Port most of scrollable.dart to fn3

packages/flutter/lib/src/fn3/homogeneous_viewport.dart

@@ -8,7 +8,7 @@ import 'package:sky/rendering.dart';
 import 'package:sky/src/fn3/framework.dart';
 import 'package:sky/src/fn3/basic.dart';
 
-typedef List<Widget> ListBuilder(int startIndex, int count, BuildContext context);
+typedef List<Widget> ListBuilder(BuildContext context, int startIndex, int count);
 
 class HomogeneousViewport extends RenderObjectWidget {
   HomogeneousViewport({
@@ -137,7 +137,7 @@ class HomogeneousViewportElement extends RenderObjectElement<HomogeneousViewport
     assert(_layoutItemCount != null);
     List<Widget> newWidgets;
     if (_layoutItemCount > 0)
-      newWidgets = widget.builder(_layoutFirstIndex, _layoutItemCount, this);
+      newWidgets = widget.builder(this, _layoutFirstIndex, _layoutItemCount);
     else
       newWidgets = <Widget>[];
     _children = updateChildren(_children, newWidgets);

packages/flutter/lib/src/fn3/scrollable.dart

@@ -0,0 +1,548 @@
+// 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:math' as math;
+import 'dart:sky' as sky;
+
+import 'package:newton/newton.dart';
+import 'package:sky/animation.dart';
+import 'package:sky/gestures.dart';
+import 'package:sky/src/rendering/box.dart';
+import 'package:sky/src/rendering/viewport.dart';
+import 'package:sky/src/fn3/basic.dart';
+import 'package:sky/src/fn3/framework.dart';
+import 'package:sky/src/fn3/gesture_detector.dart';
+import 'package:sky/src/fn3/homogeneous_viewport.dart';
+
+// The gesture velocity properties are pixels/second, config min,max limits are pixels/ms
+const double _kMillisecondsPerSecond = 1000.0;
+const double _kMinFlingVelocity = -kMaxFlingVelocity * _kMillisecondsPerSecond;
+const double _kMaxFlingVelocity = kMaxFlingVelocity * _kMillisecondsPerSecond;
+
+typedef void ScrollListener();
+
+/// A base class for scrollable widgets that reacts to user input and generates
+/// a scrollOffset.
+abstract class Scrollable extends StatefulComponent {
+  Scrollable({
+    Key key,
+    this.initialScrollOffset,
+    this.scrollDirection: ScrollDirection.vertical
+  }) : super(key: key) {
+    assert(scrollDirection == ScrollDirection.vertical ||
+           scrollDirection == ScrollDirection.horizontal);
+  }
+
+  final double initialScrollOffset;
+  final ScrollDirection scrollDirection;
+}
+
+abstract class ScrollableState<T extends Scrollable> extends ComponentState<T> {
+  ScrollableState(T config) : super(config);
+
+  AnimatedSimulation _toEndAnimation; // See _startToEndAnimation()
+  ValueAnimation<double> _toOffsetAnimation; // Started by scrollTo()
+
+  void initState(BuildContext context) {
+    if (config.initialScrollOffset is double)
+      _scrollOffset = config.initialScrollOffset;
+    _toEndAnimation = new AnimatedSimulation(_setScrollOffset);
+    _toOffsetAnimation = new ValueAnimation<double>()
+      ..addListener(() {
+        AnimatedValue<double> offset = _toOffsetAnimation.variable;
+        _setScrollOffset(offset.value);
+      });
+  }
+
+  double _scrollOffset = 0.0;
+  double get scrollOffset => _scrollOffset;
+
+  Offset get scrollOffsetVector {
+    if (config.scrollDirection == ScrollDirection.horizontal)
+      return new Offset(scrollOffset, 0.0);
+    return new Offset(0.0, scrollOffset);
+  }
+
+  ScrollBehavior _scrollBehavior;
+  ScrollBehavior createScrollBehavior();
+  ScrollBehavior get scrollBehavior {
+    if (_scrollBehavior == null)
+      _scrollBehavior = createScrollBehavior();
+    return _scrollBehavior;
+  }
+
+  GestureDragUpdateCallback _getDragUpdateHandler(ScrollDirection direction) {
+    if (config.scrollDirection != direction || !scrollBehavior.isScrollable)
+      return null;
+    return _handleDragUpdate;
+  }
+
+  GestureDragEndCallback _getDragEndHandler(ScrollDirection direction) {
