registerHitZones method
Implementation
@override
void registerHitZones(Rect area, HitZoneSink sink) {
sink.add(area, id);
for (var i = 0; i < options.length && i < area.height; i++) {
sink.add(
Rect(area.x, area.y + i, area.width, 1),
Key.composite([id, 'opt', i]),
);
}
}