RFR: JDK-8304439: Subscription based listeners [v7]

[Michael Strauß]

On Sun, 9 Jul 2023 21:20:02 GMT, John Hendrikx <jhendrikx at openjdk.org> wrote:

>> modules/javafx.base/src/main/java/javafx/beans/Observable.java line 99:
>> 
>>> 97:     /**
>>> 98:      * Creates a {@link Subscription} on this value which calls the given
>>> 99:      * {@code runnable} whenever it becomes invalid.
>> 
>> I think the documentation for these new methods should go into more detail and clearly explain the semantics. These are fundamental concepts, and I think it's a good idea to err on the side of over-explaining. Here's a suggestion:
>> 
>> 
>> Creates a {@code Subscription} for invalidation events of this {@code Observable}.
>> <p>
>> The specified {@code runnable} will be invoked when the {@code Observable} transitions to the
>> <em>invalid</em> state. This happens when the observed value is changed, usually by calling
>> the {@link ObservableValue#setValue} method. Note that the specified {@code runnable} will not
>> be invoked for subsequent value changes unless the {@code Observable} has transitioned to the
>> <em>valid</em> state again, usually by invoking the {@link ObservableValue#getValue} method.
>> <p>
>> An {@code Observable} is automatically validated on every change when a {@link ChangeListener}
>> or a {@link Consumer} or {@link BiConsumer} subscription is added.
>
> Sure, that's a good suggestion, I may have been overly brief to avoid repeating what is known for invalidation listeners, but as this method does not mention invalidation listeners (and only uses them internally for now) a full explanation would be good to add.

Another option would be to refer to the documentation for `InvalidationListener` or `Observable.addListener(InvalidationListener)`, both of which could be improved a bit in a separate PR.

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PR Review Comment: https://git.openjdk.org/jfx/pull/1069#discussion_r1257544619