title: How can I invalidate flow layout with animation like in ios?
body: <p>I'm making an app in Xcode for Mojave OSX.</p>
  
  <p>I want to make a resize of a <code>collectionview</code> and items position of that.
  Currently I call to <code>invalidateLayout()</code> method, but it recalculate and set sizes and positions without animations.</p>
  
  <p><img src="https://i.stack.imgur.com/ZBtIz.gif" alt=""></p>
  
  <p>In the GIF you could see what is the current behavior, I need that the last item go to second <code>row</code>, in an animated way.</p>
  
  <p>For this i try to override this methods of <code>NSCollectionViewFlowLayout</code></p>
  
  <pre><code>  open override func prepare(forAnimatedBoundsChange oldBounds: NSRect){
  
  
      }
  
      open override func finalizeAnimatedBoundsChange() {
  
      }
  </code></pre>
  
  <p>But these never get called, and I don't know what code I need to animate this transition.</p>