According to the JFrame spec, if the default close operation of a JFrame
is set to DO_NOTHING_ON_CLOSE, we "Don't do anything" when a frame is
closed. The spec does not say anything about the expected behavior of
the JFrame.setDefaultCloseOperation() method if the application that
displays the JFrame does nothing when the close operation is initiated
on the JFrame.

With the GNOME 2 window manager, the frame of the application that
displays the frame under test obscures the frame under test when the
close operation is initiated.

This behavior doesn't seem to match the "Don't do anything"
behavior that is expected per the JFrame spec.
This causes the JCK test for the JFrame.setDefaultCloseOperation() method
(api/javax_swing/interactive/JFrameTests.html#JFrame) to fail with the
GNOME 2 window manager.


Eric Hawkes evaluated this issue as follows:
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We spent some time investigating this bug today, and it seems that the JRE is acting as we expect it to. So, we downloaded the source code for the window manager, and we found a comment in the source code that says something like this might happen. Our usual practice is to honor the policy of the underlying window manager or operating system. Users are often confused (or worse) when Java applications work differently from native applications. We prefer to integrate as seamlessly as possible with the user's desktop.
The test sets the JWindow to use the DO_NOTHING_ON_CLOSE option. As you can see, the javadoc is pretty terse for this API (Swing's WindowConstants.DO_NOTHING_ON_CLOSE). /**
     * The do-nothing default window close operation
     */
    public static final int DO_NOTHING_ON_CLOSE = 0;

However, the docs for JFrame.setDefaultCloseOperation(int) are a little clearer:
     * <li><code>DO_NOTHING_ON_CLOSE</code> - do not do anything - require the
     * program to handle the operation in the <code>windowClosing</code>
     * method of a registered <code>WindowListener</code> object.

This says that Swing will not do anything special - the application is required to handle the operation. We believe that if the application does nothing, the operating system or window manager should control the behavior of the window.
I think the correct way to handle the problem is to add some text that will clarify our specification.
=============


The JFrame spec should be updated to clarify expected behavior of the
setDefaultCloseOperation() method if the application does nothing when the
close operation is initiated on the JFrame.