Port clients of ScrollableMixedWidgetList to LazyBlock

LazyBlock is going to replace ScrollableMixedWidgetList at some point.

dev/manual_tests/card_collection.dart

@@ -44,7 +44,6 @@ class CardCollectionState extends State<CardCollection> {
   bool _fixedSizeCards = false;
   bool _sunshine = false;
   bool _varyFontSizes = false;
-  InvalidatorCallback _invalidator;
 
   void _initVariableSizedCardModels() {
     List<double> cardHeights = <double>[
@@ -304,7 +303,6 @@ class CardCollectionState extends State<CardCollection> {
     Widget card = new Dismissable(
       key: new ObjectKey(cardModel),
       direction: _dismissDirection,
-      onResize: () { if (_invalidator != null) _invalidator(<int>[index]); },
       onDismissed: (DismissDirection direction) { dismissCard(cardModel); },
       child: new Card(
         color: _primaryColor[cardModel.color],
@@ -413,18 +411,15 @@ class CardCollectionState extends State<CardCollection> {
   Widget build(BuildContext context) {
     Widget cardCollection;
     if (_fixedSizeCards) {
-      _invalidator = null;
       cardCollection = new ScrollableList(
         snapOffsetCallback: _snapToCenter ? _toSnapOffset : null,
         itemExtent: kFixedCardHeight,
         children: _cardIndices.map/*<Widget>*/((int index) => _buildCard(context, index))
       );
     } else {
-      cardCollection = new ScrollableMixedWidgetList(
+      cardCollection = new LazyBlock(
-        builder: _buildCard,
+        delegate: new LazyBlockBuilder(_buildCard),
-        token: _cardModels.length,
+        snapOffsetCallback: _snapToCenter ? _toSnapOffset : null
-        snapOffsetCallback: _snapToCenter ? _toSnapOffset : null,
-        onInvalidatorAvailable: (InvalidatorCallback callback) { _invalidator = callback; }
       );
     }
 

dev/manual_tests/overlay_geometry.dart

@@ -90,11 +90,44 @@ class OverlayGeometryApp extends StatefulWidget {
   OverlayGeometryAppState createState() => new OverlayGeometryAppState();
 }
 
-class OverlayGeometryAppState extends State<OverlayGeometryApp> {
+typedef void CardTapCallback(Key targetKey, Point globalPosition);
+
+class CardBuilder extends LazyBlockDelegate {
+  CardBuilder({ this.cardModels, this.onTapUp });
+
+  final List<CardModel> cardModels;
+  final CardTapCallback onTapUp;
 
   static const TextStyle cardLabelStyle =
     const TextStyle(color: Colors.white, fontSize: 18.0, fontWeight: FontWeight.bold);
 
+  @override
+  Widget buildItem(BuildContext context, int index) {
+    if (index >= cardModels.length)
+      return null;
+    CardModel cardModel = cardModels[index];
+    return new GestureDetector(
+      key: cardModel.key,
+      onTapUp: (Point globalPosition) { onTapUp(cardModel.targetKey, globalPosition); },
+      child: new Card(
+        key: cardModel.targetKey,
+        color: cardModel.color,
+        child: new Container(
+          height: cardModel.height,
+          padding: const EdgeInsets.all(8.0),
+          child: new Center(child: new Text(cardModel.label, style: cardLabelStyle))
+        )
+      )
+    );
+  }
+
+  @override
+  bool shouldRebuild(CardBuilder oldDelegate) {
+    return oldDelegate.cardModels != cardModels;
+  }
+}
+
+class OverlayGeometryAppState extends State<OverlayGeometryApp> {
   List<CardModel> cardModels;
   Map<MarkerType, Point> markers = new Map<MarkerType, Point>();
   double markersScrollOffset;
@@ -125,9 +158,9 @@ class OverlayGeometryAppState extends State<OverlayGeometryApp> {
     });
   }
 
