Index: pkg/custom_element/lib/polyfill.dart |
diff --git a/pkg/custom_element/lib/polyfill.dart b/pkg/custom_element/lib/polyfill.dart |
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+// 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. |
+ |
+/** Dart APIs for interacting with the JavaScript Custom Elements polyfill. */ |
+library custom_element.polyfill; |
+ |
+import 'dart:async'; |
+import 'dart:html'; |
+import 'dart:js' as js; |
+ |
+/** |
+ * A future that completes once all custom elements in the initial HTML page |
+ * have been upgraded. |
+ * |
+ * This is needed because the native implementation can update the elements |
+ * while parsing the HTML document, but the custom element polyfill cannot, |
+ * so it completes this future once all elements are upgraded. |
+ */ |
+Future customElementsReady = () { |
+ if (_isReady) return new Future.value(); |
+ |
+ // Not upgraded. Wait for the polyfill to fire the WebComponentsReady event. |
+ return document.body.on['WebComponentsReady'].first; |
+}(); |
+ |
+// Return true if we are using the polyfill and upgrade is complete, or if we |
+// have native document.register and therefore the browser took care of it. |
+// Otherwise return false, including the case where we can't find the polyfill. |
+bool get _isReady { |
+ // If we don't have dart:js, assume things are ready |
+ if (js.context == null) return true; |
+ |
+ var customElements = js.context['CustomElements']; |
+ if (customElements == null) { |
+ // Return true if native document.register, otherwise false. |
+ // (Maybe the polyfill isn't loaded yet. Wait for it.) |
+ return document.supportsRegister; |
+ } |
+ |
+ return customElements['ready'] == true; |
+} |