title: Actual difference between UIAccessibilityLayoutChangedNotification and UIAccessibilityScreenChangedNotification?
body: <p>I’m trying to ascertain what exactly happens differently when posting a <code>UIAccessibilityLayoutChangedNotification</code>, and a <code>UIAccessibilityScreenChangedNotification</code>. From what I can see, I can use them interchangeably everywhere and nothing different happens.</p>
  
  <p>The Apple documentation simply says to use <code>LayoutChanged</code> when (for example) an element has been hidden or shown, and to use <code>ScreenChanged</code> if the entire screen changes, but I’m interested in what THEY do when I provide this information, and what I should see differently when using one or the other.</p>
  
  <p>Can anyone give a clear explanation of implementation differences between the two?</p>