docs: function initFontSystemInfo(doc) {
                  var tmpNode = doc.createElement("div");
                  tmpNode.style.cssText = "position: absolute; top: 0; left: -100000px;";
                  tmpNode.innerHTML = _p.r(23).join("");
                  doc.body.appendChild(tmpNode);
                  var rectBox = tmpNode.getElementsByTagName("text")[0].getBBox();
                  // text实际占用空间
                  FONT_CONF.spaceHeight = rectBox.height;
                  // text顶部空间
                  FONT_CONF.topSpace = -rectBox.y - FONT_CONF.baseline;
                  FONT_CONF.bottomSpace = FONT_CONF.spaceHeight - FONT_CONF.topSpace - FONT_CONF.baseHeight;
                  // text偏移值
                  FONT_CONF.offset = FONT_CONF.baseline + FONT_CONF.topSpace;
                  // baseline比例
                  FONT_CONF.baselinePosition = (FONT_CONF.topSpace + FONT_CONF.baseline) / FONT_CONF.spaceHeight;
                  // meanline比例
                  FONT_CONF.meanlinePosition = (FONT_CONF.topSpace + FONT_CONF.meanline) / FONT_CONF.spaceHeight;
                  // 上下延伸性比例
                  FONT_CONF.ascenderPosition = FONT_CONF.topSpace / FONT_CONF.spaceHeight;
                  FONT_CONF.descenderPosition = (FONT_CONF.topSpace + FONT_CONF.baseHeight) / FONT_CONF.spaceHeight;
                  doc.body.removeChild(tmpNode);
              }