-  void handlePointerDown(GlobalKey target, PointerDownEvent event) {
+  void handleTapUp(GlobalKey target, Point globalPosition) {
     setState(() {
-      markers[MarkerType.touch] = event.position;
+      markers[MarkerType.touch] = globalPosition;
       final RenderBox box = target.currentContext.findRenderObject();
       markers[MarkerType.topLeft] = box.localToGlobal(new Point(0.0, 0.0));
       final Size size = box.size;
@@ -137,25 +170,6 @@ class OverlayGeometryAppState extends State<OverlayGeometryApp> {
     });
   }
 
-  Widget builder(BuildContext context, int index) {
-    if (index >= cardModels.length)
-      return null;
-    CardModel cardModel = cardModels[index];
-    return new Listener(
-      key: cardModel.key,
-      onPointerDown: (PointerDownEvent event) { return handlePointerDown(cardModel.targetKey, event); },
-      child: new Card(
-        key: cardModel.targetKey,
-        color: cardModel.color,
-        child: new Container(
-          height: cardModel.height,
-          padding: const EdgeInsets.all(8.0),
-          child: new Center(child: new Text(cardModel.label, style: cardLabelStyle))
-        )
-      )
-    );
-  }
-
   @override
   Widget build(BuildContext context) {
     List<Widget> layers = <Widget>[
@@ -163,10 +177,12 @@ class OverlayGeometryAppState extends State<OverlayGeometryApp> {
         appBar: new AppBar(title: new Text('Tap a Card')),
         body: new Container(
           padding: const EdgeInsets.symmetric(vertical: 12.0, horizontal: 8.0),
-          child: new ScrollableMixedWidgetList(
+          child: new LazyBlock(
-            builder: builder,
+            onScroll: handleScroll,
-            token: cardModels.length,
+            delegate: new CardBuilder(
-            onScroll: handleScroll
+              cardModels: cardModels,
+              onTapUp: handleTapUp
+            )
           )
         )
       )

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

@@ -33,6 +33,18 @@ abstract class LazyBlockDelegate {
   bool shouldRebuild(LazyBlockDelegate oldDelegate);
 }
 
+class LazyBlockBuilder extends LazyBlockDelegate {
+  LazyBlockBuilder(this.builder);
+
+  final IndexedBuilder builder;
+
+  @override
+  Widget buildItem(BuildContext context, int index) => builder(context, index);
+
+  @override
+  bool shouldRebuild(LazyBlockDelegate oldDelegate) => true;
+}
+
 class LazyBlock extends Scrollable {
   LazyBlock({
     Key key,
@@ -124,18 +136,19 @@ class _RenderLazyBlock extends RenderVirtualViewport<_LazyBlockParentData> {
       child.parentData = new _LazyBlockParentData();
   }
 
-  double _noIntrinsicExtent() {
+  bool _debugThrowIfNotCheckingIntrinsics() {
     assert(() {
       if (!RenderObject.debugCheckingIntrinsics) {
-        throw new UnsupportedError(
+        throw new FlutterError(
-          'MixedViewport does not support returning intrinsic dimensions.\n'
+          'LazyBlockViewport does not support returning intrinsic dimensions.\n'
-          'Calculating the intrinsic dimensions would require walking the entire child list,\n'
+          'Calculating the intrinsic dimensions would require walking the entire '
-          'which defeats the entire point of having a lazily-built list of children.'
+          'child list, which defeats the entire point of having a lazily-built '
+          'list of children.'
         );
       }
       return true;
     });
-    return null;
+    return true;
   }
 
   double getIntrinsicWidth(BoxConstraints constraints) {
@@ -143,7 +156,8 @@ class _RenderLazyBlock extends RenderVirtualViewport<_LazyBlockParentData> {
       case Axis.horizontal:
         return constraints.constrainWidth(0.0);
       case Axis.vertical:
-        return _noIntrinsicExtent();
+        assert(_debugThrowIfNotCheckingIntrinsics());
+        return constraints.constrainWidth(0.0);
     }
   }
 
