title: scroll pane graphic bug
body: <p>I got an unexpected behavior on my JScrollPane:
   My ScrollPanel is filled with different panels
  (Transparency is needed because in the end I will have images in background instead of just colors)</p>
  
  <p>I made a quick example of my problem:</p>
  
  <pre><code>import java.awt.Color;
  import java.awt.Dimension;
  
  import javax.swing.*;
  import javax.swing.border.Border;
  
  
   public class ScrollPaneTest extends JPanel{
  
    ScrollPaneTest(){
  
      JPanel Content = new JPanel();
      BoxLayout ColumnLayout = new BoxLayout(Content,BoxLayout.Y_AXIS);
      Content.setLayout(ColumnLayout);
      for(int i = 0 ; i &lt; 10 ; i++){
          JPanel pane = new JPanel();
          JLabel elem = new JLabel("element "+i);
          pane.setBackground(new Color(0,0,0,125));
          pane.add(elem);
          Content.add(pane);
  
      }
  
  
  
      Content.setBackground(Color.ORANGE);
  
      JScrollPane scrollPane = new JScrollPane(Content);
      scrollPane.setPreferredSize(new Dimension(100,100));
      scrollPane.setBackground(new Color(0,0,0,250));
      add(scrollPane);
   }
  
   public static void main(String[] args) throws Exception {
  
      JFrame f =  new JFrame();
      JPanel bck = new JPanel();
      bck.setBackground(Color.RED);
      bck.add(new ScrollPaneTest());
      f.add(bck);
  
      f.setSize(200, 200);
      f.setVisible(true);
    }
  
  }
  </code></pre>
  
  <p>With this you can see that when I scroll, the graphics are all messed up :/
  Thanks for Helping :p</p>