I was troubleshooting a problem in IE using the samples/core/test/scopes example and noticed that for our Window-scoped beans, the @PreDestroy marked method is called twice. I added the Thread.dumpStack() calls into the @PreDestroy method of the WindowCounter bean. To replicate the test in the scopes example:

1) Open the index page
2) Click the link to the window-scope-test page
3) Change the counter value
4) Go back to the index page
5) Go back to the window-scope-test page

First it creates an instance when accessing the page with the Window-scoped bean.

org.icefaces.demo.scopes.WindowScopedCounter@1796a6ac
created >> org.icefaces.demo.scopes.WindowScopedCounter@1796a6ac

The first @PreDestroy is when leaving the page with a Window-scoped bean and going back to the index.html (a page with no JSF and no bean references):

destroyed >> org.icefaces.demo.scopes.WindowScopedCounter@1796a6ac
java.lang.Exception: Stack trace
at java.lang.Thread.dumpStack(Thread.java:1273)
at org.icefaces.demo.scopes.WindowScopedCounter.destroyed(WindowScopedCounter.java:40)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.icefaces.impl.application.WindowScopeManager.callAnnotatedMethod(WindowScopeManager.java:268)
at org.icefaces.impl.application.WindowScopeManager.notifyPreDestroy(WindowScopeManager.java:201)
at org.icefaces.impl.application.WindowScopeManager.notifyPreDestroyForAll(WindowScopeManager.java:193)
at org.icefaces.impl.application.WindowScopeManager.access$1900(WindowScopeManager.java:42)
at org.icefaces.impl.application.WindowScopeManager$AllWindowsClosedNotifier.run(WindowScopeManager.java:606)
at java.util.TimerThread.mainLoop(Timer.java:512)
at java.util.TimerThread.run(Timer.java:462)

Then if you navigate back to the page with the Window-scoped bean, it destroys it again before restoring the View and creating a new bean instance:

destroyed >> org.icefaces.demo.scopes.WindowScopedCounter@1796a6ac
java.lang.Exception: Stack trace
at java.lang.Thread.dumpStack(Thread.java:1273)
at org.icefaces.demo.scopes.WindowScopedCounter.destroyed(WindowScopedCounter.java:40)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at com.sun.faces.vendor.WebContainerInjectionProvider.invokeAnnotatedMethod(WebContainerInjectionProvider.java:117)
at com.sun.faces.vendor.WebContainerInjectionProvider.invokePreDestroy(WebContainerInjectionProvider.java:87)
at com.sun.faces.mgbean.BeanBuilder.destroy(BeanBuilder.java:116)
at com.sun.faces.mgbean.BeanManager.processEvent(BeanManager.java:125)
at javax.faces.event.SystemEvent.processListener(SystemEvent.java:106)
at com.sun.faces.application.ApplicationImpl.processListeners(ApplicationImpl.java:2168)
at com.sun.faces.application.ApplicationImpl.invokeListenersFor(ApplicationImpl.java:2144)
at com.sun.faces.application.ApplicationImpl.publishEvent(ApplicationImpl.java:295)
at com.sun.faces.application.ApplicationImpl.publishEvent(ApplicationImpl.java:246)
at org.icefaces.impl.application.WindowScopeManager$ScopeMap.discardIfExpired(WindowScopeManager.java:318)
at org.icefaces.impl.application.WindowScopeManager$ScopeMap.access$600(WindowScopeManager.java:283)
at org.icefaces.impl.application.WindowScopeManager.determineWindowID(WindowScopeManager.java:121)
at org.icefaces.impl.application.WindowScopeManager$DetermineOrDisposeScope.beforePhase(WindowScopeManager.java:538)
at com.sun.faces.lifecycle.Phase.handleBeforePhase(Phase.java:228)
at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:99)
at com.sun.faces.lifecycle.RestoreViewPhase.doPhase(RestoreViewPhase.java:116)
at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118)
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:593)
...
org.icefaces.demo.scopes.WindowScopedCounter@2b73c3aa
created >> org.icefaces.demo.scopes.WindowScopedCounter@2b73c3aa