RFR: 8175358: Memory leak when moving MenuButton into another Scene

[Jeanette Winzenburg]

On Mon, 27 Apr 2020 11:57:58 GMT, Ajit Ghaisas <aghaisas at openjdk.org> wrote:

> Issue : https://bugs.openjdk.java.net/browse/JDK-8175358
> 
> Root cause : When a MenuItem is removed from a Scene, if any accelerator has been set on MenuItem, it does not get
> removed from Scene's list of accelerators.
> Fix : If Scene changes for a Menu, remove the registered accelerators from Scene.
> 
> Testing : Added a unit test that fails before the fix and passes with it.

fix looks good to me :)

Seeing the code, I think we have two follow-up issues (not introduced here, they just jump to visibility in the light
of reading the code and recent fixes around memory leaks :)

- the listener to the control's sceneProperty is never removed, introducing a memory leak, a fix could be similar to that
  of the recently [fixed JDK-8236840](https://bugs.openjdk.java.net/browse/JDK-8236840)

- we have the exact same issue with accelerators in a contextMenu of a control that's removed from the scene (the
  accelerators are still active, as can be seen in adapting your test method). Not sure which collaborator should be
  responsible for the cleanup, could be the helper class, the control, or ?

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PR: https://git.openjdk.java.net/jfx/pull/199