CGFloat ascent, descent;        UIFont *font = [self.calFont fontWithSize:size];        CTFontRef fontRefMeasure = (__bridge CTFontRef)font;        [attrString addAttribute:(id)kCTFontAttributeName value:(__bridge id)fontRefMeasure range:NSMakeRange(0, attrString.length)];        CTLineRef line = CTLineCreateWithAttributedString((__bridge CFAttributedStringRef)attrString);        CTLineGetTypographicBounds(line, &ascent, &descent, NULL);                //calculate max font size        CGFloat calFontHeight = MIN(height, width);        self.maxFontHeight = calFontHeight;                //calculate min font size        CGFloat maxLine = self.document.maxLine * BDTZBigFontDataOriginScale;        if (maxLine <= 0) {            maxLine = 1;        }        calFontHeight = [self itemWidth] / (maxLine + (maxLine - 1) * (self.leadingRatio * BDTZBigFontDataOriginScale - 1));        self.minFontHeight = MIN(self.maxFontHeight, calFontHeight);                // longest column        int64_t n = 0;        NSArray *strArray = [self.document.content componentsSeparatedByString:@"\n"];        NSString *measureStr = self.document.content;        // 这里是针对多行文本的处理，循环次数为行数，量级较小（一般为1-10行）        for (NSString *str in strArray) {            if (str.length > n) {                n = str.length;                measureStr = str;            }        }        CGFloat fontWidthRatioOrigin = (self.document.fontWidthRatio * BDTZBigFontDataOriginScale);        CGFloat trackingRatio = (self.document.trackingRatio * BDTZBigFontDataOriginScale) * (ascent + descent) / ascent;        CGRect rect = [@"我" boundingRectWithSize:CGSizeMake(CGFLOAT_MAX, CGFLOAT_MAX) options:NSStringDrawingUsesLineFragmentOrigin attributes:@{NSFontAttributeName:self.calFont} context:nil];        CGFloat fontWidthRatio = fontWidthRatioOrigin > 0 ? fontWidthRatioOrigin * (ascent + descent) / ascent : rect.size.width / rect.size.height;        CGFloat fontHeight = width / (n * fontWidthRatio + n * trackingRatio);                if (strArray.count > 1) {            //calculate font size accoring column count            calFontHeight = [self itemWidth] / (strArray.count + (strArray.count - 1) * (self.leadingRatio * BDTZBigFontDataOriginScale - 1));            //take the min value of the above two font sizes            fontHeight = MIN(fontHeight, calFontHeight);        }                        if (fontHeight > self.maxFontHeight) {            fontHeight = self.maxFontHeight;        } else if (fontHeight < self.minFontHeight) {            fontHeight = self.minFontHeight;        }                CGFloat calSize = fontHeight;        calFontHeight = [self calculateFontHeightSize:calSize];        calSize = floorf(calSize / (calFontHeight * (ascent + descent) / ascent) * calSize);                //exact value, calculate repeatedly with frame until the path can be filled                //根据估算结果，将size逐次减1，直至能填入path，此处代码省略                if (calSize <= 0) {            return calSize;        }        calFontHeight = [self calculateFontHeightSize:calSize];        self.fontHeight = calFontHeight * (ascent + descent) / ascent;                self.font = [self.calFont fontWithSize:calSize];