item) {
     config.onItemDeleted(item);
-    setState(() {
-      _undoItem = item;
-      _isShowingSnackBar = true;
-      _snackBarStatus = PerformanceStatus.forward;
-    });
+    showSnackBar(
+      navigator: config.navigator,
+      placeholderKey: _snackBarPlaceholderKey,
+      content: new Text("Item deleted."),
+      actions: [new SnackBarAction(label: "UNDO", onPressed: () {
+        config.onItemCreated(item);
+        config.navigator.pop();
+      })]
+    );
   }
 
   Widget buildChart() {
@@ -198,25 +198,6 @@ class FeedFragmentState extends State<FeedFragment> {
     }
   }
 
-  void _handleUndo() {
-    config.onItemCreated(_undoItem);
-    setState(() {
-      _undoItem = null;
-      _isShowingSnackBar = false;
-    });
-  }
-
-  Widget buildSnackBar() {
-    if (_snackBarStatus == PerformanceStatus.dismissed)
-      return null;
-    return new SnackBar(
-      showing: _isShowingSnackBar,
-      content: new Text("Item deleted."),
-      actions: [new SnackBarAction(label: "UNDO", onPressed: _handleUndo)],
-      onDismissed: () { setState(() { _snackBarStatus = PerformanceStatus.dismissed; }); }
-    );
-  }
-
   void _handleActionButtonPressed() {
     showDialog(config.navigator, (NavigatorState navigator) => new AddItemDialog(navigator)).then((routeName) {
       if (routeName != null)
@@ -238,9 +219,9 @@ class FeedFragmentState extends State<FeedFragment> {
 
   Widget build(BuildContext context) {
     return new Scaffold(
-      toolbar: buildToolBar(),
+      toolBar: buildToolBar(),
       body: buildBody(),
-      snackBar: buildSnackBar(),
+      snackBar: new Placeholder(key: _snackBarPlaceholderKey),
       floatingActionButton: buildFloatingActionButton()
     );
   }

examples/fitness/lib/main.dart

@@ -5,7 +5,6 @@
 library fitness;
 
 import 'package:playfair/playfair.dart' as playfair;
-import 'package:sky/animation.dart';
 import 'package:sky/material.dart';
 import 'package:sky/painting.dart';
 import 'package:sky/widgets.dart';

examples/fitness/lib/meal.dart

@@ -105,7 +105,7 @@ class MealFragmentState extends State<MealFragment> {
 
   Widget build(BuildContext context) {
     return new Scaffold(
-      toolbar: buildToolBar(),
+      toolBar: buildToolBar(),
       body: buildBody()
     );
   }

examples/fitness/lib/measurement.dart

@@ -112,9 +112,10 @@ class MeasurementFragment extends StatefulComponent {
 }
 
 class MeasurementFragmentState extends State<MeasurementFragment> {
+  final GlobalKey<PlaceholderState> _snackBarPlaceholderKey = new GlobalKey<PlaceholderState>();
+
   String _weight = "";
   DateTime _when = new DateTime.now();
-  String _errorMessage = null;
 
   void _handleSave() {
     double parsedWeight;
@@ -122,9 +123,11 @@ class MeasurementFragmentState extends State<MeasurementFragment> {
       parsedWeight = double.parse(_weight);
     } on FormatException catch(e) {
       print("Exception $e");
-      setState(() {
-        _errorMessage = "Save failed";
-      });
+      showSnackBar(
+        navigator: config.navigator,
+        placeholderKey: _snackBarPlaceholderKey,
+        content: new Text('Save failed')
+      );
     }
     config.onCreated(new Measurement(when: _when, weight: parsedWeight));
     config.navigator.pop();
@@ -195,18 +198,11 @@ class MeasurementFragmentState extends State<MeasurementFragment> {
     );
   }
 
-  Widget buildSnackBar() {
-    if (_errorMessage == null)
-      return null;
-    // TODO(jackson): This doesn't show up, unclear why.
-    return new SnackBar(content: new Text(_errorMessage), showing: true);
-  }
-
   Widget build(BuildContext context) {
     return new Scaffold(
-      toolbar: buildToolBar(),
+      toolBar: buildToolBar(),
       body: buildBody(context),
-      snackBar: buildSnackBar()
+      snackBar: new Placeholder(key: _snackBarPlaceholderKey)
     );
   }
 }

examples/fitness/lib/settings.dart

@@ -122,7 +122,7 @@ class SettingsFragmentState extends State<SettingsFragment> {
 
   Widget build(BuildContext context) {
     return new Scaffold(
-      toolbar: buildToolBar(),
+      toolBar: buildToolBar(),
       body: buildSettingsPane(context)
     );
   }

examples/game/lib/main.dart

@@ -119,8 +119,10 @@ class GameDemoState extends State<GameDemo> {
             width: 128.0,
             height: 128.0
           ),
-          new Text(
-            "Last Score: $_lastScore",
+          new DefaultTextStyle(
+            child: new Text(
+              "Last Score: $_lastScore"
+            ),
             style: new TextStyle(fontSize:20.0)
           )
         ],

examples/mine_digger/lib/main.dart

@@ -182,7 +182,7 @@ class MineDiggerState extends State<MineDigger> {
     return new Title(
       title: 'Mine Digger',
       child: new Scaffold(
-        toolbar: buildToolBar(context),
+        toolBar: buildToolBar(context),
         body: new Container(
           child: new Center(child: board),
           decoration: new BoxDecoration(backgroundColor: Colors.grey[50])

examples/stocks/lib/main.dart

@@ -8,7 +8,6 @@ import 'dart:async';
 import 'dart:math' as math;
 import 'dart:sky' as sky;
 
-import 'package:sky/animation.dart';
 import 'package:sky/gestures.dart';
 import 'package:sky/material.dart';
 import 'package:sky/painting.dart';

examples/stocks/lib/stock_home.dart

@@ -6,8 +6,6 @@ part of stocks;
 
 typedef void ModeUpdater(StockMode mode);
 
-const Duration _kSnackbarSlideDuration = const Duration(milliseconds: 200);
-
 class StockHome extends StatefulComponent {
   StockHome(this.navigator, this.stocks, this.symbols, this.stockMode, this.modeUpdater);
 
@@ -22,12 +20,10 @@ class StockHome extends StatefulComponent {
 
 class StockHomeState extends State<StockHome> {
 
+  final GlobalKey<PlaceholderState> _snackBarPlaceholderKey = new GlobalKey<PlaceholderState>();
   bool _isSearching = false;
   String _searchQuery;
 
-  PerformanceStatus _snackBarStatus = PerformanceStatus.dismissed;
-  bool _isSnackBarShowing = false;
-
   void _handleSearchBegin() {
     config.navigator.pushState(this, (_) {
       setState(() {
@@ -130,6 +126,7 @@ class StockHomeState extends State<StockHome> {
 
   Widget buildToolBar() {
     return new ToolBar(
+      level: 0,
       left: new IconButton(
         icon: "navigation/menu",
         onPressed: _showDrawer
@@ -217,30 +214,20 @@ class StockHomeState extends State<StockHome> {
   }
 
   void _handleUndo() {
-    setState(() {
-      _isSnackBarShowing = false;
-    });
+    config.navigator.pop();
   }
 
-  GlobalKey snackBarKey = new GlobalKey(label: 'snackbar');
-  Widget buildSnackBar() {
-    if (_snackBarStatus == PerformanceStatus.dismissed)
-      return null;
-    return new SnackBar(
-      showing: _isSnackBarShowing,
+  void _handleStockPurchased() {
+    showSnackBar(
+      navigator: config.navigator,
+      placeholderKey: _snackBarPlaceholderKey,
       content: new Text("Stock purchased!"),
-      actions: [new SnackBarAction(label: "UNDO", onPressed: _handleUndo)],
-      onDismissed: () { setState(() { _snackBarStatus = PerformanceStatus.dismissed; }); }
+      actions: [
+        new SnackBarAction(label: "UNDO", onPressed: _handleUndo)
+      ]
     );
   }
 
-  void _handleStockPurchased() {
-    setState(() {
-      _isSnackBarShowing = true;
-      _snackBarStatus = PerformanceStatus.forward;
-    });
-  }
-
   Widget buildFloatingActionButton() {
     return new FloatingActionButton(
       child: new Icon(type: 'content/add', size: 24),
@@ -251,9 +238,9 @@ class StockHomeState extends State<StockHome> {
 
   Widget build(BuildContext context) {
     return new Scaffold(
-      toolbar: _isSearching ? buildSearchBar() : buildToolBar(),
+      toolBar: _isSearching ? buildSearchBar() : buildToolBar(),
       body: buildTabNavigator(),
-      snackBar: buildSnackBar(),
+      snackBar: new Placeholder(key: _snackBarPlaceholderKey),
       floatingActionButton: buildFloatingActionButton()
     );
   }

examples/stocks/lib/stock_menu.dart

@@ -6,12 +6,14 @@ part of stocks;
 
 enum _MenuItems { autorefresh, autorefreshCheckbox, add, remove }
 
+const double _kMenuMargin = 16.0; // 24.0 on tablet
+
 Future showStockMenu(NavigatorState navigator, { bool autorefresh, ValueChanged onAutorefreshChanged }) async {
   switch (await showMenu(
     navigator: navigator,
     position: new MenuPosition(
-      right: sky.view.paddingRight,
-      top: sky.view.paddingTop
+      right: sky.view.paddingRight + _kMenuMargin,
+      top: sky.view.paddingTop + _kMenuMargin
     ),
     builder: (NavigatorState navigator) {
       return <PopupMenuItem>[

examples/stocks/lib/stock_settings.dart

@@ -119,7 +119,7 @@ class StockSettingsState extends State<StockSettings> {
 
   Widget build(BuildContext context) {
     return new Scaffold(
-      toolbar: buildToolBar(context),
+      toolBar: buildToolBar(context),
       body: buildSettingsPane(context)
     );
   }

examples/stocks/lib/stock_symbol_viewer.dart

@@ -25,7 +25,7 @@ class StockSymbolViewerState extends State<StockSymbolViewer> {
     TextStyle headings = Theme.of(context).text.body2;
 
     return new Scaffold(
-      toolbar: new ToolBar(
+      toolBar: new ToolBar(
         left: new IconButton(
           icon: 'navigation/arrow_back',
           onPressed: config.navigator.pop

examples/widgets/card_collection.dart

@@ -342,7 +342,7 @@ class CardCollectionState extends State<CardCollection> {
     }
 
     return new Scaffold(
-      toolbar: buildToolBar(),
+      toolBar: buildToolBar(),
       body: body
     );
   }

examples/widgets/date_picker.dart

@@ -34,7 +34,7 @@ class DatePickerDemoState extends State<DatePickerDemo> {
       ),
       child: new Stack([
         new Scaffold(
-          toolbar: new ToolBar(center: new Text("Date Picker")),
+          toolBar: new ToolBar(center: new Text("Date Picker")),
           body: new Material(
             child: new Row(
               [new Text(_dateTime.toString())],

examples/widgets/drag_and_drop.dart

@@ -101,7 +101,7 @@ class DragAndDropApp extends StatefulComponent {
 class DragAndDropAppState extends State<DragAndDropApp> {
   Widget build(BuildContext context) {
     return new Scaffold(
-      toolbar: new ToolBar(
+      toolBar: new ToolBar(
         center: new Text('Drag and Drop Flutter Demo')
       ),
       body: new Material(

examples/widgets/ensure_visible.dart

@@ -89,7 +89,7 @@ class EnsureVisibleApp extends App {
         child: new Title(
           title: 'Cards',
           child: new Scaffold(
-            toolbar: new ToolBar(center: new Text('Tap a Card')),
+            toolBar: new ToolBar(center: new Text('Tap a Card')),
             body: cardCollection
           )
         )

examples/widgets/overlay_geometry.dart

@@ -138,7 +138,7 @@ class OverlayGeometryAppState extends State<OverlayGeometryApp> {
   Widget build(BuildContext context) {
     List<Widget> layers = <Widget>[
       new Scaffold(
-        toolbar: new ToolBar(center: new Text('Tap a Card')),
+        toolBar: new ToolBar(center: new Text('Tap a Card')),
         body: new Container(
           padding: const EdgeDims.symmetric(vertical: 12.0, horizontal: 8.0),
           decoration: new BoxDecoration(backgroundColor: Theme.of(context).primarySwatch[50]),

examples/widgets/pageable_list.dart

@@ -149,7 +149,7 @@ class PageableListAppState extends State<PageableListApp> {
     return new IconTheme(
       data: const IconThemeData(color: IconThemeColor.white),
       child: new Scaffold(
-        toolbar: buildToolBar(),
+        toolBar: buildToolBar(),
         body: buildBody(context)
       )
     );

