RFR: 8290040: Provide simplified deterministic way to manage listeners [v2]

[John Hendrikx]

On Wed, 31 Aug 2022 17:33:41 GMT, Nir Lisker <nlisker at openjdk.org> wrote:

>> modules/javafx.base/src/main/java/javafx/beans/value/ObservableValue.java line 311:
>> 
>>> 309:      * @since 20
>>> 310:      */
>>> 311:     default ObservableValue<T> when(ObservableValue<Boolean> condition) {
>> 
>> Discussion: name? `when`, `conditionOn`, other suggestions?  Note that this is not the same as a possible future method `filter`, as a `filter` would still keep observing its source at all times (and would use a `Predicate` as parameter).
>
> `when` sounds fine, but we need to be careful about its relation to the `When` class.
> 
> This reminds me also that some of the new functionality in `ObservableValue` can be used as a replacement for `When`, maybe we should note that like we did with `Bindings.select`.

Do you want me to make this part of the PR? Basically, `Bindings.when` with `map` or `flatMap` depending on whether or not you refer to a value or another property in `then` or `otherwise`.

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PR: https://git.openjdk.org/jfx/pull/830