Hi, This is a continuation of the discussion that stemmed from changing bidirectional bindings to use invalidation listeners instead of change listeners [1].
The relevant issue in JBS is [2]. I have looked at removing the eager evaluation when attaching an invalidation listener. I found that tests, for example, the method BooleanPropertyBaseTest#testAddingListenerWillAlwaysReceiveInvalidationEvent (only lines 428-432 are relevant) set the following requirement: 1. Start with a property in an invalid state. 2. Attach an invalidation listener. 3. Set a value which is different than the current one. Result: an invalidation event must be sent. This means that attaching an invalidation listener must validate the property, which is (at least currently) only possible by evaluating the value. This is in contrast to the comment in the JBS that invalidation listeners should not generally force eager evaluation. It is also in contrast to this line in the class doc of ObservableValue: "Implementations in this library mark themselves as invalid when the first invalidation event occurs. They do not generate any more invalidation events until their value is recomputed and valid again." So, either the requirement set by the tests is wrong, or invalidation listeners really do need to behave according to the test and the docs missed a practical requirement, or my analysis is wrong. There are more tests that fail, but the ones I looked at rely on the same concept. For example, Node_LocalToParentTransform_Test#shouldBeNotifiedWhenNodeTransforms() tests the Node#LazyTransformProperty property. Interestingly, this one is initialized with an invalid state, while Simple___Property are initialized as valid. Thoughts? [1] http://mail.openjdk.java.net/pipermail/openjfx-dev/2021-August/031778.html [2] https://bugs.openjdk.java.net/browse/JDK-8208750
