RFR: 8294809: ListenerHelper for managing and disconnecting listeners [v9]

[Kevin Rushforth]

On Mon, 14 Nov 2022 20:26:54 GMT, Andy Goryachev <angorya at openjdk.org> wrote:

>> modules/javafx.controls/src/main/java/com/sun/javafx/scene/control/ListenerHelper.java line 70:
>> 
>>> 68:  * </ul>
>>> 69:  */
>>> 70: public class ListenerHelper implements IDisconnectable {
>> 
>> This class is mixing two things- 
>> 1. Managing listeners in a generic way - by providing ability to add & removeAll (via disconnect())
>> 2. Trying to cater to *Skin specific requirement
>> 
>> Ideally, (2) above should be done separately. I mean, the class  ListenerHelper should not use `SkinBase`.
>> What do you think?
>
> you are correct: the original intent for this class was to make it a general purpose facility to help with listeners, something that might be useful at the application level (and it used `ListenerHelper.get(Node)`).  Since that would require CSR and a public discussion, we decided to hide it as an implementation detail in skins (to unblock skin memory leak fixes).
> 
> Once we go through all the necessary discussions and everyone agrees, we could introduce it as a public API in the javafx.base module.

Exactly. In its current form, `ListenerHelper` is a utility helper class for Skins, and should be reviewed with that in mind. As discussed in previous comments, there are several things that will need to change when/if this is proposed as a more general utility. We can defer that discussion, since this is entirely an internal helper class for now.

As a next step, after this is integrated and before any discussion of making this a public utility, it can be used as a replacement for `LambdaMultiplePropertyChangeListenerHandler` -- see [JDK-8296076](https://bugs.openjdk.org/browse/JDK-8296076).

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