examples/widgets/progress_indicator.dart

@@ -103,7 +103,7 @@ class ProgressIndicatorAppState extends State<ProgressIndicatorApp> {
         child: new Title(
           title: 'Progress Indicators',
           child: new Scaffold(
-            toolbar: new ToolBar(center: new Text('Progress Indicators')),
+            toolBar: new ToolBar(center: new Text('Progress Indicators')),
             body: new DefaultTextStyle(
               style: Theme.of(context).text.title,
               child: body

examples/widgets/scale.dart

@@ -59,7 +59,7 @@ class ScaleAppState extends State<ScaleApp> {
     return new Theme(
       data: new ThemeData.dark(),
       child: new Scaffold(
-        toolbar: new ToolBar(
+        toolBar: new ToolBar(
             center: new Text('Scale Demo')),
         body: new Material(
           type: MaterialType.canvas,

examples/widgets/sector.dart

@@ -124,7 +124,7 @@ class SectorApp extends App {
       child: new Title(
         title: 'Sector Layout',
         child: new Scaffold(
-          toolbar: new ToolBar(
+          toolBar: new ToolBar(
             center: new Text('Sector Layout in a Widget Tree')
           ),
           body: buildBody()

examples/widgets/styled_text.dart

@@ -106,7 +106,7 @@ HAL: This mission is too important for me to allow you to jeopardize it.''';
           color: Colors.grey[50],
           child: interactiveBody
         ),
-        toolbar: new ToolBar(
+        toolBar: new ToolBar(
           center: new Text('Hal and Dave')
         )
       )

examples/widgets/tabs.dart

@@ -131,7 +131,7 @@ class TabbedNavigatorAppState extends State<TabbedNavigatorApp> {
     );
 
     return new Scaffold(
-      toolbar: toolbar,
+      toolBar: toolbar,
       body: tabNavigator
     );
   }

packages/flutter/lib/services.dart

@@ -16,6 +16,7 @@ export 'src/services/asset_bundle.dart';
 export 'src/services/embedder.dart';
 export 'src/services/fetch.dart';
 export 'src/services/image_cache.dart';
+export 'src/services/image_decoder.dart';
 export 'src/services/image_resource.dart';
 export 'src/services/keyboard.dart';
 export 'src/services/shell.dart';

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

@@ -14,10 +14,12 @@ const double kStatusBarHeight = 50.0;
 // Mobile Portrait: 56dp
 // Tablet/Desktop: 64dp
 const double kToolBarHeight = 56.0;
+const double kSnackBarHeight = 52.0;
 
 const double kMaterialDrawerHeight = 140.0;
 const double kScrollbarSize = 10.0;
-const double kScrollbarFadeDuration = 250.0;
-const double kScrollbarFadeDelay = 300.0;
+const Duration kScrollbarFadeDuration = const Duration(milliseconds: 250);
+const Duration kScrollbarFadeDelay = const Duration(milliseconds: 300);
 const double kFadingEdgeLength = 12.0;
-const double kPressedStateDuration = 64.0;
+const double kPressedStateDuration = 64.0; // units?
+const Duration kThemeChangeDuration = const Duration(milliseconds: 200);

packages/flutter/lib/src/services/asset_bundle.dart

@@ -11,6 +11,7 @@ import 'package:mojo/core.dart' as core;
 import 'package:mojo_services/mojo/asset_bundle/asset_bundle.mojom.dart';
 import 'package:sky/src/services/fetch.dart';
 import 'package:sky/src/services/image_cache.dart';
+import 'package:sky/src/services/image_decoder.dart';
 import 'package:sky/src/services/image_resource.dart';
 import 'package:sky/src/services/shell.dart';
 
@@ -66,13 +67,13 @@ class MojoAssetBundle extends AssetBundle {
     _imageCache = null;
   }
 
+  Future<sky.Image> _fetchImage(String key) async {
+    return await decodeImageFromDataPipe(await load(key));
+  }
+
   ImageResource loadImage(String key) {
     return _imageCache.putIfAbsent(key, () {
-      Completer<sky.Image> completer = new Completer<sky.Image>();
-      load(key).then((assetData) {
-        new sky.ImageDecoder.consume(assetData.handle.h, completer.complete);
-      });
-      return new ImageResource(completer.future);
+      return new ImageResource(_fetchImage(key));
     });
   }
 

packages/flutter/lib/src/services/image_cache.dart

@@ -7,8 +7,18 @@ import 'dart:collection';
 import 'dart:sky' as sky;
 
 import 'package:mojo/mojo/url_response.mojom.dart';
-import 'package:sky/src/services/image_resource.dart';
 import 'package:sky/src/services/fetch.dart';
+import 'package:sky/src/services/image_decoder.dart';
+import 'package:sky/src/services/image_resource.dart';
+
+Future<sky.Image> _fetchImage(String url) async {
+  UrlResponse response = await fetchUrl(url);
+  if (response.statusCode >= 400) {
+    print("Failed (${response.statusCode}) to load image ${url}");
+    return null;
+  }
+  return await decodeImageFromDataPipe(response.body);
+}
 
 class _ImageCache {
   _ImageCache._();
@@ -17,16 +27,7 @@ class _ImageCache {
 
   ImageResource load(String url) {
     return _cache.putIfAbsent(url, () {
-      Completer<sky.Image> completer = new Completer<sky.Image>();
-      fetchUrl(url).then((UrlResponse response) {
-        if (response.statusCode >= 400) {
-          print("Failed (${response.statusCode}) to load image ${url}");
-          completer.complete(null);
-        } else {
-          new sky.ImageDecoder.consume(response.body.handle.h, completer.complete);
-        }
-      });
-      return new ImageResource(completer.future);
+      return new ImageResource(_fetchImage(url));
     });
   }
 }

packages/flutter/lib/src/services/image_decoder.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' show Image, ImageDecoder, ImageDecoderCallback;
+import 'dart:typed_data';
+
+import 'package:mojo/core.dart' show MojoDataPipeConsumer;
+
+final Set<ImageDecoder> _activeDecoders = new Set<ImageDecoder>();
+
+typedef ImageDecoder _DecoderFactory(ImageDecoderCallback callback);
+
+Future<Image> _decode(_DecoderFactory createDecoder) {
+  Completer<Image> completer = new Completer<Image>();
+  ImageDecoder decoder;
+  decoder = createDecoder((Image image) {
+    _activeDecoders.remove(decoder);
+    completer.complete(image);
+  });
+  _activeDecoders.add(decoder);
+  return completer.future;
+}
+
+Future<Image> decodeImageFromDataPipe(MojoDataPipeConsumer consumerHandle) {
+  return _decode((ImageDecoderCallback callback) => new ImageDecoder.consume(consumerHandle.handle.h, callback));
+}
+
+Future<Image> decodeImageFromList(Uint8List list) {
+  return _decode((ImageDecoderCallback callback) => new ImageDecoder.fromList(list, callback));
+}

packages/flutter/lib/src/widgets/animated_component.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/framework.dart';
-
-abstract class AnimatedComponent extends StatefulComponent {
-  const AnimatedComponent({ Key key, this.direction, this.duration }) : super(key: key);
-
-  final Duration duration;
-  final AnimationDirection direction;
-}
-
-abstract class AnimatedState<T extends AnimatedComponent> extends State<T> {
-  void initState() {
-    super.initState();
-    _performance = new Performance(duration: config.duration);
-    performance.addStatusListener(_handleAnimationStatusChanged);
-    if (buildDependsOnPerformance) {
-      performance.addListener(() {
-        setState(() {
-          // We don't actually have any state to change, per se,
-          // we just know that we have in fact changed state.
-        });
-      });
-    }
-    performance.play(config.direction);
-  }
-
-  void didUpdateConfig(T oldConfig) {
-    performance.duration = config.duration;
-    if (config.duration != oldConfig.duration || config.direction != oldConfig.direction)
-      performance.play(config.direction);
-  }
-
-  Performance get performance => _performance;
-  Performance _performance;
-
-  void _handleAnimationStatusChanged(PerformanceStatus status) {
-    if (status == PerformanceStatus.completed)
-      handleCompleted();
-    else if (status == PerformanceStatus.dismissed)
-      handleDismissed();
-  }
-
-  bool get buildDependsOnPerformance => false;
-  void handleCompleted() { }
-  void handleDismissed() { }
-}

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

@@ -77,10 +77,10 @@ class AnimatedContainer extends StatefulComponent {
   final Curve curve;
   final Duration duration;
 
-  AnimatedContainerState createState() => new AnimatedContainerState();
+  _AnimatedContainerState createState() => new _AnimatedContainerState();
 }
 
-class AnimatedContainerState extends State<AnimatedContainer> {
+class _AnimatedContainerState extends State<AnimatedContainer> {
   AnimatedBoxConstraintsValue _constraints;
   AnimatedBoxDecorationValue _decoration;
   AnimatedBoxDecorationValue _foregroundDecoration;

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

@@ -47,10 +47,10 @@ class App extends StatefulComponent {
   final Map<String, RouteBuilder> routes;
   final RouteGenerator onGenerateRoute;
 
-  AppState createState() => new AppState();
+  _AppState createState() => new _AppState();
 }
 
-class AppState extends State<App> {
+class _AppState extends State<App> {
 
   GlobalObjectKey _navigator;
 

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

@@ -808,10 +808,10 @@ class ImageListener extends StatefulComponent {
   final ImageFit fit;
   final ImageRepeat repeat;
 
-  ImageListenerState createState() => new ImageListenerState();
+  _ImageListenerState createState() => new _ImageListenerState();
 }
 
-class ImageListenerState extends State<ImageListener> {
+class _ImageListenerState extends State<ImageListener> {
   void initState() {
     super.initState();
     config.image.addListener(_handleImageChanged);

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

@@ -41,7 +41,7 @@ class WidgetFlutterBinding extends FlutterBinding {
     Element.finalizeTree();
   }
 
-  List<BuildableElement> _dirtyElements = new List<BuildableElement>();
+  List<BuildableElement> _dirtyElements = <BuildableElement>[];
 
   /// Adds an element to the dirty elements list so that it will be rebuilt
   /// when buildDirtyElements is called.
@@ -62,10 +62,19 @@ class WidgetFlutterBinding extends FlutterBinding {
       return;
     BuildableElement.lockState(() {
       _dirtyElements.sort((BuildableElement a, BuildableElement b) => a.depth - b.depth);
-      for (BuildableElement element in _dirtyElements)
-        element.rebuild();
+      int dirtyCount = _dirtyElements.length;
+      int index = 0;
+      while (index < dirtyCount) {
+        _dirtyElements[index].rebuild();
+        index += 1;
+        if (dirtyCount < _dirtyElements.length) {
+          _dirtyElements.sort((BuildableElement a, BuildableElement b) => a.depth - b.depth);
+          dirtyCount = _dirtyElements.length;
+        }
+      }
+      assert(!_dirtyElements.any((BuildableElement element) => element.dirty));
       _dirtyElements.clear();
-    });
+    }, building: true);
     assert(_dirtyElements.isEmpty);
   }
 }
@@ -76,7 +85,7 @@ void runApp(Widget app) {
     WidgetFlutterBinding.instance.renderViewElement.update(
       WidgetFlutterBinding.instance.describeApp(app)
     );
-  });
+  }, building: true);
 }
 
 void debugDumpApp() {

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

@@ -39,10 +39,10 @@ class DatePicker extends StatefulComponent {
   final DateTime firstDate;
   final DateTime lastDate;
 
-  DatePickerState createState() => new DatePickerState();
+  _DatePickerState createState() => new _DatePickerState();
 }
 
-class DatePickerState extends State<DatePicker> {
+class _DatePickerState extends State<DatePicker> {
   DatePickerMode _mode = DatePickerMode.day;
 
   void _handleModeChanged(DatePickerMode mode) {
@@ -70,7 +70,7 @@ class DatePickerState extends State<DatePicker> {
   static const double _calendarHeight = 210.0;
 
   Widget build(BuildContext context) {
-    Widget header = new DatePickerHeader(
+    Widget header = new _DatePickerHeader(
       selectedDate: config.selectedDate,
       mode: _mode,
       onModeChanged: _handleModeChanged
@@ -107,8 +107,8 @@ class DatePickerState extends State<DatePicker> {
 }
 
 // Shows the selected date in large font and toggles between year and day mode
-class DatePickerHeader extends StatelessComponent {
-  DatePickerHeader({ this.selectedDate, this.mode, this.onModeChanged }) {
+class _DatePickerHeader extends StatelessComponent {
+  _DatePickerHeader({ this.selectedDate, this.mode, this.onModeChanged }) {
     assert(selectedDate != null);
     assert(mode != null);
   }
@@ -290,10 +290,10 @@ class MonthPicker extends ScrollableWidgetList {
   final DateTime firstDate;
   final DateTime lastDate;
 
-  MonthPickerState createState() => new MonthPickerState();
+  _MonthPickerState createState() => new _MonthPickerState();
 }
 
