Underline text - line thickness in crossing ranges with different font sizes

Question

I am working with the attributes of textStorage of `UITextView`. I have the string and an array of the objects of my class `TextFormattingElement`. An instance of this class consists of `NSRange` (on which this element has to be applied in text) and some formatting parameters: ``` @interface TextFormattingElement : NSObject @property (nonatomic) NSRange range; @property (nonatomic, strong) NSString *fontName; //e.g. @"TimesNewRomanPSMT" @property (nonatomic) int fontSize; @property (nonatomic, strong) UIColor *fontColor; @property (nonatomic) BOOL isBold; @property (nonatomic) BOOL isItalic; @property (nonatomic) BOOL isUnderlined; @property (nonatomic) BOOL isStriked; @end ``` Now i loop through this array and successively apply this elements to the textStorage of textView. I use this method: ``` -(void)setFontWithName:(NSString*)name AndSize:(float)fontSize AndTextColor:(UIColor*)textColor AndIsBold:(BOOL)isBold AndIsItalic:(BOOL)isItalic AndIsUnderlined:(BOOL)isUnderLined andIsStri…

Accepted Answer

On iOS 7 you can do what you want with a subclass of `NSLayoutManager` that override `-drawUnderlineForGlyphRange:underlineType:baselineOffset:lineFragmentRect:lineFragmentGlyphRange:containerOrigin:` A little sample that create text system objects, and draw the wanted underline.

```
@implementation ViewController
- (void)viewDidLoad
{
    [super viewDidLoad];

// setup text handling with our subclass of NSLayoutManager
    NSTextStorage *textStorage = [[NSTextStorage alloc] initWithString:@"Alice was beginning to get very tired of sitting by her sister on the bank, and of having nothing to do;"];

MyLayoutManager *textLayout = [[MyLayoutManager alloc] init];

[textStorage addLayoutManager:textLayout];

NSTextContainer *textContainer = [[NSTextContainer alloc] initWithSize:self.view.bounds.size];

[textLayout addTextContainer:textContainer];
    UITextView *textView = [[UITextView alloc] initWithFrame:CGRectMake(0,20,self.view.bounds.size.width,self.view.bounds.size.height-20)
                                               textContainer:textContainer];
    [self.view addSubview:textView];

// setup test attributes
    UIFont *font = [UIFont fontWithName:@"TimesNewRomanPSMT" size:15];

NSMutableDictionary *attributesToSetDict = [NSMutableDictionary dictionary];

[attributesToSetDict setObject:font forKey:NSFontAttributeName];
    [attributesToSetDict setObject:[UIColor blueColor] forKey:NSForegroundColorAttributeName];
    [attributesToSetDict setObject:@1 forKey:NSUnderlineStyleAttributeName];

[textView.textStorage setAttributes:attributesToSetDict range:NSMakeRange(9, 28)];

UIFontDescriptor *fontDescriptor = [font fontDescriptor];
    attributesToSetDict = [NSMutableDictionary dictionary];
    [attributesToSetDict setObject:[UIFont fontWithDescriptor:fontDescriptor size:25] forKey:NSFontAttributeName];
    [attributesToSetDict setObject:[UIColor redColor] forKey:NSForegroundColorAttributeName];
    [attributesToSetDict setObject:@1 forKey:NSUnderlineStyleAttributeName];

[textView.textStorage setAttributes:attributesToSetDict range:NSMakeRange(26, 7)];
}
@end

@implementation MyLayoutManager
- (void)drawUnderlineForGlyphRange:(NSRange)glyphRange underlineType:(NSUnderlineStyle)underlineVal baselineOffset:(CGFloat)baselineOffset lineFragmentRect:(CGRect)lineRect lineFragmentGlyphRange:(NSRange)lineGlyphRange containerOrigin:(CGPoint)containerOrigin
{
    /* For the sample we consider that underlineVal is equals to NSUnderlineStyleSingle */

/*
     * We need to create a CTFontRef as UIFont doesn't provided 'Underline Position' and 'Underline Thickness'
     */

// get current UIFont for the glyphRange
    NSRange characterRange = [self characterRangeForGlyphRange:glyphRange actualGlyphRange:NULL];
    UIFont *font = [[self.textStorage attributesAtIndex:characterRange.location effectiveRange:NULL] objectForKey:NSFontAttributeName];

CTFontRef ctfont = CTFontCreateWithName((CFStringRef)[font fontName], [font pointSize], NULL);

CGPoint startLocation = [self locationForGlyphAtIndex:glyphRange.location];
    CGPoint endLocation = [self locationForGlyphAtIndex:NSMaxRange(glyphRange)];

CGContextRef ctx = UIGraphicsGetCurrentContext();

// -underlineGlyphRange:underlineType:lineFragmentRect:lineFragmentGlyphRange:containerOrigin: already set color and line width
    // for the current context

// reset line width with current font underline thickness
    CGContextSetLineWidth(ctx, CTFontGetUnderlineThickness(ctfont));

CGContextMoveToPoint(ctx, startLocation.x + containerOrigin.x, startLocation.y + containerOrigin.y - CTFontGetUnderlinePosition(ctfont));
    CGContextAddLineToPoint(ctx, endLocation.x + containerOrigin.x, endLocation.y + containerOrigin.y - CTFontGetUnderlinePosition(ctfont));

CGContextStrokePath(ctx);

CFRelease(ctfont);
}
```

Underline text - line thickness in crossing ranges with different font sizes

Solution

Problem