 
     */
     func collectionViewPreviewControllerWillDismiss(_ controller: CollectionViewPreviewController)
+    
+    func collectionViewPreview(_ controller: CollectionViewPreviewController, didMoveToItemAt indexPath: IndexPath)
+}
+
+extension CollectionViewPreviewControllerDelegate {
+    func collectionViewPreview(_ controller: CollectionViewPreviewController, didMoveToItemAt indexPath: IndexPath) { }
 }
 
 class BackgroundView : NSView {

    // MARK: - Transitions
    /*-------------------------------------------------------------------------------*/
    
    /**
     The duration of present/dismiss transitions
     */

        
        controller.addChildViewController(self)
        controller.view.addSubview(self.view)
        if let config = self.layoutConstraintConfiguration {
            config(controller, self)
        }
        else {
            self.view.addConstraintsToMatchParent()
        }
        
        self.collectionView.reloadData()
        
