RFR: 8349091: Charts: exception initializing in a background thread [v6]

[Andy Goryachev]

On Mon, 3 Mar 2025 21:30:42 GMT, John Hendrikx <jhendrikx at openjdk.org> wrote:

>> Was this solution considered:
>> 
>>     ObservableValue<Boolean> partOfSceneGraph = this.sceneProperty()
>>       .flatMap(Scene::windowProperty)
>>       .flatMap(Window::showingProperty)
>>       .orElse(false);
>>       
>>     symbol.focusTraversableProperty()
>>         .bind(Platform.accessibilityActiveProperty().when(partOfSceneGraph));
>>         
>> What the above code does is create a binding on the `when` statement (a listener is added on the `when` result).  However, the `when` property will not add a listener on `Platform.accessibilityActiveProperty()` until `partOfSceneGraph` is `true`.  As soon as it does though, a listener is installed on  `Platform.accessibilityActiveProperty()` and its latest value is set to `focusTraversableProperty` via the bind.
>
> The above does require though that `Platform.accessibilityActiveProperty()` is properly synchronized.  I think it may be a good idea to fix that first.  Perhaps all platform provided properties (if there are more) should ensure they're only initialized once.

unrelated, but I would rather disallow background access to any platform properties.

_per the earlier email_, this might (read: will) create concurrent access when the node is not yet attached to the scene graph:


background thread                   fx app thread
1. start creating the node
2. add listener to platform prop
3. keep initializing the node        <-- platform property change notification
4. some more code


step 3 is when concurrent access occurs.

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PR Review Comment: https://git.openjdk.org/jfx/pull/1697#discussion_r1978282003