Converted Observatory cpu-profile-table element

runtime/observatory/lib/src/elements/containers/virtual_collection.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/helpers/rendering_scheduler.dart';
 import 'package:observatory/src/elements/helpers/tag.dart';
 
 typedef HtmlElement VirtualCollectionCreateCallback();
 typedef void VirtualCollectionUpdateCallback(HtmlElement el, dynamic item,
     int index);
 
 class VirtualCollectionElement extends HtmlElement implements Renderable {
   static const tag =
       const Tag<VirtualCollectionElement>('virtual-collection');
 
   RenderingScheduler<VirtualCollectionElement> _r;
 
   Stream<RenderedEvent<VirtualCollectionElement>> get onRendered =>
       _r.onRendered;
 
   VirtualCollectionCreateCallback _create;
   VirtualCollectionCreateCallback _createHeader;
   VirtualCollectionUpdateCallback _update;
   double _itemHeight;
+  double _headerHeight = 0.0;
   int _top;
   double _height;
   List _items;
   StreamSubscription _onScrollSubscription;
   StreamSubscription _onResizeSubscription;
 
   List get items => _items;
 
   set items(Iterable value) {
     _items = new List.unmodifiable(value);
@@ skipping 62 matching lines @@
   static const int _preload = 2;
   /// L = length of all the elements loaded
   /// l = length of the visible area
   ///
   /// L = l + 2 * l / _preload
   /// l = L * _preload / (_preload + 2)
   ///
   /// tail = l / _preload = L * 1 / (_preload + 2) = L * _inverse_preload
   static const double _inverse_preload = 1 / (_preload + 2);
 
+  var _takeIntoView;
+
+  void takeIntoView(item) {
+    _takeIntoView = item;
+    _r.dirty();
+  }
+
   void render() {
     if (children.isEmpty) {
       children = [
         _scroller
           ..children = [
             _shifter
               ..children = [_create()]
           ],
       ];
       if (_createHeader != null) {
         _header.children = [_createHeader()];
         _scroller.children.insert(0, _header);
+        _headerHeight = _header.children[0].getBoundingClientRect().height;
       }
       _itemHeight = _shifter.children[0].getBoundingClientRect().height;
       _height = getBoundingClientRect().height;
     }
+
+    if (_takeIntoView != null) {
+      final index = items.indexOf(_takeIntoView);
+      if (index >= 0) {
+        final minScrollTop = _itemHeight * (index + 1) - _height;
+        final maxScrollTop = _itemHeight * index;
+        scrollTop = ((maxScrollTop - minScrollTop) / 2 + minScrollTop).floor();
+      }
+      _takeIntoView = null;
+    }
+
     final top = (scrollTop / _itemHeight).floor();
 
     _header.style.top = '${scrollTop}px';
-    _scroller.style.height = '${_itemHeight*(_items.length)}px';
+    _scroller.style.height = '${_itemHeight*(_items.length)+_headerHeight}px';
     final tail_length = (_height / _itemHeight / _preload).ceil();
     final length = tail_length * 2 + tail_length * _preload;
 
     if (_shifter.children.length < length) {
       while (_shifter.children.length != length) {
         var e = _create();
         e..style.display = 'hidden';
         _shifter.children.add(e);
       }
       _top = null; // force update;
@@ skipping 20 matching lines @@
   }
 
   void _onResize(_) {
     final newHeight = getBoundingClientRect().height;
     if (newHeight > _height) {
       _height = newHeight;
       _r.dirty();
     }
   }
 }