Re-examine the risks of JDK-8264770 breaking third party libraries and applications.

[Michael Strauß]

Thanks for the investigation!
I've prepared a PR that fixes this issue:
https://github.com/openjdk/jfx/pull/614


On Sat, Aug 28, 2021 at 11:02 PM John Hendrikx <hjohn at xs4all.nl> wrote:
>
> This actually isn't an issue because adding an invalidation listener
> revalidates the property as well (I'm not sure why, but I noticed this
> before while working on fluent bindings).
>
> However, there is another issue. When I recreate a bidirectional with
> two invalidation listeners with special logic to ignore my own
> invalidation listener triggering again when the other property gets
> updated.
>
> When you include this logic (using the "updating" field in the current
> code) in combination with invalidation listeners, the field that was
> just updated does NOT get revalidated.  Any further changes to that
> field will therefore not trigger an invalidation event and the
> bidirectional nature of the binding breaks.
>
> Try this example:
>
> import javafx.application.Application;
> import javafx.beans.InvalidationListener;
> import javafx.beans.Observable;
> import javafx.beans.property.SimpleDoubleProperty;
> import javafx.stage.Stage;
>
> public class TestBug8264770 extends Application {
>
>    public static void main(String[] args) {
>      Application.launch(args);
>    }
>
>    static SimpleDoubleProperty p1 = new SimpleDoubleProperty(2);
>    static SimpleDoubleProperty p2 = new SimpleDoubleProperty(3);
>
>    @Override
>    public void start(Stage stage) throws Exception {
>      InvalidationListener invalidationListener = obs -> invalidated(obs);
>
>      p1.addListener(invalidationListener);
>      p2.addListener(invalidationListener);
>
>      p1.setValue(4);
>      p2.setValue(5);
>
>      // Prints p1 = 4.0 (!!)
>      System.out.println("Expect p1 to be 5, but was: " + p1.getValue());
>    }
>
>    private boolean updating = false;
>
>    private void invalidated(Observable source) {
>      if (!updating) {
>        try {
>          updating = true;
>
>          if(source == p1) {
>            System.out.println("Setting p2 to " + p1.get());
>            p2.set(p1.get());
>          }
>          else {
>            System.out.println("Setting p1 to " + p2.get());
>            p1.set(p2.get());
>          }
>        }
>        finally {
>          updating = false;
>        }
>      }
>    }
> }
>
> --John
>