RFR: 8240506: TextFieldSkin/Behavior: misbehavior on switching skin

[Jeanette Winzenburg]

On Mon, 28 Jun 2021 13:18:38 GMT, Marius Hanl <mhanl at openjdk.org> wrote:

>> The issue is about memory leaks and side-effects (like NPEs) when switching skins. 
>> 
>> Details (copied from issue for convenience):
>> 
>> memory leak in TextInputControlBehavior:
>> - listener accidentally added twice (removed once)
>> - keyPad mappings not properly installed/disposed
>> 
>> memory leak TextFieldBehavior:
>> - listeners to scene/focusOwner property not removed,
>> 
>> memory leak in TextInputControlSkin:
>> - event handlers related to inputMethods not removed
>> 
>> issues in TextFieldSkin:
>> - memory leak due to behavior leaking
>> - memory leaks due to manually added change/invalidation listeners that are not removed
>> - memory leaks due to not removing children with strong references to skin
>> - side-effects (f.i. NPEs) due to listeners/bindings that are still active after dispose
>> 
>> Fix was to properly install/remove those listeners/handlers. Added tests that failed/passed before/after the fix, respectively, also added tests passing before that must pass after the fix.
>
> modules/javafx.controls/src/main/java/javafx/scene/control/skin/TextFieldSkin.java line 390:
> 
>> 388:     @Override public void dispose() {
>> 389:         if (getSkinnable() == null) return;
>> 390:         getChildren().removeAll(textGroup, handleGroup);
> 
> Also curious: Most of the skins don't remove their children in **dispose()**. Are they all wrong, or is this a special case here?

they are all wrong ;) When starting with the cleanup, we (me at least ;) weren't yet entirely certain - but not removing them let them hang in the hierarchy, reachable by strong references from their parent. Which in itself isn't pretty (and might lead to unwanted side-effects) - but if they in turn have any references to the skin (even not so obvious - for me again - like being a not static nested class of the skin ;) the skin is strongly reachable as well, making it leaky.

> modules/javafx.controls/src/test/java/test/com/sun/javafx/scene/control/behavior/BehaviorCleanupTest.java line 162:
> 
>> 160:             secondStage.hide();
>> 161:         }
>> 162: 
> 
> minor: this empty line can be removed

yeah, can do .. but do we have conventions about vertical whitespace? Tend to keep what suits my eyes :)

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PR: https://git.openjdk.java.net/jfx/pull/534