     }
     
     //MARK: collectionView delegate
+    
+    func scrollViewDidScroll(_ scrollView:UIScrollView)
+    {
+        let offsetY:CGFloat = scrollView.contentOffset.y
+        let usableOffset:CGFloat
+        
+        if offsetY < 0
+        {
+            usableOffset = 0
+        }
+        else
+        {
+            usableOffset = -offsetY
+        }
+        
+        layoutBarTop.constant = usableOffset
+    }
     
     func collectionView(_ collectionView:UICollectionView, layout collectionViewLayout:UICollectionViewLayout, sizeForItemAt indexPath:IndexPath) -> CGSize
     {

        addSubview(collectionView)
        addSubview(viewBar)
        
        NSLayoutConstraint.topToTop(
            view:viewBar,
            toView:self)
        NSLayoutConstraint.height(

class VCreate:View, UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout
{
    private(set) weak var collectionView:VCollection!
    private weak var layoutBarTop:NSLayoutConstraint!
    private let kBarHeight:CGFloat = 64
    private let kCollectionBottom:CGFloat = 40
    