-class MonthPickerState extends ScrollableWidgetListState<MonthPicker> {
+class _MonthPickerState extends ScrollableWidgetListState<MonthPicker> {
   void initState() {
     super.initState();
     _updateCurrentDate();
@@ -363,10 +363,10 @@ class YearPicker extends ScrollableWidgetList {
   final DateTime firstDate;
   final DateTime lastDate;
 
-  YearPickerState createState() => new YearPickerState();
+  _YearPickerState createState() => new _YearPickerState();
 }
 
-class YearPickerState extends ScrollableWidgetListState<YearPicker> {
+class _YearPickerState extends ScrollableWidgetListState<YearPicker> {
   int get itemCount => config.lastDate.year - config.firstDate.year + 1;
 
   List<Widget> buildItems(BuildContext context, int start, int count) {

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

@@ -131,16 +131,15 @@ class Dialog extends StatelessComponent {
   }
 }
 
-const Duration _kTransitionDuration = const Duration(milliseconds: 150);
-
-class DialogRoute extends Route {
-  DialogRoute({ this.completer, this.builder });
+class _DialogRoute extends Route {
+  _DialogRoute({ this.completer, this.builder });
 
   final Completer completer;
   final RouteBuilder builder;
 
-  Duration get transitionDuration => _kTransitionDuration;
   bool get opaque => false;
+  Duration get transitionDuration => const Duration(milliseconds: 150);
+
   Widget build(NavigatorState navigator, PerformanceView nextRoutePerformance) {
     return new FadeTransition(
       performance: performance,
@@ -157,7 +156,7 @@ class DialogRoute extends Route {
 
 Future showDialog(NavigatorState navigator, DialogBuilder builder) {
   Completer completer = new Completer();
-  navigator.push(new DialogRoute(
+  navigator.push(new _DialogRoute(
     completer: completer,
     builder: (RouteArguments args) {
       return new Focus(

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

@@ -39,15 +39,15 @@ class Dismissable extends StatefulComponent {
     this.direction: DismissDirection.horizontal
   }) : super(key: key);
 
-  Widget child;
-  ResizedCallback onResized;
-  DismissedCallback onDismissed;
-  DismissDirection direction;
+  final Widget child;
+  final ResizedCallback onResized;
+  final DismissedCallback onDismissed;
+  final DismissDirection direction;
 
-  DismissableState createState() => new DismissableState();
+  _DismissableState createState() => new _DismissableState();
 }
 
-class DismissableState extends State<Dismissable> {
+class _DismissableState extends State<Dismissable> {
   void initState() {
     super.initState();
     _fadePerformance = new Performance(duration: _kCardDismissFadeout);

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

@@ -62,10 +62,10 @@ class Draggable extends StatefulComponent {
   final Offset feedbackOffset;
   final DragAnchor dragAnchor;
 
-  DraggableState createState() => new DraggableState();
+  _DraggableState createState() => new _DraggableState();
 }
 
-class DraggableState extends State<Draggable> {
+class _DraggableState extends State<Draggable> {
   DragRoute _route;
 
   void _startDrag(sky.PointerEvent event) {

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

@@ -23,10 +23,10 @@ class DrawerItem extends StatefulComponent {
   final GestureTapCallback onPressed;
   final bool selected;
 
-  DrawerItemState createState() => new DrawerItemState();
+  _DrawerItemState createState() => new _DrawerItemState();
 }
 
-class DrawerItemState extends ButtonState<DrawerItem> {
+class _DrawerItemState extends ButtonState<DrawerItem> {
   TextStyle _getTextStyle(ThemeData themeData) {
     TextStyle result = themeData.text.body2;
     if (config.selected)

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

@@ -20,10 +20,10 @@ class FlatButton extends MaterialButton {
              enabled: enabled,
              onPressed: onPressed);
 
-  FlatButtonState createState() => new FlatButtonState();
+  _FlatButtonState createState() => new _FlatButtonState();
 }
 
-class FlatButtonState extends MaterialButtonState<FlatButton> {
+class _FlatButtonState extends MaterialButtonState<FlatButton> {
   Color getColor(BuildContext context) {
     if (!config.enabled || !highlight)
       return null;

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

@@ -27,10 +27,10 @@ class FloatingActionButton extends StatefulComponent {
   final Color backgroundColor;
   final GestureTapCallback onPressed;
 
-  FloatingActionButtonState createState() => new FloatingActionButtonState();
+  _FloatingActionButtonState createState() => new _FloatingActionButtonState();
 }
 
-class FloatingActionButtonState extends ButtonState<FloatingActionButton> {
+class _FloatingActionButtonState extends ButtonState<FloatingActionButton> {
   Widget buildContent(BuildContext context) {
     IconThemeColor iconThemeColor = IconThemeColor.white;
     Color materialColor = config.backgroundColor;

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

@@ -75,6 +75,52 @@ class Focus extends StatefulComponent {
   final bool autofocus;
   final Widget child;
 
+  static bool at(BuildContext context, Widget widget, { bool autofocus: true }) {
+    assert(widget != null);
+    assert(widget.key is GlobalKey);
+    _FocusScope focusScope = context.inheritedWidgetOfType(_FocusScope);
+    if (focusScope != null) {
+      if (autofocus)
+        focusScope._setFocusedWidgetIfUnset(widget.key);
+      return focusScope.scopeFocused &&
+             focusScope.focusedScope == null &&
+             focusScope.focusedWidget == widget.key;
+    }
+    return true;
+  }
+
+  static bool _atScope(BuildContext context, Widget widget, { bool autofocus: true }) {
+    assert(widget != null);
+    _FocusScope focusScope = context.inheritedWidgetOfType(_FocusScope);
+    if (focusScope != null) {
+      if (autofocus)
+        focusScope._setFocusedScopeIfUnset(widget.key);
+      assert(widget.key != null);
+      return focusScope.scopeFocused &&
+             focusScope.focusedScope == widget.key;
+    }
+    return true;
+  }
+
+  // Don't call moveTo() from your build() function, it's intended to be called
+  // from event listeners, e.g. in response to a finger tap or tab key.
+
+  static void moveTo(BuildContext context, Widget widget) {
+    assert(widget != null);
+    assert(widget.key is GlobalKey);
+    _FocusScope focusScope = context.inheritedWidgetOfType(_FocusScope);
+    if (focusScope != null)
+      focusScope.focusState._setFocusedWidget(widget.key);
+  }
+
+  static void _moveScopeTo(BuildContext context, Focus component) {
+    assert(component != null);
+    assert(component.key != null);
+    _FocusScope focusScope = context.inheritedWidgetOfType(_FocusScope);
+    if (focusScope != null)
+      focusScope.focusState._setFocusedScope(component.key);
+  }
+
   FocusState createState() => new FocusState();
 }
 
@@ -155,7 +201,7 @@ class FocusState extends State<Focus> {
   void initState() {
     super.initState();
     if (config.autofocus)
-      FocusState._moveScopeTo(context, config);
+      Focus._moveScopeTo(context, config);
     _updateWidgetRemovalListener(_focusedWidget);
     _updateScopeRemovalListener(_focusedScope);
   }
@@ -169,56 +215,10 @@ class FocusState extends State<Focus> {
   Widget build(BuildContext context) {
     return new _FocusScope(
       focusState: this,
-      scopeFocused: FocusState._atScope(context, config),
+      scopeFocused: Focus._atScope(context, config),
       focusedScope: _focusedScope == _noFocusedScope ? null : _focusedScope,
       focusedWidget: _focusedWidget,
       child: config.child
     );
   }
-
-  static bool at(BuildContext context, Widget widget, { bool autofocus: true }) {
-    assert(widget != null);
-    assert(widget.key is GlobalKey);
-    _FocusScope focusScope = context.inheritedWidgetOfType(_FocusScope);
-    if (focusScope != null) {
-      if (autofocus)
-        focusScope._setFocusedWidgetIfUnset(widget.key);
-      return focusScope.scopeFocused &&
-             focusScope.focusedScope == null &&
-             focusScope.focusedWidget == widget.key;
-    }
-    return true;
-  }
-
-  static bool _atScope(BuildContext context, Widget widget, { bool autofocus: true }) {
-    assert(widget != null);
-    _FocusScope focusScope = context.inheritedWidgetOfType(_FocusScope);
-    if (focusScope != null) {
-      if (autofocus)
-        focusScope._setFocusedScopeIfUnset(widget.key);
-      assert(widget.key != null);
-      return focusScope.scopeFocused &&
-             focusScope.focusedScope == widget.key;
-    }
-    return true;
-  }
-
-  // Don't call moveTo() from your build() function, it's intended to be called
-  // from event listeners, e.g. in response to a finger tap or tab key.
-
-  static void moveTo(BuildContext context, Widget widget) {
-    assert(widget != null);
-    assert(widget.key is GlobalKey);
-    _FocusScope focusScope = context.inheritedWidgetOfType(_FocusScope);
-    if (focusScope != null)
-      focusScope.focusState._setFocusedWidget(widget.key);
-  }
-
-  static void _moveScopeTo(BuildContext context, Focus component) {
-    assert(component != null);
-    assert(component.key != null);
-    _FocusScope focusScope = context.inheritedWidgetOfType(_FocusScope);
-    if (focusScope != null)
-      focusScope.focusState._setFocusedScope(component.key);
-  }
 }

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

@@ -50,7 +50,7 @@ typedef void GlobalKeyRemoveListener(GlobalKey key);
 /// A GlobalKey is one that must be unique across the entire application. It is
 /// used by components that need to communicate with other components across the
 /// application's element tree.
-abstract class GlobalKey extends Key {
+abstract class GlobalKey<T extends State> extends Key {
   const GlobalKey.constructor() : super.constructor(); // so that subclasses can call us, since the Key() factory constructor shadows the implicit constructor
 
   /// Constructs a LabeledGlobalKey, which is a GlobalKey with a label used for debugging.
@@ -96,9 +96,9 @@ abstract class GlobalKey extends Key {
   Element get _currentElement => _registry[this];
   BuildContext get currentContext => _currentElement;
   Widget get currentWidget => _currentElement?.widget;
-  State get currentState {
+  T get currentState {
     Element element = _currentElement;
-    if (element is StatefulComponentElement)
+    if (element is StatefulComponentElement<dynamic, T>)
       return element.state;
     return null;
   }
@@ -186,8 +186,8 @@ abstract class Widget {
     final List<String> data = <String>[];
     debugFillDescription(data);
     if (data.isEmpty)
-      return 'name';
-    return 'name(${data.join("; ")})';
+      return '$name';
+    return '$name(${data.join("; ")})';
    }
 
   void debugFillDescription(List<String> description) { }
@@ -550,7 +550,7 @@ abstract class Element<T extends Widget> implements BuildContext {
   /// Wrapper around visitChildren for BuildContext.
   void visitChildElements(void visitor(Element element)) {
     // don't allow visitChildElements() during build, since children aren't necessarily built yet
-    assert(BuildableElement._debugStateLockLevel == 0);
+    assert(!BuildableElement._debugStateLocked);
     visitChildren(visitor);
   }
 
@@ -858,6 +858,8 @@ abstract class BuildableElement<T extends Widget> extends Element<T> {
     assert(_child != null);
   }
 
+  static BuildableElement _debugCurrentBuildTarget;
+
   /// Reinvokes the build() method of the StatelessComponent object (for
   /// stateless components) or the State object (for stateful components) and
   /// then updates the widget tree.
@@ -874,6 +876,12 @@ abstract class BuildableElement<T extends Widget> extends Element<T> {
     assert(_debugLifecycleState == _ElementLifecycle.active);
     assert(_debugStateLocked);
     assert(_debugSetAllowIgnoredCallsToMarkNeedsBuild(true));
+    BuildableElement debugPreviousBuildTarget;
+    assert(() {
+      debugPreviousBuildTarget = _debugCurrentBuildTarget;
+      _debugCurrentBuildTarget = this;
+     return true;
+    });
     Widget built;
     try {
       built = _builder(this);
@@ -896,12 +904,19 @@ abstract class BuildableElement<T extends Widget> extends Element<T> {
       built = new ErrorWidget();
       _child = updateChild(null, built, slot);
     }
+
+    assert(() {
+      assert(_debugCurrentBuildTarget == this);
+      _debugCurrentBuildTarget = debugPreviousBuildTarget;
+      return true;
+    });
   }
 
   static BuildScheduler scheduleBuildFor;
 
   static int _debugStateLockLevel = 0;
   static bool get _debugStateLocked => _debugStateLockLevel > 0;
+  static bool _debugBuilding = false;
 
   /// Establishes a scope in which component build functions can run.
   ///
@@ -913,13 +928,31 @@ abstract class BuildableElement<T extends Widget> extends Element<T> {
   /// After unwinding the last build scope on the stack, the framework verifies
   /// that each global key is used at most once and notifies listeners about
   /// changes to global keys.
-  static void lockState(void callback()) {
+  static void lockState(void callback(), { bool building: false }) {
+    assert(_debugStateLockLevel >= 0);
+    assert(() {
+      if (building) {
+        assert(!_debugBuilding);
+        assert(_debugCurrentBuildTarget == null);
+        _debugBuilding = true;
+      }
       _debugStateLockLevel += 1;
+      return true;
+    });
     try {
       callback();
     } finally {
+      assert(() {
         _debugStateLockLevel -= 1;
+        if (building) {
+          assert(_debugBuilding);
+          assert(_debugCurrentBuildTarget == null);
+          _debugBuilding = false;
+        }
+        return true;
+      });
     }
+    assert(_debugStateLockLevel >= 0);
   }
 
