From 01403e0371a4be0e5583e327edabfe43280dcb2a Mon Sep 17 00:00:00 2001
From: Prasanta Sadhukhan <prasanta.sadhukhan@oracle.com>
Date: Mon, 10 Nov 2025 10:23:34 +0000
Subject: [PATCH 01/10] 8255248: NullPointerException in JFXPanel due to race
 condition in HostContainer

---
 .../sun/javafx/tk/quantum/EmbeddedScene.java  |   4 +-
 .../java/javafx/embed/swing/JFXPanel.java     | 104 +++++++++++----
 .../javafx/embed/swing/JFXPanelNPETest.java   | 126 ++++++++++++++++++
 3 files changed, 208 insertions(+), 26 deletions(-)
 create mode 100644 tests/system/src/test/java/test/javafx/embed/swing/JFXPanelNPETest.java

diff --git a/modules/javafx.graphics/src/main/java/com/sun/javafx/tk/quantum/EmbeddedScene.java b/modules/javafx.graphics/src/main/java/com/sun/javafx/tk/quantum/EmbeddedScene.java
index a84d6b736e2..8455b059f4b 100644
--- a/modules/javafx.graphics/src/main/java/com/sun/javafx/tk/quantum/EmbeddedScene.java
+++ b/modules/javafx.graphics/src/main/java/com/sun/javafx/tk/quantum/EmbeddedScene.java
@@ -155,7 +155,9 @@ public void setPixelScaleFactors(float scalex, float scaley) {
         entireSceneNeedsRepaint();
         Platform.runLater(() -> {
             QuantumToolkit.runWithRenderLock(() -> {
-                updateSceneState();
+                if (getSceneState() != null) {
+                    updateSceneState();
+                }
                 return null;
             });
         });
diff --git a/modules/javafx.swing/src/main/java/javafx/embed/swing/JFXPanel.java b/modules/javafx.swing/src/main/java/javafx/embed/swing/JFXPanel.java
index 8b6e2d70c85..4a62949bd85 100644
--- a/modules/javafx.swing/src/main/java/javafx/embed/swing/JFXPanel.java
+++ b/modules/javafx.swing/src/main/java/javafx/embed/swing/JFXPanel.java
@@ -205,6 +205,21 @@ public class JFXPanel extends JComponent {
     @SuppressWarnings("doclint:missing")
     private JFXPanelInteropN jfxPanelIOP;
 
+    private static final boolean debugPrint;
+    private static final String debugPrefix = "JFXPanel:>> ";
+    private static final String JFXPANEL_DEBUG = "jfxpanel.debug";
+    static {
+        String debugStr = System.getProperty(JFXPANEL_DEBUG);
+
+        debugPrint = "true".equalsIgnoreCase(debugStr);
+    }
+
+    protected static void debug_println(String str) {
+        if (debugPrint) {
+            System.out.println(debugPrefix + " " + str);
+        }
+    }
+
     private synchronized void registerFinishListener() {
         if (instanceCount.getAndIncrement() > 0) {
             // Already registered
@@ -274,6 +289,7 @@ private synchronized static void initFx() {
     public JFXPanel() {
         super();
 
+        debug_println("JFXPanel Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
         jfxPanelIOP = new JFXPanelInteropN();
         initFx();
 
@@ -299,6 +315,7 @@ public JFXPanel() {
      * @return the {@code Scene} attached to this {@code JFXPanel}
      */
     public Scene getScene() {
+        debug_println("getScene Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
         return scene;
     }
 
@@ -313,6 +330,7 @@ public Scene getScene() {
      * @see javafx.application.Platform#isFxApplicationThread()
      */
     public void setScene(final Scene newScene) {
+        debug_println("setScene Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
         if (Toolkit.getToolkit().isFxUserThread()) {
             setSceneImpl(newScene);
         } else {
@@ -360,6 +378,7 @@ private void setSceneImpl(Scene newScene) {
      */
     @Override
     public final void setOpaque(boolean opaque) {
+        debug_println("setOpaque Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
         // Don't let user control opacity
         if (!opaque) {
             super.setOpaque(opaque);
@@ -376,6 +395,7 @@ public final void setOpaque(boolean opaque) {
      */
     @Override
     public final boolean isOpaque() {
+        debug_println("isOpaque Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
         return false;
     }
 
@@ -418,7 +438,8 @@ private Point2D convertSwingToFxPixel(GraphicsConfiguration g, double wx, double
     }
 
     private void sendMouseEventToFX(MouseEvent e) {
-        if (scenePeer == null || !isFxEnabled()) {
+        var hScenePeer = scenePeer;
+        if (hScenePeer == null || !isFxEnabled()) {
             return;
         }
 
@@ -467,7 +488,7 @@ private void sendMouseEventToFX(MouseEvent e) {
         int fxYOnScreen = (int)Math.round(onScreen.getY());
 
         if(e.getID() == MouseEvent.MOUSE_WHEEL) {
-            scenePeer.scrollEvent(AbstractEvents.MOUSEEVENT_VERTICAL_WHEEL,
+            hScenePeer.scrollEvent(AbstractEvents.MOUSEEVENT_VERTICAL_WHEEL,
                     0, -SwingEvents.getWheelRotation(e),
                     0, 0, // total scroll
                     40, 40, // multiplier
@@ -478,7 +499,7 @@ private void sendMouseEventToFX(MouseEvent e) {
                     (extModifiers & MouseEvent.ALT_DOWN_MASK) != 0,
                     (extModifiers & MouseEvent.META_DOWN_MASK) != 0, false);
         } else {
-            scenePeer.mouseEvent(
+            hScenePeer.mouseEvent(
                     SwingEvents.mouseIDToEmbedMouseType(e.getID()),
                     SwingEvents.mouseButtonToEmbedMouseButton(e.getButton(), extModifiers),
                     primaryBtnDown, middleBtnDown, secondaryBtnDown,
@@ -492,7 +513,7 @@ private void sendMouseEventToFX(MouseEvent e) {
                     popupTrigger);
         }
         if (e.isPopupTrigger()) {
-            scenePeer.menuEvent(e.getX(), e.getY(), fxXOnScreen, fxYOnScreen, false);
+            hScenePeer.menuEvent(e.getX(), e.getY(), fxXOnScreen, fxYOnScreen, false);
         }
     }
 
@@ -505,6 +526,7 @@ private void sendMouseEventToFX(MouseEvent e) {
      */
     @Override
     protected void processMouseEvent(MouseEvent e) {
+        debug_println("processMouseEvent Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
         if ((e.getID() == MouseEvent.MOUSE_PRESSED) &&
             (e.getButton() == MouseEvent.BUTTON1)) {
             if (isFocusable() && !hasFocus()) {
@@ -532,6 +554,7 @@ protected void processMouseEvent(MouseEvent e) {
      */
     @Override
     protected void processMouseMotionEvent(MouseEvent e) {
+        debug_println("processMouseMotionEvent Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
         sendMouseEventToFX(e);
         super.processMouseMotionEvent(e);
     }
@@ -546,12 +569,14 @@ protected void processMouseMotionEvent(MouseEvent e) {
      */
     @Override
     protected void processMouseWheelEvent(MouseWheelEvent e) {
+        debug_println("processMouseWheelEvent Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
         sendMouseEventToFX(e);
         super.processMouseWheelEvent(e);
     }
 
     private void sendKeyEventToFX(final KeyEvent e) {
-        if (scenePeer == null || !isFxEnabled()) {
+        var hScenePeer = scenePeer;
+        if (hScenePeer == null || !isFxEnabled()) {
             return;
         }
 
@@ -559,7 +584,7 @@ private void sendKeyEventToFX(final KeyEvent e) {
                        ? new char[] {}
                        : new char[] { SwingEvents.keyCharToEmbedKeyChar(e.getKeyChar()) };
 
