@Override
	public void paint( Graphics g, JComponent c ) {
		super.paint( g, c );

		// must paint tab area after content border was painted
		if( !scrollableTabLayoutEnabled() && _tabPane.getTabCount() > 0 )
			paintTabArea( g, _tabPane.getTabPlacement(), _tabPane.getSelectedIndex(), c );
	}
The content border insets are used to create a separator between tabs and content.
If client property JTabbedPane.hasFullBorder is true, then the content border insets
are also used for the border.
flatlaf-jide-oss/src/main/java/com/formdev/flatlaf/jideoss/ui/FlatJideTabbedPaneUI.java