I've created a custom NSCollectionView layout that is vertical in design and it supports dragging and dropping. However, the drawn drop indicator only is a vertical line in the middle of the inter gap or drop zones specified. Ideally, I'd like for this line to be horizontal, extending the width of the frame rather than the vertical and extending the height. Basically, I am trying to replicate the drop indicator that's used in NSTableView or NSOutlineView.
Is there any way to accomplish this?