-        scenePeer.keyEvent(
+        hScenePeer.keyEvent(
                 SwingEvents.keyIDToEmbedKeyType(e.getID()),
                 e.getKeyCode(), chars,
                 SwingEvents.keyModifiersToEmbedKeyModifiers(e.getModifiersEx()));
@@ -574,11 +599,13 @@ private void sendKeyEventToFX(final KeyEvent e) {
      */
     @Override
     protected void processKeyEvent(KeyEvent e) {
+        debug_println("processKeyEVent Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
         sendKeyEventToFX(e);
         super.processKeyEvent(e);
     }
 
     private void sendResizeEventToFX() {
+        debug_println("sendResizeEventToFX Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
         if (stagePeer != null) {
             stagePeer.setSize(pWidth, pHeight);
         }
@@ -598,6 +625,7 @@ private void sendResizeEventToFX() {
      */
     @Override
     protected void processComponentEvent(ComponentEvent e) {
+        debug_println("processComponentEVent Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
         switch (e.getID()) {
             case ComponentEvent.COMPONENT_RESIZED: {
                 updateComponentSize();
@@ -627,6 +655,7 @@ private AffineTransform getCurrentTransform() {
 
     // called on EDT only
     private void updateComponentSize() {
+        debug_println("updateComponentSize Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
         int oldWidth = pWidth;
         int oldHeight = pHeight;
         if (getBorder() != null) {
@@ -649,8 +678,9 @@ private void updateComponentSize() {
             newScaleFactorX != scaleFactorX || newScaleFactorY != scaleFactorY)
         {
             createResizePixelBuffer(newScaleFactorX, newScaleFactorY);
-            if (scenePeer != null) {
-                scenePeer.setPixelScaleFactors((float) newScaleFactorX,
+            var hScenePeer = scenePeer;
+            if (hScenePeer != null) {
+                hScenePeer.setPixelScaleFactors((float) newScaleFactorX,
                                                (float) newScaleFactorY);
             }
             scaleFactorX = newScaleFactorX;
@@ -692,6 +722,7 @@ private void sendMoveEventToFX() {
      */
     @Override
     protected void processHierarchyBoundsEvent(HierarchyEvent e) {
+        debug_println("processHierarchyBoundsEVent Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
         if (e.getID() == HierarchyEvent.ANCESTOR_MOVED) {
             if (updateScreenLocation()) {
                 sendMoveEventToFX();
@@ -702,6 +733,7 @@ protected void processHierarchyBoundsEvent(HierarchyEvent e) {
 
     @Override
     protected void processHierarchyEvent(HierarchyEvent e) {
+        debug_println("processHierarchyEVent Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
         if ((e.getChangeFlags() & HierarchyEvent.SHOWING_CHANGED) != 0) {
             if (updateScreenLocation()) {
                 sendMoveEventToFX();
@@ -739,13 +771,15 @@ private void sendFocusEventToFX(final FocusEvent e) {
      */
     @Override
     protected void processFocusEvent(FocusEvent e) {
+        debug_println("processFocusEVent Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
         sendFocusEventToFX(e);
         super.processFocusEvent(e);
     }
 
     // called on EDT only
     private void createResizePixelBuffer(double newScaleFactorX, double newScaleFactorY) {
-        if (scenePeer == null || pWidth <= 0 || pHeight <= 0) {
+        var hScenePeer = scenePeer;
+        if (hScenePeer == null || pWidth <= 0 || pHeight <= 0) {
             pixelsIm = null;
         } else {
             BufferedImage oldIm = pixelsIm;
@@ -753,7 +787,7 @@ private void createResizePixelBuffer(double newScaleFactorX, double newScaleFact
             int newPixelH = (int) Math.ceil(pHeight * newScaleFactorY);
             pixelsIm = new BufferedImage(newPixelW, newPixelH,
                                          SwingFXUtils.getBestBufferedImageType(
-                                             scenePeer.getPixelFormat(), null, false));
+                                             hScenePeer.getPixelFormat(), null, false));
             if (oldIm != null) {
                 double ratioX = newScaleFactorX / scaleFactorX;
                 double ratioY = newScaleFactorY / scaleFactorY;
@@ -773,6 +807,7 @@ private void createResizePixelBuffer(double newScaleFactorX, double newScaleFact
 
     @Override
     protected void processInputMethodEvent(InputMethodEvent e) {
+        debug_println("processInputMethodEVent Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
         if (e.getID() == InputMethodEvent.INPUT_METHOD_TEXT_CHANGED) {
             sendInputMethodEventToFX(e);
         }
@@ -803,8 +838,11 @@ private void sendInputMethodEventToFX(InputMethodEvent e) {
      * @see #isOpaque()
      */
     @Override
-    protected void paintComponent(Graphics g) {
-        if (scenePeer == null) {
+    protected synchronized void paintComponent(Graphics g) {
+        debug_println("paintComponent Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+        var hScenePeer = scenePeer;
+        var hStage = stage;
+        if (hScenePeer == null || hStage == null) {
             return;
         }
         if (pixelsIm == null) {
@@ -816,7 +854,7 @@ protected void paintComponent(Graphics g) {
         DataBufferInt dataBuf = (DataBufferInt)pixelsIm.getRaster().getDataBuffer();
         int[] pixelsData = dataBuf.getData();
         IntBuffer buf = IntBuffer.wrap(pixelsData);
-        if (!scenePeer.getPixels(buf, pWidth, pHeight)) {
+        if (!hScenePeer.getPixels(buf, pWidth, pHeight)) {
             // In this case we just render what we have so far in the buffer.
         }
 
@@ -824,7 +862,7 @@ protected void paintComponent(Graphics g) {
         try {
             ComponentOrientation cor = this.getComponentOrientation();
             boolean rtl = ComponentOrientation.RIGHT_TO_LEFT.equals(cor);
-            stage.setNodeOrientation(rtl ? NodeOrientation.RIGHT_TO_LEFT :
+            hStage.setNodeOrientation(rtl ? NodeOrientation.RIGHT_TO_LEFT :
                                            NodeOrientation.LEFT_TO_RIGHT);
 
             gg = g.create();
@@ -845,7 +883,7 @@ protected void paintComponent(Graphics g) {
             if (scaleFactorX != newScaleFactorX || scaleFactorY != newScaleFactorY) {
                 createResizePixelBuffer(newScaleFactorX, newScaleFactorY);
                 // The scene will request repaint.
-                scenePeer.setPixelScaleFactors((float) newScaleFactorX,
+                hScenePeer.setPixelScaleFactors((float) newScaleFactorX,
                                                (float) newScaleFactorY);
                 scaleFactorX = newScaleFactorX;
                 scaleFactorY = newScaleFactorY;
@@ -869,6 +907,7 @@ protected void paintComponent(Graphics g) {
      */
     @Override
     public Dimension getPreferredSize() {
+        debug_println("getPreferredSize Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
         if (isPreferredSizeSet() || scenePeer == null) {
             return super.getPreferredSize();
         }
@@ -943,6 +982,7 @@ private void setFxEnabled(boolean enabled) {
      */
     @Override
     public void addNotify() {
+        debug_println("addNotify Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
         super.addNotify();
 
         registerFinishListener();
@@ -960,6 +1000,7 @@ public void addNotify() {
 
     @Override
     public InputMethodRequests getInputMethodRequests() {
+        debug_println("getInputMethodRequests Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
         EmbeddedSceneInterface scene = scenePeer;
         if (scene == null) {
             return new InputMethodSupport.InputMethodRequestsAdapter(null);
@@ -973,6 +1014,7 @@ public InputMethodRequests getInputMethodRequests() {
      * chain of parent components are removed.
      */
     @Override public void removeNotify() {
+        debug_println("removeNotify Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
         SwingNodeHelper.runOnFxThread(() -> {
             if ((stage != null) && stage.isShowing()) {
                 stage.hide();
@@ -1006,16 +1048,18 @@ private class HostContainer implements HostInterface {
 