+    if (config.scrollDirection != direction || !scrollBehavior.isScrollable)
+      return null;
+    return _handleDragEnd;
+  }
+
+  Widget build(BuildContext context) {
+    return new GestureDetector(
+      onVerticalDragUpdate: _getDragUpdateHandler(ScrollDirection.vertical),
+      onVerticalDragEnd: _getDragEndHandler(ScrollDirection.vertical),
+      onHorizontalDragUpdate: _getDragUpdateHandler(ScrollDirection.horizontal),
+      onHorizontalDragEnd: _getDragEndHandler(ScrollDirection.horizontal),
+      child: new Listener(
+        child: buildContent(context),
+        onPointerDown: _handlePointerDown
+      )
+    );
+  }
+
+  Widget buildContent(BuildContext context);
+
+  Future _startToOffsetAnimation(double newScrollOffset, Duration duration, Curve curve) {
+    _stopAnimations();
+    _toOffsetAnimation
+      ..variable = new AnimatedValue<double>(scrollOffset,
+        end: newScrollOffset,
+        curve: curve
+      )
+      ..progress = 0.0
+      ..duration = duration;
+    return _toOffsetAnimation.play();
+  }
+
+  void _stopAnimations() {
+    if (_toOffsetAnimation.isAnimating)
+      _toOffsetAnimation.stop();
+    if (_toEndAnimation.isAnimating)
+      _toEndAnimation.stop();
+  }
+
+  void _startToEndAnimation({ double velocity: 0.0 }) {
+    _stopAnimations();
+    Simulation simulation = scrollBehavior.release(scrollOffset, velocity);
+    if (simulation != null)
+      _toEndAnimation.start(simulation);
+  }
+
+  void dispose() {
+    _stopAnimations();
+  }
+
+  void _setScrollOffset(double newScrollOffset) {
+    if (_scrollOffset == newScrollOffset)
+      return;
+    setState(() {
+      _scrollOffset = newScrollOffset;
+    });
+    if (_listeners.length > 0)
+      _notifyListeners();
+  }
+
+  Future scrollTo(double newScrollOffset, { Duration duration, Curve curve: ease }) {
+    if (newScrollOffset == _scrollOffset)
+      return new Future.value();
+
+    if (duration == null) {
+      _stopAnimations();
+      _setScrollOffset(newScrollOffset);
+      return new Future.value();
+    }
+
+    return _startToOffsetAnimation(newScrollOffset, duration, curve);
+  }
+
+  Future scrollBy(double scrollDelta, { Duration duration, Curve curve }) {
+    double newScrollOffset = scrollBehavior.applyCurve(_scrollOffset, scrollDelta);
+    return scrollTo(newScrollOffset, duration: duration, curve: curve);
+  }
+
+  void settleScrollOffset() {
+    _startToEndAnimation();
+  }
+
+  double _scrollVelocity(sky.Offset velocity) {
+    double scrollVelocity = config.scrollDirection == ScrollDirection.horizontal
+      ? -velocity.dx
+      : -velocity.dy;
+    return scrollVelocity.clamp(_kMinFlingVelocity, _kMaxFlingVelocity) / _kMillisecondsPerSecond;
+  }
+
+  void _handlePointerDown(_) {
+    _stopAnimations();
+  }
+
+  void _handleDragUpdate(double delta) {
+    // We negate the delta here because a positive scroll offset moves the
+    // the content up (or to the left) rather than down (or the right).
+    scrollBy(-delta);
+  }
+
+  void _handleDragEnd(Offset velocity) {
+    if (velocity != Offset.zero) {
+      _startToEndAnimation(velocity: _scrollVelocity(velocity));
+    } else if (!_toEndAnimation.isAnimating && (_toOffsetAnimation == null || !_toOffsetAnimation.isAnimating)) {
+      settleScrollOffset();
+    }
+  }
+
+  final List<ScrollListener> _listeners = new List<ScrollListener>();
+  void addListener(ScrollListener listener) {
+    _listeners.add(listener);
+  }
+
+  void removeListener(ScrollListener listener) {
+    _listeners.remove(listener);
+  }
+
+  void _notifyListeners() {
+    List<ScrollListener> localListeners = new List<ScrollListener>.from(_listeners);
+    for (ScrollListener listener in localListeners)
+      listener();
+  }
+}
+
+// TODO(abarth): findScrollableAncestor
+// TODO(abarth): ensureWidgetIsVisible
+
