catapult/third_party/polymer/components/core-media-query/core-media-query.html

<!--
Copyright (c) 2014 The Polymer Project Authors. All rights reserved.
This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
Code distributed by Google as part of the polymer project is also
subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
-->
<!--
/**
 * @group Polymer Core Elements
 * @element core-media-query
 * @status beta
 * @homepage github.io
 *
 * core-media-query can be used to data bind to a CSS media query.
 * The "query" property is a bare CSS media query.
 * The "queryMatches" property will be a boolean representing if the page matches that media query.
 *
 * core-media-query uses media query listeners to dynamically update the "queryMatches" property.
 * A "core-media-change" event also fires when queryMatches changes.
 *
 * Example:
 *
 *      <core-media-query query="max-width: 640px" queryMatches="{{phoneScreen}}"></core-media-query>
 *
 */

 /**
  * Fired when the media query state changes
  *
  * @event core-media-change
  */
-->
<link rel="import" href="../polymer/polymer.html">

<polymer-element name="core-media-query" attributes="query queryMatches">
  <template>
    <style>
      :host {
        display: none;
      }
    </style>
  </template>
  <script>
    Polymer('core-media-query', {

      /**
       * The Boolean return value of the media query
       *
       * @attribute queryMatches
       * @type Boolean
       * @default false
       */
      queryMatches: false,

      /**
       * The CSS media query to evaulate
       *
       * @attribute query
       * @type string
       * @default ''
       */
      query: '',
      ready: function() {
        this._mqHandler = this.queryHandler.bind(this);
        this._mq = null;
      },
      queryChanged: function() {
        if (this._mq) {
          this._mq.removeListener(this._mqHandler);
        }
        var query = this.query;
        if (query[0] !== '(') {
          query = '(' + this.query + ')';
        }
        this._mq = window.matchMedia(query);
        this._mq.addListener(this._mqHandler);
        this.queryHandler(this._mq);
      },
      queryHandler: function(mq) {
        this.queryMatches = mq.matches;
        this.asyncFire('core-media-change', mq);
      }
    });
  </script>
</polymer-element>