Swing locks up during event handling of a simple button... bug or feature?

Question

I have the following code:
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JToolBar;
import javax.swing.SwingUtilities;
public class Test extends JFrame {
     private static final long serialVersionUID = 1L;
     private JButton button;
     public static void main(String[] args)
          SwingUtilities.invokeLater(new Runnable(){public void run(){new Test();}});
     public Test()
          setSize(200,00);
          setLayout(new BorderLayout());
          JToolBar toolbar = new JToolBar();
          button = new JButton("button");
          button.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { button.setEnabled(false);}});
          toolbar.add(button);
          getContentPane().add(toolbar, BorderLayout.SOUTH);
          JPanel panel = new JPanel();
          panel.setPreferredSize(new Dimension(200,10000));
          for(int i=0;i<10000; i++) { panel.add(new JLabel(""+(Math.random()*1000))); }
          JScrollPane scrollpane = new JScrollPane();
          scrollpane.getViewport().add(panel);
          scrollpane.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_NEVER);
          scrollpane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
          scrollpane.setPreferredSize(getSize());
          scrollpane.setSize(getSize());
          getContentPane().add(scrollpane, BorderLayout.CENTER);
          setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          setLocationRelativeTo(null);
          setVisible(true);
          pack();
}This code is lethal to swing: when pressing the button, for no identifiable reason the entire UI will lock up, even though all the event handler is doing is setting the button's "enabled" property to false. The more content is located in the panel, the longer this locking takes (set -Xmx1024M and the label loop to 1000000 items, then enjoy timing how long it takes swing to realise that all it has to do is disable the button...)
Does anyone here know of how to bypass this behaviour (and if so, how?), or is it something disastrous that cannot be coded around because it's inherent Swing behaviour?
I tried putting the setEnabled(false) call in a WorkerThread... that does nothing. It feels very much like somehow all components are locked, while the entire UI is revalidated, but timing revalidation shows that the panel revalidates in less than 50ms, after which Swing's stalled for no reason that I can identify.
Bug? Feature?
how do I make it stop doing this =(
- Mike

Answer 1

However, if you replace "setEnabled(false)" with "setForeground(Color.red)") the change is instant,I added a second button to the toolbar and invoked setEnabled(true) on the first button and the change is instant as well. I was just looking at the Component code to see the difference between the two. There are a couple of differences:
    public void setEnabled(boolean b) {
        enable(b);
     * @deprecated As of JDK version 1.1,
     * replaced by <code>setEnabled(boolean)</code>.
    @Deprecated
    public void enable() {
        if (!enabled) {
            synchronized (getTreeLock()) {
                enabled = true;
                ComponentPeer peer = this.peer;
                if (peer != null) {
                    peer.enable();
                    if (visible) {
                        updateCursorImmediately();
            if (accessibleContext != null) {
                accessibleContext.firePropertyChange(
                    AccessibleContext.ACCESSIBLE_STATE_PROPERTY,
                    null, AccessibleState.ENABLED);
     * @deprecated As of JDK version 1.1,
     * replaced by <code>setEnabled(boolean)</code>.
    @Deprecated
    public void enable(boolean b) {
        if (b) {
            enable();
        } else {
            disable();
     * @deprecated As of JDK version 1.1,
     * replaced by <code>setEnabled(boolean)</code>.
    @Deprecated
    public void disable() {
        if (enabled) {
            KeyboardFocusManager.clearMostRecentFocusOwner(this);
            synchronized (getTreeLock()) {
                enabled = false;
                if (isFocusOwner()) {
                    // Don't clear the global focus owner. If transferFocus
                    // fails, we want the focus to stay on the disabled
                    // Component so that keyboard traversal, et. al. still
                    // makes sense to the user.
                    autoTransferFocus(false);
                ComponentPeer peer = this.peer;
                if (peer != null) {
                    peer.disable();
                    if (visible) {
                        updateCursorImmediately();
            if (accessibleContext != null) {
                accessibleContext.firePropertyChange(
                    AccessibleContext.ACCESSIBLE_STATE_PROPERTY,
                    null, AccessibleState.ENABLED);
    }The main difference appears to be with the KeyboardFocusManager. So instead of using a toolbar, I changed it to a JPanel (so the buttons are focusable). I then notice the same lag when I try to tab between the two buttons. So the problem is with the focus manager, not the setEnabled() method.