         @Override
         public void setEmbeddedStage(EmbeddedStageInterface embeddedStage) {
+            debug_println("HostContainer.setEmbeddedStage Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
             stagePeer = embeddedStage;
-            if (stagePeer == null) {
+            var hStagePeer = stagePeer;
+            if (hStagePeer == null) {
                 return;
             }
             if (pWidth > 0 && pHeight > 0) {
-                stagePeer.setSize(pWidth, pHeight);
+                hStagePeer.setSize(pWidth, pHeight);
             }
             invokeOnClientEDT(() -> {
-                if (stagePeer != null && JFXPanel.this.isFocusOwner()) {
-                    stagePeer.setFocused(true, AbstractEvents.FOCUSEVENT_ACTIVATED);
+                if (hStagePeer != null && JFXPanel.this.isFocusOwner()) {
+                    hStagePeer.setFocused(true, AbstractEvents.FOCUSEVENT_ACTIVATED);
                 }
             });
             sendMoveEventToFX();
@@ -1023,11 +1067,13 @@ public void setEmbeddedStage(EmbeddedStageInterface embeddedStage) {
 
         @Override
         public void setEmbeddedScene(EmbeddedSceneInterface embeddedScene) {
+            debug_println("HostContainer.setEmbeddedScene Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
             if (scenePeer == embeddedScene) {
                 return;
             }
             scenePeer = embeddedScene;
-            if (scenePeer == null) {
+            var hScenePeer = scenePeer;
+            if (hScenePeer == null) {
                 invokeOnClientEDT(() -> {
                     if (dnd != null) {
                         dnd.removeNotify();
@@ -1037,26 +1083,28 @@ public void setEmbeddedScene(EmbeddedSceneInterface embeddedScene) {
                 return;
             }
             if (pWidth > 0 && pHeight > 0) {
-                scenePeer.setSize(pWidth, pHeight);
+                hScenePeer.setSize(pWidth, pHeight);
             }
-            scenePeer.setPixelScaleFactors((float) scaleFactorX, (float) scaleFactorY);
+            hScenePeer.setPixelScaleFactors((float) scaleFactorX, (float) scaleFactorY);
 
             invokeOnClientEDT(() -> {
-                dnd = new SwingDnD(JFXPanel.this, scenePeer);
+                dnd = new SwingDnD(JFXPanel.this, hScenePeer);
                 dnd.addNotify();
-                if (scenePeer != null) {
-                    scenePeer.setDragStartListener(dnd.getDragStartListener());
+                if (hScenePeer != null) {
+                    hScenePeer.setDragStartListener(dnd.getDragStartListener());
                 }
             });
         }
 
         @Override
         public boolean requestFocus() {
+            debug_println("HostContainer.requestFocus Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
             return requestFocusInWindow();
         }
 
         @Override
         public boolean traverseFocusOut(boolean forward) {
+            debug_println("HostContainer.traverseFocusOut Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
             KeyboardFocusManager kfm = KeyboardFocusManager.getCurrentKeyboardFocusManager();
             if (forward) {
                 kfm.focusNextComponent(JFXPanel.this);
@@ -1068,6 +1116,7 @@ public boolean traverseFocusOut(boolean forward) {
 
         @Override
         public void setPreferredSize(final int width, final int height) {
+            debug_println("HostContainer.setPreferredSize Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
             invokeOnClientEDT(() -> {
                 JFXPanel.this.pPreferredWidth = width;
                 JFXPanel.this.pPreferredHeight = height;
@@ -1077,6 +1126,7 @@ public void setPreferredSize(final int width, final int height) {
 
         @Override
         public void repaint() {
+            debug_println("HostContainer.repaint Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
             invokeOnClientEDT(() -> {
                 JFXPanel.this.repaint();
             });
@@ -1084,11 +1134,13 @@ public void repaint() {
 
         @Override
         public void setEnabled(final boolean enabled) {
+            debug_println("HostContainer.setEnabled Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
             JFXPanel.this.setFxEnabled(enabled);
         }
 
         @Override
         public void setCursor(CursorFrame cursorFrame) {
+            debug_println("HostContainer.setCursor Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
             final Cursor cursor = getPlatformCursor(cursorFrame);
             invokeOnClientEDT(() -> {
                 JFXPanel.this.setCursor(cursor);
@@ -1113,6 +1165,7 @@ private Cursor getPlatformCursor(final CursorFrame cursorFrame) {
 
         @Override
         public boolean grabFocus() {
+            debug_println("HostContainer.grabFocus Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
             // On X11 grab is limited to a single XDisplay connection,
             // so we can't delegate it to another GUI toolkit.
             if (PlatformUtil.isLinux()) return true;
@@ -1129,6 +1182,7 @@ public boolean grabFocus() {
 
         @Override
         public void ungrabFocus() {
+            debug_println("HostContainer.ungrabFocus Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
             // On X11 grab is limited to a single XDisplay connection,
             // so we can't delegate it to another GUI toolkit.
             if (PlatformUtil.isLinux()) return;
diff --git a/tests/system/src/test/java/test/javafx/embed/swing/JFXPanelNPETest.java b/tests/system/src/test/java/test/javafx/embed/swing/JFXPanelNPETest.java
new file mode 100644
index 00000000000..e451a09deee
--- /dev/null
+++ b/tests/system/src/test/java/test/javafx/embed/swing/JFXPanelNPETest.java
@@ -0,0 +1,126 @@
+/*
+ * Copyright (c) 2025, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+package test.javafx.embed.swing;
+
+import javafx.application.Application;
+import javafx.application.Platform;
+import javafx.embed.swing.JFXPanel;
+import javafx.scene.Scene;
+import javafx.scene.web.WebView;
+import javafx.stage.Stage;
+
+import javax.swing.JFrame;
+import javax.swing.SwingUtilities;
+import javax.swing.WindowConstants;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.CountDownLatch;
+
+import org.junit.jupiter.api.AfterAll;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+
+import test.util.Util;
+
+public class JFXPanelNPETest {
+    private static WebView webView;
+    private static JFrame jFrame;
+    private static JFXPanel contentPane;
+    private static AtomicBoolean failure;
+    // Used to launch the application before running any test
+    private static final CountDownLatch launchLatch = new CountDownLatch(1);
+
+    // Application class. An instance is created and initialized before running
+    // the first test, and it lives through the execution of all tests.
+    public static class MyApp extends Application {
+        @Override
+        public void start(Stage primaryStage) throws Exception {
+            Platform.setImplicitExit(false);
+            Assertions.assertTrue(Platform.isFxApplicationThread());
+            Assertions.assertNotNull(primaryStage);
+
+            launchLatch.countDown();
+        }
+    }
+
+    @BeforeAll
+    public static void doSetupOnce() throws Exception {
+        Util.launch(launchLatch, MyApp.class);
+        Assertions.assertEquals(0, launchLatch.getCount());
+    }
+
+    @AfterAll
+    public static void doTeardownOnce() {
+        Util.shutdown();
+    }
+
+    @AfterEach
+    public void doCleanup() {
+        if (jFrame != null) {
+            SwingUtilities.invokeLater(() -> jFrame.dispose());
+        }
+    }
+
+    @Test
+    public void testSceneNPE() throws Exception {
+        failure = new AtomicBoolean(false);
+        Thread.setDefaultUncaughtExceptionHandler(new Thread.UncaughtExceptionHandler() {
+            @Override
+            public void uncaughtException(Thread t, Throwable e) {
+                e.printStackTrace();
+                failure.set(true);
+            }
+        });
+        SwingUtilities.invokeAndWait(JFXPanelNPETest::createUI);
+        for (int i = 0; i < 300; i++) {
+            SwingUtilities.invokeLater(contentPane::repaint);
+            Platform.runLater(() -> contentPane.setScene(null));
+            Thread.sleep(100);
+            Platform.runLater(() -> contentPane.setScene(webView.getScene()));
+            Thread.sleep(100);
+        }
+        System.out.println("failure = " + failure.get());
+        Assertions.assertFalse(failure.get());
+    }
+
+    protected static void createUI() {
+        jFrame = new JFrame();
+        contentPane = new JFXPanel();
+        Platform.runLater(() -> fx(contentPane));
+        jFrame.setContentPane(contentPane);
+        jFrame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
+        jFrame.setSize(400,400);
+        jFrame.setVisible(true);
+    }
+
+    private static void fx(final JFXPanel contentPane) {
+        webView = new WebView();
+        final var engine = webView.getEngine();
+        engine.loadContent("hello!");
+        contentPane.setScene(new Scene(webView));
+    }
+}
+

