text: /**
   * @license
   * Copyright 2015 Google Inc. All Rights Reserved.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  foam.CLASS({
    package: 'foam.u2',
    name: 'AttrSlot',
    implements: [ 'foam.core.Slot' ],
  
    documentation: 'A Value bound to an Element attribute. Used to bind values to DOM.',
  
    properties: [
      {
        name: 'element',
        required: true
      },
      'value',
      [ 'property', 'value'  ],
      [ 'event',    'change' ]
    ],
  
    methods: [
      function get() {
        return this.element.getAttribute(this.property);
      },
  
      function set(value) {
        this.element.setAttribute(this.property, value);
  
        // The next line is necessary to fire a change event.
        // This is necessary because DOM isn't proper MVC and
        // doesn't fire a change event when the value is explicitly set.
        this.value = value;
      },
  
      function sub(l) {
        // TODO: remove listener on unsubscribe. But how?
        if ( ! this.hasListeners() ) {
          var self = this;
          this.element.on(this.event, function() {
            self.value = self.get();
          });
        }
        return this.SUPER('propertyChange', 'value', l);
      },
  
      function toString() {
        return 'AttrSlot(' + this.event + ', ' + this.property + ')';
      }
    ]
  });
  