On Tue, 14 Apr 2020 13:01:18 GMT, Jeanette Winzenburg <faste...@openjdk.org>
wrote:
>> This is needed to future safe the code from an NPE from scenarios as in
>> below test case,
>>
>> class TabPaneSkin1 extends TabPaneSkin {
>> TabPaneSkin1(TabPane tabPane) {
>> super(tabPane);
>> }
>> }
>>
>> @Test
>> public void testNPEOnSwitchSkinAndRemoveTabPane() {
>> TabPane testPane = new TabPane(new Tab("tab0"), new Tab("tab1"));
>> Group root = new Group(testPane);
>> Scene scene = new Scene(root);
>> Stage stage = new Stage();
>> stage.setScene(scene);
>> stage.show();
>> tk.firePulse();
>>
>> testPane.setSkin(new TabPaneSkin1(testPane));
>> tk.firePulse();
>> testPane.getSelectionModel().select(1);
>> tk.firePulse();
>> }
>>
>> But currently this throws an NPE at different code,
>> java.lang.NullPointerException
>> at
>> javafx.controls/javafx.scene.control.skin.TabPaneSkin.isHorizontal(TabPaneSkin.java:699)
>> at
>> javafx.controls/javafx.scene.control.skin.TabPaneSkin$TabHeaderArea.layoutChildren(TabPaneSkin.java:1134)
>> at javafx.graphics/javafx.scene.Parent.layout(Parent.java:1207)
>>
>> This is part of an another problem that skins should remove all listeners
>> when switched.
>> So I think we can not add this test with this fix.
>
> thanks for the test :)
>
> Good catch, and I can reproduce it, though with a twist:
>
> - with firing the pulse I see the error you cited
> - without firing the pulse, I see the error in the selected item listener
> (because the skinnable is null) which to me
> appears to be "nearer" the real reason
>
> Whatever the error, though, we learned that we must be extremely careful with
> (even weak) listeners - at least when
> they fall into some categories. So far we had
> - listeners to path properties
> - listeners that change global state (like in the button skin issue)
> - ?? maybe all
>
> Personally, I would tend to keep and ignore that test with doc: the ignore
> could point to
> https://bugs.openjdk.java.net/browse/JDK-8242621 (memory leak on switching
> tab, which might or not be related), the
> removing code could have a code comment explaining why it is needed. What do
> you think?
Looked again, and actually seeing two different issues ;)
A) your test - that is with firing the pulse: fails for both not/removing the
listener
B) basically same test, but not firing the pulse - it fails without removing
and passes with removing the listener
So I think we should include B as it is directly related to this fix (and
verifies the need to remove the listener). As
to A: we should keep it somewhere to not forget, but where?
Test code B:
@Test
public void testNPEOnSwitchSkinAndSelect() {
// want to replace the skin - test doesn't make sense without
if (!showBeforeReplaceSM) return;
TabPane testPane = new TabPane(new Tab("tab0"), new Tab("tab1"));
Group root = new Group(testPane);
Scene scene = new Scene(root);
Stage stage = new Stage();
stage.setScene(scene);
stage.show();
testPane.setSkin(new TabPaneSkin1(testPane));
testPane.getSelectionModel().select(1);
}
The exception (seen on the test stack when rewiring the uncaughthandler as
usual, else on sysout):
Exception in thread "main" java.lang.NullPointerException
at
javafx.controls/javafx.scene.control.skin.TabPaneSkin.lambda$0(TabPaneSkin.java:447)
at
javafx.base/javafx.beans.WeakInvalidationListener.invalidated(WeakInvalidationListener.java:83)
at
javafx.base/com.sun.javafx.binding.ExpressionHelper$Generic.fireValueChangedEvent(ExpressionHelper.java:348)
at
javafx.base/com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:80)
at
javafx.base/javafx.beans.property.ReadOnlyObjectPropertyBase.fireValueChangedEvent(ReadOnlyObjectPropertyBase.java:74)
at
javafx.base/javafx.beans.property.ReadOnlyObjectWrapper.fireValueChangedEvent(ReadOnlyObjectWrapper.java:102)
at
javafx.base/javafx.beans.property.ObjectPropertyBase.markInvalid(ObjectPropertyBase.java:113)
at
javafx.base/javafx.beans.property.ObjectPropertyBase.set(ObjectPropertyBase.java:147)
at
javafx.controls/javafx.scene.control.SelectionModel.setSelectedItem(SelectionModel.java:105)
at
javafx.controls/javafx.scene.control.TabPane$TabPaneSelectionModel.select(TabPane.java:736)
at
javafx.controls/test.javafx.scene.control.SelectionFocusModelMemoryTest.testNPEOnSwitchSkinAndRemoveTabPaneFirePulse(SelectionFocusModelMemoryTest.java:261)
-------------
PR: https://git.openjdk.java.net/jfx/pull/175
