| // Copyright (c) 2014, 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. |
| |
| /// Provides support for associating a Dart type for Javascript Custom Elements. |
| /// This will not work unless `dart_support.js` is loaded. |
| library web_components.interop; |
| |
| import 'dart:html' show document, Element; |
| import 'dart:js' show JsObject, JsFunction; |
| |
| final _doc = new JsObject.fromBrowserObject(document); |
| |
| /// Returns whether [registerDartType] is supported, which requires to have |
| /// `dart_support.js` already loaded in the page. |
| bool get isSupported => _doc.hasProperty('_registerDartTypeUpgrader'); |
| |
| /// Watches when Javascript custom elements named [tagName] are created and |
| /// associates the created element with the given [dartType]. Only one Dart type |
| /// can be registered for a given tag name. |
| void registerDartType(String tagName, Type dartType, {String extendsTag}) { |
| if (!isSupported) { |
| throw new UnsupportedError("Couldn't find " |
| "`document._registerDartTypeUpgrader`. Please make sure that " |
| "`packages/web_components/interop_support.html` is loaded and " |
| "available before calling this function."); |
| } |
| |
| var upgrader = |
| document.createElementUpgrader(dartType, extendsTag: extendsTag); |
| |
| // Unfortunately the dart:html upgrader will throw on an already-upgraded |
| // element, so we need to duplicate the type check to prevent that. |
| // An element can be upgraded twice if it extends another element and calls |
| // createdCallback on the superclass. Since that's a valid use case we must |
| // wrap at both levels, and guard against it here. |
| upgradeElement(e) { |
| if (e.runtimeType != dartType) upgrader.upgrade(e); |
| } |
| |
| _doc.callMethod('_registerDartTypeUpgrader', [tagName, upgradeElement]); |
| } |
| |
| /// This function is mainly used to save resources. By default, we save a log of |
| /// elements that are created but have no Dart type associated with them. This |
| /// is so we can upgrade them as soon as [registerDartType] is invoked. This |
| /// function can be called to indicate that we no longer are interested in |
| /// logging element creations and that it is sufficient to only upgrade new |
| /// elements as they are being created. Typically this is called after the last |
| /// call to [registerDartType] or as soon as you know that no element will be |
| /// created until the call to [registerDartType] is made. |
| void onlyUpgradeNewElements() => _doc.callMethod('_onlyUpgradeNewElements'); |