Question

I have one string as instance var and I want to draw it in two different fonts in parts.
to be specific it reads : xyz(abc) .

ie: I want to draw ‘xyz()’ part with normal font and ‘abc‘ in italics.

This string is a property and the view is generic . Only in a specific case It should display string like this.

I tried NSAttributedString and its Mutable version but it seems its not fully supported on iOS.

Couldn’t get the Keys for attributes, How should I go about this ?

Is there anywayto use NSAttributedString here ?

Answer 1

I would subclass UIView to draw using core text and pass it a customized NSAttributed string,

Off the top of my head something like this:

CustomLabel.h
#import <CoreText/CoreText.h>

@interface CustomLabel : UIView
@property NSAttributedString *attributedText;
@end

CustomLabel.m

@interface SMAttributedTextView ()
{
    @protected
    CTFramesetterRef _framesetter;
}

@implementation SMAttributedTextView

@synthesize attributedString = _attributedString;
    //need dealloc even with ARC method to release framesetter if it still exists
- (void)dealloc{
    if (_framesetter) CFRelease(_framesetter);
}

- (void)setAttributedString:(NSAttributedString *)aString
{
    _attributedString = aString;
    [self setNeedsDisplay];//force redraw
}

- (void)drawRect:(CGRect)rect
{
    CGContextRef context = UIGraphicsGetCurrentContext();

    //Context Drawing Setup
    CGContextSetTextMatrix(context, CGAffineTransformIdentity);
    CGContextTranslateCTM(context, 0, self.frame.size.height);
    CGContextScaleCTM(context, 1.0, -1.0);
    CGContextSetShouldSubpixelPositionFonts(context, YES);
    CGContextSetShouldSubpixelQuantizeFonts(context, YES);
    CGContextSetShouldAntialias(context, YES);

    CGMutablePathRef path = CGPathCreateMutable();
    CGPathAddRect(path, NULL, rect);

    CTFramesetterRef framesetter = [self framesetter];
    CTFrameRef frame = CTFramesetterCreateFrame(framesetter, CFRangeMake(0, [_attributedText length]), path, NULL);
    CTFrameDraw(frame, context);
    CFRelease(frame);
    CFRelease(path);

    UIGraphicsPushContext(context);
}

@end

so outside of this you would call the setter for the attribtued string and it should redraw.
you would also apply custom traits to ranges of the NSAttributd string BEFORE you send it to the view. You could use regexp or just general string searching to find it.

i.e

NSMutableAttributedString *aString = [[NSMutableAttributedString alloc] initWithString:@"xyz(abc)"];
NSRange rangeOfABC = NSMakeRange(4,3);
//make style dictionary **see core text docs - I can't remeber off the top of my head sorry
[aString addAttributes:newAttrs range:rangeOfABC];

[customlabel setAttributedString:aString];

code wise it might be slightly different – am on my non-work machine sorry so can’t validate it 100%,

also from memory this is how you can apply an italic trait to the current font of the attributed string

NSString *targetString = @"xyc(abc)";
NSMutableAttributedString *attString = [[NSMutableAttributedString alloc] initWithString:targetString];
NSRange entireRange = NSMakeRange(0, (targetString.length -1));
NSDictionary *attDict = [attString attributesAtIndex:entireRange.location effectiveRange:&entireRange];
CTFontRef curFontRef = (__bridge CTFontRef)[attDict objectForKey:@"NSFont"];
CTFontSymbolicTraits traits = CTFontGetSymbolicTraits(curFontRef);
BOOL isItalic = ((traits & kCTFontItalicTrait) == kCTFontItalicTrait);

NSMutableDictionary *newAttrs = [NSMutableDictionary dictionary];
CTFontRef italicRef = CTFontCreateCopyWithSymbolicTraits(curFontRef,
                                                         CTFontGetSize(curFontRef),
                                                         NULL,
                                                         kCTFontItalicTrait,
                                                         kCTFontItalicTrait);

if (italicRef)
{
    newAttrs = [NSDictionary dictionaryWithObjectsAndKeys:(__bridge id)italicRef, kCTFontAttributeName,nil];
    [attString addAttributes:newAttrs range:NSMakeRange(4,3)];//or whatever range you want
    CFRelease(italicRef);
}

Hope it helps.