getTop method
Get the top position of the widget
Implementation
double getTop() {
final box = key!.currentContext!.findRenderObject() as RenderBox;
final boxOffset = box.localToGlobal(const Offset(0.0, 0.0));
if (boxOffset.dy.isNaN) return 0 - padding.top;
final topLeft = box.size.topLeft(boxOffset);
return topLeft.dy - padding.top;
}