drawArrow(_:highlight:)
Draws the scroll button indicated by arrow, which is either NSScrollerIncrementArrow (the down or right scroll button) or NSScrollerDecrementArrow (up or left).
Declaration
func drawArrow(_ whichArrow: NSScroller.Arrow, highlight flag: Bool)Discussion
If flag is true, the button is drawn highlighted; otherwise it’s drawn normally. You should never need to invoke this method directly, but may wish to override it to customize the appearance of scroll buttons.