Painting behind transparent components

Question

Hi All,
My problem is quite simple. I want to paint on a panel to which I then add a JEditorPane inside a JScrollPane both of which are transparent (using setOpaque(false)). I'm expecting whatever I paint to appear behind any text rendered by the JEditorPane as the component on which it is begin painted is behind the JEditorPane.
What actually happens is that everything drawn on the panel appears above everything else. The following is a self contained example that should display the Google logo BEHIND the GNU GPL but instead paints it on top. Any ideas what the problem is?
import javax.swing.*;
import java.net.URL;
import java.awt.*;
public class Test extends JFrame
     public static void main(String args[]) throws Exception
          Test t = new Test();
     public Test() throws Exception
          setSize(500,500);
          setTitle("Test");
          JPanel backPanel = new JPanel(new BorderLayout())
               ImageIcon background = new ImageIcon(new URL("http://www.google.com/images/logo.gif"));
               public void paint(Graphics g)
                    super.paint(g);
                    g.drawImage(background.getImage(),50,150,this);
          backPanel.setOpaque(true);
          backPanel.setBackground(Color.white);
          JEditorPane textPane = new JEditorPane(new URL("http://www.gnu.org/licenses/gpl.txt"));
          textPane.setEditable(false);
          textPane.setOpaque(false);
          JScrollPane scroller = new JScrollPane(textPane);
          scroller.setOpaque(false);
          scroller.getViewport().setOpaque(false);
          backPanel.add(scroller,BorderLayout.CENTER);
          getContentPane().add(backPanel,BorderLayout.CENTER);
          setVisible(true);
}

Answer 1

You can paint directly on the text component:
import java.awt.*;
import javax.swing.*;
public class TextPaneBackground extends JFrame
     ImageIcon icon;
     public TextPaneBackground()
          icon = new ImageIcon("mong.jpg");
          JTextPane textPane = new JTextPane()
               public void paintComponent(Graphics g)
                    g.drawImage(icon.getImage(), 0, 0, null);
                    super.paintComponent(g);
          textPane.setOpaque( false );
          textPane.setText( "This is some text" );
          JScrollPane scrollPane = new JScrollPane( textPane );
          getContentPane().add( scrollPane );
     public static void main(String[] args)
          TextPaneBackground frame = new TextPaneBackground();
          frame.setDefaultCloseOperation( EXIT_ON_CLOSE );
          frame.setSize(200, 200);
          frame.setVisible(true);
}Not positive, but I believe this approach would be more efficient. When Swing trys to paint a non-opaque component it needs to search the components ancestors until it finds an opaque component to paint the background. So I think in your case you have multiple ancestor, JViewport, JScrollPane, JPanel.