CODEWITHSUNDEEP
macoscocoacore-textnstextviewnsattributedstring
stevel
stevel

Reputation: 1622

NSAttributedString highlight/background color shows between lines (ugly)

I'm trying to nicely display paragraphs of highlighted in a NSTextView. Right now, I'm doing this by creating a NSAttributedString with a background color. Here's some simplified code:

NSDictionary *attributes = @{NSBackgroundColorAttributeName:NSColor.greenColor};
NSAttributedString *attrString = [[NSAttributedString alloc] initWithString:@"Here is a single line of text with single spacing" attributes:attributes];

[textView.textStorage setAttributedString:attrString];

This approach basically works, in that it produces highlighted text.

Single line single spaced

Unfortunately, when multiple lines exist, the highlight covers the vertical space between the lines in addition to the lines themselves, resulting in ugliness.

Multi line double spaced text

Does anyone know of a way to do this kind of highlighting in Cocoa? The picture below is basically what I'm looking for (ignore the shadow on the white boxes):

whiteout text

I'd be willing to use CoreText, html, or whatever is necessary to make things look nicer.

Upvotes: 19

Views: 4660

Answers (3)

machoasif
machoasif

Reputation: 1

The paragraph needs to be highlighted when user taps on it. this is how I implemented it and don't confuse with the highlight color, it is a custom NSAttributedString key I created for this purpose.

extension NSAttributedString.Key {
    public static let highlightColor = NSAttributedString.Key.init("highlightColor")
}

class ReaderLayoutManager: NSLayoutManager {

    // MARK: - Draw Background
    override func drawBackground(forGlyphRange glyphsToShow: NSRange, at origin: CGPoint) {
        super.drawBackground(forGlyphRange: glyphsToShow, at: origin)
        self.enumerateLineFragments(forGlyphRange: glyphsToShow) { (_, usedRect, _, range, _) in
            guard let highlightColor = self.currentHighlightColor(range: range) else { return }
            guard let context = UIGraphicsGetCurrentContext() else { return }
            var lineRect = usedRect
            lineRect.origin.y += 10
            lineRect.size.height -= 2
            context.saveGState()
            let path = UIBezierPath(roundedRect: lineRect, cornerRadius: 2)
            highlightColor.setFill()
            path.fill()
            context.restoreGState()
        }
    }

    private func currentHighlightColor(range: NSRange) -> UIColor? {
        guard let textStorage = textStorage else { return nil }
        guard let highlightColor = textStorage.attributes(at: range.location, effectiveRange: nil)[.highlightColor] as? UIColor else { return nil }
        return highlightColor
    }
}

when user clicks on it, I set the highlight color for the range and reset the TextView.

attributedString.addAttributes([.highlightColor: theme.textUnderlineColor], range: range)

Upvotes: 0

nzeltzer
nzeltzer

Reputation: 521

You will need to subclass NSLayoutManager and override:

- (void)fillBackgroundRectArray:(const CGRect *)rectArray
                      count:(NSUInteger)rectCount
          forCharacterRange:(NSRange)charRange
                      color:(UIColor *)color;

This is the primitive method for drawing background color rectangles.

Upvotes: 3

Hussain Shabbir
Hussain Shabbir

Reputation: 15015

Try this:-

     -(IBAction)chooseOnlylines:(id)sender
{

 NSString *allTheText =[tv string];
    NSArray *lines = [allTheText componentsSeparatedByString:@"\n"];
    NSString *str=[[NSString alloc]init];
    NSMutableAttributedString *attr;
    BOOL isNext=YES;
    [tv setString:@""];
    for (str in lines)
    {
        attr=[[NSMutableAttributedString alloc]initWithString:str];
        if ([str length] > 0)
        {

        NSRange range=NSMakeRange(0, [str length]);
        [attr addAttribute:NSBackgroundColorAttributeName value:[NSColor greenColor] range:range];
        [tv .textStorage appendAttributedString:attr];
            isNext=YES;
        }
        else
        {
            NSString *str=@"\n";
            NSAttributedString *attr=[[NSAttributedString alloc]initWithString:str];
            [tv .textStorage appendAttributedString:attr];
            isNext=NO;
        }
        if (isNext==YES)
        {
            NSString *str=@"\n";
            NSAttributedString *attr=[[NSAttributedString alloc]initWithString:str];
            [tv .textStorage appendAttributedString:attr];

        }
     }
}

Upvotes: 0

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