FULL PRODUCT VERSION :
java version "10" 2018-03-20
Java(TM) SE Runtime Environment 18.3 (build 10+46)
Java HotSpot(TM) 64-Bit Server VM 18.3 (build 10+46, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Any OS running Java 10, for example latest Windows 10

A DESCRIPTION OF THE PROBLEM :
Clicking a JFXPanel having setFocusable(false) causes its processMouseEvent method to loop forever.

Depending on the contents of the JFXPanel, the results may be catastrophic. With a JavaFX media player contained in a JFXPanel, the Swing app hangs immediately and after a few seconds I get out of memory errors.

Please compare:

Java 10's javafx.swing/javafx/embed/swing/JFXPanel.java
-----------------------------------------------------------
    @Override
    protected void processMouseEvent(MouseEvent e) {
        if ((e.getID() == MouseEvent.MOUSE_PRESSED) &&
            (e.getButton() == MouseEvent.BUTTON1)) {
            if (!hasFocus()) {
                requestFocus();
                // this focus request event goes to eventqueue and will be
                // asynchronously handled so MOUSE_PRESSED event will not be
                // honoured by FX immediately due to lack of focus in fx
                // component. Fire the same MOUSE_PRESSED event after
                // requestFocus() so that 2nd mouse press will be honoured
                // since now fx have focus
                AppContext context = SunToolkit.targetToAppContext(this);
                if (context != null) {
                    SunToolkit.postEvent(context, e);
                }
            }
        }

        sendMouseEventToFX(e);
        super.processMouseEvent(e);
    }
-----------------------------------------------------------

to:

Java 9's javafx.swing/javafx/embed/swing/JFXPanel.java
-----------------------------------------------------------
    @Override
    protected void processMouseEvent(MouseEvent e) {
        if ((e.getID() == MouseEvent.MOUSE_PRESSED) &&
            (e.getButton() == MouseEvent.BUTTON1)) {
            if (!hasFocus()) {
                requestFocus();
            }
        }

        sendMouseEventToFX(e);
        super.processMouseEvent(e);
    }
-----------------------------------------------------------


Obviously with Java 10, if, for any reason (for example because JFXPanel.setFocusable(false)), JFXPanel never gets the focus then processMouseEvent() loops for ever.

A simple fix is to replace:

---
if (!hasFocus()) {
---

by:

---
if (isFocusable() && !hasFocus()) {
---

Or better, do not bother invoking "requestFocus();" at all because it's the responsiblity of the client code of the JFXPanel to ensure that JavaFX gets the focus (if needed).



REGRESSION. Last worked in version 9.0.4

ADDITIONAL REGRESSION INFORMATION:
It last worked with:

java version "9.0.4"
Java(TM) SE Runtime Environment (build 9.0.4+11)
Java HotSpot(TM) 64-Bit Server VM (build 9.0.4+11, mixed mode)


STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
1) Compile attached code saved as NonFocusableJFXPanel.java

javac NonFocusableJFXPanel.java

2) Run it using Java 10 from a command prompt to see the messages printed by the Swing app

java -cp . NonFocusableJFXPanel

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
After clicking the button just once, should print :

1
ACTUAL -
After clicking the button just once, prints :

1
2
3
...
4464
4465
4466
...
INCREMENTS FOR EVER

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import java.awt.BorderLayout;
import javax.swing.SwingUtilities;
import javax.swing.JPanel;
import javax.swing.JFrame;
import javafx.application.Platform;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.embed.swing.JFXPanel;

/*
 * Compile attached code saved as NonFocusableJFXPanel.java:
 *
 * javac NonFocusableJFXPanel.java
 *
 * Run it from a command prompt to see the messages printed by the Swing app:
 *
 * java -cp . NonFocusableJFXPanel
 *
 * Works fine with Java 1.8.0_162, Java 9.0.4 but not with Java 10.
 */
public class NonFocusableJFXPanel {
    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                initAndShowGUI();
            }
        });
    }

    public static void initAndShowGUI() {
        JFrame frame = new JFrame("NonFocusableJFXPanel");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JPanel workArea = (JPanel) frame.getContentPane();

        final JFXPanel fxPanel = new JFXPanel();

        // With Java 10, works fine with .setFocusable(true).
        fxPanel.setFocusable(false);

        workArea.add(fxPanel, BorderLayout.CENTER);

        Platform.runLater(new Runnable() {
            public void run() {
                initFX(fxPanel);
            }
        });

        frame.setSize(600, 200);
        frame.setVisible(true);
    }

    private static int clickCount = 0;

    private static void initFX(JFXPanel fxPanel) {
        Button button = new Button("Click me ONCE and look at your console.");
        button.setOnMousePressed(e -> System.err.println(++clickCount));

        Scene scene = new Scene(button);
        fxPanel.setScene(scene);
    }
}

---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Comment out:

fxPanel.setFocusable(false);

or replace it by:

fxPanel.setFocusable(true);