Resize CATextLayer to fit text on iOS

Question

All my research so far seems to indicate it is not possible to do this accurately. The only two options available to me at the outset were:

a) Using a La

Answer 1

Try this:

- (CGFloat)boundingHeightForWidth:(CGFloat)inWidth withAttributedString:(NSAttributedString *)attributedString {
    CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString( (CFMutableAttributedStringRef) attributedString); 
    CGSize suggestedSize = CTFramesetterSuggestFrameSizeWithConstraints(framesetter, CFRangeMake(0, 0), NULL, CGSizeMake(inWidth, CGFLOAT_MAX), NULL);
    CFRelease(framesetter);
    return suggestedSize.height;
}

You'll have to convert your NSString to NSAttributedString. In-case of CATextLayer, you can use following CATextLayer subclass method:

- (NSAttributedString *)attributedString {

    // If string is an attributed string
    if ([self.string isKindOfClass:[NSAttributedString class]]) {
        return self.string;
    }

    // Collect required parameters, and construct an attributed string
    NSString *string = self.string;
    CGColorRef color = self.foregroundColor;
    CTFontRef theFont = self.font;
    CTTextAlignment alignment;

    if ([self.alignmentMode isEqualToString:kCAAlignmentLeft]) {
        alignment = kCTLeftTextAlignment;

    } else if ([self.alignmentMode isEqualToString:kCAAlignmentRight]) {
        alignment = kCTRightTextAlignment;

    } else if ([self.alignmentMode isEqualToString:kCAAlignmentCenter]) {
        alignment = kCTCenterTextAlignment;

    } else if ([self.alignmentMode isEqualToString:kCAAlignmentJustified]) {
        alignment = kCTJustifiedTextAlignment;

    } else if ([self.alignmentMode isEqualToString:kCAAlignmentNatural]) {
        alignment = kCTNaturalTextAlignment;
    }

    // Process the information to get an attributed string
    CFMutableAttributedStringRef attrString = CFAttributedStringCreateMutable(kCFAllocatorDefault, 0);

    if (string != nil)
        CFAttributedStringReplaceString (attrString, CFRangeMake(0, 0), (CFStringRef)string);

    CFAttributedStringSetAttribute(attrString, CFRangeMake(0, CFAttributedStringGetLength(attrString)), kCTForegroundColorAttributeName, color);
    CFAttributedStringSetAttribute(attrString, CFRangeMake(0, CFAttributedStringGetLength(attrString)), kCTFontAttributeName, theFont);

    CTParagraphStyleSetting settings[] = {kCTParagraphStyleSpecifierAlignment, sizeof(alignment), &alignment};
    CTParagraphStyleRef paragraphStyle = CTParagraphStyleCreate(settings, sizeof(settings) / sizeof(settings[0]));
    CFAttributedStringSetAttribute(attrString, CFRangeMake(0, CFAttributedStringGetLength(attrString)), kCTParagraphStyleAttributeName, paragraphStyle);    
    CFRelease(paragraphStyle);

    NSMutableAttributedString *ret = (NSMutableAttributedString *)attrString;

    return [ret autorelease];
}

HTH.

Answer 2

With LabelKit you don't need CATextLayer anymore. No more wrong line spacing and wider characters, all is drawn in the same way as UILabel does, while still animated.

Answer 3

I have a much easier solution, that may or may not work for you.

If you aren't doing anything special with the CATextLayer that you can't do a UILabel, instead make a CALayer and add the layer of the UILabel to the CALayer

UILabel*label = [[UILabel alloc]init];

//Do Stuff to label

CALayer *layer = [CALayer layer];

//Set Size/Position

[layer addSublayer:label.layer];

//Do more stuff to layer

Answer 4

This page gave me enough to create a simple centered horizontally CATextLayer : http://lists.apple.com/archives/quartz-dev/2008/Aug/msg00016.html

- (void)drawInContext:(CGContextRef)ctx {
  CGFloat height, fontSize;

  height = self.bounds.size.height;
  fontSize = self.fontSize;

  CGContextSaveGState(ctx);
  CGContextTranslateCTM(ctx, 0.0, (fontSize-height)/2.0 * -1.0);
  [super drawInContext:ctx];
  CGContextRestoreGState(ctx);
}