code: function getFixedParent(target){
              var documentElement = document.documentElement;
              var node = target;
              var nodeName, path, offset, left, top, savedParent;
              var notFirstNode = false; // 当前点击控件以可见范围内进行定位，其它以全局定位（很多局部控件是不可见的）
              while(node !== null){
                  nodeName = node.nodeName.toLowerCase();
                  if(nodeName !== '#document-fragment'){
                      path = getDomPath(node, notFirstNode);
                      if(path === null){
                          break;
                      }
                      offset = node.getBoundingClientRect();
                      left = parseInt(offset.left, 10);
                      top = parseInt(offset.top, 10);
                      savedParent = mapParentsOffset[path];
                      if(savedParent && left === savedParent.left && top === savedParent.top){
                          return {
                              path: path,
                              left: left,
                              top: top
                          };
                      }
                  }
                  if(nodeName === 'html'){
                      node = null;
                  }
                  else{
                      node = node.parentNode;
                  }
                  notFirstNode = true;
              }
              path = getDomPath(target);
              if(path !== null){
                  offset = target.getBoundingClientRect();
                  return {
                      path: path,
                      left: offset.left,
                      top: offset.top
                  };
              }
              else{
                  return null;
              }
          }
docs: get the fixed offset parent