text: /**
   * @file descriptions-button.js
   */
  import TextTrackButton from './text-track-button.js';
  import Component from '../../component.js';
  import * as Fn from '../../utils/fn.js';
  
  /**
   * The button component for toggling and selecting descriptions
   *
   * @extends TextTrackButton
   */
  class DescriptionsButton extends TextTrackButton {
  
    /**
     * Creates an instance of this class.
     *
     * @param {Player} player
     *        The `Player` that this class should be attached to.
     *
     * @param {Object} [options]
     *        The key/value store of player options.
     *
     * @param {Component~ReadyCallback} [ready]
     *        The function to call when this component is ready.
     */
    constructor(player, options, ready) {
      super(player, options, ready);
  
      const tracks = player.textTracks();
      const changeHandler = Fn.bind(this, this.handleTracksChange);
  
      tracks.addEventListener('change', changeHandler);
      this.on('dispose', function() {
        tracks.removeEventListener('change', changeHandler);
      });
    }
  
    /**
     * Handle text track change
     *
     * @param {EventTarget~Event} event
     *        The event that caused this function to run
     *
     * @listens TextTrackList#change
     */
    handleTracksChange(event) {
      const tracks = this.player().textTracks();
      let disabled = false;
  
      // Check whether a track of a different kind is showing
      for (let i = 0, l = tracks.length; i < l; i++) {
        const track = tracks[i];
  
        if (track.kind !== this.kind_ && track.mode === 'showing') {
          disabled = true;
          break;
        }
      }
  
      // If another track is showing, disable this menu button
      if (disabled) {
        this.disable();
      } else {
        this.enable();
      }
    }
  
    /**
     * Builds the default DOM `className`.
     *
     * @return {string}
     *         The DOM `className` for this object.
     */
    buildCSSClass() {
      return `dk-vjs-descriptions-button ${super.buildCSSClass()}`;
    }
  
    buildWrapperCSSClass() {
      return `dk-vjs-descriptions-button ${super.buildWrapperCSSClass()}`;
    }
  }
  
  /**
   * `kind` of TextTrack to look for to associate it with this menu.
   *
   * @type {string}
   * @private
   */
  DescriptionsButton.prototype.kind_ = 'descriptions';
  
  /**
   * The text that should display over the `DescriptionsButton`s controls. Added for localization.
   *
   * @type {string}
   * @private
   */
  DescriptionsButton.prototype.controlText_ = 'Descriptions';
  
  Component.registerComponent('DescriptionsButton', DescriptionsButton);
  export default DescriptionsButton;
  