From 4cae04111079703a3b031601f52badd507f78ff4 Mon Sep 17 00:00:00 2001
From: Prasanta Sadhukhan <prasanta.sadhukhan@oracle.com>
Date: Tue, 11 Nov 2025 02:57:20 +0000
Subject: [PATCH 02/10] debug fix

---
 .../src/main/java/javafx/embed/swing/JFXPanel.java   | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/modules/javafx.swing/src/main/java/javafx/embed/swing/JFXPanel.java b/modules/javafx.swing/src/main/java/javafx/embed/swing/JFXPanel.java
index 4a62949bd85..a56fdea537b 100644
--- a/modules/javafx.swing/src/main/java/javafx/embed/swing/JFXPanel.java
+++ b/modules/javafx.swing/src/main/java/javafx/embed/swing/JFXPanel.java
@@ -205,17 +205,11 @@ public class JFXPanel extends JComponent {
     @SuppressWarnings("doclint:missing")
     private JFXPanelInteropN jfxPanelIOP;
 
-    private static final boolean debugPrint;
+    private static final boolean DEBUG = Boolean.getBoolean("jfxpanel.debug");
     private static final String debugPrefix = "JFXPanel:>> ";
-    private static final String JFXPANEL_DEBUG = "jfxpanel.debug";
-    static {
-        String debugStr = System.getProperty(JFXPANEL_DEBUG);
 
-        debugPrint = "true".equalsIgnoreCase(debugStr);
-    }
-
-    protected static void debug_println(String str) {
-        if (debugPrint) {
+    private static void debug_println(String str) {
+        if (DEBUG) {
             System.out.println(debugPrefix + " " + str);
         }
     }

From e29a2aff482edee56d4409b2825a9f58c1aa1d37 Mon Sep 17 00:00:00 2001
From: Prasanta Sadhukhan <prasanta.sadhukhan@oracle.com>
Date: Thu, 13 Nov 2025 03:24:14 +0000
Subject: [PATCH 03/10] debug log fix

---
 .../java/javafx/embed/swing/JFXPanel.java     | 154 ++++++++++++++----
 1 file changed, 121 insertions(+), 33 deletions(-)

diff --git a/modules/javafx.swing/src/main/java/javafx/embed/swing/JFXPanel.java b/modules/javafx.swing/src/main/java/javafx/embed/swing/JFXPanel.java
index a56fdea537b..d475cdee034 100644
--- a/modules/javafx.swing/src/main/java/javafx/embed/swing/JFXPanel.java
+++ b/modules/javafx.swing/src/main/java/javafx/embed/swing/JFXPanel.java
@@ -209,9 +209,7 @@ public class JFXPanel extends JComponent {
     private static final String debugPrefix = "JFXPanel:>> ";
 
     private static void debug_println(String str) {
-        if (DEBUG) {
-            System.out.println(debugPrefix + " " + str);
-        }
+        System.out.println(debugPrefix + " " + str);
     }
 
     private synchronized void registerFinishListener() {
@@ -283,7 +281,10 @@ private synchronized static void initFx() {
     public JFXPanel() {
         super();
 
-        debug_println("JFXPanel Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+        if (DEBUG) {
+            debug_println("JFXPanel Thread " + Thread.currentThread().getName() +
+                          " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+        }
         jfxPanelIOP = new JFXPanelInteropN();
         initFx();
 
@@ -309,7 +310,10 @@ public JFXPanel() {
      * @return the {@code Scene} attached to this {@code JFXPanel}
      */
     public Scene getScene() {
-        debug_println("getScene Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+        if (DEBUG) {
+            debug_println("getScene Thread " + Thread.currentThread().getName() +
+                          " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+        }
         return scene;
     }
 
@@ -324,7 +328,10 @@ public Scene getScene() {
      * @see javafx.application.Platform#isFxApplicationThread()
      */
     public void setScene(final Scene newScene) {
-        debug_println("setScene Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+        if (DEBUG) {
+            debug_println("setScene Thread " + Thread.currentThread().getName() +
+                          " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+        }
         if (Toolkit.getToolkit().isFxUserThread()) {
             setSceneImpl(newScene);
         } else {
@@ -372,7 +379,10 @@ private void setSceneImpl(Scene newScene) {
      */
     @Override
     public final void setOpaque(boolean opaque) {
-        debug_println("setOpaque Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+        if (DEBUG) {
+            debug_println("setOpaque Thread " + Thread.currentThread().getName() +
+                          " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+        }
         // Don't let user control opacity
         if (!opaque) {
             super.setOpaque(opaque);
@@ -389,7 +399,10 @@ public final void setOpaque(boolean opaque) {
      */
     @Override
     public final boolean isOpaque() {
-        debug_println("isOpaque Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+        if (DEBUG) {
+            debug_println("isOpaque Thread " + Thread.currentThread().getName() +
+                          " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+        }
         return false;
     }
 
@@ -520,7 +533,10 @@ private void sendMouseEventToFX(MouseEvent e) {
      */
     @Override
     protected void processMouseEvent(MouseEvent e) {
-        debug_println("processMouseEvent Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+        if (DEBUG) {
+            debug_println("processMouseEvent Thread " + Thread.currentThread().getName() +
+                          " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+        }
         if ((e.getID() == MouseEvent.MOUSE_PRESSED) &&
             (e.getButton() == MouseEvent.BUTTON1)) {
             if (isFocusable() && !hasFocus()) {
@@ -548,7 +564,10 @@ protected void processMouseEvent(MouseEvent e) {
      */
     @Override
     protected void processMouseMotionEvent(MouseEvent e) {
-        debug_println("processMouseMotionEvent Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+        if (DEBUG) {
+            debug_println("processMouseMotionEvent Thread " + Thread.currentThread().getName() +
+                          " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+        }
         sendMouseEventToFX(e);
         super.processMouseMotionEvent(e);
     }
@@ -563,7 +582,10 @@ protected void processMouseMotionEvent(MouseEvent e) {
      */
     @Override
     protected void processMouseWheelEvent(MouseWheelEvent e) {
-        debug_println("processMouseWheelEvent Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+        if (DEBUG) {
+            debug_println("processMouseWheelEvent Thread " + Thread.currentThread().getName() +
+                          " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+        }
         sendMouseEventToFX(e);
         super.processMouseWheelEvent(e);
     }
@@ -593,13 +615,19 @@ private void sendKeyEventToFX(final KeyEvent e) {
      */
     @Override
     protected void processKeyEvent(KeyEvent e) {
-        debug_println("processKeyEVent Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+        if (DEBUG) {
+            debug_println("processKeyEvent Thread " + Thread.currentThread().getName() +
+                          " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+        }
         sendKeyEventToFX(e);
         super.processKeyEvent(e);
     }
 
     private void sendResizeEventToFX() {
-        debug_println("sendResizeEventToFX Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+        if (DEBUG) {
+            debug_println("sendResizeEventToFX Thread " + Thread.currentThread().getName() +
+                          " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+        }
         if (stagePeer != null) {
             stagePeer.setSize(pWidth, pHeight);
         }
@@ -619,7 +647,10 @@ private void sendResizeEventToFX() {
      */
     @Override
     protected void processComponentEvent(ComponentEvent e) {
-        debug_println("processComponentEVent Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+        if (DEBUG) {
+            debug_println("processComponentEvent Thread " + Thread.currentThread().getName() +
+                          " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+        }
         switch (e.getID()) {
             case ComponentEvent.COMPONENT_RESIZED: {
                 updateComponentSize();
@@ -716,7 +747,10 @@ private void sendMoveEventToFX() {
      */
     @Override
     protected void processHierarchyBoundsEvent(HierarchyEvent e) {
-        debug_println("processHierarchyBoundsEVent Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+        if (DEBUG) {
+            debug_println("processHierarchyBoundsEvent Thread " + Thread.currentThread().getName() +
+                          " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+        }
         if (e.getID() == HierarchyEvent.ANCESTOR_MOVED) {
             if (updateScreenLocation()) {
                 sendMoveEventToFX();
@@ -727,7 +761,10 @@ protected void processHierarchyBoundsEvent(HierarchyEvent e) {
 
