NSLevelIndicatorCell is a subclass of
NSActionCell that provides several level indicator display styles including: capacity, ranking and relevancy. The capacity style provides both continuous and discrete modes.
Initializing NSLevelIndicatorCell Objects
Configuring the Range of Values
Managing Tick Marks
func tickMarkValue(at: Int)
Returns the receiver’s value represented by the tick mark at index (the minimum-value tick mark has an index of 0).
func rectOfTickMark(at: Int)
Returns the bounding rectangle of the tick mark identified by
index (the minimum-value tick mark is at index 0).
Setting the Level-Indicator Image