finding location of specific characters in UILabel on iPhone - iphone

Question

I have a UILabel with some text, say "Hello World abcdefg" The label can have multiple lines, different font sizes etc.
Question: How do I find the coordinates of all letters "d" in this UILabel.
Logical first step is find the position of those characters in the string (UILabel.text), but then how do I translate that into coordinates when it's actually drawn on screen
The idea is to find those coordinates and draw something custom on top of that character (basically to cover it with a custom image)

Answer 1

The basic tools for measuring text on iPhone are in UIStringDrawing.h but none of them do what you need. You will basically have to iterate through substrings one character at a time measuring each. When a line wraps (the result is taller), split after the last character that did not wrap and add the line height to your y coordinate.
- (CGSize)sizeWithFont:(UIFont *)font forWidth:(CGFloat)width lineBreakMode:(UILineBreakMode)lineBreakMode;

Answer 2

Methods have changed since iOS 7.0 came out. Try this
- (CGFloat)charactersOffsetBeforeDayPartOfLabel {
NSRange range = [[self stringFromDate:self.currentDate] rangeOfString:[NSString stringWithFormat:#"%i",[self dayFromDate:self.currentDate]]];
NSString *chars = [[self stringFromDate:self.currentDate] substringToIndex:range.location];
NSMutableArray *arrayOfChars = [[NSMutableArray alloc]init];
[chars enumerateSubstringsInRange:NSMakeRange(0, [chars length]) options:(NSStringEnumerationByComposedCharacterSequences) usingBlock:^(NSString *substring, NSRange substringRange, NSRange enclosingRange, BOOL *stop) {
[arrayOfChars addObject:substring];
}];
CGFloat charsOffsetTotal = 0;
for (NSString *i in arrayOfChars){
NSDictionary *attributes = #{NSFontAttributeName: [UIFont fontWithName:#"Helvetica Neue" size:16.0f]};
charsOffsetTotal += [i sizeWithAttributes:attributes].width;
}
return charsOffsetTotal;
}

Answer 3

Here ya go:
fileprivate let selfSizing = UILabel()
class DualColorLabel: UILabel
{
var filled: UIColor?
var unfilled: UIColor?
var origin: String?
var widths: [CGFloat] = []
var fuckupLockup = false
override var text: String? {
didSet {
if fuckupLockup {
print ("SDBOFLAG-13822 wtf?")
}
}
}
func setupColorsAndText(filled: UIColor,
unfilled: UIColor)
{
self.filled = filled
self.unfilled = unfilled
guard let text = origin, text.count > 0 else {
assertionFailure("usage error")
return
}
guard font != nil else {
usageError()
return
}
for index in 1...text.count {
let s = String.Index(utf16Offset: 0, in: text)
let e = String.Index(utf16Offset: index, in: text)
let beginning = text[s..<e]
let p = String(beginning)
selfSizing.font = font
selfSizing.text = p
let size = selfSizing.sizeThatFits(CGSize(width: CGFloat.greatestFiniteMagnitude, height: CGFloat.greatestFiniteMagnitude))
let width = size.width
widths.append(width)
}
}
func setupfill(adjusted: CGRect)
{
assert(adjusted.origin.x <= 0, "fixed this code for fill in the middle: currently supported only fill at start")
let endOffset = adjusted.width + adjusted.origin.x
guard let font = self.font else {
usageError()
return
}
guard let origin = origin, let filled = filled,
let unfilled = unfilled else {
usageError()
return
}
var idx = String.Index(utf16Offset: origin.count, in: origin)
for (index, width) in widths.enumerated() {
if endOffset < width {
idx = String.Index(utf16Offset: index, in: origin)
print ("SDBOFLAG-13822 index \(index) for text \(origin)")
break
}
}
let total = NSMutableAttributedString()
do {
let s = String.Index(utf16Offset: 0, in: origin)
let beginning = origin[s..<idx]
let p = String(beginning)
print("SDBOFLAG-13822 filled text \(p)")
let filledAttributes:
[NSAttributedString.Key : Any] = [NSAttributedString.Key.foregroundColor:
// UIColor.yellow,
filled,
NSAttributedString.Key.font:
font
]
let filledPortion = NSAttributedString(string: p, attributes: filledAttributes)
total.append(filledPortion)
}
let unfilledAttributes:
[NSAttributedString.Key : Any] = [NSAttributedString.Key.foregroundColor:
// UIColor.blue,
unfilled,
NSAttributedString.Key.font: font]
let e = String.Index(utf16Offset: origin.count, in: origin)
let ending = origin[idx..<e]
let str = String(ending)
print("SDBOFLAG-13822 unfilled text \(str)")
let unfilledPortion = NSAttributedString(string: str, attributes: unfilledAttributes)
total.append(unfilledPortion)
self.attributedText = total
fuckupLockup = true
}
/*
// Only override draw() if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
override func draw(_ rect: CGRect) {
// Drawing code
}
*/
}
func usageError()
{
assertionFailure("usage error")
}
The width calculation for fragments goes into widths array per suggestions provided.