On Thu, 16 Apr 2020 07:34:40 GMT, John Hendrikx <jhendr...@openjdk.org> wrote:
>> Looking at the commit >> https://github.com/openjdk/jfx/commit/e21606d3a1b73cd4b44383babc750a4b4721edfd >> it seems that the long listener lists are actually part of the `Scene`'s >> `Window` property and the `Window`'s `Showing` >> property. Each `Node` registers itself on those and so the listener lists >> for those properties would scale with the >> number of nodes. >> >> A test case showing this problem would really be great as then the patch can >> also be verified to solve the problem, but >> I suppose it could be reproduced simply by having a large number of Nodes in >> a scene. @dannygonzalez could you give us >> an idea how many Nodes we're talking about? 1000? 10.000? It also means >> there might be other options, do Nodes really >> need to add these listeners and for which functionality and are there >> alternatives? It would also be possible to >> target only these specific properties with an optimized listener list to >> reduce the impact of this change. > > The listeners added by `Node` are apparently internally required for internal > properties `TreeShowing` and > `TreeVisible`, and are used to take various decisions like whether to > play/pause animations. There is also a couple of > listeners registering on these properties in turn (in `PopupWindow`, > `SwingNode`, `WebView` and `MediaView`). A lot of > the checks for visibility / showing could easily be done by using the `Scene` > property and checking visibility / > showing status from there. No need for so many listeners. The other classes > mentioned might register their own > listener, instead of having `Node` do it for them (and thus impacting *every* > node). Alternatively, `Node` may lazily > register the listeners for Scene.Window and Window.Showing only when needed > (which from what I can see is for pretty > specific classes only, not classes that you'd see a lot in a TableView...) If it is of any help, I have attached a VisualVM snapshot (v1.4.4) where the ExpressionHelper.removeListener is using 61% of the JavaFX thread whilst running our application. [snapshot-1587024308245.nps.zip](https://github.com/openjdk/jfx/files/4485728/snapshot-1587024308245.nps.zip) If you show only the JavaFX Application thread, press the "HotSpot" and "Reverse Calls" button you can take a look to see which classes are calling the removeListener function.  ------------- PR: https://git.openjdk.java.net/jfx/pull/108
