<Swing Dev> <AWT Dev> [9] Review request for JDK-8039383: NPE when changing Windows Theme

[Anthony Petrov]

Hi Alexey,

> With this change, property "win.xpstyle.themeActive" change is fired on the toolkit thread

Is it possible to install a change listener for this property from user 
code, and hence eventually allow executing some user code on the toolkit 
thread with your fix?

--
best regards,
Anthony

On 4/18/2014 12:09 PM, Alexey Ivanov wrote:
> Hello Swing and AWT teams,
>
> Could you please review the fix for jdk9:
>      bug: https://bugs.openjdk.java.net/browse/JDK-8039383
>      webrev: http://cr.openjdk.java.net/~dmarkov/8039383/jdk9/webrev.00/
>
> 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 "cached" in XPStyle object. When the theme is
> switched to a classic one, HTHEME handle becomes unavailable and data
> cannot be accessed from the theme any more. The change in theme in
> posted to EDT via invokeLater. At the same time, the UI needs to repaint
> itself as soon as Windows changed the theme, and paint code is often
> called before the theme change is handled in Java. This leads to NPE and
> InternalError as the code tries to access the data that has become
> unavailable.
>
> The fix:
> Update "win.xpstyle.themeActive" desktop property and invalidate the
> cached XPStyle as soon as windowsSettingChange() is called from native
> code. Thus when Swing code needs to access theme data, it will see no
> theme is available and will fallback to classic painting.
>
> Note: Before the fix, PropertyChangeEvents for desktop properties in
> Windows were fired on the Event Dispatch Thread. With this change,
> property "win.xpstyle.themeActive" change is fired on the toolkit
> thread; all other properties are changed on the EDT as before.
>
>
> Regards,
> Alexey.