UILabel default kerning different from CATextLayer

Question

I have a UILabel with the string \'LA\'. I also have a CATextLayer with the same characters in an NSAttributedString assigned to its

Answer 1

you should add attribute to your NSMutableAttributedString.

For the kerning:

    CGFloat characterspacing = 10.0f;
    CFNumberRef num = CFNumberCreate(kCFAllocatorDefault,kCFNumberSInt8Type,&characterspacing);
    [string addAttribute:(id)kCTKernAttributeName value:(id)num range:NSMakeRange(0 , [string length])];
    CFRelease(num);

If you also need the line spacing, or set LineBreadMode:

    CTLineBreakMode linebreak = kCTLineBreakByCharWrapping;
    CTParagraphStyleSetting linebreakStyle;
    linebreakStyle.spec = kCTParagraphStyleSpecifierLineBreakMode;
    linebreakStyle.valueSize = sizeof(linebreak);
    linebreakStyle.value = &linebreak;

    CTParagraphStyleSetting lineSpaceStyle;
    CGFloat linespacing = self.linesSpacing;
    lineSpaceStyle.spec = kCTParagraphStyleSpecifierLineSpacingAdjustment;
    lineSpaceStyle.valueSize = sizeof(linespacing);
    lineSpaceStyle.value =&linespacing;
    CTParagraphStyleSetting settings[ ] ={linebreakStyle,lineSpaceStyle};
    CTParagraphStyleRef style = CTParagraphStyleCreate(settings ,2);
    [string addAttribute:(id)kCTParagraphStyleAttributeName value:(id)style range:NSMakeRange(0 , [string length])];
    CFRelease(style);

At the end, may you need calculate the number of line(linenum) about your kerning,line spacing and LineBreakMode:

CTFramesetterRef myframesetter = CTFramesetterCreateWithAttributedString((CFAttributedStringRef)string);
CGMutablePathRef leftColumnPath = CGPathCreateMutable();
CGPathAddRect(leftColumnPath, NULL ,CGRectMake(0 , 0 , Lable.frame.size.width, MAXFLOAT));
CTFrameRef leftFrame = CTFramesetterCreateFrame(myframesetter,CFRangeMake(0, 0), leftColumnPath , NULL);
CFArrayRef lines = CTFrameGetLines(leftFrame);
linenum = (int)CFArrayGetCount(lines);
CFRelease(myframesetter);
CFRelease(leftFrame);
CGPathRelease(leftColumnPath);