docs: function adjustmentPosition(position, operator, radicand, exponent) {
                  var exponentBox = null, opOffset = {
                      x: 0,
                      y: 0
                  }, opBox = operator.getFixRenderBox();
                  exponent.scale(.66);
                  exponentBox = exponent.getFixRenderBox();
                  if (exponentBox.width > 0 && exponentBox.height > 0) {
                      opOffset.y = exponentBox.height - opBox.height / 2;
                      // 指数不超出根号， 则移动指数
                      if (opOffset.y < 0) {
                          exponent.translate(0, -opOffset.y);
                          opOffset.y = 0;
                      }
                      opOffset.x = exponentBox.width + opBox.height / 2 * tan15 - position.x;
                  }
                  operator.translate(opOffset.x, opOffset.y);
                  radicand.translate(opOffset.x + position.x + SHAPE_DATA_WIDTH, opOffset.y + 2 * SHAPE_DATA_WIDTH);
              }