initState method
Init state and trigger the hidden overlay to measure its size
Implementation
@override
void initState()
{
// set opener
opener = widget.model.openMethod ?? (System().mouse ? OpenMethods.hover : OpenMethods.longpress);
super.initState();
WidgetsBinding.instance.addPostFrameCallback((_) => _loadHiddenOverlay(context));
WidgetsBinding.instance.addObserver(this);
}