code: function () {
              var t = this,
                  fixedFullWidth = t.o.fixedFullWidth,
                  $box = t.$box;
  
              if (!t.o.fixedBtnPane) {
                  return;
              }
  
              t.isFixed = false;
  
              $(window)
                  .on('scroll.' + t.eventNamespace + ' resize.' + t.eventNamespace, function () {
                      if (!$box) {
                          return;
                      }
  
                      t.syncCode();
  
                      var scrollTop = $(window).scrollTop(),
                          offset = $box.offset().top + 1,
                          bp = t.$btnPane,
                          oh = bp.outerHeight() - 2;
  
                      if ((scrollTop - offset > 0) && ((scrollTop - offset - t.height) < 0)) {
                          if (!t.isFixed) {
                              t.isFixed = true;
                              bp.css({
                                  position: 'fixed',
                                  top: 0,
                                  left: fixedFullWidth ? '0' : 'auto',
                                  zIndex: 7
                              });
                              $([t.$ta, t.$ed]).css({marginTop: bp.height()});
                          }
                          bp.css({
                              width: fixedFullWidth ? '100%' : (($box.width() - 1) + 'px')
                          });
  
                          $('.' + t.o.prefix + 'fixed-top', $box).css({
                              position: fixedFullWidth ? 'fixed' : 'absolute',
                              top: fixedFullWidth ? oh : oh + (scrollTop - offset) + 'px',
                              zIndex: 15
                          });
                      } else if (t.isFixed) {
                          t.isFixed = false;
                          bp.removeAttr('style');
                          $([t.$ta, t.$ed]).css({marginTop: 0});
                          $('.' + t.o.prefix + 'fixed-top', $box).css({
                              position: 'absolute',
                              top: oh
                          });
                      }
                  });
          }
docs: Management of fixed button pane