When 2 JScrollPanes are in a container(with BoxLayout), allocating space is wiered. The first ScrollPane gets bigger whenever it needs repainting as a result of:
1) resize of main frame.
2) get focus again.

To reproduce this bug, run the following test app.
Test Procedure:
1. try resize main frame( make it bigger or smaller )
2. click second tab and first tab. repeat it.

// Test App
import java.awt.*;
import java.awt.event.*;
import com.sun.java.swing.*;

public class Test extends JFrame {
    JScrollPane sp1, sp2;
    JPanel onePanel;
    JPanel otherPanel;
    JTabbedPane tp;

    public Test() {
        super("test");
        addWindowListener(wl);

        TreeNode root1 = new TreeNode("test1");
        JTree tree1 = new JTree(root1);

        TreeNode root2 = new TreeNode("test2");
        JTree tree2 = new JTree(root2);

        onePanel = new JPanel();
        onePanel.setLayout(new BoxLayout(onePanel, BoxLayout.X_AXIS));

        sp1 = new JScrollPane();
sp2 = new JScrollPane();
        sp1.getViewport().add(tree1);
        sp2.getViewport().add(tree2);

        onePanel.add(sp1);
        onePanel.add(sp2);

        otherPanel = new JPanel();
        
        tp = new JTabbedPane();
        tp.addTab("test-tab1", null, onePanel);
        tp.addTab("test-tab2", null, otherPanel);

        tp.setSelectedIndex(0);

        add("Center",tp);

        setSize(500,400);
        show();
    }


    WindowListener wl = new WindowAdapter(){
        public void windowClosing(WindowEvent event){
            System.exit(0);
        }
    };

    public static void main(String args[]) {
        Test frame = new Test();
    }
}
// end of app
 
bae-chul.kim@Eng 1997-06-26