+/// A simple scrollable widget that has a single child. Use this component if
+/// you are not worried about offscreen widgets consuming resources.
+class ScrollableViewport extends Scrollable {
+  ScrollableViewport({
+    Key key,
+    this.child,
+    double initialScrollOffset,
+    ScrollDirection scrollDirection: ScrollDirection.vertical
+  }) : super(
+    key: key,
+    scrollDirection: scrollDirection,
+    initialScrollOffset: initialScrollOffset
+  );
+
+  final Widget child;
+
+  ScrollableViewportState createState() => new ScrollableViewportState(this);
+}
+
+class ScrollableViewportState extends ScrollableState<ScrollableViewport> {
+  ScrollableViewportState(ScrollableViewport config) : super(config);
+
+  ScrollBehavior createScrollBehavior() => new OverscrollWhenScrollableBehavior();
+  OverscrollWhenScrollableBehavior get scrollBehavior => super.scrollBehavior;
+
+  double _viewportSize = 0.0;
+  double _childSize = 0.0;
+  void _handleViewportSizeChanged(Size newSize) {
+    _viewportSize = config.scrollDirection == ScrollDirection.vertical ? newSize.height : newSize.width;
+    setState(() {
+      _updateScrollBehaviour();
+    });
+  }
+  void _handleChildSizeChanged(Size newSize) {
+    _childSize = config.scrollDirection == ScrollDirection.vertical ? newSize.height : newSize.width;
+    setState(() {
+      _updateScrollBehaviour();
+    });
+  }
+  void _updateScrollBehaviour() {
+    // if you don't call this from build() or syncConstructorArguments(), you must call it from setState().
+    scrollTo(scrollBehavior.updateExtents(
+      contentExtent: _childSize,
+      containerExtent: _viewportSize,
+      scrollOffset: scrollOffset
+    ));
+  }
+
+  Widget buildContent(BuildContext context) {
+    return new SizeObserver(
+      callback: _handleViewportSizeChanged,
+      child: new Viewport(
+        scrollOffset: scrollOffsetVector,
+        scrollDirection: config.scrollDirection,
+        child: new SizeObserver(
+          callback: _handleChildSizeChanged,
+          child: config.child
+        )
+      )
+    );
+  }
+}
+
+/// A mashup of [ScrollableViewport] and [BlockBody]. Useful when you have a small,
+/// fixed number of children that you wish to arrange in a block layout and that
+/// might exceed the height of its container (and therefore need to scroll).
+class Block extends StatelessComponent {
+  Block(this.children, {
+    Key key,
+    this.initialScrollOffset,
+    this.scrollDirection: ScrollDirection.vertical
+  }) : super(key: key);
+
+  final List<Widget> children;
+  final double initialScrollOffset;
+  final ScrollDirection scrollDirection;
+
+  BlockDirection get _direction {
+    if (scrollDirection == ScrollDirection.vertical)
+      return BlockDirection.vertical;
+    return BlockDirection.horizontal;
+  }
+
+  Widget build(BuildContext context) {
+    return new ScrollableViewport(
+      initialScrollOffset: initialScrollOffset,
+      scrollDirection: scrollDirection,
+      child: new BlockBody(children, direction: _direction)
+    );
+  }
+}
+
+/// An optimized scrollable widget for a large number of children that are all
+/// the same size (extent) in the scrollDirection. For example for
+/// ScrollDirection.vertical itemExtent is the height of each item. Use this
+/// widget when you have a large number of children or when you are concerned
+// about offscreen widgets consuming resources.
+abstract class ScrollableWidgetList extends Scrollable {
+  ScrollableWidgetList({
+    Key key,
+    double initialScrollOffset,
+    ScrollDirection scrollDirection: ScrollDirection.vertical,
+    this.itemsWrap: false,
+    this.itemExtent,
+    this.padding
+  }) : super(key: key, initialScrollOffset: initialScrollOffset, scrollDirection: scrollDirection) {
+    assert(itemExtent != null);
+  }
+
+  EdgeDims padding;
+  bool itemsWrap;
+  double itemExtent;
