jmesserly@google.com
c053cbaefe
R=sigmund@google.com Review URL: https://codereview.chromium.org//341003002 git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@37472 260f80e4-7a28-3924-810f-c04153c831b5
54 lines
2.6 KiB
Dart
54 lines
2.6 KiB
Dart
// Copyright (c) 2014, 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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/// Provides support for associating a Dart type for Javascript Custom Elements.
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/// This will not work unless `dart_support.js` is loaded.
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library web_components.interop;
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import 'dart:async' show Stream, StreamController;
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import 'dart:html' show document, Element;
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import 'dart:js' show JsObject, JsFunction;
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final _doc = new JsObject.fromBrowserObject(document);
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/// Returns whether [registerDartType] is supported, which requires to have
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/// `dart_support.js` already loaded in the page.
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bool get isSupported => _doc.hasProperty('_registerDartTypeUpgrader');
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/// Watches when Javascript custom elements named [tagName] are created and
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/// associates the created element with the given [dartType]. Only one Dart type
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/// can be registered for a given tag name.
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void registerDartType(String tagName, Type dartType, {String extendsTag}) {
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if (!isSupported) {
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throw new UnsupportedError("Couldn't find "
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"`document._registerDartTypeUpgrader`. Please make sure that "
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"`packages/web_components/dart_support.js` is loaded and available "
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"before calling this function.");
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}
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var upgrader = document.createElementUpgrader(
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dartType, extendsTag: extendsTag);
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// Unfortunately the dart:html upgrader will throw on an already-upgraded
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// element, so we need to duplicate the type check to prevent that.
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// An element can be upgraded twice if it extends another element and calls
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// createdCallback on the superclass. Since that's a valid use case we must
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// wrap at both levels, and guard against it here.
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upgradeElement(e) {
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if (e.runtimeType != dartType) upgrader.upgrade(e);
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}
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_doc.callMethod('_registerDartTypeUpgrader', [tagName, upgradeElement]);
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}
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/// This function is mainly used to save resources. By default, we save a log of
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/// elements that are created but have no Dart type associated with them. This
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/// is so we can upgrade them as soon as [registerDartType] is invoked. This
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/// function can be called to indicate that we no longer are interested in
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/// logging element creations and that it is sufficient to only upgrade new
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/// elements as they are being created. Typically this is called after the last
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/// call to [registerDartType] or as soon as you know that no element will be
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/// created until the call to [registerDartType] is made.
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void onlyUpgradeNewElements() => _doc.callMethod('_onlyUpgradeNewElements');
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