         
         switch( context.focusHeading ) {
         case UIFocusHeading.Left:
-            
             _preferredFocusedViewIndex = _preferredFocusedViewIndex - 1
+            self.setNeedsFocusUpdate()
+            //self.updateFocusIfNeeded()
             break
         case UIFocusHeading.Right:
             _preferredFocusedViewIndex = _preferredFocusedViewIndex + 1
+            self.setNeedsFocusUpdate()
+            //self.updateFocusIfNeeded()
             break
         default:
             break
         }
         
-        self.setNeedsFocusUpdate()
-        self.updateFocusIfNeeded()
        
         
     }

    
    override public func didUpdateFocusInContext(context: UIFocusUpdateContext, withAnimationCoordinator coordinator: UIFocusAnimationCoordinator) {
        super.didUpdateFocusInContext(context, withAnimationCoordinator: coordinator)
        
        print( "UIPDFCollectionViewController.didUpdateFocusInContext" )
    }
    

 
// MARK: <Focus Engine>
 
    public func collectionView(collectionView: UICollectionView, didUpdateFocusInContext context: UICollectionViewFocusUpdateContext, withAnimationCoordinator coordinator: UIFocusAnimationCoordinator) {
        
        if let i = context.nextFocusedIndexPath {
            self.showSlide(at: UInt(i.row))
            
        }
    }
    
    
    public func collectionView(collectionView: UICollectionView, canFocusItemAtIndexPath indexPath: NSIndexPath) -> Bool {
        print( "UIPDFCollectionViewController.canFocusItemAtIndexPath(\(indexPath.row))" )
        return true
    }