+  Size containerSize = Size.zero;
+}
+
+abstract class ScrollableWidgetListState<T extends ScrollableWidgetList> extends ScrollableState<T> {
+  ScrollableWidgetListState(T config) : super(config);
+
+  /// Subclasses must implement `get itemCount` to tell ScrollableWidgetList
+  /// how many items there are in the list.
+  int get itemCount;
+  int _previousItemCount;
+
+  void didUpdateConfig(T oldConfig) {
+    super.didUpdateConfig(oldConfig);
+
+    bool scrollBehaviorUpdateNeeded =
+      config.padding != oldConfig.padding ||
+      config.itemExtent != oldConfig.itemExtent ||
+      config.scrollDirection != oldConfig.scrollDirection;
+
+    if (config.itemsWrap != oldConfig.itemsWrap) {
+      _scrollBehavior = null;
+      scrollBehaviorUpdateNeeded = true;
+    }
+
+    if (itemCount != _previousItemCount) {
+      scrollBehaviorUpdateNeeded = true;
+      _previousItemCount = itemCount;
+    }
+
+    if (scrollBehaviorUpdateNeeded)
+      _updateScrollBehavior();
+  }
+
+  ScrollBehavior createScrollBehavior() => new OverscrollBehavior();
+  ExtentScrollBehavior get scrollBehavior => super.scrollBehavior;
+
+  double get _containerExtent {
+    return config.scrollDirection == ScrollDirection.vertical
+      ? config.containerSize.height
+      : config.containerSize.width;
+  }
+
+  void _handleSizeChanged(Size newSize) {
+    setState(() {
+      config.containerSize = newSize;
+      _updateScrollBehavior();
+    });
+  }
+
+  double get _leadingPadding {
+    EdgeDims padding = config.padding;
+    if (config.scrollDirection == ScrollDirection.vertical)
+      return padding != null ? padding.top : 0.0;
+    return padding != null ? padding.left : -.0;
+  }
+
+  double get _trailingPadding {
+    EdgeDims padding = config.padding;
+    if (config.scrollDirection == ScrollDirection.vertical)
+      return padding != null ? padding.bottom : 0.0;
+    return padding != null ? padding.right : 0.0;
+  }
+
+  EdgeDims get _crossAxisPadding {
+    EdgeDims padding = config.padding;
+    if (padding == null)
+      return null;
+    if (config.scrollDirection == ScrollDirection.vertical)
+      return new EdgeDims.only(left: padding.left, right: padding.right);
+    return new EdgeDims.only(top: padding.top, bottom: padding.bottom);
+  }
+
+  void _updateScrollBehavior() {
+    // if you don't call this from build() or syncConstructorArguments(), you must call it from setState().
+    double contentExtent = config.itemExtent * itemCount;
+    if (config.padding != null)
+      contentExtent += _leadingPadding + _trailingPadding;
+    scrollTo(scrollBehavior.updateExtents(
+      contentExtent: contentExtent,
+      containerExtent: _containerExtent,
+      scrollOffset: scrollOffset
+    ));
+  }
+
+  Widget buildContent(BuildContext context) {
+    if (itemCount != _previousItemCount) {
+      _previousItemCount = itemCount;
+      _updateScrollBehavior();
+    }
+
+    return new SizeObserver(
+      callback: _handleSizeChanged,
+      child: new Container(
+        padding: _crossAxisPadding,
+        child: new HomogeneousViewport(
+          builder: _buildItems,
+          itemsWrap: config.itemsWrap,
+          itemExtent: config.itemExtent,
+          itemCount: itemCount,
+          direction: config.scrollDirection,
+          startOffset: scrollOffset - _leadingPadding
+        )
+      )
+    );
+  }
+
+  List<Widget> _buildItems(BuildContext context, int start, int count) {
+    List<Widget> result = buildItems(context, start, count);
+    assert(result.every((item) => item.key != null));
+    return result;
+  }
+
+  List<Widget> buildItems(BuildContext context, int start, int count);
+
+}
+
+typedef Widget ItemBuilder<T>(BuildContext context, T item);
+
+/// A wrapper around [ScrollableWidgetList] that helps you translate a list of