   /// Marks the element as dirty and adds it to the global list of widgets to
@@ -934,10 +967,23 @@ abstract class BuildableElement<T extends Widget> extends Element<T> {
     if (!_active)
       return;
     assert(_debugLifecycleState == _ElementLifecycle.active);
-    assert(!_debugStateLocked || (_debugAllowIgnoredCallsToMarkNeedsBuild && dirty));
+    assert(() {
+      if (_debugBuilding) {
+        bool foundTarget = false;
+        visitAncestorElements((Element element) {
+          if (element == _debugCurrentBuildTarget) {
+            foundTarget = true;
+            return false;
+          }
+          return true;
+        });
+        if (foundTarget)
+          return true;
+      }
+      return !_debugStateLocked || (_debugAllowIgnoredCallsToMarkNeedsBuild && dirty);
+    });
     if (dirty)
       return;
-    assert(!_debugStateLocked);
     _dirty = true;
     assert(scheduleBuildFor != null);
     scheduleBuildFor(this);
@@ -1101,11 +1147,12 @@ class InheritedElement extends StatelessComponentElement<InheritedWidget> {
   }
 
   void _notifyDescendants() {
-    final Type ourRuntimeType = runtimeType;
+    final Type ourRuntimeType = widget.runtimeType;
     void notifyChildren(Element child) {
       if (child._dependencies != null &&
-          child._dependencies.contains(ourRuntimeType))
+          child._dependencies.contains(ourRuntimeType)) {
         child.dependenciesChanged();
+      }
       if (child.runtimeType != ourRuntimeType)
         child.visitChildren(notifyChildren);
     }

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

@@ -59,10 +59,10 @@ class GestureDetector extends StatefulComponent {
   final GestureScaleUpdateCallback onScaleUpdate;
   final GestureScaleEndCallback onScaleEnd;
 
-  GestureDetectorState createState() => new GestureDetectorState();
+  _GestureDetectorState createState() => new _GestureDetectorState();
 }
 
-class GestureDetectorState extends State<GestureDetector> {
+class _GestureDetectorState extends State<GestureDetector> {
   final PointerRouter _router = FlutterBinding.instance.pointerRouter;
 
   TapGestureRecognizer _tap;

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

@@ -30,7 +30,7 @@ class HomogeneousViewport extends RenderObjectWidget {
   final ScrollDirection direction;
   final double startOffset;
 
-  HomogeneousViewportElement createElement() => new HomogeneousViewportElement(this);
+  _HomogeneousViewportElement createElement() => new _HomogeneousViewportElement(this);
 
   // we don't pass constructor arguments to the RenderBlockViewport() because until
   // we know our children, the constructor arguments we could give have no effect
@@ -48,8 +48,8 @@ class HomogeneousViewport extends RenderObjectWidget {
   // all the actual work is done in the element
 }
 
-class HomogeneousViewportElement extends RenderObjectElement<HomogeneousViewport> {
-  HomogeneousViewportElement(HomogeneousViewport widget) : super(widget);
+class _HomogeneousViewportElement extends RenderObjectElement<HomogeneousViewport> {
+  _HomogeneousViewportElement(HomogeneousViewport widget) : super(widget);
 
   List<Element> _children = const <Element>[];
   int _layoutFirstIndex;

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

@@ -61,7 +61,7 @@ class Icon extends StatelessComponent {
   final IconThemeColor color;
   final sky.ColorFilter colorFilter;
 
-  String getColorSuffix(BuildContext context) {
+  String _getColorSuffix(BuildContext context) {
     IconThemeColor iconThemeColor = color;
     if (iconThemeColor == null) {
       IconThemeData iconThemeData = IconTheme.of(context);
@@ -90,7 +90,7 @@ class Icon extends StatelessComponent {
     // TODO(eseidel): This clearly isn't correct.  Not sure what would be.
     // Should we use the ios images on ios?
     String density = 'drawable-xxhdpi';
-    String colorSuffix = getColorSuffix(context);
+    String colorSuffix = _getColorSuffix(context);
     return new AssetImage(
       bundle: _iconBundle,
       name: '${category}/${density}/ic_${subtype}_${colorSuffix}_${size}dp.png',

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

@@ -26,8 +26,8 @@ double _getSplashTargetSize(Size bounds, Point position) {
   return math.max(math.max(d1, d2), math.max(d3, d4)).ceil().toDouble();
 }
 
-class InkSplash {
-  InkSplash(this.position, this.well) {
+class _InkSplash {
+  _InkSplash(this.position, this.well) {
     _targetRadius = _getSplashTargetSize(well.size, position);
     _radius = new AnimatedValue<double>(
         _kSplashInitialSize, end: _targetRadius, curve: easeOut);
@@ -42,7 +42,7 @@ class InkSplash {
   }
 
   final Point position;
-  final RenderInkWell well;
+  final _RenderInkWell well;
 
   double _targetRadius;
   double _pinnedRadius;
@@ -98,8 +98,8 @@ class InkSplash {
   }
 }
 
-class RenderInkWell extends RenderProxyBox {
-  RenderInkWell({
+class _RenderInkWell extends RenderProxyBox {
+  _RenderInkWell({
     RenderBox child,
     GestureTapCallback onTap,
     GestureLongPressCallback onLongPress
@@ -122,7 +122,7 @@ class RenderInkWell extends RenderProxyBox {
     _syncLongPressRecognizer();
   }
 
-  final List<InkSplash> _splashes = new List<InkSplash>();
+  final List<_InkSplash> _splashes = new List<_InkSplash>();
 
   TapGestureRecognizer _tap;
   LongPressGestureRecognizer _longPress;
@@ -131,7 +131,7 @@ class RenderInkWell extends RenderProxyBox {
     if (event.type == 'pointerdown' && (_tap != null || _longPress != null)) {
       _tap?.addPointer(event);
       _longPress?.addPointer(event);
-      _splashes.add(new InkSplash(entry.localPosition, this));
+      _splashes.add(new _InkSplash(entry.localPosition, this));
     }
   }
 
@@ -196,7 +196,7 @@ class RenderInkWell extends RenderProxyBox {
       canvas.save();
       canvas.translate(offset.dx, offset.dy);
       canvas.clipRect(Point.origin & size);
-      for (InkSplash splash in _splashes)
+      for (_InkSplash splash in _splashes)
         splash.paint(canvas);
       canvas.restore();
     }
@@ -215,9 +215,9 @@ class InkWell extends OneChildRenderObjectWidget {
   final GestureTapCallback onTap;
   final GestureLongPressCallback onLongPress;
 
-  RenderInkWell createRenderObject() => new RenderInkWell(onTap: onTap, onLongPress: onLongPress);
+  _RenderInkWell createRenderObject() => new _RenderInkWell(onTap: onTap, onLongPress: onLongPress);
 
-  void updateRenderObject(RenderInkWell renderObject, InkWell oldWidget) {
+  void updateRenderObject(_RenderInkWell renderObject, InkWell oldWidget) {
     renderObject.onTap = onTap;
     renderObject.onLongPress = onLongPress;
   }

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

@@ -39,10 +39,10 @@ class Input extends Scrollable {
   final String placeholder;
   final StringValueChanged onChanged;
 
-  InputState createState() => new InputState();
+  _InputState createState() => new _InputState();
 }
 
-class InputState extends ScrollableState<Input> {
+class _InputState extends ScrollableState<Input> {
   String _value;
   EditableString _editableValue;
   KeyboardHandle _keyboardHandle = KeyboardHandle.unattached;
@@ -71,7 +71,7 @@ class InputState extends ScrollableState<Input> {
 
   Widget buildContent(BuildContext context) {
     ThemeData themeData = Theme.of(context);
-    bool focused = FocusState.at(context, config);
+    bool focused = Focus.at(context, config);
 
     if (focused && !_keyboardHandle.attached) {
       _keyboardHandle = keyboard.show(_editableValue.stub, config.keyboardType);
@@ -122,11 +122,11 @@ class InputState extends ScrollableState<Input> {
         )
       ),
       onPointerDown: (_) {
-        if (FocusState.at(context, config)) {
+        if (Focus.at(context, config)) {
           assert(_keyboardHandle.attached);
           _keyboardHandle.showByRequest();
         } else {
-          FocusState.moveTo(context, config);
+          Focus.moveTo(context, config);
           // we'll get told to rebuild and we'll take care of the keyboard then
         }
       }

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

@@ -12,7 +12,7 @@ import 'package:sky/src/widgets/theme.dart';
 
 enum MaterialType { canvas, card, circle, button }
 
-const Map<MaterialType, double> edges = const {
+const Map<MaterialType, double> _kEdges = const <MaterialType, double>{
   MaterialType.canvas: null,
   MaterialType.card: 2.0,
   MaterialType.circle: null,
@@ -35,7 +35,7 @@ class Material extends StatelessComponent {
   final int level;
   final Color color;
 
-  Color getBackgroundColor(BuildContext context) {
+  Color _getBackgroundColor(BuildContext context) {
     if (color != null)
       return color;
     switch (type) {
@@ -55,10 +55,10 @@ class Material extends StatelessComponent {
         style: Theme.of(context).text.body1,
         child: contents
       );
-      if (edges[type] != null) {
+      if (_kEdges[type] != null) {
         contents = new ClipRRect(
-          xRadius: edges[type],
-          yRadius: edges[type],
+          xRadius: _kEdges[type],
+          yRadius: _kEdges[type],
           child: contents
         );
       }
@@ -67,10 +67,10 @@ class Material extends StatelessComponent {
       style: Theme.of(context).text.body1,
       child: new AnimatedContainer(
         curve: ease,
-        duration: const Duration(milliseconds: 200),
+        duration: kThemeChangeDuration,
         decoration: new BoxDecoration(
-          backgroundColor: getBackgroundColor(context),
-          borderRadius: edges[type],
+          backgroundColor: _getBackgroundColor(context),
+          borderRadius: _kEdges[type],
           boxShadow: level == 0 ? null : shadows[level],
           shape: type == MaterialType.circle ? Shape.circle : Shape.rectangle
         ),

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

@@ -9,7 +9,7 @@ import 'package:sky/src/widgets/framework.dart';
 import 'package:sky/src/widgets/ink_well.dart';
 import 'package:sky/src/widgets/material.dart';
 
-// Rather than using this class directly, please use FlatButton or RaisedButton.
+/// Rather than using this class directly, please use FlatButton or RaisedButton.
 abstract class MaterialButton extends StatefulComponent {
   MaterialButton({
     Key key,

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

@@ -31,7 +31,7 @@ class MixedViewport extends RenderObjectWidget {
   final ExtentsUpdateCallback onExtentsUpdate;
   final InvalidatorAvailableCallback onInvalidatorAvailable;
 
-  MixedViewportElement createElement() => new MixedViewportElement(this);
+  _MixedViewportElement createElement() => new _MixedViewportElement(this);
 
   // we don't pass constructor arguments to the RenderBlockViewport() because until
   // we know our children, the constructor arguments we could give have no effect
@@ -60,8 +60,8 @@ class _ChildKey {
   String toString() => "_ChildKey(type: $type, key: $key)";
 }
 
-class MixedViewportElement extends RenderObjectElement<MixedViewport> {
-  MixedViewportElement(MixedViewport widget) : super(widget) {
+class _MixedViewportElement extends RenderObjectElement<MixedViewport> {
+  _MixedViewportElement(MixedViewport widget) : super(widget) {
     if (widget.onInvalidatorAvailable != null)
       widget.onInvalidatorAvailable(invalidate);
   }

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

@@ -18,7 +18,7 @@ class RouteArguments {
 typedef Widget RouteBuilder(RouteArguments args);
 typedef RouteBuilder RouteGenerator(String name);
 typedef void StateRouteCallback(StateRoute route);
-typedef void NotificationCallback();
+typedef void _RouteCallback(Route route);
 
 class Navigator extends StatefulComponent {
   Navigator({
@@ -51,7 +51,7 @@ class NavigatorState extends State<Navigator> {
     PageRoute route = new PageRoute(config.routes['/']);
     assert(route != null);
     assert(!route.ephemeral);
-    _history.add(route);
+    _insertRoute(route);
   }
 
   void pushState(State owner, Function callback) {
@@ -63,29 +63,30 @@ class NavigatorState extends State<Navigator> {
   }
 
   void pushNamed(String name) {
-    RouteBuilder builder;
-    if (!config.routes.containsKey(name)) {
+    RouteBuilder generateRoute() {
       assert(config.onGenerateRoute != null);
-      builder = config.onGenerateRoute(name);
-    } else {
-      builder = config.routes[name];
+      return config.onGenerateRoute(name);
     }
-    if (builder == null)
-      builder = config.onUnknownRoute; // 404!
-    assert(builder != null); // 404 getting your 404!
+    RouteBuilder builder = config.routes[name] ?? generateRoute() ?? config.onUnknownRoute;
     push(new PageRoute(builder));
   }
 
