  
  If the view uses auto layout to define its height, call
  `setup(with:heightConstraint:)` once all required views
- are available. If it does not use auto layout, call the
- `setup(with:)` function instead.
+ are available. If not, call `setup(with:)` instead.
  
  Once everything is setup, simply call `handleScroll(in:)`
  in the `scrollViewDidScroll(:)` delegate function. This

        return displayHeight / baseHeight
    }
    
    public var isStretching: Bool {
        guard let view = scrollView else { return false }
        return view.contentOffset.y < -baseHeight

    
    open func handleScroll(in scrollView: UIScrollView) {
        setup(with: scrollView)
        guard isSetup else { return }
        updateHeight(for: scrollView)
        updateOffset(for: scrollView)
    }
