title: Layout and constraint based drawing iOS with and without autolayout
body: <p>Where can I find cleaner example and understanding of following methods.
  How they work, who call them and when ? and what is call stack.</p>
  
  <pre><code>func systemLayoutSizeFitting(_ targetSize: CGSize, withHorizontalFittingPriority horizontalFittingPriority: UILayoutPriority, verticalFittingPriority: UILayoutPriority) -&gt; CGSize
  
  func systemLayoutSizeFitting(_ targetSize: CGSize) -&gt; CGSize
  
  func setNeedsLayout()
  func layoutIfNeeded()
  func layoutSubviews()
  
  func setNeedsUpdateConstraints()
  func updateConstraintsIfNeeded()
  func updateConstraints()
  
  var intrinsicContentSize
  func invalidateIntrinsicContentSize()
  </code></pre>
  
  <p>I have tried to understand documentation on <a href="https://docs.apple.com" rel="nofollow noreferrer">https://developer.apple.com/documentation/</a>, but could not understand all cases. Can some one provide me example or well written documentation?</p>