+  void _insertRoute(Route route) {
+    _history.insert(_currentPosition, route);
+    route._onDismissed = _handleRouteDismissed;
+    route._onRemoveRoute = _handleRemoveRoute;
+    route.didPush();
+  }
+
   void push(Route route) {
     assert(!_debugCurrentlyHaveRoute(route));
     setState(() {
       while (currentRoute.ephemeral) {
-        assert(currentRoute.ephemeral);
         currentRoute.didPop(null);
         _currentPosition -= 1;
       }
-      _history.insert(_currentPosition + 1, route);
       _currentPosition += 1;
+      _insertRoute(route);
     });
   }
 
@@ -107,10 +108,6 @@ class NavigatorState extends State<Navigator> {
 
   void pop([dynamic result]) {
     setState(() {
-      while (currentRoute.ephemeral) {
-        currentRoute.didPop(null);
-        _currentPosition -= 1;
-      }
       assert(_currentPosition > 0);
       currentRoute.didPop(result);
       _currentPosition -= 1;
@@ -122,6 +119,19 @@ class NavigatorState extends State<Navigator> {
     return index >= 0 && index <= _currentPosition;
   }
 
+  void _handleRouteDismissed(Route route) {
+    assert(_history.contains(route));
+    if (_history.lastIndexOf(route) <= _currentPosition)
+      popRoute(route);
+  }
+
+  void _handleRemoveRoute(Route route) {
+    assert(_history.contains(route));
+    setState(() {
+      _history.remove(route);
+    });
+  }
+
   Widget build(BuildContext context) {
     List<Widget> visibleRoutes = new List<Widget>();
     bool alreadyInsertModalBarrier = false;
@@ -132,20 +142,6 @@ class NavigatorState extends State<Navigator> {
         assert(!route.modal);
         continue;
       }
-      route.ensurePerformance(
-        direction: (i <= _currentPosition) ? AnimationDirection.forward : AnimationDirection.reverse
-      );
-      route._onDismissed = () {
-        assert(_history.contains(route));
-        if (_history.lastIndexOf(route) <= _currentPosition)
-          popRoute(route);
-      };
-      route._onRemoveRoute = () {
-        assert(_history.contains(route));
-        setState(() {
-          _history.remove(route);
-        });
-      };
       visibleRoutes.add(
         new KeyedSubtree(
           key: new ObjectKey(route),
@@ -171,11 +167,14 @@ class NavigatorState extends State<Navigator> {
 
 
 abstract class Route {
+  Route() {
+    _performance = createPerformance();
+  }
 
   PerformanceView get performance => _performance?.view;
   Performance _performance;
-  NotificationCallback _onDismissed;
-  NotificationCallback _onRemoveRoute;
+  _RouteCallback _onDismissed;
+  _RouteCallback _onRemoveRoute;
 
   Performance createPerformance() {
     Duration duration = transitionDuration;
@@ -184,26 +183,15 @@ abstract class Route {
         ..addStatusListener((PerformanceStatus status) {
           if (status == PerformanceStatus.dismissed) {
             if (_onDismissed != null)
-              _onDismissed();
+              _onDismissed(this);
             if (_onRemoveRoute != null)
-              _onRemoveRoute();
+              _onRemoveRoute(this);
           }
         });
     }
     return null;
   }
 
-  void ensurePerformance({ AnimationDirection direction }) {
-    assert(direction != null);
-    if (_performance == null)
-      _performance = createPerformance();
-    if (_performance != null) {
-      PerformanceStatus desiredStatus = direction == AnimationDirection.forward ? PerformanceStatus.forward : PerformanceStatus.reverse;
-      if (_performance.status != desiredStatus)
-        _performance.play(direction);
-    }
-  }
-
   /// If hasContent is true, then the route represents some on-screen state.
   ///
   /// If hasContent is false, then no performance will be created, and the values of
@@ -262,9 +250,15 @@ abstract class Route {
   bool get isActuallyOpaque => (performance == null || _performance.isCompleted) && opaque;
 
   Widget build(NavigatorState navigator, PerformanceView nextRoutePerformance);
+
+  void didPush() {
+    _performance?.forward();
+  }
+
   void didPop([dynamic result]) {
+    _performance?.reverse();
     if (performance == null && _onRemoveRoute != null)
-      _onRemoveRoute();
+      _onRemoveRoute(this);
   }
 
   String toString() => '$runtimeType()';

packages/flutter/lib/src/widgets/placeholder.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/src/widgets/basic.dart';
+import 'package:sky/src/widgets/framework.dart';
+
+class Placeholder extends StatefulComponent {
+  Placeholder({ Key key }) : super(key: key);
+
+  PlaceholderState createState() => new PlaceholderState();
+}
+
+class PlaceholderState extends State<Placeholder> {
+  Widget get child => _child;
+  Widget _child;
+  void set child(Widget child) {
+    if (_child == child)
+      return;
+    setState(() {
+      _child = child;
+    });
+  }
+
+  Widget build(BuildContext context) {
+    if (_child != null)
+      return child;
+    return new SizedBox(width: 0.0, height: 0.0);
+  }
+}

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

@@ -21,7 +21,6 @@ import 'package:sky/src/widgets/transitions.dart';
 const Duration _kMenuDuration = const Duration(milliseconds: 300);
 const double _kMenuCloseIntervalEnd = 2.0 / 3.0;
 const double _kMenuWidthStep = 56.0;
-const double _kMenuMargin = 16.0; // 24.0 on tablet
 const double _kMenuMinWidth = 2.0 * _kMenuWidthStep;
 const double _kMenuMaxWidth = 5.0 * _kMenuWidthStep;
 const double _kMenuHorizontalPadding = 16.0;
@@ -75,8 +74,6 @@ class PopupMenu extends StatelessComponent {
     return new FadeTransition(
       performance: performance,
       opacity: new AnimatedValue<double>(0.0, end: 1.0, curve: new Interval(0.0, 1.0 / 3.0)),
-      child: new Container(
-        margin: new EdgeDims.all(_kMenuMargin),
       child: new BuilderTransition(
         performance: performance,
         variables: [width, height],
@@ -108,7 +105,6 @@ class PopupMenu extends StatelessComponent {
           );
         }
       )
-      )
     );
   }
 }
@@ -121,8 +117,8 @@ class MenuPosition {
   final double left;
 }
 
-class MenuRoute extends Route {
-  MenuRoute({ this.completer, this.position, this.builder, this.level });
+class _MenuRoute extends Route {
+  _MenuRoute({ this.completer, this.position, this.builder, this.level });
 
   final Completer completer;
   final MenuPosition position;
@@ -137,7 +133,7 @@ class MenuRoute extends Route {
     return result;
   }
 
-  bool get ephemeral => false; // we could make this true, but then we'd have to use popRoute(), not pop(), in menus
+  bool get ephemeral => true;
   bool get modal => true;
   bool get opaque => false;
   Duration get transitionDuration => _kMenuDuration;
@@ -169,7 +165,7 @@ class MenuRoute extends Route {
 
 Future showMenu({ NavigatorState navigator, MenuPosition position, PopupMenuItemsBuilder builder, int level: 4 }) {
   Completer completer = new Completer();
-  navigator.push(new MenuRoute(
+  navigator.push(new _MenuRoute(
     completer: completer,
     position: position,
     builder: builder,

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

@@ -31,10 +31,10 @@ abstract class ProgressIndicator extends StatefulComponent {
 
   Widget _buildIndicator(BuildContext context, double performanceValue);
 
-  ProgressIndicatorState createState() => new ProgressIndicatorState();
+  _ProgressIndicatorState createState() => new _ProgressIndicatorState();
 }
 
-class ProgressIndicatorState extends State<ProgressIndicator> {
+class _ProgressIndicatorState extends State<ProgressIndicator> {
 
   ValuePerformance<double> _performance;
 

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

@@ -14,7 +14,7 @@ const sky.Color _kDarkOffColor = const sky.Color(0xB2FFFFFF);
 
 typedef RadioValueChanged(Object value);
 
-class Radio extends StatefulComponent {
+class Radio extends StatelessComponent {
   Radio({
     Key key,
     this.value,
@@ -28,13 +28,9 @@ class Radio extends StatefulComponent {
   final Object groupValue;
   final RadioValueChanged onChanged;
 
-  RadioState createState() => new RadioState();
-}
-
-class RadioState extends State<Radio> {
   Color _getColor(BuildContext context) {
     ThemeData themeData = Theme.of(context);
-    if (config.value == config.groupValue)
+    if (value == groupValue)
       return themeData.accentColor;
     return themeData.brightness == ThemeBrightness.light ? _kLightOffColor : _kDarkOffColor;
   }
@@ -44,7 +40,7 @@ class RadioState extends State<Radio> {
     const double kOuterRadius = kDiameter / 2;
     const double kInnerRadius = 5.0;
     return new GestureDetector(
-      onTap: () => config.onChanged(config.value),
+      onTap: () => onChanged(value),
       child: new Container(
         margin: const EdgeDims.symmetric(horizontal: 5.0),
         width: kDiameter,
@@ -60,7 +56,7 @@ class RadioState extends State<Radio> {
             canvas.drawCircle(const Point(kOuterRadius, kOuterRadius), kOuterRadius, paint);
 
             // Draw the inner circle
-            if (config.value == config.groupValue) {
+            if (value == groupValue) {
               paint.setStyle(sky.PaintingStyle.fill);
               canvas.drawCircle(const Point(kOuterRadius, kOuterRadius), kInnerRadius, paint);
             }

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

@@ -22,10 +22,10 @@ class RaisedButton extends MaterialButton {
     assert(enabled != null);
   }
 
-  RaisedButtonState createState() => new RaisedButtonState();
+  _RaisedButtonState createState() => new _RaisedButtonState();
 }
 
-class RaisedButtonState extends MaterialButtonState<RaisedButton> {
+class _RaisedButtonState extends MaterialButtonState<RaisedButton> {
   Color getColor(BuildContext context) {
     if (config.enabled) {
       switch (Theme.of(context).brightness) {

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

@@ -6,247 +6,88 @@ import 'dart:sky' as sky;
 
 import 'package:sky/material.dart';
 import 'package:sky/rendering.dart';
+import 'package:sky/src/widgets/basic.dart';
 import 'package:sky/src/widgets/framework.dart';
 
