RFR: 8294809: ListenerHelper for managing and disconnecting listeners [v6]

[Andy Goryachev]

> Introduction
> 
> There is a number of places where various listeners (strong as well as weak) are added, to be later disconnected in one go. For example, Skin implementations use dispose() method to clean up the listeners installed in the corresponding Control (sometimes using LambdaMultiplePropertyChangeListenerHandler class).
> 
> This pattern is also used by app developers, but there is no public utility class to do that, so every one must invent their own, see for instance
> https://github.com/andy-goryachev/FxTextEditor/blob/master/src/goryachev/fx/FxDisconnector.java
> 
> Proposal
> 
> It might be beneficial to create a class (ListenerHelper, feel free to suggest a better name) which:
> 
> - provides convenient methods like addChangeListener, addInvalidationListener, addWeakChangeListener, etc.
> - keeps track of the listeners and the corresponding ObservableValues
> - provides a single disconnect() method to remove all the listeners in one go.
> - optionally, it should be possible to add a lambda (Runnable) to a group of properties
> - optionally, there should be a boolean flag to fire the lambda immediately
> - strongly suggest implementing an IDisconnectable functional interface with a single disconnect() method
> 
> Make it Public Later
> 
> Initially, I think we could place the new class in package com.sun.javafx.scene.control; to be made publicly accessible later.
> 
> Where It Will Be Useful
> 
> [JDK-8294589](https://bugs.openjdk.org/browse/JDK-8294589) "MenuBarSkin: memory leak when changing skin"
> and other skins, as a replacement for LambdaMultiplePropertyChangeListenerHandler.
> 
> https://github.com/openjdk/jfx/pull/908#:~:text=19%20hours%20ago-,8295175%3A%20SplitPaneSkinSkin%3A%20memory%20leak%20when%20changing%20skin%20%23911,-Draft
> 
> https://github.com/openjdk/jfx/pull/914

Andy Goryachev has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 20 additional commits since the last revision:

 - 8294809: map change listener
 - Merge remote-tracking branch 'origin/master' into 8294809.listener.helper
 - 8294809: generics
 - 8294809: is alive
 - Revert "8294809: removed weak listeners support"
   
   This reverts commit 2df4a85db638d76cacaf6c54ba669cdb3dd91a18.
 - 8294809: removed weak listeners support
 - 8294809: use weak reference correctly this time
 - 8294809: tests
 - 8294809: remove
 - 8294809: change listener with callback
 - ... and 10 more: https://git.openjdk.org/jfx/compare/ad0c8cb8...7a1fa625

-------------

Changes:
  - all: https://git.openjdk.org/jfx/pull/908/files
  - new: https://git.openjdk.org/jfx/pull/908/files/71ca35ee..7a1fa625

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=908&range=05
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=908&range=04-05

  Stats: 164 lines in 90 files changed: 61 ins; 11 del; 92 mod
  Patch: https://git.openjdk.org/jfx/pull/908.diff
  Fetch: git fetch https://git.openjdk.org/jfx pull/908/head:pull/908

PR: https://git.openjdk.org/jfx/pull/908