docs: function(expr, sup, sub) {
                      var opShape = generateOperator.call(this), expBox = expr.getFixRenderBox(), scriptHanlder = this.parentExpression.isSideScript() ? "applySide" : "applyUpDown", space = new ScriptController(this, opShape, sup, sub, {
                          zoom: .5
                      })[scriptHanlder](), padding = 5, diff = (space.height + space.top + space.bottom - expBox.height) / 2;
                      // 应用偏移， 使图形在正确的位置上
                      opShape.translate(0, space.top);
                      sup.translate(0, space.top);
                      sub.translate(0, space.top);
                      if (diff >= 0) {
                          expr.translate(space.width + padding, diff);
                      } else {
                          diff = -diff;
                          opShape.translate(0, diff);
                          sup.translate(0, diff);
                          sub.translate(0, diff);
                          expr.translate(space.width + padding, 0);
                      }
                      // 只扩展左边， 不扩展右边， 所以padding不 *2
                      this.parentExpression.expand(padding, padding * 2);
                      this.parentExpression.translateElement(padding, padding);
                  }