-// Slots are painted in this order and hit tested in reverse of this order
-enum ScaffoldSlots {
-  body,
-  statusBar,
-  toolbar,
-  snackBar,
-  floatingActionButton,
-  drawer
-}
-
-class RenderScaffold extends RenderBox {
-
-  RenderScaffold({
-    RenderBox body,
-    RenderBox statusBar,
-    RenderBox toolbar,
-    RenderBox snackBar,
-    RenderBox floatingActionButton,
-    RenderBox drawer
-  }) {
-    this[ScaffoldSlots.body] = body;
-    this[ScaffoldSlots.statusBar] = statusBar;
-    this[ScaffoldSlots.toolbar] = toolbar;
-    this[ScaffoldSlots.snackBar] = snackBar;
-    this[ScaffoldSlots.floatingActionButton] = floatingActionButton;
-    this[ScaffoldSlots.drawer] = drawer;
-  }
-
-  Map<ScaffoldSlots, RenderBox> _slots = new Map<ScaffoldSlots, RenderBox>();
-  RenderBox operator[] (ScaffoldSlots slot) => _slots[slot];
-  void operator[]= (ScaffoldSlots slot, RenderBox value) {
-    RenderBox old = _slots[slot];
-    if (old == value)
-      return;
-    if (old != null)
-      dropChild(old);
-    if (value == null) {
-      _slots.remove(slot);
-    } else {
-      _slots[slot] = value;
-      adoptChild(value);
-    }
-    markNeedsLayout();
-  }
-
-  void attachChildren() {
-    for (ScaffoldSlots slot in ScaffoldSlots.values) {
-      RenderBox box = _slots[slot];
-      if (box != null)
-        box.attach();
-    }
-  }
-
-  void detachChildren() {
-    for (ScaffoldSlots slot in ScaffoldSlots.values) {
-      RenderBox box = _slots[slot];
-      if (box != null)
-        box.detach();
-    }
-  }
-
-  void visitChildren(RenderObjectVisitor visitor) {
-    for (ScaffoldSlots slot in ScaffoldSlots.values) {
-      RenderBox box = _slots[slot];
-      if (box != null)
-        visitor(box);
-    }
-  }
-
-  ScaffoldSlots remove(RenderBox child) {
-    assert(child != null);
-    for (ScaffoldSlots slot in ScaffoldSlots.values) {
-      if (_slots[slot] == child) {
-        this[slot] = null;
-        return slot;
-      }
-    }
-    return null;
-  }
-
-  bool get sizedByParent => true;
-  void performResize() {
-    size = constraints.biggest;
-    assert(!size.isInfinite);
-  }
-
-  // TODO(eseidel): These change based on device size!
-  // http://www.google.com/design/spec/layout/metrics-keylines.html#metrics-keylines-keylines-spacing
-  static const kButtonX = 16.0; // left from right edge of body
-  static const kButtonY = 16.0; // up from bottom edge of body
-
-  void performLayout() {
-    double bodyHeight = size.height;
-    double bodyPosition = 0.0;
-    double fabOffset = 0.0;
-    if (_slots[ScaffoldSlots.statusBar] != null) {
-      RenderBox statusBar = _slots[ScaffoldSlots.statusBar];
-      statusBar.layout(new BoxConstraints.tight(new Size(size.width, kStatusBarHeight)));
-      assert(statusBar.parentData is BoxParentData);
-      statusBar.parentData.position = new Point(0.0, size.height - kStatusBarHeight);
-      bodyHeight -= kStatusBarHeight;
-    }
-    if (_slots[ScaffoldSlots.toolbar] != null) {
-      RenderBox toolbar = _slots[ScaffoldSlots.toolbar];
-      double toolbarHeight = kToolBarHeight + sky.view.paddingTop;
-      toolbar.layout(new BoxConstraints.tight(new Size(size.width, toolbarHeight)));
-      assert(toolbar.parentData is BoxParentData);
-      toolbar.parentData.position = Point.origin;
-      bodyPosition += toolbarHeight;
-      bodyHeight -= toolbarHeight;
-    }
-    if (_slots[ScaffoldSlots.body] != null) {
-      RenderBox body = _slots[ScaffoldSlots.body];
-      body.layout(new BoxConstraints.tight(new Size(size.width, bodyHeight)));
-      assert(body.parentData is BoxParentData);
-      body.parentData.position = new Point(0.0, bodyPosition);
-    }
-    if (_slots[ScaffoldSlots.snackBar] != null) {
-      RenderBox snackBar = _slots[ScaffoldSlots.snackBar];
-      // TODO(jackson): On tablet/desktop, minWidth = 288, maxWidth = 568
-      snackBar.layout(
-        new BoxConstraints(minWidth: size.width, maxWidth: size.width, minHeight: 0.0, maxHeight: bodyHeight),
-        parentUsesSize: true
-      );
-      assert(snackBar.parentData is BoxParentData);
-      snackBar.parentData.position = new Point(0.0, bodyPosition + bodyHeight - snackBar.size.height);
-      fabOffset += snackBar.size.height;
-    }
-    if (_slots[ScaffoldSlots.floatingActionButton] != null) {
-      RenderBox floatingActionButton = _slots[ScaffoldSlots.floatingActionButton];
-      Size area = new Size(size.width - kButtonX, size.height - kButtonY);
-      floatingActionButton.layout(new BoxConstraints.loose(area), parentUsesSize: true);
-      assert(floatingActionButton.parentData is BoxParentData);
-      floatingActionButton.parentData.position = (area - floatingActionButton.size).toPoint() + new Offset(0.0, -fabOffset);
-    }
-    if (_slots[ScaffoldSlots.drawer] != null) {
-      RenderBox drawer = _slots[ScaffoldSlots.drawer];
-      drawer.layout(new BoxConstraints(minWidth: 0.0, maxWidth: size.width, minHeight: size.height, maxHeight: size.height));
-      assert(drawer.parentData is BoxParentData);
-      drawer.parentData.position = Point.origin;
-    }
-  }
-
-  void paint(PaintingContext context, Offset offset) {
-    for (ScaffoldSlots slot in ScaffoldSlots.values) {
-      RenderBox box = _slots[slot];
-      if (box != null) {
-        assert(box.parentData is BoxParentData);
-        context.paintChild(box, box.parentData.position + offset);
-      }
-    }
-  }
-
-  void hitTestChildren(HitTestResult result, { Point position }) {
-    for (ScaffoldSlots slot in ScaffoldSlots.values.reversed) {
-      RenderBox box = _slots[slot];
-      if (box != null) {
-        assert(box.parentData is BoxParentData);
-        if (box.hitTest(result, position: (position - box.parentData.position).toPoint()))
-          return;
-      }
-    }
-  }
-
-  String debugDescribeChildren(String prefix) {
-    return _slots.keys.map((slot) => '${prefix}${slot}: ${_slots[slot].toStringDeep(prefix)}').join();
-  }
-}
-
-class Scaffold extends RenderObjectWidget {
+class Scaffold extends StatelessComponent {
   Scaffold({
     Key key,
-    Widget body,
-    Widget statusBar,
-    Widget toolbar,
-    Widget snackBar,
-    Widget floatingActionButton,
-    Widget drawer
-  }) : super(key: key) {
-    _children[ScaffoldSlots.body] = body;
-    _children[ScaffoldSlots.statusBar] = statusBar;
-    _children[ScaffoldSlots.toolbar] = toolbar;
-    _children[ScaffoldSlots.snackBar] = snackBar;
-    _children[ScaffoldSlots.floatingActionButton] = floatingActionButton;
-    _children[ScaffoldSlots.drawer] = drawer;
-  }
-
-  final Map<ScaffoldSlots, Widget> _children = new Map<ScaffoldSlots, Widget>();
-
-  RenderScaffold createRenderObject() => new RenderScaffold();
-
-  ScaffoldElement createElement() => new ScaffoldElement(this);
-}
-
-class ScaffoldElement extends RenderObjectElement<Scaffold> {
-  ScaffoldElement(Scaffold widget) : super(widget);
-
-  Map<ScaffoldSlots, Element> _children;
-
-  RenderScaffold get renderObject => super.renderObject;
-
-  void visitChildren(ElementVisitor visitor) {
-    for (ScaffoldSlots slot in ScaffoldSlots.values) {
-      Element element = _children[slot];
-      if (element != null)
-        visitor(element);
-    }
-  }
-
-  void mount(Element parent, dynamic newSlot) {
-    super.mount(parent, newSlot);
-    _children = new Map<ScaffoldSlots, Element>();
-    for (ScaffoldSlots slot in ScaffoldSlots.values) {
-      Element newChild = widget._children[slot]?.createElement();
-      _children[slot] = newChild;
-      newChild?.mount(this, slot);
-    }
-  }
-
-  void update(Scaffold newWidget) {
-    super.update(newWidget);
-    assert(widget == newWidget);
-    for (ScaffoldSlots slot in ScaffoldSlots.values) {
-      _children[slot] = updateChild(_children[slot], widget._children[slot], slot);
-      assert((_children[slot] == null) == (widget._children[slot] == null));
-    }
+    this.body,
+    this.statusBar,
+    this.toolBar,
+    this.snackBar,
+    this.floatingActionButton
+  }) : super(key: key);
+
+  final Widget body;
+  final Widget statusBar;
+  final Widget toolBar;
+  final Widget snackBar;
+  final Widget floatingActionButton;
+
+  Widget build(BuildContext context) {
+    double toolBarHeight = 0.0;
+    if (toolBar != null)
+      toolBarHeight = kToolBarHeight + sky.view.paddingTop;
+
+    double statusBarHeight = 0.0;
+    if (statusBar != null)
+      statusBarHeight = kStatusBarHeight;
+
+    List<Widget> children = <Widget>[];
+
+    if (body != null) {
+      children.add(new Positioned(
+        top: toolBarHeight, right: 0.0, bottom: statusBarHeight, left: 0.0,
+        child: body
+      ));
+    }
+
+    if (statusBar != null) {
+      children.add(new Positioned(
+        right: 0.0, bottom: 0.0, left: 0.0,
+        child: new SizedBox(
+          height: statusBarHeight,
+          child: statusBar
+        )
+      ));
+    }
+
+    if (toolBar != null) {
+      children.add(new Positioned(
+        top: 0.0, right: 0.0, left: 0.0,
+        child: new SizedBox(
+          height: toolBarHeight,
+          child: toolBar
+        )
+      ));
+    }
+
+    if (snackBar != null || floatingActionButton != null) {
+      List<Widget> floatingChildren = <Widget>[];
+
+      if (floatingActionButton != null) {
+        floatingChildren.add(new Padding(
+          // TODO(eseidel): These change based on device size!
+          padding: const EdgeDims.only(right: 16.0, bottom: 16.0),
+          child: floatingActionButton
+        ));
       }
 
-  void insertChildRenderObject(RenderObject child, ScaffoldSlots slot) {
-    renderObject[slot] = child;
+      // TODO(jackson): On tablet/desktop, minWidth = 288, maxWidth = 568
+      if (snackBar != null) {
+        floatingChildren.add(new ConstrainedBox(
+          constraints: const BoxConstraints(maxHeight: kSnackBarHeight),
+          child: snackBar
+        ));
       }
 
-  void moveChildRenderObject(RenderObject child, dynamic slot) {
-    removeChildRenderObject(child);
-    insertChildRenderObject(child, slot);
+      children.add(new Positioned(
+        right: 0.0, bottom: statusBarHeight, left: 0.0,
+        child: new Column(floatingChildren, alignItems: FlexAlignItems.end)
+      ));
     }
 
-  void removeChildRenderObject(RenderObject child) {
-    assert(renderObject == child.parent);
-    renderObject.remove(child);
+    return new Stack(children);
   }
 }

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

@@ -575,7 +575,7 @@ typedef void PageChangedCallback(int newPage);
 class PageableList<T> extends ScrollableList<T> {
   PageableList({
     Key key,
-    double initialScrollOffset,
+    int initialPage,
     ScrollDirection scrollDirection: ScrollDirection.horizontal,
     ScrollListener onScroll,
     List<T> items,
@@ -588,7 +588,7 @@ class PageableList<T> extends ScrollableList<T> {
     this.curve: ease
   }) : super(
     key: key,
-    initialScrollOffset: initialScrollOffset,
+    initialScrollOffset: initialPage == null ? null : initialPage * itemExtent,
     scrollDirection: scrollDirection,
     onScroll: onScroll,
     items: items,

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

@@ -6,21 +6,18 @@ import 'package:sky/animation.dart';
 import 'package:sky/gestures.dart';
 import 'package:sky/material.dart';
 import 'package:sky/painting.dart';
-import 'package:sky/src/widgets/animated_component.dart';
 import 'package:sky/src/widgets/basic.dart';
 import 'package:sky/src/widgets/framework.dart';
 import 'package:sky/src/widgets/gesture_detector.dart';
 import 'package:sky/src/widgets/material.dart';
+import 'package:sky/src/widgets/navigator.dart';
+import 'package:sky/src/widgets/placeholder.dart';
 import 'package:sky/src/widgets/theme.dart';
 import 'package:sky/src/widgets/transitions.dart';
 
-typedef void SnackBarDismissedCallback();
-
-const Duration _kSlideInDuration = const Duration(milliseconds: 200);
-const double kSnackHeight = 52.0;
-const double kSideMargins = 24.0;
-const double kVerticalPadding = 14.0;
-const Color kSnackBackground = const Color(0xFF323232);
+const double _kSideMargins = 24.0;
+const double _kVerticalPadding = 14.0;
+const Color _kSnackBackground = const Color(0xFF323232);
 
 class SnackBarAction extends StatelessComponent {
   SnackBarAction({Key key, this.label, this.onPressed }) : super(key: key) {
@@ -34,70 +31,60 @@ class SnackBarAction extends StatelessComponent {
     return new GestureDetector(
       onTap: onPressed,
       child: new Container(
-        margin: const EdgeDims.only(left: kSideMargins),
-        padding: const EdgeDims.symmetric(vertical: kVerticalPadding),
+        margin: const EdgeDims.only(left: _kSideMargins),
+        padding: const EdgeDims.symmetric(vertical: _kVerticalPadding),
         child: new Text(label)
       )
     );
   }
 }
 
-class SnackBar extends AnimatedComponent {
+class SnackBar extends StatelessComponent {
   SnackBar({
     Key key,
     this.content,
     this.actions,
-    bool showing,
-    this.onDismissed
-  }) : super(key: key, direction: showing ? AnimationDirection.forward : AnimationDirection.reverse, duration: _kSlideInDuration) {
+    this.performance
+  }) : super(key: key) {
     assert(content != null);
   }
 
   final Widget content;
   final List<SnackBarAction> actions;
-  final SnackBarDismissedCallback onDismissed;
-
-  SnackBarState createState() => new SnackBarState();
-}
-
-class SnackBarState extends AnimatedState<SnackBar> {
-  void handleDismissed() {
-    if (config.onDismissed != null)
-      config.onDismissed();
-  }
+  final PerformanceView performance;
 
