code: function getPermissionX(dragTd, evt) {
          var ut = getUETable(dragTd);
          if (ut) {
              var preTd = ut.getSameEndPosCells(dragTd, "x")[0],
                  nextTd = ut.getSameStartPosXCells(dragTd)[0],
                  mouseX = mouseCoords(evt).x,
                  left = (preTd ? domUtils.getXY(preTd).x : domUtils.getXY(ut.table).x) + 20 ,
                  right = nextTd ? domUtils.getXY(nextTd).x + nextTd.offsetWidth - 20 : (me.body.offsetWidth + 5 || parseInt(domUtils.getComputedStyle(me.body, "width"), 10));
  
              left += cellMinWidth;
              right -= cellMinWidth;
  
              return mouseX < left ? left : mouseX > right ? right : mouseX;
          }
      }
docs: 获取拖动时允许的X轴坐标
  @param dragTd
  @param evt