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coretext绘制 个人理解为

一个CTFrame有几个CTLine组成，有几行文字就有几行CTLine。一个CTLine有包含多个CTRun，一个CTRun是所有属性都相同的那部分富文本的绘制单元。所以CTRun是CTFrame的

基本绘制单元

。

资料博客链接地址:http://www.jianshu.com/p/6db3289fb05d

计算绘制的coreText内容的高度

+ (int)getAttributedStringHeightWithString:(NSAttributedString *)string WidthValue:(int)width

{

int total_height = 0;

CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString((CFAttributedStringRef)string); //string 为要计算高度的NSAttributedString

CGRect drawingRect = CGRectMake(0, 0, width, 1000); //这里的高要设置足够大

CGMutablePathRef path = CGPathCreateMutable();

CGPathAddRect(path, NULL, drawingRect);

CTFrameRef textFrame = CTFramesetterCreateFrame(framesetter,CFRangeMake(0,0), path, NULL);

CGPathRelease(path);

CFRelease(framesetter);

NSArray *linesArray = (NSArray *) CTFrameGetLines(textFrame);

CGPoint origins[[linesArray count]];

CTFrameGetLineOrigins(textFrame, CFRangeMake(0, 0), origins);

int line_y = (int) origins[[linesArray count] -1].y; //最后一行line的原点y坐标

CGFloat ascent;

CGFloat descent;

CGFloat leading;

CTLineRef line = (__bridge CTLineRef) [linesArray objectAtIndex:[linesArray count]-1];

CTLineGetTypographicBounds(line, &ascent, &descent, &leading);

total_height = 1000 - line_y + (int) descent +1; //+1为了纠正descent转换成int小数点后舍去的值

CFRelease(textFrame);

return total_height;

}