sdk/lib/html/templates/html/dart2js/factoryprovider_MutationObserver.darttemplate

// Copyright (c) 2012, 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.

part of html;

class $FACTORYPROVIDER {
  static $CONSTRUCTOR create$(CONSTRUCTOR)(MutationCallback callback) {

    // This is a hack to cause MutationRecord to appear to be instantiated.
    //
    // MutationCallback has a parameter type List<MutationRecord>.  From this we
    // infer a list is created in the browser, but not the element type, because
    // other native fields and methods return plain List which is too general
    // and would imply creating anything.  This statement is a work-around.
    JS('MutationRecord','0');

    return _create$(CONSTRUCTOR)(callback);
  }

  static $CONSTRUCTOR _create$(CONSTRUCTOR)(MutationCallback callback) native '''
    var constructor =
        window.MutationObserver || window.WebKitMutationObserver ||
        window.MozMutationObserver;
    return new constructor(callback);
  ''';

  // TODO(sra): Dart2js inserts a conversion when a Dart function (i.e. an
  // object with a call method) is passed to a native method.  This is so the
  // native code sees a JavaScript function.
  //
  // This does not happen when a function is 'passed' to a JS-form so it is not
  // possible to rewrite the above code to, e.g. (simplified):
  //
  // static createMutationObserver(MutationCallback callback) =>
  //    JS('var', 'new (window.MutationObserver)(#)', callback);
}