Move VariableHeightScrollable to sdk/lib/widgets

sky/sdk/lib/widgets/block_viewport.dart

Index: sky/sdk/lib/widgets/block_viewport.dart
diff --git a/sky/sdk/lib/widgets/block_viewport.dart b/sky/sdk/lib/widgets/block_viewport.dart
index 8aa0f0c3756dd5379739ca19977e2cf0cc7417af..c46a04bb0bc36e7ba321fe37008a44a6e149698e 100644
--- a/sky/sdk/lib/widgets/block_viewport.dart
+++ b/sky/sdk/lib/widgets/block_viewport.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'dart:collection';
+
 import '../rendering/block.dart';
 import '../rendering/box.dart';
 import '../rendering/object.dart';
@@ -10,6 +12,12 @@ import 'widget.dart';
 // return null if index is greater than index of last entry
 typedef Widget IndexedBuilder(int index);
 
+typedef void LayoutChangedCallback(
+  int firstVisibleWidgetIndex, 
+  int visibleWidgetCount,
+  UnmodifiableListView<double> widgetOffsets,
+  bool lastWidgetReached);

[Hixie, 2015/07/10 22:51:38]

paren on its own line

[hansmuller, 2015/07/10 23:42:05]

Done.

+
 class _Key {
   const _Key(this.type, this.key);
   factory _Key.fromWidget(Widget widget) => new _Key(widget.runtimeType, widget.key);
@@ -20,12 +28,13 @@ class _Key {
 }
 
 class BlockViewport extends RenderObjectWrapper {
-  BlockViewport({ this.builder, this.startOffset, this.token, String key })
+  BlockViewport({ this.builder, this.startOffset, this.token, this.onLayoutChanged, String key })
     : super(key: key);
 
   IndexedBuilder builder;
   double startOffset;
   Object token;
+  LayoutChangedCallback onLayoutChanged;
 
   RenderBlockViewport get root => super.root;
   RenderBlockViewport createNode() => new RenderBlockViewport();
@@ -83,6 +92,7 @@ class BlockViewport extends RenderObjectWrapper {
   List<double> _offsets = <double>[0.0];
   int _currentStartIndex = 0;
   int _currentChildCount = 0;
+  bool _lastWidgetReached = false;

[Hixie, 2015/07/10 22:51:37]

lastWidgetReached would store a Widget. If you want to store a boolean, call it
something like didReachLastWidget or some such. Sine you call it a child count
and not a widget count, maybe didReachLastChild?

[hansmuller, 2015/07/10 23:42:05]

I've changed all the fooWidget names I added to fooChild.

 
   int _findIndexForOffsetBeforeOrAt(double offset) {
     int left = 0;
@@ -113,6 +123,7 @@ class BlockViewport extends RenderObjectWrapper {
       builder = newNode.builder;
       token = newNode.token;
       _offsets = <double>[0.0];
+      _lastWidgetReached = false;
     }
     return true;
   }
@@ -249,8 +260,10 @@ class BlockViewport extends RenderObjectWrapper {
       while (_offsets[index] < endOffset) {
         if (!builtChildren.containsKey(index)) {
           Widget widget = _getWidget(index, innerConstraints);
-          if (widget == null)
-            break; // reached the end of the list
+          if (widget == null) {
+            _lastWidgetReached = true;
+            break;
+          }
           newChildren[new _Key.fromWidget(widget)] = widget;
           builtChildren[index] = widget;
         }
@@ -287,6 +300,14 @@ class BlockViewport extends RenderObjectWrapper {
     _childrenByKey = newChildren;
     _currentStartIndex = startIndex;
     _currentChildCount = _childrenByKey.length;
+
+    if (onLayoutChanged != null) {
+      onLayoutChanged(
+          _currentStartIndex,

[Hixie, 2015/07/10 22:51:38]

this should be indented with two spaces.

[hansmuller, 2015/07/10 23:42:05]

Done.

+          _currentChildCount, 
+          new UnmodifiableListView<double>(_offsets),
+          _lastWidgetReached);

[Hixie, 2015/07/10 22:51:37]

closing paren should be on its own line.

[hansmuller, 2015/07/10 23:42:05]

Done.

+    }
   }
 
 }