     @Override
     protected void processHierarchyEvent(HierarchyEvent e) {
-        debug_println("processHierarchyEVent Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+        if (DEBUG) {
+            debug_println("processHierarchyEvent Thread " + Thread.currentThread().getName() +
+                          " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+        }
         if ((e.getChangeFlags() & HierarchyEvent.SHOWING_CHANGED) != 0) {
             if (updateScreenLocation()) {
                 sendMoveEventToFX();
@@ -765,7 +802,10 @@ private void sendFocusEventToFX(final FocusEvent e) {
      */
     @Override
     protected void processFocusEvent(FocusEvent e) {
-        debug_println("processFocusEVent Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+        if (DEBUG) {
+            debug_println("processFocusEvent Thread " + Thread.currentThread().getName() +
+                          " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+        }
         sendFocusEventToFX(e);
         super.processFocusEvent(e);
     }
@@ -801,7 +841,10 @@ private void createResizePixelBuffer(double newScaleFactorX, double newScaleFact
 
     @Override
     protected void processInputMethodEvent(InputMethodEvent e) {
-        debug_println("processInputMethodEVent Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+        if (DEBUG) {
+            debug_println("processInputMethodEvent Thread " + Thread.currentThread().getName() +
+                          " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+        }
         if (e.getID() == InputMethodEvent.INPUT_METHOD_TEXT_CHANGED) {
             sendInputMethodEventToFX(e);
         }
@@ -833,7 +876,10 @@ private void sendInputMethodEventToFX(InputMethodEvent e) {
      */
     @Override
     protected synchronized void paintComponent(Graphics g) {
-        debug_println("paintComponent Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+        if (DEBUG) {
+            debug_println("paintComponent Thread " + Thread.currentThread().getName() +
+                          " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+        }
         var hScenePeer = scenePeer;
         var hStage = stage;
         if (hScenePeer == null || hStage == null) {
@@ -901,7 +947,10 @@ protected synchronized void paintComponent(Graphics g) {
      */
     @Override
     public Dimension getPreferredSize() {
-        debug_println("getPreferredSize Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+        if (DEBUG) {
+            debug_println("getPreferredSize Thread " + Thread.currentThread().getName() +
+                          " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+        }
         if (isPreferredSizeSet() || scenePeer == null) {
             return super.getPreferredSize();
         }
@@ -976,7 +1025,10 @@ private void setFxEnabled(boolean enabled) {
      */
     @Override
     public void addNotify() {
-        debug_println("addNotify Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+        if (DEBUG) {
+            debug_println("addNotify Thread " + Thread.currentThread().getName() +
+                          " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+        }
         super.addNotify();
 
         registerFinishListener();
@@ -994,7 +1046,10 @@ public void addNotify() {
 
     @Override
     public InputMethodRequests getInputMethodRequests() {
-        debug_println("getInputMethodRequests Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+        if (DEBUG) {
+            debug_println("getInputMethodRequests Thread " + Thread.currentThread().getName() +
+                          " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+        }
         EmbeddedSceneInterface scene = scenePeer;
         if (scene == null) {
             return new InputMethodSupport.InputMethodRequestsAdapter(null);
@@ -1008,7 +1063,10 @@ public InputMethodRequests getInputMethodRequests() {
      * chain of parent components are removed.
      */
     @Override public void removeNotify() {
-        debug_println("removeNotify Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+        if (DEBUG) {
+            debug_println("removeNotify Thread " + Thread.currentThread().getName() +
+                          " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+        }
         SwingNodeHelper.runOnFxThread(() -> {
             if ((stage != null) && stage.isShowing()) {
                 stage.hide();
@@ -1042,7 +1100,10 @@ private class HostContainer implements HostInterface {
 
         @Override
         public void setEmbeddedStage(EmbeddedStageInterface embeddedStage) {
-            debug_println("HostContainer.setEmbeddedStage Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+            if (DEBUG) {
+                debug_println("HostContainer.setEmbeddedStage Thread " + Thread.currentThread().getName() +
+                              " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+            }
             stagePeer = embeddedStage;
             var hStagePeer = stagePeer;
             if (hStagePeer == null) {
@@ -1061,7 +1122,10 @@ public void setEmbeddedStage(EmbeddedStageInterface embeddedStage) {
 
         @Override
         public void setEmbeddedScene(EmbeddedSceneInterface embeddedScene) {
-            debug_println("HostContainer.setEmbeddedScene Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+            if (DEBUG) {
+                debug_println("HostContainer.setEmbeddedScene Thread " + Thread.currentThread().getName() +
+                              " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+            }
             if (scenePeer == embeddedScene) {
                 return;
             }
@@ -1092,13 +1156,19 @@ public void setEmbeddedScene(EmbeddedSceneInterface embeddedScene) {
 
         @Override
         public boolean requestFocus() {
-            debug_println("HostContainer.requestFocus Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+            if (DEBUG) {
+                debug_println("HostContainer.requestFocus Thread " + Thread.currentThread().getName() +
+                              " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+            }
             return requestFocusInWindow();
         }
 
         @Override
         public boolean traverseFocusOut(boolean forward) {
-            debug_println("HostContainer.traverseFocusOut Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+            if (DEBUG) {
+                debug_println("HostContainer.traverseFocusOut Thread " + Thread.currentThread().getName() +
+                              " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+            }
             KeyboardFocusManager kfm = KeyboardFocusManager.getCurrentKeyboardFocusManager();
             if (forward) {
                 kfm.focusNextComponent(JFXPanel.this);
@@ -1110,7 +1180,10 @@ public boolean traverseFocusOut(boolean forward) {
 
         @Override
         public void setPreferredSize(final int width, final int height) {
-            debug_println("HostContainer.setPreferredSize Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+            if (DEBUG) {
+                debug_println("HostContainer.setPreferredSize Thread " + Thread.currentThread().getName() +
+                              " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+            }
             invokeOnClientEDT(() -> {
                 JFXPanel.this.pPreferredWidth = width;
                 JFXPanel.this.pPreferredHeight = height;
@@ -1120,7 +1193,10 @@ public void setPreferredSize(final int width, final int height) {
 
         @Override
         public void repaint() {
-            debug_println("HostContainer.repaint Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+            if (DEBUG) {
+                debug_println("HostContainer.repaint Thread " + Thread.currentThread().getName() +
+                              " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+            }
             invokeOnClientEDT(() -> {
                 JFXPanel.this.repaint();
             });
@@ -1128,13 +1204,19 @@ public void repaint() {
 
         @Override
         public void setEnabled(final boolean enabled) {
-            debug_println("HostContainer.setEnabled Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+            if (DEBUG) {
+                debug_println("HostContainer.setEnabled Thread " + Thread.currentThread().getName() +
+                              " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+            }
             JFXPanel.this.setFxEnabled(enabled);
         }
 
         @Override
         public void setCursor(CursorFrame cursorFrame) {
-            debug_println("HostContainer.setCursor Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+            if (DEBUG) {
+                debug_println("HostContainer.setCursor Thread " + Thread.currentThread().getName() +
+                              " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+            }
             final Cursor cursor = getPlatformCursor(cursorFrame);
             invokeOnClientEDT(() -> {
                 JFXPanel.this.setCursor(cursor);
@@ -1159,7 +1241,10 @@ private Cursor getPlatformCursor(final CursorFrame cursorFrame) {
 
