> 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 ------------- Changes: https://git.openjdk.org/jfx/pull/830/files Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=830&range=12 Stats: 400 lines in 3 files changed: 398 ins; 1 del; 1 mod Patch: https://git.openjdk.org/jfx/pull/830.diff Fetch: git fetch https://git.openjdk.org/jfx pull/830/head:pull/830 PR: https://git.openjdk.org/jfx/pull/830