   Widget build(BuildContext context) {
     List<Widget> children = [
       new Flexible(
         child: new Container(
-          margin: const EdgeDims.symmetric(vertical: kVerticalPadding),
+          margin: const EdgeDims.symmetric(vertical: _kVerticalPadding),
           child: new DefaultTextStyle(
             style: Typography.white.subhead,
-            child: config.content
+            child: content
           )
         )
       )
     ];
-    if (config.actions != null)
-      children.addAll(config.actions);
+    if (actions != null)
+      children.addAll(actions);
     return new SquashTransition(
-      performance: performance.view,
+      performance: performance,
       height: new AnimatedValue<double>(
         0.0,
-        end: kSnackHeight,
+        end: kSnackBarHeight,
         curve: easeIn,
         reverseCurve: easeOut
       ),
       child: new ClipRect(
         child: new OverflowBox(
-          minHeight: kSnackHeight,
-          maxHeight: kSnackHeight,
+          minHeight: kSnackBarHeight,
+          maxHeight: kSnackBarHeight,
           child: new Material(
             level: 2,
-            color: kSnackBackground,
+            color: _kSnackBackground,
             type: MaterialType.canvas,
             child: new Container(
-              margin: const EdgeDims.symmetric(horizontal: kSideMargins),
+              margin: const EdgeDims.symmetric(horizontal: _kSideMargins),
               child: new DefaultTextStyle(
                 style: new TextStyle(color: Theme.of(context).accentColor),
                 child: new Row(children)
@@ -109,3 +96,28 @@ class SnackBarState extends AnimatedState<SnackBar> {
     );
   }
 }
+
+class _SnackBarRoute extends Route {
+  _SnackBarRoute({ this.content, this.actions });
+
+  final Widget content;
+  final List<SnackBarAction> actions;
+
+  bool get hasContent => false;
+  bool get ephemeral => true;
+  bool get modal => false;
+  Duration get transitionDuration => const Duration(milliseconds: 200);
+
+  Widget build(NavigatorState navigator, PerformanceView nextRoutePerformance) => null;
+}
+
+void showSnackBar({ NavigatorState navigator, GlobalKey<PlaceholderState> placeholderKey, Widget content, List<SnackBarAction> actions }) {
+  Route route = new _SnackBarRoute();
+  SnackBar snackBar = new SnackBar(
+    content: content,
+    actions: actions,
+    performance: route.performance
+  );
+  placeholderKey.currentState.child = snackBar;
+  navigator.push(route);
+}

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

@@ -11,6 +11,7 @@ import 'package:sky/gestures.dart';
 import 'package:sky/material.dart';
 import 'package:sky/painting.dart';
 import 'package:sky/rendering.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/icon.dart';
@@ -19,8 +20,8 @@ import 'package:sky/src/widgets/scrollable.dart';
 import 'package:sky/src/widgets/theme.dart';
 import 'package:sky/src/widgets/transitions.dart';
 
-typedef void SelectedIndexChanged(int selectedIndex);
-typedef void LayoutChanged(Size size, List<double> widths);
+typedef void TabSelectedIndexChanged(int selectedIndex);
+typedef void TabLayoutChanged(Size size, List<double> widths);
 
 // See https://www.google.com/design/spec/components/tabs.html#tabs-specs
 const double _kTabHeight = 46.0;
@@ -33,14 +34,14 @@ const int _kTabIconSize = 24;
 const double _kTabBarScrollDrag = 0.025;
 const Duration _kTabBarScroll = const Duration(milliseconds: 200);
 
-class TabBarParentData extends BoxParentData with
+class _TabBarParentData extends BoxParentData with
     ContainerParentDataMixin<RenderBox> { }
 
-class RenderTabBar extends RenderBox with
-    ContainerRenderObjectMixin<RenderBox, TabBarParentData>,
-    RenderBoxContainerDefaultsMixin<RenderBox, TabBarParentData> {
+class _RenderTabBar extends RenderBox with
+    ContainerRenderObjectMixin<RenderBox, _TabBarParentData>,
+    RenderBoxContainerDefaultsMixin<RenderBox, _TabBarParentData> {
 
-  RenderTabBar(this.onLayoutChanged);
+  _RenderTabBar(this.onLayoutChanged);
 
   int _selectedIndex;
   int get selectedIndex => _selectedIndex;
@@ -51,15 +52,6 @@ class RenderTabBar extends RenderBox with
     }
   }
 
-  Color _backgroundColor;
-  Color get backgroundColor => _backgroundColor;
-  void set backgroundColor(Color value) {
-    if (_backgroundColor != value) {
-      _backgroundColor = value;
-      markNeedsPaint();
-    }
-  }
-
   Color _indicatorColor;
   Color get indicatorColor => _indicatorColor;
   void set indicatorColor(Color value) {
@@ -97,8 +89,8 @@ class RenderTabBar extends RenderBox with
   }
 
   void setupParentData(RenderBox child) {
-    if (child.parentData is! TabBarParentData)
-      child.parentData = new TabBarParentData();
+    if (child.parentData is! _TabBarParentData)
+      child.parentData = new _TabBarParentData();
   }
 
   double getMinIntrinsicWidth(BoxConstraints constraints) {
@@ -109,7 +101,7 @@ class RenderTabBar extends RenderBox with
     RenderBox child = firstChild;
     while (child != null) {
       maxWidth = math.max(maxWidth, child.getMinIntrinsicWidth(widthConstraints));
-      assert(child.parentData is TabBarParentData);
+      assert(child.parentData is _TabBarParentData);
       child = child.parentData.nextSibling;
     }
     double width = isScrollable ? maxWidth : maxWidth * childCount;
@@ -124,7 +116,7 @@ class RenderTabBar extends RenderBox with
     RenderBox child = firstChild;
     while (child != null) {
       maxWidth = math.max(maxWidth, child.getMaxIntrinsicWidth(widthConstraints));
-      assert(child.parentData is TabBarParentData);
+      assert(child.parentData is _TabBarParentData);
       child = child.parentData.nextSibling;
     }
     double width = isScrollable ? maxWidth : maxWidth * childCount;
@@ -148,7 +140,7 @@ class RenderTabBar extends RenderBox with
     RenderBox child = firstChild;
     while (child != null) {
       child.layout(tabConstraints);
-      assert(child.parentData is TabBarParentData);
+      assert(child.parentData is _TabBarParentData);
       child.parentData.position = new Point(x, 0.0);
       x += tabWidth;
       child = child.parentData.nextSibling;
@@ -166,7 +158,7 @@ class RenderTabBar extends RenderBox with
     RenderBox child = firstChild;
     while (child != null) {
       child.layout(tabConstraints, parentUsesSize: true);
-      assert(child.parentData is TabBarParentData);
+      assert(child.parentData is _TabBarParentData);
       child.parentData.position = new Point(x, 0.0);
       x += child.size.width;
       child = child.parentData.nextSibling;
@@ -176,7 +168,7 @@ class RenderTabBar extends RenderBox with
 
   Size layoutSize;
   List<double> layoutWidths;
-  LayoutChanged onLayoutChanged;
+  TabLayoutChanged onLayoutChanged;
 
   void reportLayoutChangedIfNeeded() {
     assert(onLayoutChanged != null);
@@ -240,17 +232,10 @@ class RenderTabBar extends RenderBox with
   }
 
   void paint(PaintingContext context, Offset offset) {
-    if (backgroundColor != null) {
-      double width = layoutWidths != null
-        ? layoutWidths.reduce((sum, width) => sum + width)
-        : size.width;
-      Rect rect = offset & new Size(width, size.height);
-      context.canvas.drawRect(rect, new Paint()..color = backgroundColor);
-    }
     int index = 0;
     RenderBox child = firstChild;
     while (child != null) {
-      assert(child.parentData is TabBarParentData);
+      assert(child.parentData is _TabBarParentData);
       context.paintChild(child, child.parentData.position + offset);
       if (index++ == selectedIndex)
         _paintIndicator(context.canvas, child, offset);
@@ -264,7 +249,6 @@ class _TabBarWrapper extends MultiChildRenderObjectWidget {
     Key key,
     List<Widget> children,
     this.selectedIndex,
-    this.backgroundColor,
     this.indicatorColor,
     this.indicatorRect,
     this.textAndIcons,
@@ -273,22 +257,20 @@ class _TabBarWrapper extends MultiChildRenderObjectWidget {
   }) : super(key: key, children: children);
 
   final int selectedIndex;
-  final Color backgroundColor;
   final Color indicatorColor;
   final Rect indicatorRect;
   final bool textAndIcons;
   final bool isScrollable;
-  final LayoutChanged onLayoutChanged;
+  final TabLayoutChanged onLayoutChanged;
 
-  RenderTabBar createRenderObject() {
-    RenderTabBar result = new RenderTabBar(onLayoutChanged);
+  _RenderTabBar createRenderObject() {
+    _RenderTabBar result = new _RenderTabBar(onLayoutChanged);
     updateRenderObject(result, null);
     return result;
   }
 
-  void updateRenderObject(RenderTabBar renderObject, _TabBarWrapper oldWidget) {
+  void updateRenderObject(_RenderTabBar renderObject, _TabBarWrapper oldWidget) {
     renderObject.selectedIndex = selectedIndex;
-    renderObject.backgroundColor = backgroundColor;
     renderObject.indicatorColor = indicatorColor;
     renderObject.indicatorRect = indicatorRect;
     renderObject.textAndIcons = textAndIcons;
@@ -399,13 +381,13 @@ class TabBar extends Scrollable {
 
   final Iterable<TabLabel> labels;
   final int selectedIndex;
-  final SelectedIndexChanged onChanged;
+  final TabSelectedIndexChanged onChanged;
   final bool isScrollable;
 
-  TabBarState createState() => new TabBarState();
+  _TabBarState createState() => new _TabBarState();
 }
 
-class TabBarState extends ScrollableState<TabBar> {
+class _TabBarState extends ScrollableState<TabBar> {
   void initState() {
     super.initState();
     _indicatorAnimation = new ValuePerformance<Rect>()
@@ -537,7 +519,7 @@ class TabBarState extends ScrollableState<TabBar> {
         textAndIcons = true;
     }
 
-    Widget tabBar = new IconTheme(
+    Widget content = new IconTheme(
       data: new IconThemeData(color: iconThemeColor),
       child: new DefaultTextStyle(
         style: textStyle,
@@ -548,7 +530,6 @@ class TabBarState extends ScrollableState<TabBar> {
             return new _TabBarWrapper(
               children: tabs,
               selectedIndex: config.selectedIndex,
-              backgroundColor: backgroundColor,
               indicatorColor: indicatorColor,
               indicatorRect: _indicatorRect.value,
               textAndIcons: textAndIcons,
@@ -560,18 +541,25 @@ class TabBarState extends ScrollableState<TabBar> {
       )
     );
 
-    if (!config.isScrollable)
-      return tabBar;
-
-    return new SizeObserver(
+    if (config.isScrollable) {
+      content = new SizeObserver(
         callback: _handleViewportSizeChanged,
         child: new Viewport(
           scrollDirection: ScrollDirection.horizontal,
           scrollOffset: new Offset(scrollOffset, 0.0),
-        child: tabBar
+          child: content
         )
       );
     }
+
+    return new AnimatedContainer(
+      decoration: new BoxDecoration(
+        backgroundColor: backgroundColor
+      ),
+      duration: kThemeChangeDuration,
+      child: content
+    );
+  }
 }
 
 class TabNavigatorView {
@@ -598,21 +586,16 @@ class TabNavigator extends StatelessComponent {
 
   final List<TabNavigatorView> views;
   final int selectedIndex;
-  final SelectedIndexChanged onChanged;
+  final TabSelectedIndexChanged onChanged;
   final bool isScrollable;
 
-  void _handleSelectedIndexChanged(int tabIndex) {
-    if (onChanged != null)
-      onChanged(tabIndex);
-  }
-
   Widget build(BuildContext context) {
     assert(views != null && views.isNotEmpty);
     assert(selectedIndex >= 0 && selectedIndex < views.length);
     return new Column([
       new TabBar(
         labels: views.map((view) => view.label),
-        onChanged: _handleSelectedIndexChanged,
+        onChanged: onChanged,
         selectedIndex: selectedIndex,
         isScrollable: isScrollable
       ),

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

@@ -4,35 +4,36 @@
 
 import 'package:sky/material.dart';
 import 'package:sky/painting.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/icon.dart';
 import 'package:sky/src/widgets/theme.dart';
-import 'package:sky/src/rendering/flex.dart';
 
 class ToolBar extends StatelessComponent {
-
   ToolBar({
     Key key,
     this.left,
     this.center,
     this.right,
+    this.level: 2,
     this.backgroundColor
   }) : super(key: key);
 
   final Widget left;
   final Widget center;
   final List<Widget> right;
+  final int level;
   final Color backgroundColor;
 
