RFR: 8252935: Add treeShowing listener only when needed [v4]

[Kevin Rushforth]

On Wed, 10 Feb 2021 10:49:52 GMT, Jeanette Winzenburg <fastegal at openjdk.org> wrote:

> any of old/new scene can be null (or what am I missing?) If that's not covered by the tests .. ;)

Yep. And if you look at the checks run by GitHub actions, there are failing tests. For example:

2021-02-09T20:57:51.7835652Z test.com.sun.javafx.scene.control.infrastructure.ControlSkinFactoryTest > testAlternativeSkinAssignable FAILED
2021-02-09T20:57:51.7838200Z     java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
2021-02-09T20:57:51.7841382Z         at test.com.sun.javafx.scene.control.infrastructure.ControlSkinFactory.createAlternativeSkin(ControlSkinFactory.java:323)
2021-02-09T20:57:51.7845300Z         at test.com.sun.javafx.scene.control.infrastructure.ControlSkinFactory.replaceSkin(ControlSkinFactory.java:302)
2021-02-09T20:57:51.7852081Z         at test.com.sun.javafx.scene.control.infrastructure.ControlSkinFactoryTest.testAlternativeSkinAssignable(ControlSkinFactoryTest.java:91)
2021-02-09T20:57:51.7854816Z 
2021-02-09T20:57:51.7855105Z         Caused by:
2021-02-09T20:57:51.7855858Z         java.lang.reflect.InvocationTargetException
2021-02-09T20:57:51.7857628Z             at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
2021-02-09T20:57:51.7860264Z             at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:64)
2021-02-09T20:57:51.7863798Z             at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
2021-02-09T20:57:51.7866625Z             at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:500)
2021-02-09T20:57:51.7868214Z             at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:481)
2021-02-09T20:57:51.7870982Z             at test.com.sun.javafx.scene.control.infrastructure.ControlSkinFactory.createAlternativeSkin(ControlSkinFactory.java:321)
2021-02-09T20:57:51.7873192Z             ... 2 more
2021-02-09T20:57:51.7873407Z 
2021-02-09T20:57:51.7873689Z             Caused by:
2021-02-09T20:57:51.7874236Z             java.lang.NullPointerException
2021-02-09T20:57:51.7875765Z                 at javafx.graphics/com.sun.javafx.scene.TreeShowingExpression.sceneChanged(TreeShowingExpression.java:127)
2021-02-09T20:57:51.7877830Z                 at javafx.graphics/com.sun.javafx.scene.TreeShowingExpression.<init>(TreeShowingExpression.java:66)
2021-02-09T20:57:51.7879836Z                 at javafx.controls/javafx.scene.control.skin.ProgressIndicatorSkin.<init>(ProgressIndicatorSkin.java:130)
2021-02-09T20:57:51.7881678Z                 at javafx.controls/javafx.scene.control.skin.ProgressBarSkin.<init>(ProgressBarSkin.java:97)
2021-02-09T20:57:51.7883928Z                 at test.com.sun.javafx.scene.control.infrastructure.ControlSkinFactory$ProgressBarSkin1.<init>(ControlSkinFactory.java:515)
2021-02-09T20:57:51.7885496Z                 ... 8 more

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PR: https://git.openjdk.java.net/jfx/pull/185