@@ -162,9 +176,10 @@ class _RenderLazyBlock extends RenderVirtualViewport<_LazyBlockParentData> {
   double getIntrinsicHeight(BoxConstraints constraints) {
     switch (mainAxis) {
       case Axis.horizontal:
-        return constraints.constrainWidth(0.0);
+        return constraints.constrainHeight(0.0);
       case Axis.vertical:
-        return _noIntrinsicExtent();
+        assert(_debugThrowIfNotCheckingIntrinsics());
+        return constraints.constrainHeight(0.0);
     }
   }
 
@@ -259,13 +274,19 @@ class _LazyBlockElement extends RenderObjectElement {
     LazyBlockViewport oldWidget = widget;
     super.update(newWidget);
     renderObject.mainAxis = widget.direction;
-    if (newWidget.delegate.runtimeType != oldWidget.delegate.runtimeType ||
+    LazyBlockDelegate newDelegate = newWidget.delegate;
-        newWidget.delegate.shouldRebuild(oldWidget.delegate)) {
+    LazyBlockDelegate oldDelegate = oldWidget.delegate;
-      IndexedBuilder builder = widget.delegate.buildItem;
+    if (newDelegate != oldDelegate && (newDelegate.runtimeType != oldDelegate.runtimeType || newDelegate.shouldRebuild(oldDelegate))) {
-      List<Widget> widgets = new List<Widget>(_children.length);
+      IndexedBuilder builder = newDelegate.buildItem;
-      for (int i = 0; i < widgets.length; ++i)
+      List<Widget> widgets = <Widget>[];
-        widgets[i] = builder(this, _firstChildLogicalIndex + i);
+      for (int i = 0; i < widgets.length; ++i) {
-      _children = updateChildren(_children, widgets);
+        int logicalIndex = _firstChildLogicalIndex + i;
+        Widget childWidget = builder(this, logicalIndex);
+        if (childWidget == null)
+          break;
+        widgets[i] = new RepaintBoundary.wrap(childWidget, logicalIndex);
+      }
+      _children = new List<Element>.from(updateChildren(_children, widgets));
     }
     // If the new start offset can be displayed properly with the items
     // currently represented in _children, we just need to update the paint
@@ -316,8 +337,9 @@ class _LazyBlockElement extends RenderObjectElement {
 
         while (currentLogicalIndex > 0 && currentLogicalOffset > startLogicalOffset) {
           currentLogicalIndex -= 1;
-          Widget newWidget = new RepaintBoundary.wrap(builder(this, currentLogicalIndex), currentLogicalIndex);
+          Widget newWidget = builder(this, currentLogicalIndex);
           assert(newWidget != null);
+          newWidget = new RepaintBoundary.wrap(newWidget, currentLogicalIndex);
           newChildren.add(inflateWidget(newWidget, null));
           RenderBox child = block.firstChild;
           assert(child == newChildren.last.renderObject);
@@ -383,9 +405,10 @@ class _LazyBlockElement extends RenderObjectElement {
         int physicalIndex = currentLogicalIndex - _firstChildLogicalIndex;
         if (physicalIndex >= _children.length) {
           assert(physicalIndex == _children.length);
-          Widget newWidget = new RepaintBoundary.wrap(builder(this, currentLogicalIndex), currentLogicalIndex);
+          Widget newWidget = builder(this, currentLogicalIndex);
           if (newWidget == null)
             break;
+          newWidget = new RepaintBoundary.wrap(newWidget, currentLogicalIndex);
           Element previousChild = _children.isEmpty ? null : _children.last;
           _children.add(inflateWidget(newWidget, previousChild));
         }

packages/flutter/test/widget/scrollable_list_with_inherited_test.dart

@@ -21,13 +21,9 @@ Widget buildCard(BuildContext context, int index) {
   );
 }
 
-InvalidatorCallback invalidator;
-
 Widget buildFrame() {
-  return new ScrollableMixedWidgetList(
+  return new LazyBlock(
-    builder: buildCard,
+    delegate: new LazyBlockBuilder(buildCard)
-    token: items.length,
-    onInvalidatorAvailable: (InvalidatorCallback callback) { invalidator = callback; }
   );
 }