jmesserly@google.com
0acc931fc4
R=sigmund@google.com Review URL: https://codereview.chromium.org//25740006 git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@29139 260f80e4-7a28-3924-810f-c04153c831b5
64 lines
2.4 KiB
Dart
64 lines
2.4 KiB
Dart
// Copyright (c) 2013, the Dart project authors. Please see the AUTHORS file
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// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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/** Dart APIs for interacting with the JavaScript Custom Elements polyfill. */
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library custom_element.polyfill;
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import 'dart:async';
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import 'dart:html';
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import 'dart:js' as js;
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/**
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* A future that completes once all custom elements in the initial HTML page
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* have been upgraded.
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*
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* This is needed because the native implementation can update the elements
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* while parsing the HTML document, but the custom element polyfill cannot,
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* so it completes this future once all elements are upgraded.
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*/
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Future customElementsReady = () {
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if (_isReady) return new Future.value();
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// Not upgraded. Wait for the polyfill to fire the WebComponentsReady event.
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// Note: we listen on document (not on document.body) to allow this polyfill
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// to be loaded in the HEAD element.
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return document.on['WebComponentsReady'].first;
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}();
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// Return true if we are using the polyfill and upgrade is complete, or if we
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// have native document.register and therefore the browser took care of it.
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// Otherwise return false, including the case where we can't find the polyfill.
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bool get _isReady {
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// If we don't have dart:js, assume things are ready
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if (js.context == null) return true;
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var customElements = js.context['CustomElements'];
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if (customElements == null) {
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// Return true if native document.register, otherwise false.
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// (Maybe the polyfill isn't loaded yet. Wait for it.)
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return document.supportsRegister;
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}
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return customElements['ready'] == true;
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}
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/**
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* Loads `custom-elements.debug.js` or `custom-elements.min.js` by adding the
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* script tag to the page. Returns a future that completes when custom elements
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* are ready (equivalent to [customElementsReady]).
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*
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* Normally you should add this to your HTML file
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* (the Polymer package will do this automatically), but loading dynamically
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* can be useful for scenarios such as tests.
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*/
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Future loadCustomElementPolyfill() {
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if (!document.supportsRegister && !js.context.hasProperty('CustomElements')) {
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var script = new ScriptElement()
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..src = '/packages/custom_element/custom-elements.debug.js';
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document.head.append(script);
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return document.on['WebComponentsReady'].first;
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}
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return new Future.value();
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}
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