Added new implementations for virtual containers

runtime/observatory/lib/src/elements/containers/virtual_tree.dart

+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// for details. 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:html';
+import 'package:observatory/src/elements/containers/virtual_collection.dart';
+import 'package:observatory/src/elements/helpers/rendering_scheduler.dart';
+import 'package:observatory/src/elements/helpers/tag.dart';
+
+typedef HtmlElement CreateElementCallback(toggle({bool forward}));
+typedef void UpdateElementCallback(HtmlElement el, dynamic item, int depth);
+typedef Iterable<dynamic> GetChildrenCallback(dynamic value);
+
+class VirtualTreeElement extends HtmlElement implements Renderable {
+  static const tag =
+      const Tag<VirtualTreeElement>('virtual-tree', dependencies: const [
+        VirtualCollectionElement.tag
+      ]);
+
+  RenderingScheduler<VirtualTreeElement> _r;
+
+  Stream<RenderedEvent<VirtualTreeElement>> get onRendered => _r.onRendered;
+
+  GetChildrenCallback _children;
+  List _items;
+  List _depths;
+  final Set _expanded = new Set();
+
+  List get items => _items;
+
+  set items(Iterable value) {
+    _items = new List.unmodifiable(value);
+    _expanded.clear();
+    _r.dirty();
+  }
+
+  factory VirtualTreeElement(CreateElementCallback create,
+      UpdateElementCallback update, GetChildrenCallback children,
+      {Iterable items: const [], RenderingQueue queue}) {
+    assert(create != null);
+    assert(update != null);
+    assert(children != null);
+    assert(items != null);
+    VirtualTreeElement e = document.createElement(tag.name);
+    e._r = new RenderingScheduler(e, queue: queue);
+    e._children = children;
+    e._collection = new VirtualCollectionElement(() {
+      var element;
+      return element = create(({bool forward: false}) {
+        var item = e._collection.getItemFromElement(element);
+        if (e.isExpanded(item)) {
+          e.collapse(item, forward: forward);
+        } else {
+          e.expand(item, forward: forward);
+        }
+      });
+    }, (HtmlElement el, dynamic item, int index) {
+      update(el, item, e._depths[index]);
+    }, queue: queue);
+    e._items = new List.unmodifiable(items);
+    return e;
+  }
+
+  VirtualTreeElement.created() : super.created();
+
+  bool isExpanded(item) {
+    return _expanded.contains(item);
+  }
+
+  void expand(item, {bool forward: false}) {
+    if (_expanded.add(item)) _r.dirty();
+    if (forward) {
+      var children = _children(item);
+      while (children.length == 1) {
+        _expanded.add(children.first);
+        children = _children(children.first);
+      }
+    }
+  }
+
+  void collapse(item, {bool forward: false}) {
+    if (_expanded.remove(item)) _r.dirty();
+    if (forward) {
+      var children = _children(item);
+      while (children.length == 1) {
+        _expanded.remove(children.first);
+        children = _children(children.first);
+      }
+    }
+  }
+
+  @override
+  attached() {
+    super.attached();
+    _r.enable();
+  }
+
+ @override
+  detached() {
+    super.detached(); _r.disable(notify: true);
+    children = const [];
+  }
+
+  VirtualCollectionElement _collection;
+
+  void render() {
+    if (children.length == 0) {
+      children = [_collection];
+    }
+    Iterable _toList(item) {
+      if (isExpanded(item)) {
+        Iterable children = _children(item);
+        if (children.isNotEmpty) {
+          return [item]..addAll(children.expand(_toList));
+        }
+      }
+      return [item];
+    }
+    _collection.items = _items.expand(_toList);
+    var depth = 0;
+    Iterable _toDepth(item) {
+      if (isExpanded(item)) {
+        Iterable children = _children(item);
+        if (children.isNotEmpty) {
+          depth++;
+          return children.expand(_toDepth).toList()
+              ..insert(0, --depth);
+        }
+      }
+      return [depth];
+    }
+    _depths = _items.expand(_toDepth).toList();
+  }
+}