Qt6 compatibility

[macdew]

I'm trying the waiting spinner in my Qt6 project, and it looks like the "center on parent" isn't working when the widget is used in application modal mode:
auto waiting_spinner = new WaitingSpinnerWidget(Qt::ApplicationModal, this, true, true);

In this mode, I think the widget is being made a top-level window (presumably due to windows flags set at creation) and as a result, the calls to WaitingSpinnerWidget::updatePosition are in global screen coordinates, not relative to the parent widget, and thus the spinner appears outside of my application window!

I've fixed it for now by offsetting the coordinates using parentWidget()->mapToGlobal(), but this may be something to investigate?