@Override
		public void focusLost(FocusEvent e) {
			Component opp = e.getOppositeComponent();
			if (attachees.contains(opp)) {
				focus = (JTextField) opp;
			}
			else if (opp == list) {
				// Do nothing
			}
			else {
				setCompletionListVisible(false);
				focus = null;
			}
		}
A listener to handle all the callbacks
Ghidra/Framework/Docking/src/main/java/docking/widgets/autocomplete/TextFieldAutocompleter.java