On Mon, 12 Dec 2022 21:57:18 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 with a new target base due to a > merge or a rebase. The pull request now contains 17 commits: > > - Merge branch 'openjdk:master' into feature/conditional-bindings > - Remove example referencing Node#shownProperty > - Remove changes to javafx.graphics Node > - Improve wording in javadoc and comments > - Adjust Node > > - Fixed javadoc > - Added comment for code that avoid eager instantiation > - Changed `isShown` to use property if it is available > - Fix javadoc error > - Fix comment in test > - Improve documentation of shown property > - Merge remote-tracking branch 'origin/master' into > feature/conditional-bindings > > # Conflicts: > # > modules/javafx.base/src/test/java/test/javafx/beans/value/LazyObjectBindingTest.java > - Fix review comments > - ... and 7 more: https://git.openjdk.org/jfx/compare/8763e8b0...24872f09 Looks good. The additional tests for `when` look to be quite thorough and are very easy to follow. I left one minor formatting comment. I'll reapprove if you fix that. modules/javafx.base/src/test/java/test/javafx/beans/value/ObservableValueFluentBindingsTest.java line 931: > 929: @Nested > 930: class WithNotNullReturns_ObservableValue_Which { > 931: private ObjectProperty<Boolean> condition = new > SimpleObjectProperty<Boolean>(true); // using object property here so it can > be set to null for testing Minor: can you wrap this line? (it's a fair bit longer than the recommended max of 120 or so) ------------- Marked as reviewed by kcr (Lead). PR: https://git.openjdk.org/jfx/pull/830
