RFR: 8377850: AbstractPrimaryTimer: concurrent addAnimationTimer() causes lost timers and hangs

[Kevin Rushforth]

On Tue, 17 Feb 2026 21:37:59 GMT, Andy Goryachev <angorya at openjdk.org> wrote:

> > the question is: why do you observe a background thread calling out to addAnimationTimer()
> 
> wasn't it explicitly disallowed after https://bugs.openjdk.org/browse/JDK-8159048 ?

After follow-on fix [JDK-8324658](https://bugs.openjdk.org/browse/JDK-8324658) the Animation play/start/stop/pause methods may be called on any thread. However, the underlying animation engine must only be called on the FX application thread. That's why the fix for JDK-8324658 was to call `Platform.runLater` in those methods to do the actual work if not already on the FX app thread. See the discussion on PR #1352

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PR Comment: https://git.openjdk.org/jfx/pull/2074#issuecomment-3917244720