Unwanted Vertical Padding from iOS 6 on CATextLayer

Question

Background: I started my project in iOS 5 and built out a beautiful button with layer. I added a textLayer onto the button and center it using the following cod

Answer 1

Wile I am waiting for an ultimate solution, I studied about RTLabel and TTTAttributedLabel, and made a simple class to draw text on a CALayer as Steve suggested. Hope it helps, and please don't hesitant to point out any mistake I have made.

CustomTextLayer.h

#import 

@interface CustomTextLayer : CALayer {
    NSString                        *_text;
    UIColor                         *_textColor;

    NSString                        *_font;
    float                           _fontSize;

    UIColor                         *_strokeColor;
    float                           _strokeWidth;

    CTTextAlignment                 _textAlignment;
    int                             _lineBreakMode;

    float                           _suggestHeight;
}

-(float) suggestedHeightForWidth:(float) width;

@property (nonatomic, retain) NSString *text;
@property (nonatomic, retain) UIColor *textColor;

@property (nonatomic, retain) NSString *font;
@property (nonatomic, assign) float fontSize;

@property (nonatomic, retain) UIColor *strokeColor;
@property (nonatomic, assign) float strokeWidth;

@property (nonatomic, assign) CTTextAlignment textAlignment;

@end

CustomTextLayer.m

#import 
#import "CustomTextLayer.h"

@implementation CustomTextLayer

@synthesize text = _text, textColor = _textColor;
@synthesize font = _font, fontSize = _fontSize;
@synthesize strokeColor = _strokeColor, strokeWidth = _strokeWidth;
@synthesize textAlignment = _textAlignment;

-(id) init {
    if (self = [super init]) {
        _text = @"";
        _textColor = [UIColor blackColor];

        _font = @"Helvetica";
        _fontSize = 12;

        _strokeColor = [UIColor whiteColor];
        _strokeWidth = 0.0;

        _textAlignment = kCTLeftTextAlignment;
        _lineBreakMode = kCTLineBreakByWordWrapping;

    }
    return self;
}

-(void) dealloc {
    [_text release];
    [_textColor release];

    [_font release];

    [_strokeColor release];

    [super dealloc];
}

-(void) setText:(NSString *)text {
    [_text release];
    _text = [text retain];
    [self setNeedsDisplay];
}

-(void) setTextColor:(UIColor *)textColor {
    [_textColor release];
    _textColor = [textColor retain];
    [self setNeedsDisplay];
}

-(void) setFont:(NSString *)font {
    [_font release];
    _font = [font retain];
    [self setNeedsDisplay];
}

-(void) setFontSize:(float)fontSize {
    _fontSize = fontSize;
    [self setNeedsDisplay];
}

-(void) setStrokeColor:(UIColor *)strokeColor {
    [_strokeColor release];
    _strokeColor = strokeColor;
    [self setNeedsDisplay];
}

-(void) setStrokeWidth:(float)strokeWidth {
    _strokeWidth = 0 ? (strokeWidth < 0) : (-1 * strokeWidth);
    [self setNeedsDisplay];
}

-(void) setTextAlignment:(CTTextAlignment)textAlignment {
    _textAlignment = textAlignment;
    [self setNeedsDisplay];
}

-(void) setFrame:(CGRect)frame {
    [super setFrame: frame];
    [self setNeedsDisplay];
}

-(float) suggestedHeightForWidth:(float) width {

    CTFontRef fontRef = CTFontCreateWithName((CFStringRef)_font, _fontSize, NULL);

    CTParagraphStyleSetting paragraphStyles[2] = {
        {.spec = kCTParagraphStyleSpecifierLineBreakMode, .valueSize = sizeof(CTLineBreakMode), .value = (const void *) &_lineBreakMode},
        {.spec = kCTParagraphStyleSpecifierAlignment, .valueSize = sizeof(CTTextAlignment), .value = (const void *) &_textAlignment}
    };
    CTParagraphStyleRef paragraphStyle = CTParagraphStyleCreate(paragraphStyles, 2);

    NSDictionary *attrDict = [[NSDictionary alloc] initWithObjectsAndKeys:(id)fontRef, (NSString *)kCTFontAttributeName, (id)_textColor.CGColor, (NSString *)(kCTForegroundColorAttributeName), (id)_strokeColor.CGColor, (NSString *)(kCTStrokeColorAttributeName), (id)[NSNumber numberWithFloat: _strokeWidth], (NSString *)(kCTStrokeWidthAttributeName), (id)paragraphStyle, (NSString *)(kCTParagraphStyleAttributeName), nil];

    CFRelease(fontRef);
    CFRelease(paragraphStyle);

    NSAttributedString *attrStr = [[NSAttributedString alloc] initWithString:_text attributes: attrDict];

    // Determine suggested frame height
    CFRange textRange = CFRangeMake(0, [attrStr length]);
    CGSize constraint = CGSizeMake(width, 9999);

    CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString((CFAttributedStringRef)attrStr);
    CGSize textSize = CTFramesetterSuggestFrameSizeWithConstraints(framesetter, textRange, NULL, constraint, NULL);
    textSize = CGSizeMake(ceilf(textSize.width), ceilf(textSize.height));

