RFR: 8241455: ChoiceBox - memory leak on replacing selectionModel

[Kevin Rushforth]

On Mon, 23 Mar 2020 23:45:21 GMT, Kevin Rushforth <kcr at openjdk.org> wrote:

>> ChoiceBox leaves a memory leak when replacing the selectionModel. Culprit is ChoiceBoxSelectionModel which registers
>> listener with strong references. Fix is to change these to weak references.
>> Added test that fails before and passes after the test.
>> 
>> for convenience, the bug reference https://bugs.openjdk.java.net/browse/JDK-8241455
>
> I have basically the same comment / question as I asked in #147
> 
> In general, there are two approaches to avoiding listener-related memory leaks. One is to use a WeakListener; the other
> is to explicitly remove the listener when the object is removed or otherwise no longer needed.
> Using a WeakListener is certainly easier, but runs the risk of the listener being removed too early and not cleaning up
> after itself. I'm not suggesting that's the case here, but it is worth looking at.

@arapte @aghaisas - Can you both review this?

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PR: https://git.openjdk.java.net/jfx/pull/148