didFollowDragBack method
Implementation
@protected
void didFollowDragBack(Offset followed) {
if (_dragBackExtent.width == 0) {
return;
}
final value = 1 - followed.dx / _dragBackExtent.width;
final held = clampDouble(value, _dragEdge, 1 - _dragEdge);
dragBackController.value = held;
_dragBackOverdrag.value = math.max(0, value - held);
}