    [attrDict release];
    [attrStr release];

    return textSize.height;
}

-(void) renderText:(CGContextRef)ctx {
    CGContextSetTextMatrix(ctx, CGAffineTransformIdentity);
    CGContextTranslateCTM(ctx, 0, self.bounds.size.height);
    CGContextScaleCTM(ctx, 1.0, -1.0);

    CTFontRef fontRef = CTFontCreateWithName((CFStringRef)_font, _fontSize, NULL);

    CTParagraphStyleSetting paragraphStyles[2] = {
        {.spec = kCTParagraphStyleSpecifierLineBreakMode, .valueSize = sizeof(CTLineBreakMode), .value = (const void *) &_lineBreakMode},
        {.spec = kCTParagraphStyleSpecifierAlignment, .valueSize = sizeof(CTTextAlignment), .value = (const void *) &_textAlignment}
    };
    CTParagraphStyleRef paragraphStyle = CTParagraphStyleCreate(paragraphStyles, 2);

    NSDictionary *attrDict = [[NSDictionary alloc] initWithObjectsAndKeys:(id)fontRef, (NSString *)kCTFontAttributeName, (id)_textColor.CGColor, (NSString *)(kCTForegroundColorAttributeName), (id)_strokeColor.CGColor, (NSString *)(kCTStrokeColorAttributeName), (id)[NSNumber numberWithFloat: _strokeWidth], (NSString *)(kCTStrokeWidthAttributeName), (id)paragraphStyle, (NSString *)(kCTParagraphStyleAttributeName), nil];

    CFRelease(fontRef);
    CFRelease(paragraphStyle);

    NSAttributedString *attrStr = [[NSAttributedString alloc] initWithString:_text attributes: attrDict];

    CGMutablePathRef path = CGPathCreateMutable();
    CGPathAddRect(path, NULL, self.bounds);
    CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString((CFAttributedStringRef)attrStr);

    CFRange textRange = CFRangeMake(0, [attrStr length]);
    CTFrameRef frame = CTFramesetterCreateFrame(framesetter, textRange, path, NULL);
    CFArrayRef lines = CTFrameGetLines(frame);
    NSInteger numberOfLines = CFArrayGetCount(lines);
    CGPoint lineOrigins[numberOfLines];
    CTFrameGetLineOrigins(frame, CFRangeMake(0, numberOfLines), lineOrigins);

    for (CFIndex lineIndex = 0; lineIndex < numberOfLines; lineIndex++) {
        CGPoint lineOrigin = lineOrigins[lineIndex];
        CGContextSetTextPosition(ctx, lineOrigin.x,  lineOrigin.y);
        CTLineRef line = CFArrayGetValueAtIndex(lines, lineIndex);

        if (lineIndex == numberOfLines - 1) {
            CFRange lastLineRange = CTLineGetStringRange(line);

            if (!(lastLineRange.length == 0 && lastLineRange.location == 0) && lastLineRange.location + lastLineRange.length < textRange.location + textRange.length) {
                NSUInteger truncationAttributePosition = lastLineRange.location;
                CTLineTruncationType truncationType;
                if (numberOfLines != 1) {
                    truncationType = kCTLineTruncationEnd;
                    truncationAttributePosition += (lastLineRange.length - 1);
                }

                NSAttributedString *tokenString = [[NSAttributedString alloc] initWithString:@"\u2026" attributes:attrDict];
                CTLineRef truncationToken = CTLineCreateWithAttributedString((CFAttributedStringRef)tokenString);

                NSMutableAttributedString *truncationString = [[attrStr attributedSubstringFromRange: NSMakeRange(lastLineRange.location, lastLineRange.length)] mutableCopy];
                if (lastLineRange.length > 0) {
                    unichar lastCharacter = [[truncationString string] characterAtIndex: lastLineRange.length - 1];
                    if ([[NSCharacterSet newlineCharacterSet] characterIsMember:lastCharacter]) {
                        [truncationString deleteCharactersInRange:NSMakeRange(lastLineRange.length - 1, 1)];
                    }
                }
                [truncationString appendAttributedString: tokenString];
                CTLineRef truncationLine = CTLineCreateWithAttributedString((CFAttributedStringRef) truncationString);

                CTLineRef truncatedLine = CTLineCreateTruncatedLine(truncationLine, self.bounds.size.width, truncationType, truncationToken);
                if (!truncatedLine) {
                    // If the line is not as wide as the truncationToken, truncatedLine is NULL
                    truncatedLine = CFRetain(truncationToken);
                }

                CTLineDraw(truncatedLine, ctx);

                CFRelease(truncatedLine);
                CFRelease(truncationLine);
                CFRelease(truncationToken);
            } else {
                CTLineDraw(line, ctx);
            }
        } else {
            CTLineDraw(line, ctx);
        }
    }

    [attrStr release];
    [attrDict release];

    CFRelease(path);
    CFRelease(frame);
    CFRelease(framesetter);

}

-(void) drawInContext:(CGContextRef)ctx {
    [super drawInContext: ctx];
    [self renderText: ctx];
}

@end