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

        
        controller.addChildViewController(self)
        controller.view.addSubview(self.view)
        self.view.addConstraintsToMatchParent()
        
        self.collectionView.reloadData()
        

        return cell!
    }
    
    open func collectionView(_ collectionView: CollectionView, didSelectItemsAt indexPaths: Set<IndexPath>) {
        if let ip = indexPaths.first {
            self.delegate?.collectionViewPreview(self, didMoveToItemAt: ip)
        }
    }
    
    // MARK: - Interactive Gesture
    /*-------------------------------------------------------------------------------*/
    
