tickMarkShape property Null safety
The shape that will be used to draw the Slider's tick marks.
The SliderTickMarkShape.getPreferredSize is used to help determine the location of each tick mark on the track. The slider's minimum size will be at least this big.
The default value is RoundSliderTickMarkShape.
- RoundRangeSliderTickMarkShape, which is the default tick mark shape for the range slider.
final SliderTickMarkShape? tickMarkShape;