RFR: 8185886: Improve scrolling performance of TableView and TreeTableView

[dannygonzalez]

On Fri, 17 Apr 2020 10:22:15 GMT, John Hendrikx <jhendrikx at openjdk.org> wrote:

>> @hjohn Thanks for looking into this. It looks like your changes do improve the issue with the JavaFX thread being
>> swamped with listener de-registrations. Looking at the JavaFX thread in VisualVM, the removeListener call has dropped
>> off the hotspots in the same way it did with my pull request.  I wasn't fully confident of making changes to the Node
>> hierarchy to remove listeners hence why I approached the issue from the other direction i.e. the obvious bottleneck
>> which was the listener de-registration slowness.  I do worry however that any changes down the road which add listeners
>> to the Node hierarchy again without fully understanding the implications would lead us to the same point we are now
>> where the slowness of listener de-registrations becomes an issue again. There are no tests that catch this scenario.  I
>> feel that ideally both solutions are needed but am happy to bow to the more experienced OpenJFX devs opinions here as I
>> know my changes may be more fundamental and hence risky.
>
> The problem is that there are usually many nodes, but only very few scenes and windows, so registering a listener for
> each node on a scene or window is pretty bad design (also consider the amount of notifications that a scene change
> would trigger in such scenarios).  As far as I can see, this is the only such listener and only needed for two very
> limited cases, and its addition in the past may have slipped through the cracks.  Adding a performance unit test that
> specifically checks add/remove performance of nodes may prevent such future regressions.

@hjohn, agreed regards the issues of adding a listener to each node.

Would it be worth doing the additional work of updating PopupWindow and ProgressIndicatorSkin to add their own
listeners to make this a pull request that can be reviewed officially?

I await any further comments from @kevinrushforth et al.

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PR: https://git.openjdk.java.net/jfx/pull/108