RFR: 8269907 memory leak - Dirty Nodes / Parent removed

[Florian Kirmaier]

On Wed, 21 Jul 2021 11:29:38 GMT, Florian Kirmaier <fkirmaier at openjdk.org> wrote:

> After thinking about this issue for some time, I've now got a solution.
> I know put the scene in the state it is, before is was shown, when the dirtyNodes are unset, the whole scene is basically considered dirty. 
> This has the drawback of rerendering, whenever a window is "reshown", but it restores sanity about memory behaviour, which should be considered more important.

During the past PRs the unit tests were quite unstable, but they seem to work.

I've reworked my fix. It now registers a pulseListener for the cleanup. The is also how i initially thought, the fix should look like. To do so, I've added the option to the Toolkit to register such listeners. 

The fix no longer has the drawback, of rerendering the whole window, when it's showing property is changed.

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PR: https://git.openjdk.java.net/jfx/pull/584