On Thu, 1 Sep 2022 13:51:21 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. > > John Hendrikx has updated the pull request incrementally with one additional > commit since the last revision: > > Update javadoc of "when" with better phrasing modules/javafx.base/src/main/java/javafx/beans/value/ObservableValue.java line 268: > 266: * for garbage collection while its source isn't. However, when > using {@code when} this {@code ObservableValue} > 267: * can still be eligible for garbage collection when {@code > condition} holds {@code false} and {@code condition} > 268: * itself is also eligible for garbage collection. I think that these 2 paragraphs can be combined. There is some repetition in the last sentence ("However...") of the 1st paragraph. Maybe add to the 1st paragraph at the end: > This is in contrast to the general behavior of bindings, where the binding is > never eligible for GC as long as the source isn't. If you think it's important to note that. Then remove the 2nd paragraph? ------------- PR: https://git.openjdk.org/jfx/pull/830
