On Fri, 15 Jul 2022 09:03:35 GMT, John Hendrikx <jhendr...@openjdk.org> wrote:
> This PR adds a new (lazy*) property on `Node` which provides a boolean which > indicates whether or not the `Node` is currently part of a `Scene`, which in > turn is part of a currently showing `Window`. > > It also adds a new fluent binding method on `ObservableValue` dubbed `when` > (open for discussion, originally I had `conditionOn` here). > > Both of these together means it becomes much easier to break strong > references that prevent garbage collection between a long lived property and > one that should be shorter lived. A good example is when a `Label` is bound > to a long lived property: > > > label.textProperty().bind(longLivedProperty.when(label::isShowingProperty)); > > The above basically ties the life cycle of the label to the long lived > property **only** when the label is currently showing. When it is not > showing, the label can be eligible for GC as the listener on > `longLivedProperty` is removed when the condition provided by > `label::isShowingProperty` is `false`. A big advantage is that these > listeners stop observing the long lived property **immediately** when the > label is no longer showing, in contrast to weak bindings which may keep > observing the long lived property (and updating the label, and triggering its > listeners in turn) until the next GC comes along. > > The issue in JBS also describes making the `Subscription` API public, but I > think that might best be a separate PR. > > Note that this PR contains a bugfix in `ObjectBinding` for which there is > another open PR: https://github.com/openjdk/jfx/pull/829 -- this is because > the tests for the newly added method would fail otherwise; once it has been > integrated to jfx19 and then to master, I can take the fix out. > > (*) Lazy means here that the property won't be creating any listeners unless > observed itself, to avoid problems creating too many listeners on > Scene/Window. This pull request has now been integrated. Changeset: adfc0220 Author: John Hendrikx <jhendr...@openjdk.org> Committer: Nir Lisker <nlis...@openjdk.org> URL: https://git.openjdk.org/jfx/commit/adfc022060087490d0a620f38104a826411820ae Stats: 401 lines in 3 files changed: 399 ins; 1 del; 1 mod 8290040: Provide simplified deterministic way to manage listeners Reviewed-by: nlisker, angorya, kcr, mstrauss ------------- PR: https://git.openjdk.org/jfx/pull/830