title: UIPopoverPresentationController on iPhone with iOS 10
body: <p>I'm trying to display a ViewController as a popover on an iPhone. I have already been through several answers on SO and the rest of the web but none have worked so far. I wrote a simple app to test this.</p>
  
  <p>ViewController.swift:</p>
  
  <pre><code>import UIKit
  
  class ViewController: UIViewController, UIPopoverPresentationControllerDelegate {
      override func viewDidLoad() {
          super.viewDidLoad()
          navigationItem.rightBarButtonItem = UIBarButtonItem(barButtonSystemItem: .done, target: self, action: #selector(clicked(_:)))
      }
  
      func clicked(_ sender: Any) {
          let vc = UIViewController()
          vc.view.backgroundColor = UIColor.blue
          vc.preferredContentSize = CGSize(width: 200, height: 200)
          vc.modalPresentationStyle = .popover
          present(vc, animated: true, completion: nil)
  
          let ppc = vc.popoverPresentationController
          ppc?.permittedArrowDirections = .any
          ppc?.delegate = self
          ppc?.barButtonItem = navigationItem.rightBarButtonItem
      }
  
      func adaptivePresentationStyle(for controller: UIPresentationController) -&gt; UIModalPresentationStyle {
          return .none
      }
  
      func adaptivePresentationStyle(for controller: UIPresentationController, traitCollection: UITraitCollection) -&gt; UIModalPresentationStyle {
          return .none
      }
  }
  </code></pre>
  
  <p>The storyboard has an empty ViewController embedded in a NavigationController. </p>
  
  <p>Running this, I expected a popover view controller to show under the "done" button. Instead, the blue view controller is presented full screen.</p>
  
  <p>Is there a way to change this behaviour?</p>