Hi,

The following code extract successfully creates a list box anchored to
the top-left, and that expands vertically, but has a fixed width.

public class EPoS3 extends JFrame {

 public EPoS3() {
   super("EPoS");
 
   this.setSize(600, 400);
   this.setLocation(50, 50);

   Container content = this.getContentPane();
   SpringLayout sl = new SpringLayout();
   content.setLayout(sl);

   //--"Messages" list box--
   String items [] = { "Alpha", "Beta", "Gamma" };
   JList lstMessages = new JList(items);  
   
   //--Current Message panel--
   JPanel pnlMessage = new JPanel();
   pnlMessage.setBackground(Color.blue);
   
   //--Spring layout--
   content.add(lstMessages);
 
   sl.getConstraints(lstMessages).setHeight(Spring.constant(10, 100,
32767));

   sl.getConstraints(lstMessages).setWidth(Spring.constant(100));
   
   sl.putConstraint(SpringLayout.WEST, lstMessages,
                    5,
                    SpringLayout.WEST, content);
                   
   sl.putConstraint(SpringLayout.NORTH, lstMessages,
                    5,
                    SpringLayout.NORTH, content);

   sl.putConstraint(SpringLayout.EAST, content,
                    5,
                    SpringLayout.EAST, lstMessages);
                   
   sl.putConstraint(SpringLayout.SOUTH, content,
                    5,
                    SpringLayout.SOUTH, lstMessages);
 }
}

Q1: For the first two constraints the anchor is the panel and the
dependant is the listbox. However for the last two, this is inverted.
I can't quite figure out why, this may explain why I'm having other
issues.

If the following is now added to the bottom...

   //--panel--
   content.add(pnlMessage);
 
   sl.getConstraints(pnlMessage).setHeight(Spring.constant(10, 100,
32767));

   sl.getConstraints(pnlMessage).setWidth(Spring.constant(10, 10,
32767));
   
   sl.putConstraint(SpringLayout.WEST, pnlMessage,
                    5,
                    SpringLayout.EAST, lstMessages);
                   
   sl.putConstraint(SpringLayout.NORTH, pnlMessage,
                    5,
                    SpringLayout.NORTH, content);

   sl.putConstraint(SpringLayout.EAST, content,
                    5,
                    SpringLayout.EAST, pnlMessage);
                   
   sl.putConstraint(SpringLayout.SOUTH, content,
                    5,
                    SpringLayout.SOUTH, pnlMessage);

Q2: This no longer works.  The list box is suddenly taking on the
preferred height instead of expanding with a 5 pixel margin. If I set
it to a very large value, the margin is not created.  I've tried
switching the south constraint anchor/dependency around, and both
combinations using the panel and listbox, i.e. linking the south of
the panel to the south of the listbox.

I've looked at the SUN + O'Reilly tutorials on SpringLayout, but still
can't get it. All Help gratefully received, as this is driving me
nuts.

I'm using 1.4.2_02 on Win XP.

Cheers

Simon