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);
}