         @Override
         public boolean grabFocus() {
-            debug_println("HostContainer.grabFocus Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+            if (DEBUG) {
+                debug_println("HostContainer.grabFocus Thread " + Thread.currentThread().getName() +
+                              " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+            }
             // On X11 grab is limited to a single XDisplay connection,
             // so we can't delegate it to another GUI toolkit.
             if (PlatformUtil.isLinux()) return true;
@@ -1176,7 +1261,10 @@ public boolean grabFocus() {
 
         @Override
         public void ungrabFocus() {
-            debug_println("HostContainer.ungrabFocus Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+            if (DEBUG) {
+                debug_println("HostContainer.ungrabFocus Thread " + Thread.currentThread().getName() +
+                              " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
+            }
             // On X11 grab is limited to a single XDisplay connection,
             // so we can't delegate it to another GUI toolkit.
             if (PlatformUtil.isLinux()) return;

From 115001f6c92b587574c67624f0033cabaabe04d0 Mon Sep 17 00:00:00 2001
From: Prasanta Sadhukhan <prasanta.sadhukhan@oracle.com>
Date: Thu, 13 Nov 2025 03:25:46 +0000
Subject: [PATCH 04/10] debug log fix

---
 .../javafx.swing/src/main/java/javafx/embed/swing/JFXPanel.java  | 1 -
 1 file changed, 1 deletion(-)

diff --git a/modules/javafx.swing/src/main/java/javafx/embed/swing/JFXPanel.java b/modules/javafx.swing/src/main/java/javafx/embed/swing/JFXPanel.java
index d475cdee034..405058f5995 100644
--- a/modules/javafx.swing/src/main/java/javafx/embed/swing/JFXPanel.java
+++ b/modules/javafx.swing/src/main/java/javafx/embed/swing/JFXPanel.java
@@ -680,7 +680,6 @@ private AffineTransform getCurrentTransform() {
 
     // called on EDT only
     private void updateComponentSize() {
-        debug_println("updateComponentSize Thread " + Thread.currentThread().getName() + " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
         int oldWidth = pWidth;
         int oldHeight = pHeight;
         if (getBorder() != null) {

From 7bf8a91e364aeed228738d963688f2b0a094ecc6 Mon Sep 17 00:00:00 2001
From: Prasanta Sadhukhan <prasanta.sadhukhan@oracle.com>
Date: Mon, 17 Nov 2025 16:31:41 +0000
Subject: [PATCH 05/10] Remove debug, store transient var in temp var in EDT
 methods

---
 .../java/javafx/embed/swing/JFXPanel.java     | 176 +++---------------
 1 file changed, 26 insertions(+), 150 deletions(-)

diff --git a/modules/javafx.swing/src/main/java/javafx/embed/swing/JFXPanel.java b/modules/javafx.swing/src/main/java/javafx/embed/swing/JFXPanel.java
index 405058f5995..491372c0f9e 100644
--- a/modules/javafx.swing/src/main/java/javafx/embed/swing/JFXPanel.java
+++ b/modules/javafx.swing/src/main/java/javafx/embed/swing/JFXPanel.java
@@ -205,13 +205,6 @@ public class JFXPanel extends JComponent {
     @SuppressWarnings("doclint:missing")
     private JFXPanelInteropN jfxPanelIOP;
 
-    private static final boolean DEBUG = Boolean.getBoolean("jfxpanel.debug");
-    private static final String debugPrefix = "JFXPanel:>> ";
-
-    private static void debug_println(String str) {
-        System.out.println(debugPrefix + " " + str);
-    }
-
     private synchronized void registerFinishListener() {
         if (instanceCount.getAndIncrement() > 0) {
             // Already registered
@@ -281,10 +274,6 @@ private synchronized static void initFx() {
     public JFXPanel() {
         super();
 
-        if (DEBUG) {
-            debug_println("JFXPanel Thread " + Thread.currentThread().getName() +
-                          " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
-        }
         jfxPanelIOP = new JFXPanelInteropN();
         initFx();
 
@@ -310,10 +299,6 @@ public JFXPanel() {
      * @return the {@code Scene} attached to this {@code JFXPanel}
      */
     public Scene getScene() {
-        if (DEBUG) {
-            debug_println("getScene Thread " + Thread.currentThread().getName() +
-                          " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
-        }
         return scene;
     }
 
@@ -328,10 +313,6 @@ public Scene getScene() {
      * @see javafx.application.Platform#isFxApplicationThread()
      */
     public void setScene(final Scene newScene) {
-        if (DEBUG) {
-            debug_println("setScene Thread " + Thread.currentThread().getName() +
-                          " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
-        }
         if (Toolkit.getToolkit().isFxUserThread()) {
             setSceneImpl(newScene);
         } else {
@@ -379,10 +360,6 @@ private void setSceneImpl(Scene newScene) {
      */
     @Override
     public final void setOpaque(boolean opaque) {
-        if (DEBUG) {
-            debug_println("setOpaque Thread " + Thread.currentThread().getName() +
-                          " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
-        }
         // Don't let user control opacity
         if (!opaque) {
             super.setOpaque(opaque);
@@ -399,10 +376,6 @@ public final void setOpaque(boolean opaque) {
      */
     @Override
     public final boolean isOpaque() {
-        if (DEBUG) {
-            debug_println("isOpaque Thread " + Thread.currentThread().getName() +
-                          " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
-        }
         return false;
     }
 
@@ -533,10 +506,7 @@ private void sendMouseEventToFX(MouseEvent e) {
      */
     @Override
     protected void processMouseEvent(MouseEvent e) {
-        if (DEBUG) {
-            debug_println("processMouseEvent Thread " + Thread.currentThread().getName() +
-                          " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
-        }
+        var hStagePeer = stagePeer;
         if ((e.getID() == MouseEvent.MOUSE_PRESSED) &&
             (e.getButton() == MouseEvent.BUTTON1)) {
             if (isFocusable() && !hasFocus()) {
@@ -544,9 +514,9 @@ protected void processMouseEvent(MouseEvent e) {
                 // The extra simulated mouse pressed event is removed by making the JavaFX scene focused.
                 // It is safe, because in JavaFX only the method "setFocused(true)" is called,
                 // which doesn't have any side-effects when called multiple times.
-                if (stagePeer != null) {
+                if (hStagePeer != null) {
                     int focusCause = AbstractEvents.FOCUSEVENT_ACTIVATED;
-                    stagePeer.setFocused(true, focusCause);
+                    hStagePeer.setFocused(true, focusCause);
                 }
             }
         }
@@ -564,10 +534,6 @@ protected void processMouseEvent(MouseEvent e) {
      */
     @Override
     protected void processMouseMotionEvent(MouseEvent e) {
-        if (DEBUG) {
-            debug_println("processMouseMotionEvent Thread " + Thread.currentThread().getName() +
-                          " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
-        }
         sendMouseEventToFX(e);
         super.processMouseMotionEvent(e);
     }
@@ -582,10 +548,6 @@ protected void processMouseMotionEvent(MouseEvent e) {
      */
     @Override
     protected void processMouseWheelEvent(MouseWheelEvent e) {
-        if (DEBUG) {
-            debug_println("processMouseWheelEvent Thread " + Thread.currentThread().getName() +
-                          " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
-        }
         sendMouseEventToFX(e);
         super.processMouseWheelEvent(e);
     }
@@ -615,24 +577,18 @@ private void sendKeyEventToFX(final KeyEvent e) {
      */
     @Override
     protected void processKeyEvent(KeyEvent e) {
-        if (DEBUG) {
-            debug_println("processKeyEvent Thread " + Thread.currentThread().getName() +
-                          " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
-        }
         sendKeyEventToFX(e);
         super.processKeyEvent(e);
     }
 
     private void sendResizeEventToFX() {
-        if (DEBUG) {
-            debug_println("sendResizeEventToFX Thread " + Thread.currentThread().getName() +
-                          " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
-        }
-        if (stagePeer != null) {
-            stagePeer.setSize(pWidth, pHeight);
+        var hStagePeer = stagePeer;
+        var hScenePeer = scenePeer;
+        if (hStagePeer != null) {
+            hStagePeer.setSize(pWidth, pHeight);
         }
-        if (scenePeer != null) {
-            scenePeer.setSize(pWidth, pHeight);
+        if (hScenePeer != null) {
+            hScenePeer.setSize(pWidth, pHeight);
         }
     }
 
