Resizing a UILabel to accommodate insets

Here's a label class that calculates sizes correctly. The posted code is in Swift 3, but you can also download Swift 2 or Objective-C versions.

How does it work?

By calculating the proper textRect all of the sizeToFit and auto layout stuff works as expected. The trick is to first subtract the insets, then calculate the original label bounds, and finally to add the insets again.

Code (Swift 5)

class NRLabel: UILabel {
    var textInsets = UIEdgeInsets.zero {
        didSet { invalidateIntrinsicContentSize() }
    }
    
    override func textRect(forBounds bounds: CGRect, limitedToNumberOfLines numberOfLines: Int) -> CGRect {
        let insetRect = bounds.inset(by: textInsets)
        let textRect = super.textRect(forBounds: insetRect, limitedToNumberOfLines: numberOfLines)
        let invertedInsets = UIEdgeInsets(
            top: -textInsets.top,
            left: -textInsets.left,
            bottom: -textInsets.bottom,
            right: -textInsets.right
        )
        return textRect.inset(by: invertedInsets)
    }
    
    override func drawText(in rect: CGRect) {
        super.drawText(in: rect.inset(by: textInsets))
    }
}

Optional: Interface Builder support

If you want to setup text insets in storyboards you can use the following extension to enable Interface Builder support:

@IBDesignable
extension NRLabel {

    // currently UIEdgeInsets is no supported IBDesignable type,
    // so we have to fan it out here:
    @IBInspectable
    var leftTextInset: CGFloat {
        set { textInsets.left = newValue }
        get { return textInsets.left }
    }

    // Same for the right, top and bottom edges.
}

Now you can conveniently setup your insets in IB and then just press ⌘= to adjust the label's size to fit.

Disclaimer:

All code is in the public domain. Do as you please.

Here is a Swift version of a UILabel subclass (same as @Nikolai's answer) that creates an additional padding around the text of a UILabel:

class EdgeInsetLabel : UILabel {
    var edgeInsets:UIEdgeInsets = UIEdgeInsetsZero

    override func textRectForBounds(bounds: CGRect, limitedToNumberOfLines numberOfLines: Int) -> CGRect {
        var rect = super.textRectForBounds(UIEdgeInsetsInsetRect(bounds, edgeInsets), limitedToNumberOfLines: numberOfLines)

        rect.origin.x -= edgeInsets.left
        rect.origin.y -= edgeInsets.top
        rect.size.width  += (edgeInsets.left + edgeInsets.right);
        rect.size.height += (edgeInsets.top + edgeInsets.bottom);

        return rect
    }

    override func drawTextInRect(rect: CGRect) {
        super.drawTextInRect(UIEdgeInsetsInsetRect(rect, edgeInsets))
    }
}

Here is the C# version (usefull for Xamarin) based on Nikolai's code :

public class UIEdgeableLabel : UILabel
{
    public UIEdgeableLabel() : base() { }
    public UIEdgeableLabel(NSCoder coder) : base(coder) { }
    public UIEdgeableLabel(CGRect frame) : base(frame) { }
    protected UIEdgeableLabel(NSObjectFlag t) : base(t) { }

    private UIEdgeInsets _edgeInset = UIEdgeInsets.Zero;
    public UIEdgeInsets EdgeInsets
    {
        get { return _edgeInset; }
        set
        {
            _edgeInset = value;
            this.InvalidateIntrinsicContentSize();
        }
    }

    public override CGRect TextRectForBounds(CGRect bounds, nint numberOfLines)
    {
        var rect = base.TextRectForBounds(EdgeInsets.InsetRect(bounds), numberOfLines);
        return new CGRect(x: rect.X - EdgeInsets.Left,
                          y: rect.Y - EdgeInsets.Top,
                          width: rect.Width + EdgeInsets.Left + EdgeInsets.Right,
                          height: rect.Height + EdgeInsets.Top + EdgeInsets.Bottom);
    }

    public override void DrawText(CGRect rect)
    {
        base.DrawText(this.EdgeInsets.InsetRect(rect));
    }
}

Swift 5 version of Nikolai Ruhe answer:

extension UIEdgeInsets {
   func apply(_ rect: CGRect) -> CGRect {
      return rect.inset(by: self)
   }
}

class EdgeInsetLabel: UILabel {
  var textInsets = UIEdgeInsets.zero {
      didSet { invalidateIntrinsicContentSize() }
  }

  override func textRect(forBounds bounds: CGRect, limitedToNumberOfLines numberOfLines: Int) -> CGRect {
    let insetRect = bounds.inset(by: textInsets)
    let textRect = super.textRect(forBounds: insetRect, limitedToNumberOfLines: numberOfLines)
    let invertedInsets = UIEdgeInsets(top: -textInsets.top,
                                      left: -textInsets.left,
                                      bottom: -textInsets.bottom,
                                      right: -textInsets.right)
    return textRect.inset(by: invertedInsets)
  }

  override func drawText(in rect: CGRect) {
      super.drawText(in: rect.inset(by: textInsets))
  }}