public static void main( String[] args ) {
		SwingUtilities.invokeLater( () -> {
			FlatLightLaf.setup();

			JFrame frame = new JFrame( "HTML Button Test" );
			frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );

			JPanel panel = new JPanel( new GridBagLayout() );
			panel.setBorder( new EmptyBorder( 20, 20, 20, 20 ) );

			createButtons( panel, "center", SwingConstants.CENTER, SwingConstants.CENTER, null );
			createButtons( panel, "left", SwingConstants.LEFT, SwingConstants.CENTER, null );
			createButtons( panel, "right", SwingConstants.RIGHT, SwingConstants.CENTER, null );

			createButtons( panel, "center with margin 30,4,4,4", SwingConstants.CENTER, SwingConstants.CENTER, new Insets( 30, 4, 4, 4 ) );
			createButtons( panel, "left with margin 30,4,4,4", SwingConstants.LEFT, SwingConstants.CENTER, new Insets( 30, 4, 4, 4 ) );
			createButtons( panel, "left/top with margin 30,4,4,4", SwingConstants.LEFT, SwingConstants.TOP, new Insets( 30, 4, 4, 4 ) );

			frame.add( new JLabel( "Java version " + System.getProperty( "java.version" ) ), BorderLayout.NORTH );
			frame.add( panel );
			frame.pack();
			frame.setVisible( true );
		} );
	}
https://github.com/openjdk/jdk/pull/8407#issuecomment-1761583430
flatlaf-testing/src/main/java/com/formdev/flatlaf/testing/jdk/HtmlButtonTest.java