The following example illustrate the issue. The "Slave" windows cannot be iconify.

It was working with previous jdk8 releases.


/*
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package javafxapplication50;

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.TextArea;
import javafx.stage.Stage;
import javafx.stage.StageStyle;

/**
 *
 * @author Daniel
 */
public class JavaFXApplication50 extends Application {

    private Stage stage;

    @Override
    public void start(Stage primaryStage) {

        Scene scene = new Scene(new TextArea("I'm the master"));

        primaryStage.setTitle("Master");
        primaryStage.setScene(scene);
        primaryStage.show();

        stage = new Stage(StageStyle.DECORATED);
        stage.initOwner(primaryStage);

        final Scene scene2 = new Scene(new TextArea("I'm a slave"));
        stage.setTitle("Slave");
        stage.setScene(scene2);
        stage.showAndWait();

    }

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        launch(args);
    }

}