hitTestBehavior property
How to behave during hit testing.
This defaults to HitTestBehavior.opaque if null.
Implementation
HitTestBehavior? get hitTestBehavior => behavior;Implementation
set hitTestBehavior(HitTestBehavior? value) {
  final HitTestBehavior newValue = value ?? HitTestBehavior.opaque;
  if (behavior != newValue) {
    behavior = newValue;
    // Trigger [MouseTracker]'s device update to recalculate mouse states.
    markNeedsPaint();
  }
}