RFR: 8279228 Leak in ScrollPaneSkin, related to touch events

[Florian Kirmaier]

On Thu, 23 Dec 2021 17:43:19 GMT, Florian Kirmaier <fkirmaier at openjdk.org> wrote:

> Fixing memoryleak, related to touch events in ScrollPaneWhen touchDetected or mouseDown is true, the sbTouch animation is running, 
> and the node is removed from the Scene, then the animation will never stop, causing a memory leak.
> A simple fix is to also check, whether the Node is visible, by checking the "isTreeShowing" property.

1.)
It's not only called at the beginning of the `startSBReleasedAnimation`, but whenever the animation is repeated, which is the cause for the leak. It happens when `touchDetected == true || mouseDown == true` is true. The animation is then basically restarted every frame. With my change, it also checks whether the node is still visible, which fixes the problem.

2.)
It's probably possible if there is a way to simulate Touch Events. The Robot doesn't seem to support it. A test would also require a way to set the "IS_TOUCH_SUPPORTED" property.
Honestly, I don't think it's a good time investment, because the fix is quite simple. I don't even know exactly when it happens - I've just made sure it no longer loops the animation when the ScrollPane is no longer visible.

I've also applied the fix in an affected application, and it clearly fixes the problem.

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PR: https://git.openjdk.java.net/jfx/pull/701