docs: function () {
          if (u.hasClass(this._header, this._CssClasses.IS_ANIMATING)) {
              return;
          }
  
          if (this._content.scrollTop > 0 && !u.hasClass(this._header, this._CssClasses.IS_COMPACT)) {
              u.addClass(this._header, this._CssClasses.CASTING_SHADOW)
                  .addClass(this._header, this._CssClasses.IS_COMPACT)
                  .addClass(this._header, this._CssClasses.IS_ANIMATING);
          } else if (this._content.scrollTop <= 0 && u.hasClass(this._header, this._CssClasses.IS_COMPACT)) {
              u.removeClass(this._header, this._CssClasses.CASTING_SHADOW)
                  .removeClass(this._header, this._CssClasses.IS_COMPACT)
                  .addClass(this._header, this._CssClasses.IS_ANIMATING);
          }
      }