        return { element: el, id: el.id };
        }
      }
      el = parent;
    }
  },

  deactivate: function () {
    this.$container.classList.remove('active');
    this._activeEl = null;
    this.activeElBounds = null;
    this.active = false;
  }
}

var referencePane = {
  init: function() {
    this.$container = document.createElement('div');
    this.$container.setAttribute('id', 'references-pane-container');

    var $spacer = document.createElement('div');
    $spacer.setAttribute('id', 'refere