NSString boundingRectWithSize slightly underestimating the correct height - why?

Question

I\'m attempting to resize a text field / view automatically depending on its current width. In other words I want the width to stay constant but resize the height according

Answer 1

I found that NSString#boundingRectWithSize is never exactly correct, the only thing that seems to work well is the one described here: https://developer.apple.com/library/content/documentation/Cocoa/Conceptual/TextLayout/Tasks/StringHeight.html

class func sizeForString(_ text : String, withFont font: NSFont, inWidth maxWidth: CGFloat) -> NSSize {
    let textStorage = NSTextStorage(string: text)
    let textContainer = NSTextContainer(containerSize: NSSize(width: maxWidth, height: CGFloat.greatestFiniteMagnitude))
    let layoutManager = NSLayoutManager()
    layoutManager.addTextContainer(textContainer)
    textStorage.addLayoutManager(layoutManager)
    textStorage.addAttribute(NSFontAttributeName, value: font, range: NSMakeRange(0, textStorage.length))
textContainer.lineFragmentPadding = 0
    layoutManager.glyphRange(for: textContainer)
    return layoutManager.usedRect(for: textContainer).size
 }