code: function beginControlsAutoHide( viewer ) {
      if ( !viewer.autoHideControls ) {
          return;
      }
      viewer.controlsShouldFade = true;
      viewer.controlsFadeBeginTime =
          $.now() +
          viewer.controlsFadeDelay;
  
      window.setTimeout( function(){
          scheduleControlsFade( viewer );
      }, viewer.controlsFadeDelay );
  }
docs: initiates an animation to hide the controls