@@ -647,10 +603,6 @@ private void sendResizeEventToFX() {
      */
     @Override
     protected void processComponentEvent(ComponentEvent e) {
-        if (DEBUG) {
-            debug_println("processComponentEvent Thread " + Thread.currentThread().getName() +
-                          " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
-        }
         switch (e.getID()) {
             case ComponentEvent.COMPONENT_RESIZED: {
                 updateComponentSize();
@@ -728,11 +680,9 @@ private boolean updateScreenLocation() {
     }
 
     private void sendMoveEventToFX() {
-        if (stagePeer == null) {
-            return;
+        if (stagePeer != null) {
+            stagePeer.setLocation(screenX, screenY);
         }
-
-        stagePeer.setLocation(screenX, screenY);
     }
 
     /**
@@ -746,10 +696,6 @@ private void sendMoveEventToFX() {
      */
     @Override
     protected void processHierarchyBoundsEvent(HierarchyEvent e) {
-        if (DEBUG) {
-            debug_println("processHierarchyBoundsEvent Thread " + Thread.currentThread().getName() +
-                          " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
-        }
         if (e.getID() == HierarchyEvent.ANCESTOR_MOVED) {
             if (updateScreenLocation()) {
                 sendMoveEventToFX();
@@ -760,10 +706,6 @@ protected void processHierarchyBoundsEvent(HierarchyEvent e) {
 
     @Override
     protected void processHierarchyEvent(HierarchyEvent e) {
-        if (DEBUG) {
-            debug_println("processHierarchyEvent Thread " + Thread.currentThread().getName() +
-                          " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
-        }
         if ((e.getChangeFlags() & HierarchyEvent.SHOWING_CHANGED) != 0) {
             if (updateScreenLocation()) {
                 sendMoveEventToFX();
@@ -773,7 +715,8 @@ protected void processHierarchyEvent(HierarchyEvent e) {
     }
 
     private void sendFocusEventToFX(final FocusEvent e) {
-        if ((stage == null) || (stagePeer == null) || !isFxEnabled()) {
+        var hStagePeer = stagePeer;
+        if ((stage == null) || (hStagePeer == null) || !isFxEnabled()) {
             return;
         }
 
@@ -788,7 +731,7 @@ private void sendFocusEventToFX(final FocusEvent e) {
                 focusCause = AbstractEvents.FOCUSEVENT_TRAVERSED_BACKWARD;
             }
         }
-        stagePeer.setFocused(focused, focusCause);
+        hStagePeer.setFocused(focused, focusCause);
     }
 
     /**
@@ -801,10 +744,6 @@ private void sendFocusEventToFX(final FocusEvent e) {
      */
     @Override
     protected void processFocusEvent(FocusEvent e) {
-        if (DEBUG) {
-            debug_println("processFocusEvent Thread " + Thread.currentThread().getName() +
-                          " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
-        }
         sendFocusEventToFX(e);
         super.processFocusEvent(e);
     }
@@ -840,10 +779,6 @@ private void createResizePixelBuffer(double newScaleFactorX, double newScaleFact
 
     @Override
     protected void processInputMethodEvent(InputMethodEvent e) {
-        if (DEBUG) {
-            debug_println("processInputMethodEvent Thread " + Thread.currentThread().getName() +
-                          " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
-        }
         if (e.getID() == InputMethodEvent.INPUT_METHOD_TEXT_CHANGED) {
             sendInputMethodEventToFX(e);
         }
@@ -857,11 +792,13 @@ private void sendInputMethodEventToFX(InputMethodEvent e) {
         if (e.getCaret() != null) {
             insertionIndex = e.getCaret().getInsertionIndex();
         }
-        scenePeer.inputMethodEvent(
-                javafx.scene.input.InputMethodEvent.INPUT_METHOD_TEXT_CHANGED,
-                InputMethodSupport.inputMethodEventComposed(t, e.getCommittedCharacterCount()),
-                t.substring(0, e.getCommittedCharacterCount()),
-                insertionIndex);
+        if (scenePeer != null) {
+            scenePeer.inputMethodEvent(
+                    javafx.scene.input.InputMethodEvent.INPUT_METHOD_TEXT_CHANGED,
+                    InputMethodSupport.inputMethodEventComposed(t, e.getCommittedCharacterCount()),
+                    t.substring(0, e.getCommittedCharacterCount()),
+                    insertionIndex);
+        }
     }
 
     /**
@@ -874,14 +811,9 @@ private void sendInputMethodEventToFX(InputMethodEvent e) {
      * @see #isOpaque()
      */
     @Override
-    protected synchronized void paintComponent(Graphics g) {
-        if (DEBUG) {
-            debug_println("paintComponent Thread " + Thread.currentThread().getName() +
-                          " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
-        }
+    protected void paintComponent(Graphics g) {
         var hScenePeer = scenePeer;
-        var hStage = stage;
-        if (hScenePeer == null || hStage == null) {
+        if (hScenePeer == null || stage == null) {
             return;
         }
         if (pixelsIm == null) {
@@ -901,7 +833,7 @@ protected synchronized void paintComponent(Graphics g) {
         try {
             ComponentOrientation cor = this.getComponentOrientation();
             boolean rtl = ComponentOrientation.RIGHT_TO_LEFT.equals(cor);
-            hStage.setNodeOrientation(rtl ? NodeOrientation.RIGHT_TO_LEFT :
+            stage.setNodeOrientation(rtl ? NodeOrientation.RIGHT_TO_LEFT :
                                            NodeOrientation.LEFT_TO_RIGHT);
 
             gg = g.create();
@@ -946,10 +878,6 @@ protected synchronized void paintComponent(Graphics g) {
      */
     @Override
     public Dimension getPreferredSize() {
-        if (DEBUG) {
-            debug_println("getPreferredSize Thread " + Thread.currentThread().getName() +
-                          " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
-        }
         if (isPreferredSizeSet() || scenePeer == null) {
             return super.getPreferredSize();
         }
@@ -1024,10 +952,6 @@ private void setFxEnabled(boolean enabled) {
      */
     @Override
     public void addNotify() {
-        if (DEBUG) {
-            debug_println("addNotify Thread " + Thread.currentThread().getName() +
-                          " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
-        }
         super.addNotify();
 
         registerFinishListener();
@@ -1038,17 +962,13 @@ public void addNotify() {
         SwingNodeHelper.runOnFxThread(() -> {
             if ((stage != null) && !stage.isShowing()) {
                 stage.show();
-                sendMoveEventToFX();
             }
         });
+        sendMoveEventToFX();
     }
 
     @Override
     public InputMethodRequests getInputMethodRequests() {
-        if (DEBUG) {
-            debug_println("getInputMethodRequests Thread " + Thread.currentThread().getName() +
-                          " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
-        }
         EmbeddedSceneInterface scene = scenePeer;
         if (scene == null) {
             return new InputMethodSupport.InputMethodRequestsAdapter(null);
@@ -1062,10 +982,6 @@ public InputMethodRequests getInputMethodRequests() {
      * chain of parent components are removed.
      */
     @Override public void removeNotify() {
-        if (DEBUG) {
-            debug_println("removeNotify Thread " + Thread.currentThread().getName() +
-                          " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
-        }
         SwingNodeHelper.runOnFxThread(() -> {
             if ((stage != null) && stage.isShowing()) {
                 stage.hide();
@@ -1099,10 +1015,6 @@ private class HostContainer implements HostInterface {
 
