Make the drawer, popup menus, dialogs, and settings page scrollable.

sky/sdk/lib/widgets/scrollable_viewport.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 '../animation/scroll_behavior.dart';
+import 'basic.dart';
+import 'scrollable.dart';
+
+class ScrollableViewport extends Scrollable {
+
+  ScrollableViewport({ String key, this.child }) : super(key: key);
+
+  Widget child;
+
+  void syncFields(ScrollableViewport source) {
+    child = source.child;
+    super.syncFields(source);
+  }
+
+  ScrollBehavior createScrollBehavior() => new FlingBehavior();
+  FlingBehavior get scrollBehavior => super.scrollBehavior;
+
+  double _viewportHeight = 0.0;
+  double _childHeight = 0.0;
+  void _handleViewportSizeChanged(Size newSize) {
+    setState(() {
+      _viewportHeight = newSize.height;
+      _updateScrollBehaviour();
+    });
+  }
+  void _handleChildSizeChanged(Size newSize) {
+    setState(() {
+      _childHeight = newSize.height;
+      _updateScrollBehaviour();
+    });
+  }
+  void _updateScrollBehaviour() {
+    scrollBehavior.contentsSize = _childHeight;
+    scrollBehavior.containerSize = _viewportHeight;
+    if (scrollOffset > scrollBehavior.maxScrollOffset)
+      settleScrollOffset();
+  }
+
+  Widget buildContent() {
+    return new SizeObserver(
+      callback: _handleViewportSizeChanged,
+      child: new Viewport(
+        offset: scrollOffset,
+        child: new SizeObserver(
+          callback: _handleChildSizeChanged,
+          child: child
+        )
+      )
+    );
+  }
+
+}
+
+class ScrollableBlock extends Component {
+
+  ScrollableBlock(this.children, { String key }) : super(key: key);
+
+  final List<Widget> children;
+
+  Widget build() {
+    return new ScrollableViewport(
+      child: new Block(children)
+    );
+  }
+
+}