title: Find frame in window of collection view cell
body: <p>I'm getting all the visible cells in a <code>UICollectionViewController</code> like this.</p>
  
  <pre><code>NSArray&lt;__kindof UICollectionViewCell *&gt; *cells = [self.collectionView.visibleCells visibleCells];
  </code></pre>
  
  <p>How do I find the frame for the cell in the window?</p>