+/// model objects into a scrollable list of widgets. Assumes all the widgets
+/// have the same height.
+class ScrollableList<T> extends ScrollableWidgetList {
+  ScrollableList({
+    Key key,
+    double initialScrollOffset,
+    ScrollDirection scrollDirection: ScrollDirection.vertical,
+    this.items,
+    this.itemBuilder,
+    itemsWrap: false,
+    double itemExtent,
+    EdgeDims padding
+  }) : super(
+    key: key,
+    initialScrollOffset: initialScrollOffset,
+    scrollDirection: scrollDirection,
+    itemsWrap: itemsWrap,
+    itemExtent: itemExtent,
+    padding: padding);
+
+  final List<T> items;
+  final ItemBuilder<T> itemBuilder;
+
+  ScrollableListState<T, ScrollableList<T>> createState() => new ScrollableListState<T, ScrollableList<T>>(this);
+}
+
+class ScrollableListState<T, Config extends ScrollableList<T>> extends ScrollableWidgetListState<Config> {
+  ScrollableListState(Config config) : super(config);
+
+  ScrollBehavior createScrollBehavior() {
+    return config.itemsWrap ? new UnboundedBehavior() : super.createScrollBehavior();
+  }
+
+  int get itemCount => config.items.length;
+
+  List<Widget> buildItems(BuildContext context, int start, int count) {
+    List<Widget> result = new List<Widget>();
+    int begin = config.itemsWrap ? start : math.max(0, start);
+    int end = config.itemsWrap ? begin + count : math.min(begin + count, config.items.length);
+    for (int i = begin; i < end; ++i)
+      result.add(config.itemBuilder(context, config.items[i % itemCount]));
+    return result;
+  }
+}
+
+typedef void PageChangedCallback(int newPage);
+
+class PageableList<T> extends ScrollableList<T> {
+  PageableList({
+    Key key,
+    double initialScrollOffset,
+    ScrollDirection scrollDirection: ScrollDirection.horizontal,
+    List<T> items,
+    ItemBuilder<T> itemBuilder,
+    bool itemsWrap: false,
+    double itemExtent,
+    PageChangedCallback this.pageChanged,
+    EdgeDims padding,
+    this.duration: const Duration(milliseconds: 200),
+    this.curve: ease
+  }) : super(
+    key: key,
+    initialScrollOffset: initialScrollOffset,
+    scrollDirection: scrollDirection,
+    items: items,
+    itemBuilder: itemBuilder,
+    itemsWrap: itemsWrap,
+    itemExtent: itemExtent,
+    padding: padding
+  );
+
+  Duration duration;
+  Curve curve;
+  PageChangedCallback pageChanged;
+}
+
+class PageableListState<T> extends ScrollableListState<T, PageableList<T>> {
+  PageableListState(PageableList<T> config) : super(config);
+
+  double _snapScrollOffset(double newScrollOffset) {
+    double scaledScrollOffset = newScrollOffset / config.itemExtent;
+    double previousScrollOffset = scaledScrollOffset.floor() * config.itemExtent;
+    double nextScrollOffset = scaledScrollOffset.ceil() * config.itemExtent;
+    double delta = newScrollOffset - previousScrollOffset;
+    return (delta < config.itemExtent / 2.0 ? previousScrollOffset : nextScrollOffset)
+      .clamp(scrollBehavior.minScrollOffset, scrollBehavior.maxScrollOffset);
+  }
+
+  void _handleDragEnd(sky.Offset velocity) {
+    double scrollVelocity = _scrollVelocity(velocity);
+    double newScrollOffset = _snapScrollOffset(scrollOffset + scrollVelocity.sign * config.itemExtent)
+      .clamp(_snapScrollOffset(scrollOffset - config.itemExtent / 2.0),
+             _snapScrollOffset(scrollOffset + config.itemExtent / 2.0));
+    scrollTo(newScrollOffset, duration: config.duration, curve: config.curve).then(_notifyPageChanged);
+  }
+
+  int get currentPage => (scrollOffset / config.itemExtent).floor() % itemCount;
+
+  void _notifyPageChanged(_) {
+    if (config.pageChanged != null)
+      config.pageChanged(currentPage);
+  }
+
+  void settleScrollOffset() {
+    scrollTo(_snapScrollOffset(scrollOffset), duration: config.duration, curve: config.curve).then(_notifyPageChanged);
+  }
+}
+
+// TODO(abarth): ScrollableMixedWidgetList

