Get frame of word in a substring in a multiline label

Iulian Onofrei Published at Dev

Iulian Onofrei

I want to find the position and size of a word from a label's text that has 2 lines.

Let's assume that this is my label:

 ____________
|            |
|This is the |
|            |
|label       |
|____________|

and I want to find the frame of the word label, which would be something like {{0, 24}, {40, 24}} but by using

- (CGRect)getFrameOfString:(NSString *)substring fromString:(NSString *)string inLabel:(UILabel *)label {

    NSRange range = [string rangeOfString:substring];
    NSString *prefix = [string substringToIndex:range.location];
    NSStringDrawingContext *stringDrawingContext = [[NSStringDrawingContext alloc] init];

    stringDrawingContext.minimumScaleFactor = 0.5;

    CGRect prefixFrame = [prefix boundingRectWithSize:label.frame.size options:NSStringDrawingUsesLineFragmentOrigin attributes:[Util getAttributesforFont:label.font] context:stringDrawingContext];
    CGRect substringFrame = [substring boundingRectWithSize:label.frame.size options:NSStringDrawingUsesLineFragmentOrigin attributes:[Util getAttributesforFont:label.font] context:stringDrawingContext];

    prefixFrame = CGRectIntegral(prefixFrame);
    substringFrame = CGRectIntegral(substringFrame);

    return CGRectMake(prefixFrame.size.width, prefixFrame.origin.y, substringFrame.size.width, substringFrame.size.height);
}

I get {{100, 0}, {40, 24}} as if the word was positioned like:

 ____________
|            |
|This is the |label
|            |
|            |
|____________|

Iulian Onofrei

I solved it using this:

+ (CGRect)getFrameOfString:(NSString *)substring inLabel:(UILabel *)label {

    NSString *string = label.text;
    CGRect labelFrame = label.frame;

    NSRange substringRange = [string rangeOfString:substring];
    NSString *prefixString = [string substringToIndex:substringRange.location];

    NSStringDrawingContext *stringDrawingContext = [[NSStringDrawingContext alloc] init];

    stringDrawingContext.minimumScaleFactor = label.minimumScaleFactor;

    CGRect prefixFrame = [prefixString boundingRectWithSize:CGSizeMake(CGFLOAT_MAX, labelFrame.size.height) options:NSStringDrawingUsesLineFragmentOrigin attributes:[Util getAttributesforFont:label.font] context:stringDrawingContext];
    CGRect substringFrame = [substring boundingRectWithSize:labelFrame.size options:NSStringDrawingUsesLineFragmentOrigin attributes:[Util getAttributesforFont:label.font] context:stringDrawingContext];

    prefixFrame = CGRectIntegral(prefixFrame);
    substringFrame = CGRectIntegral(substringFrame);

    NSInteger labelWidth = labelFrame.size.width;

    BOOL isOnNextLine = prefixFrame.size.width >= labelWidth;

    CGFloat left = prefixFrame.size.width - (isOnNextLine ? labelWidth : 0); // the substrings on the other lines are offset by the label frame's width
    CGFloat top = isOnNextLine ? substringFrame.size.height : 0; // the substrings on the other lines have the top position equal to it's height
    CGFloat width = substringFrame.size.width;
    CGFloat height = substringFrame.size.height;

    return CGRectMake(left, top, width, height);
}

which I think it now only works for labels with two lines.

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