<AWT Dev> <Swing Dev> [7u-dev] Review request for JDK-8046559: NPE when changing Windows theme

Petr Pchelko petr.pchelko at oracle.com
Fri Jul 11 05:47:49 UTC 2014

Hello, Alexey.

Looks OK to me too.

With best regards. Petr.

> On Jul 11, 2014, at 1:43 AM, Anthony Petrov <anthony.petrov at oracle.com> wrote:
> Hi Alexey,
> I skimmed through the changes and they look fine to me. +1.
> --
> best regards,
> Anthony
> On 7/10/2014 7:59 PM, Alexey Ivanov wrote:
>> Hi AWT, Swing teams,
>> Could you please review the backport of JDK-8046559 to jdk7:
>>     bug: https://bugs.openjdk.java.net/browse/JDK-8046559
>>     webrev: http://cr.openjdk.java.net/~aivanov/8046559/jdk7/webrev.00/
>> Changes between jdk9 and jdk7:
>> I replaced labmda expression in WToolkit.java with anonymous class.
>> It is the only change from the previous webrev:
>> http://mail.openjdk.java.net/pipermail/awt-dev/2014-July/008147.html
>> http://mail.openjdk.java.net/pipermail/swing-dev/2014-July/003657.html
>> Latest jdk9 webrev:
>> http://cr.openjdk.java.net/~aivanov/8046559/jdk9/webrev.01/
>> The information is below is copied from jdk9 review for the sake of
>> completeness.
>> Problem description:
>> When changing Windows themes from a theme with visual styles (Windows
>> Aero or Windows Basic) to a classic one, NullPointerException could be
>> thrown from Swing code during component tree validation, or
>> InternalError could be thrown during component painting.
>> Root cause:
>> Windows theme data are accessed via XPStyle and ThemeReader. When the
>> theme is switched to a classic one, theme handles become unavailable,
>> and theme data cannot be accessed any more. The change in theme is
>> posted to EDT; at the same time, the UI often needs to repaint before
>> the theme change is completely handled in Swing. This leads to NPE and
>> InternalError as the code tries to access the data that has become
>> unavailable.
>> The fix:
>> Windows desktop properties are updated right on Windows Toolkit thread,
>> and the value of "win.xpstyle.themeActive" is stored in
>> ThemeReader.xpStyleEnabled field. PropertyChangeEvents for desktop
>> properties are delivered either synchronously on EDT or asynchronously
>> via DesktopPropertyChangeSupport, as it used to be.
>> Getters in XPStyle class check for null values and return dummy defaults
>> if ThemeReader returned null. SkinPainters also check whether theming is
>> still available before asking ThemeReader to paint.
>> Access to XPStyle.xp instance is blocked as soon as user switches
>> themes. The object will be cleaned when the corresponding
>> PropertyChangeEvent is handled by Swing.
>> This new version of the fix addresses issues found with the initial
>> submission of JDK-8039383 fix:
>>   - JDK-8046239: Build failure in 9-client on all non-Windows platforms
>>   - JDK-8046391: Hang displaying JFileChooser with Windows L&F
>> See also
>> http://mail.openjdk.java.net/pipermail/awt-dev/2014-June/007975.html
>> and http://cr.openjdk.java.net/~aivanov/8039383/jdk9/webrev.03/
>> Regression test:
>> No regression test is provided due to its complexity. Whether
>> NullPointerException or InternalError are thrown depends on the order of
>> event handling, sometimes exceptions do not occur when changing theme of
>> visual styles enabled theme to a classic theme.
>> I included regression test for hang in JFileChooser, JDK-8046391.
>> Thank you,
>> Alexey.

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