The scroll direction of the layout.
- macOS 10.11+
The flow layout scrolls along one axis only, either horizontally or vertically. When the scroll direction is
NSCollection, the width of the content never exceeds the width of the collection view itself but the height grows as needed to accommodate the current items. When the scroll direction is
NSCollection, the height never exceeds the height of the collection view but the width grows as needed.
The default value of this property is