   Widget build(BuildContext context) {
-    Color toolbarColor = backgroundColor;
+    Color color = backgroundColor;
     IconThemeData iconThemeData;
     TextStyle centerStyle = Typography.white.title;
     TextStyle sideStyle = Typography.white.body1;
-    if (toolbarColor == null) {
+    if (color == null) {
       ThemeData themeData = Theme.of(context);
-      toolbarColor = themeData.primaryColor;
+      color = themeData.primaryColor;
       if (themeData.primaryColorBrightness == ThemeBrightness.light) {
         centerStyle = Typography.black.title;
         sideStyle = Typography.black.body2;
@@ -44,11 +45,9 @@ class ToolBar extends StatelessComponent {
 
     List<Widget> children = new List<Widget>();
 
-    // left children
     if (left != null)
       children.add(left);
 
-    // center children (left-aligned, but takes all remaining space)
     children.add(
       new Flexible(
         child: new Padding(
@@ -58,11 +57,16 @@ class ToolBar extends StatelessComponent {
       )
     );
 
-    // right children
     if (right != null)
       children.addAll(right);
 
-    Widget content = new Container(
+    Widget content = new AnimatedContainer(
+      duration: kThemeChangeDuration,
+      padding: new EdgeDims.symmetric(horizontal: 8.0),
+      decoration: new BoxDecoration(
+        backgroundColor: color,
+        boxShadow: level == 0 ? null : shadows[2]
+      ),
       child: new DefaultTextStyle(
         style: sideStyle,
         child: new Column([
@@ -73,11 +77,6 @@ class ToolBar extends StatelessComponent {
           ],
           justifyContent: FlexJustifyContent.end
         )
-      ),
-      padding: new EdgeDims.symmetric(horizontal: 8.0),
-      decoration: new BoxDecoration(
-        backgroundColor: toolbarColor,
-        boxShadow: shadows[2]
       )
     );
 

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

@@ -21,10 +21,10 @@ abstract class TransitionComponent extends StatefulComponent {
 
   Widget build(BuildContext context);
 
-  TransitionState createState() => new TransitionState();
+  _TransitionState createState() => new _TransitionState();
 }
 
-class TransitionState extends State<TransitionComponent> {
+class _TransitionState extends State<TransitionComponent> {
   void initState() {
     super.initState();
     config.performance.addListener(_performanceChanged);

packages/flutter/lib/widgets.dart

@@ -5,7 +5,6 @@
 /// The Flutter widget framework.
 library widgets;
 
-export 'src/widgets/animated_component.dart';
 export 'src/widgets/animated_container.dart';
 export 'src/widgets/app.dart';
 export 'src/widgets/basic.dart';
@@ -37,6 +36,7 @@ export 'src/widgets/material_button.dart';
 export 'src/widgets/mimic.dart';
 export 'src/widgets/mixed_viewport.dart';
 export 'src/widgets/navigator.dart';
+export 'src/widgets/placeholder.dart';
 export 'src/widgets/popup_menu.dart';
 export 'src/widgets/popup_menu_item.dart';
 export 'src/widgets/progress_indicator.dart';

packages/flutter/pubspec.yaml

 name: sky
-version: 0.0.52
+version: 0.0.53
 author: Flutter Authors <flutter-dev@googlegroups.com>
 description: A framework for writing Flutter applications
 homepage: http://flutter.io
@@ -9,8 +9,8 @@ dependencies:
   mojo_services: '>=0.1.0 <0.2.0'
   mojo: '>=0.1.0 <0.2.0'
   newton: ^0.1.4
-  sky_engine: ^0.0.30
-  sky_services: ^0.0.30
+  sky_engine: ^0.0.31
+  sky_services: ^0.0.31
   sky_tools: ^0.0.15
   vector_math: ^1.4.3
   intl: ^0.12.4+2

packages/flutter_sprites/lib/physics_body.dart

@@ -9,49 +9,219 @@ class PhysicsBody {
   PhysicsBody(this.shape, {
     this.tag: null,
     this.type: PhysicsBodyType.dynamic,
-    this.density: 1.0,
-    this.friction: 0.0,
-    this.restitution: 0.0,
-    this.isSensor: false,
-    this.linearVelocity: Offset.zero,
-    this.angularVelocity: 0.0,
+    double density: 1.0,
+    double friction: 0.0,
+    double restitution: 0.0,
+    bool isSensor: false,
+    Offset linearVelocity: Offset.zero,
+    double angularVelocity: 0.0,
     this.linearDampening: 0.0,
-    this.angularDampening: 0.0,
-    this.allowSleep: true,
-    this.awake: true,
-    this.fixedRotation: false,
-    this.bullet: false,
-    this.active: true,
+    double awakeangularDampening: 0.0,
+    bool allowSleep: true,
+    bool awake: true,
+    bool fixedRotation: false,
+    bool bullet: false,
+    bool active: true,
     this.gravityScale: 1.0
-  });
+  }) {
+    this.density = density;
+    this.friction = friction;
+    this.restitution = restitution;
+    this.isSensor = isSensor;
+
+    this.linearVelocity = linearVelocity;
+    this.angularVelocity = angularVelocity;
+    this.angularDampening = angularDampening;
+
+    this.allowSleep = allowSleep;
+    this.awake = awake;
+    this.fixedRotation = fixedRotation;
+    this.bullet = bullet;
+    this.active = active;
+  }
 
   Object tag;
 
-  PhysicsShape shape;
+  final PhysicsShape shape;
 
   PhysicsBodyType type;
 
-  double density;
-  double friction;
-  double restitution;
-  bool isSensor;
+  double _density;
+
+  double get density => _density;
+
+  set density(double density) {
+    _density = density;
+
+    if (_body == null)
+      return;
+    for (box2d.Fixture f = _body.getFixtureList(); f != null; f = f.getNext()) {
+      f.setDensity(density);
+    }
+  }
+
+  double _friction;
+
+  double get friction => _friction;
+
+  set friction(double friction) {
+    _friction = friction;
+
+    if (_body == null)
+      return;
+    for (box2d.Fixture f = _body.getFixtureList(); f != null; f = f.getNext()) {
+      f.setFriction(friction);
+    }
+  }
+
+  double _restitution;
+
+  double get restitution => _restitution;
+
+  set restitution(double restitution) {
+    _restitution = restitution;
+
+    if (_body == null)
+      return;
+    for (box2d.Fixture f = _body.getFixtureList(); f != null; f = f.getNext()) {
+      f.setRestitution(restitution);
+    }
+  }
+
+  bool _isSensor;
+
+  bool get isSensor => _isSensor;
+
+  set isSensor(bool isSensor) {
+    _isSensor = isSensor;
+
+    if (_body == null)
+      return;
+    for (box2d.Fixture f = _body.getFixtureList(); f != null; f = f.getNext()) {
+      f.setSensor(isSensor);
+    }
+  }
+
+  Offset _linearVelocity;
+
+  Offset get linearVelocity {
+    if (_body == null)
+      return _linearVelocity;
+    else {
+      double dx = _body.linearVelocity.x * _physicsNode.b2WorldToNodeConversionFactor;
+      double dy = _body.linearVelocity.y * _physicsNode.b2WorldToNodeConversionFactor;
+      return new Offset(dx, dy);
+    }
+  }
+
+  set linearVelocity(Offset linearVelocity) {
+    _linearVelocity = linearVelocity;
+
+    if (_body != null) {
+      Vector2 vec = new Vector2(
+        linearVelocity.dx / _physicsNode.b2WorldToNodeConversionFactor,
+        linearVelocity.dy / _physicsNode.b2WorldToNodeConversionFactor
+      );
+      _body.linearVelocity = vec;
+    }
+  }
+
+  double _angularVelocity;
 
-  Offset linearVelocity;
-  double angularVelocity;
+  double get angularVelocity {
+    if (_body == null)
+      return _angularVelocity;
+    else
+      return _body.angularVelocity;
+  }
+
+  set angularVelocity(double angularVelocity) {
+    _angularVelocity = angularVelocity;
+
+    if (_body != null) {
+      _body.angularVelocity = angularVelocity;
+    }
+  }
+
+  // TODO: Should this be editable in box2d.Body ?
+  final double linearDampening;
+
+  double _angularDampening;
+
+  double get angularDampening => _angularDampening;
 
-  double linearDampening;
+  set angularDampening(double angularDampening) {
+    _angularDampening = angularDampening;
 
-  double angularDampening;
+    if (_body != null)
+      _body.angularDamping = angularDampening;
+  }
+
+  bool _allowSleep;
 
-  bool allowSleep;
+  bool get allowSleep => _allowSleep;
 
-  bool awake;
+  set allowSleep(bool allowSleep) {
+    _allowSleep = allowSleep;
 
-  bool fixedRotation;
+    if (_body != null)
+      _body.setSleepingAllowed(allowSleep);
+  }
 
-  bool bullet;
+  bool _awake;
+
+  bool get awake {
+    if (_body != null)
+      return _body.isAwake();
+    else
+      return _awake;
+  }
+
+  set awake(bool awake) {
+    _awake = awake;
+
+    if (_body != null)
+      _body.setAwake(awake);
+  }
 
-  bool active;
+  bool _fixedRotation;
+
+  bool get fixedRotation => _fixedRotation;
+
+  set fixedRotation(bool fixedRotation) {
+    _fixedRotation = fixedRotation;
+
+    if (_body != null)
+      _body.setFixedRotation(fixedRotation);
+  }
+
+  bool _bullet;
+
+  bool get bullet => _bullet;
+
+  set bullet(bool bullet) {
+    _bullet = bullet;
+
+    if (_body != null) {
+      _body.setBullet(bullet);
+    }
+  }
+
+  bool _active;
+
+  bool get active {
+    if (_body != null)
+      return _body.isActive();
+    else
+      return _active;
+  }
+
+  set active(bool active) {
+    _active = active;
+
+    if (_body != null)
+      _body.setActive(active);
+  }
 
   double gravityScale;
 

packages/unit/test/widget/build_scope_test.dart

@@ -66,6 +66,10 @@ class BadDisposeWidgetState extends State<BadDisposeWidget> {
 void main() {
   dynamic cachedException;
 
+  // ** WARNING **
+  // THIS TEST OVERRIDES THE NORMAL EXCEPTION HANDLING
+  // AND DOES NOT REPORT EXCEPTIONS FROM THE FRAMEWORK
+
   setUp(() {
     assert(cachedException == null);
     debugWidgetsExceptionHandler = (String context, dynamic exception, StackTrace stack) {

packages/unit/test/widget/focus_test.dart

+import 'package:sky/widgets.dart';
+import 'package:test/test.dart';
+
+import 'widget_tester.dart';
+
+class TestFocusable extends StatelessComponent {
+  TestFocusable(this.no, this.yes, GlobalKey key) : super(key: key);
+  final String no;
+  final String yes;
+  Widget build(BuildContext context) {
+    bool focused = Focus.at(context, this);
+    return new GestureDetector(
+      onTap: () { Focus.moveTo(context, this); },
+      child: new Text(focused ? yes : no)
+    );
+  }
+}
+
+void main() {
+  test('Can have multiple focused children and they update accordingly', () {
+    testWidgets((WidgetTester tester) {
+      GlobalKey keyA = new GlobalKey();
+      GlobalKey keyB = new GlobalKey();
+      tester.pumpWidget(
+        new Focus(
+          child: new Column([
+            // reverse these when you fix https://github.com/flutter/engine/issues/1495
+            new TestFocusable('b', 'B FOCUSED', keyB),
+            new TestFocusable('a', 'A FOCUSED', keyA),
+          ])
+        )
+      );
+      expect(tester.findText('a'),         isNull);
+      expect(tester.findText('A FOCUSED'), isNotNull);
+      expect(tester.findText('b'),         isNotNull);
+      expect(tester.findText('B FOCUSED'), isNull);
+      tester.tap(tester.findText('A FOCUSED'));
+      tester.pump();
+      expect(tester.findText('a'),         isNull);
+      expect(tester.findText('A FOCUSED'), isNotNull);
+      expect(tester.findText('b'),         isNotNull);
+      expect(tester.findText('B FOCUSED'), isNull);
+      tester.tap(tester.findText('A FOCUSED'));
+      tester.pump();
+      expect(tester.findText('a'),         isNull);
+      expect(tester.findText('A FOCUSED'), isNotNull);
+      expect(tester.findText('b'),         isNotNull);
+      expect(tester.findText('B FOCUSED'), isNull);
+      tester.tap(tester.findText('b'));
+      tester.pump();
+      expect(tester.findText('a'),         isNotNull);
+      expect(tester.findText('A FOCUSED'), isNull);
+      expect(tester.findText('b'),         isNull);
+      expect(tester.findText('B FOCUSED'), isNotNull);
+      tester.tap(tester.findText('a'));
+      tester.pump();
+      expect(tester.findText('a'),         isNull);
+      expect(tester.findText('A FOCUSED'), isNotNull);
+      expect(tester.findText('b'),         isNotNull);
+      expect(tester.findText('B FOCUSED'), isNull);
+    });
+  });
+}