Support for observable models, fixes #259

lib/observe/html.dart

+// Copyright (c) 2013, 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.
+
+// TODO(jmesserly): can we handle this better? This seems like an unfortunate
+// limitation of our read barriers.
+
+/** Helpers for exposing dart:html as observable data. */
+library web_ui.observe.html;
+
+import 'dart:html';
+import 'package:web_ui/observe.dart';
+
+ObservableReference<String> _hash;
+
+/** An observable version of [window.location.hash]. */
+String get locationHash {
+  if (_hash == null) {
+    _hash = new ObservableReference(window.location.hash);
+
+    window.onHashChange.listen(_updateLocationHash);
+    window.onPopState.listen(_updateLocationHash);
+  }
+
+  return _hash.value;
+}
+
+/**
+ * Pushes a new URL state, similar to the affect of clicking a link.
+ * Has no effect if the [value] already equals [window.location.hash].
+ */
+set locationHash(String value) {
+  if (value == window.location.hash) return;
+
+  window.history.pushState(const {}, '', value);
+  _updateLocationHash(null);
+}
+
+
+// listen on changes to #hash in the URL
+// Note: listen on both popState and hashChange, because IE9 doesnh't support
+// history API, and it doesn't work properly on Opera 12.
+// See http://dartbug.com/5483
+_updateLocationHash(_) {
+  if (_hash != null) {
+    _hash.value = window.location.hash;
+  }
+}