packages/unit/test/fn3/coordinates_test.dart

@@ -1,3 +1,4 @@
+import 'package:sky/rendering.dart';
 import 'package:sky/src/fn3.dart';
 import 'package:test/test.dart';
 
@@ -9,7 +10,6 @@ void main() {
 
     Key keyA = new GlobalKey();
     Key keyB = new GlobalKey();
-    Key keyC = new GlobalKey();
 
     tester.pumpFrame(
       new Stack([
@@ -34,13 +34,13 @@ void main() {
       ])
     );
 
-    expect(tester.findElementByKey(keyA).renderObject.localToGlobal(const Point(0.0, 0.0)),
+    expect((tester.findElementByKey(keyA).renderObject as RenderBox).localToGlobal(const Point(0.0, 0.0)),
            equals(const Point(100.0, 100.0)));
 
-    expect(tester.findElementByKey(keyB).renderObject.localToGlobal(const Point(0.0, 0.0)),
+    expect((tester.findElementByKey(keyB).renderObject as RenderBox).localToGlobal(const Point(0.0, 0.0)),
            equals(const Point(100.0, 200.0)));
 
-    expect(tester.findElementByKey(keyB).renderObject.globalToLocal(const Point(110.0, 205.0)),
+    expect((tester.findElementByKey(keyB).renderObject as RenderBox).globalToLocal(const Point(110.0, 205.0)),
            equals(const Point(10.0, 5.0)));
   });
 }

packages/unit/test/fn3/homogeneous_viewport_test.dart

@@ -33,7 +33,7 @@ void main() {
 
     Widget builder() {
       return new TestComponent(new HomogeneousViewport(
-        builder: (int start, int count, BuildContext context) {
+        builder: (BuildContext context, int start, int count) {
           List<Widget> result = <Widget>[];
           for (int index = start; index < start + count; index += 1) {
             callbackTracker.add(index);
@@ -52,18 +52,19 @@ void main() {
 
     tester.pumpFrame(builder());
 
-    TestComponentState testComponent = tester.findElement((element) => element.widget is TestComponent).state;
+    StatefulComponentElement testComponent = tester.findElement((element) => element.widget is TestComponent);
+    TestComponentState testComponentState = testComponent.state;
 
     expect(callbackTracker, equals([0, 1, 2, 3, 4, 5]));
 
     callbackTracker.clear();
-    testComponent.go(false);
+    testComponentState.go(false);
     tester.pumpFrameWithoutChange();
 
     expect(callbackTracker, equals([]));
 
     callbackTracker.clear();
-    testComponent.go(true);
+    testComponentState.go(true);
     tester.pumpFrameWithoutChange();
 
     expect(callbackTracker, equals([0, 1, 2, 3, 4, 5]));
@@ -80,7 +81,7 @@ void main() {
 
     double offset = 300.0;
 
-    ListBuilder itemBuilder = (int start, int count, BuildContext context) {
+    ListBuilder itemBuilder = (BuildContext context, int start, int count) {
       List<Widget> result = <Widget>[];
       for (int index = start; index < start + count; index += 1) {
         callbackTracker.add(index);
@@ -130,7 +131,7 @@ void main() {
 
     double offset = 300.0;
 
-    ListBuilder itemBuilder = (int start, int count, BuildContext context) {
+    ListBuilder itemBuilder = (BuildContext context, int start, int count) {
       List<Widget> result = <Widget>[];
       for (int index = start; index < start + count; index += 1) {
         callbackTracker.add(index);

packages/unit/test/widget/block_test.dart

@@ -1,4 +1,3 @@
-import 'package:quiver/testing/async.dart';
 import 'package:sky/widgets.dart';
 import 'package:test/test.dart';