@Override
		public void componentResized( ComponentEvent e ) {
			if( e.getSource() == popupWindow )
				updateDropShadowWindowBounds();
		}
Fixes popup background flashing effect when using dark theme on light platform theme,
where the light popup background is shown for a fraction of a second before
the dark popup content is shown.
This is fixed by setting popup background to content background.
<p>
Defers hiding of heavy weight popup window for an event cycle,
which allows reusing popup window to avoid flicker when "moving" popup.
flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatPopupFactory.java