void showImpl() {
			if( delegate != null ) {
				showPopupAndFixLocation( delegate, popupWindow );

				// increase tooltip size if necessary because it may be too small on HiDPI screens
				//    https://bugs.openjdk.java.net/browse/JDK-8213535
				if( contents instanceof JToolTip && popupWindow == null ) {
					Container parent = contents.getParent();
					if( parent instanceof JPanel ) {
						Dimension prefSize = parent.getPreferredSize();
						if( !prefSize.equals( parent.getSize() ) ) {
							Container mediumWeightPanel = SwingUtilities.getAncestorOfClass( Panel.class, parent );
							Container c = (mediumWeightPanel != null)
								? mediumWeightPanel // medium weight popup
								: parent;           // light weight popup
							c.setSize( prefSize );
							c.validate();
						}
					}
				}
			}
		}
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