Event or signal to find out when a graph of widgets have finished layout

I am working on a full-screen app with a status area for notification bubbles.

If the user changes their desktop resolution, the status area moves to stay on screen, but the notification bubble (inherited from tooltip) is absolutely positioned so stays in the same place.

I have some code which runs after telling the app to layout to the new resolution, but the status area isn't ready by the time the code needs its new position for the bubble.

So assuming calls to setGeometry() or setMinimumSize() are asynchronous, how does the main execution know when everything has finished laying out?