RFR: 8349105: Pagination: exception initializing in a background thread [v3]

[Kevin Rushforth]

On Fri, 7 Feb 2025 23:00:37 GMT, Andy Goryachev <angorya at openjdk.org> wrote:

>> ## Root Cause
>> Animation gets started in a background thread, which causes the animation handler to run in the FX application thread, thus creating simultaneous access to the control's fields (list of children in this case).
>> 
>> ## Solution
>> Postpone the animation unless running in the FX application thread.  There is no functional difference if the component is created/used in the FX application thread.
>
> Andy Goryachev has updated the pull request incrementally with one additional commit since the last revision:
> 
>   gc

With the explicit call to `System.gc()` this now passes for me. I was also able to reproduce the failure without your fix using the latest version of the test, and confirm that it passes with your fix.

I think the frequency of calling `System.gc()` is probably too high. Perhaps calling it every 10 or 100 times through the loop would suffice (and then it would be a better stress test of object allocation, since System.gc() effectively introduces delay)? That might be difficult to do without modifying the `test` method, so we could consider this for a follow-up.

Somewhat related, I'm convinced that there is a leak somewhere. If I run just the pagination test for 100 seconds rather than 5, it's easy to see that the memory keeps growing -- with or without the fix for this bug. We should file a follow-up bug for this.

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Marked as reviewed by kcr (Lead).

PR Review: https://git.openjdk.org/jfx/pull/1698#pullrequestreview-2606530903