Long delay during first resize of visible JFrame (help!)

Question

I need to increase the size of a component in a visible JFrame (and with it the size of the frame itself). The way I did this using jdk 1.3.1 causes a problem in 1.4.0 and 1.4.1.
When a component in a visible JFrame (such as a JPanel) is resized - using a setPreferredSize()-pack() sequence, there is a VERY long delay (~ 5 seconds) before the frame is fully redrawn. This only occurs the FIRST time the component is resized. Subsequent setPreferredSize()-pack() sequences take a reasonable amount of time.
Here's a simple example:
import java.awt.*;
import javax.swing.*;
public class PackDelayTest extends JFrame {
    JPanel pan;
    int width;
    static long tm;
    public static void main(String[] argv) {
            tm = System.currentTimeMillis();
        PackDelayTest2 test = new PackDelayTest();
            elapsed("in constructor");
        test.replace(); elapsed("repack 1");
        test.replace(); elapsed("repack 2");
        test.replace(); elapsed("repack 2");
        test.replace(); elapsed("repack 2");  
        System.exit(0);
    public PackDelayTest() {
        pan = new JPanel();
        pan.setLayout(new BoxLayout(pan,BoxLayout.Y_AXIS));
        getContentPane().add(pan);        
        JLabel label = new JLabel("Label 0");
        pan.add(label);  
        pack();
        setVisible(true);
        width = pan.getPreferredSize().width;
    public void replace() {            
       Dimension d = pan.getPreferredSize();
       pan.setPreferredSize(new Dimension(++width,d.height));     
       pack();
    static void elapsed(String mess) {
        long ct = System.currentTimeMillis();
        System.out.println("Elapsed milliseconds, " + mess + ": " +
                           (ct - tm));
        tm = ct;
}Running this with Sun jdk 1.3.1 yields the timings:
Elapsed milliseconds, in constructor: 2226
Elapsed milliseconds, repack 1: 26
Elapsed milliseconds, repack 2: 24
Elapsed milliseconds, repack 2: 25
Elapsed milliseconds, repack 2: 24Running the same code with jdk 1.4.1_0 yields
Elapsed milliseconds, in constructor: 1773
Elapsed milliseconds, repack 1: [bold]5747[/bold]
Elapsed milliseconds, repack 2: 32
Elapsed milliseconds, repack 2: 7
Elapsed milliseconds, repack 2: 1Note the FIVE SECOND delay during the first setPreferredSize()- pack() sequence.
This problem also occurs with 1.4.0, Blackdown 1.4.1 and IBM 1.4.0, so presumably it is something in Sun's 1.4 code.
The only way I've found to avoid the initial delay is to set frame invisible
before the setPreferredSize(), pack() sequence and visible afterwards. But of course this makes the window 'flash' and is very unplesant for users.
I've looked at the source for pack() but it hasn't gotten me anywhere. If anyone has an idea about fixing this problem or working around it, I'd appreciate hearing about it.
FYI I ran these tests under Linux, vanilla installations of SuSE 8.0 and 8.1
Thanks,
bw

Answer 1

It turns out that this problem occurs under SuSE (8.0 and 8.1) but NOT under Redhat 8.0
I do NOT understand how this is possible, but it is the case. Has anyone encountered any SuSE specific problems?
fyi I've reproduced the problem on two rather different i386 machines (an AMD k7 and a Pentium III thinkpad), so it certainly doesn't have anything to do with hardware.
bw