@Override
	public void paintIcon( Component c, Graphics g, int x, int y ) {
        if ( c == null ) {
            return;
        }
        
        Color color = c.getBackground();
        g.setColor( color );
        g.fillOval( x, y, width, height );
    }
Paints an oval of the given size, based upon the Component passed to 
{@link #paintIcon(Component, Graphics, int, int)}.  If the component is null, then no 
painting will take place.
Ghidra/Framework/Gui/src/main/java/resources/icons/OvalBackgroundColorIcon.java