protected Color getBackgroundBase( JComponent c, boolean def ) {
		if( FlatUIUtils.isAWTPeer( c ) )
			return background;

		// use component background if explicitly set
		Color bg = c.getBackground();
		if( isCustomBackground( bg ) )
			return bg;

		return def ? defaultBackground : bg;
	}
Similar to BasicButtonUI.paint(), but does not use zero insets for HTML text,
which is done in BasicButtonUI.layout() since Java 19.
See https://github.com/openjdk/jdk/pull/8407
and https://github.com/openjdk/jdk/pull/8407#issuecomment-1761583430
flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatButtonUI.java