where to catch the function about marker disappears or appears with dataEntrance

[zq190693370]

Hi~
Like the following two pictures:


if i scroll chart view , the marker view can be hided/appeared , but my cumtom marker view still appears on the both sides, i added a delegate 'delegate?.didDragMarker(xoffset: rect.origin.x + rect.size.width / 2)' in the BalloonMarker's 'draw' function, this funciton will be called only when the dataEntrance is in the chart view area... now i need to disppear/appear my own martker view with the dataEntrance, how should i do? thanks~~