         @Override
         public void setEmbeddedStage(EmbeddedStageInterface embeddedStage) {
-            if (DEBUG) {
-                debug_println("HostContainer.setEmbeddedStage Thread " + Thread.currentThread().getName() +
-                              " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
-            }
             stagePeer = embeddedStage;
             var hStagePeer = stagePeer;
             if (hStagePeer == null) {
@@ -1115,16 +1027,12 @@ public void setEmbeddedStage(EmbeddedStageInterface embeddedStage) {
                 if (hStagePeer != null && JFXPanel.this.isFocusOwner()) {
                     hStagePeer.setFocused(true, AbstractEvents.FOCUSEVENT_ACTIVATED);
                 }
+                sendMoveEventToFX();
             });
-            sendMoveEventToFX();
         }
 
         @Override
         public void setEmbeddedScene(EmbeddedSceneInterface embeddedScene) {
-            if (DEBUG) {
-                debug_println("HostContainer.setEmbeddedScene Thread " + Thread.currentThread().getName() +
-                              " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
-            }
             if (scenePeer == embeddedScene) {
                 return;
             }
@@ -1155,19 +1063,11 @@ public void setEmbeddedScene(EmbeddedSceneInterface embeddedScene) {
 
         @Override
         public boolean requestFocus() {
-            if (DEBUG) {
-                debug_println("HostContainer.requestFocus Thread " + Thread.currentThread().getName() +
-                              " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
-            }
             return requestFocusInWindow();
         }
 
         @Override
         public boolean traverseFocusOut(boolean forward) {
-            if (DEBUG) {
-                debug_println("HostContainer.traverseFocusOut Thread " + Thread.currentThread().getName() +
-                              " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
-            }
             KeyboardFocusManager kfm = KeyboardFocusManager.getCurrentKeyboardFocusManager();
             if (forward) {
                 kfm.focusNextComponent(JFXPanel.this);
@@ -1179,10 +1079,6 @@ public boolean traverseFocusOut(boolean forward) {
 
         @Override
         public void setPreferredSize(final int width, final int height) {
-            if (DEBUG) {
-                debug_println("HostContainer.setPreferredSize Thread " + Thread.currentThread().getName() +
-                              " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
-            }
             invokeOnClientEDT(() -> {
                 JFXPanel.this.pPreferredWidth = width;
                 JFXPanel.this.pPreferredHeight = height;
@@ -1192,10 +1088,6 @@ public void setPreferredSize(final int width, final int height) {
 
         @Override
         public void repaint() {
-            if (DEBUG) {
-                debug_println("HostContainer.repaint Thread " + Thread.currentThread().getName() +
-                              " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
-            }
             invokeOnClientEDT(() -> {
                 JFXPanel.this.repaint();
             });
@@ -1203,19 +1095,11 @@ public void repaint() {
 
         @Override
         public void setEnabled(final boolean enabled) {
-            if (DEBUG) {
-                debug_println("HostContainer.setEnabled Thread " + Thread.currentThread().getName() +
-                              " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
-            }
             JFXPanel.this.setFxEnabled(enabled);
         }
 
         @Override
         public void setCursor(CursorFrame cursorFrame) {
-            if (DEBUG) {
-                debug_println("HostContainer.setCursor Thread " + Thread.currentThread().getName() +
-                              " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
-            }
             final Cursor cursor = getPlatformCursor(cursorFrame);
             invokeOnClientEDT(() -> {
                 JFXPanel.this.setCursor(cursor);
@@ -1240,10 +1124,6 @@ private Cursor getPlatformCursor(final CursorFrame cursorFrame) {
 
         @Override
         public boolean grabFocus() {
-            if (DEBUG) {
-                debug_println("HostContainer.grabFocus Thread " + Thread.currentThread().getName() +
-                              " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
-            }
             // On X11 grab is limited to a single XDisplay connection,
             // so we can't delegate it to another GUI toolkit.
             if (PlatformUtil.isLinux()) return true;
@@ -1260,10 +1140,6 @@ public boolean grabFocus() {
 
         @Override
         public void ungrabFocus() {
-            if (DEBUG) {
-                debug_println("HostContainer.ungrabFocus Thread " + Thread.currentThread().getName() +
-                              " isFXUserThread " + Toolkit.getToolkit().isFxUserThread());
-            }
             // On X11 grab is limited to a single XDisplay connection,
             // so we can't delegate it to another GUI toolkit.
             if (PlatformUtil.isLinux()) return;

From fc830a7effba76949bda37104d5893b60da9bb2b Mon Sep 17 00:00:00 2001
From: Prasanta Sadhukhan <prasanta.sadhukhan@oracle.com>
Date: Tue, 18 Nov 2025 13:20:04 +0000
Subject: [PATCH 06/10] temp-var handling in few other methods

---
 .../java/javafx/embed/swing/JFXPanel.java     | 82 ++++++++++++++++---
 1 file changed, 70 insertions(+), 12 deletions(-)

diff --git a/modules/javafx.swing/src/main/java/javafx/embed/swing/JFXPanel.java b/modules/javafx.swing/src/main/java/javafx/embed/swing/JFXPanel.java
index 491372c0f9e..6b78e8b973d 100644
--- a/modules/javafx.swing/src/main/java/javafx/embed/swing/JFXPanel.java
+++ b/modules/javafx.swing/src/main/java/javafx/embed/swing/JFXPanel.java
@@ -150,12 +150,15 @@ public class JFXPanel extends JComponent {
 
     private transient HostContainer hostContainer;
 
+    // Set in FX thread and accessed in EDT/FX threads
     private transient volatile EmbeddedWindow stage;
+
     private transient volatile Scene scene;
 
     // Accessed on EDT only
     private transient SwingDnD dnd;
 
+    // Set in FX thread and accessed in EDT/FX threads
     private transient EmbeddedStageInterface stagePeer;
     private transient EmbeddedSceneInterface scenePeer;
 
@@ -417,6 +420,7 @@ private Point2D convertSwingToFxPixel(GraphicsConfiguration g, double wx, double
         return new Point2D(newx, newy);
     }
 
+    // Called on EDT thread
     private void sendMouseEventToFX(MouseEvent e) {
         var hScenePeer = scenePeer;
         if (hScenePeer == null || !isFxEnabled()) {
@@ -506,6 +510,9 @@ private void sendMouseEventToFX(MouseEvent e) {
      */
     @Override
     protected void processMouseEvent(MouseEvent e) {
+
+        // Called on EDT thread.
+
         var hStagePeer = stagePeer;
         if ((e.getID() == MouseEvent.MOUSE_PRESSED) &&
             (e.getButton() == MouseEvent.BUTTON1)) {
@@ -534,6 +541,9 @@ protected void processMouseEvent(MouseEvent e) {
      */
     @Override
     protected void processMouseMotionEvent(MouseEvent e) {
+
+        // Called on EDT thread.
+
         sendMouseEventToFX(e);
         super.processMouseMotionEvent(e);
     }
@@ -548,11 +558,17 @@ protected void processMouseMotionEvent(MouseEvent e) {
      */
     @Override
     protected void processMouseWheelEvent(MouseWheelEvent e) {
+
+        // Called on EDT thread.
+
         sendMouseEventToFX(e);
         super.processMouseWheelEvent(e);
     }
 
     private void sendKeyEventToFX(final KeyEvent e) {
+
+        // Called on EDT thread.
+
         var hScenePeer = scenePeer;
         if (hScenePeer == null || !isFxEnabled()) {
             return;
@@ -577,11 +593,17 @@ private void sendKeyEventToFX(final KeyEvent e) {
      */
     @Override
     protected void processKeyEvent(KeyEvent e) {
+
+        // Called on EDT thread.
+
         sendKeyEventToFX(e);
         super.processKeyEvent(e);
     }
 
     private void sendResizeEventToFX() {
+
+        // Called on EDT thread.
+
         var hStagePeer = stagePeer;
         var hScenePeer = scenePeer;
         if (hStagePeer != null) {
@@ -603,6 +625,9 @@ private void sendResizeEventToFX() {
      */
     @Override
     protected void processComponentEvent(ComponentEvent e) {
+
+        // Called on EDT thread.
+
         switch (e.getID()) {
             case ComponentEvent.COMPONENT_RESIZED: {
                 updateComponentSize();
@@ -657,7 +682,7 @@ private void updateComponentSize() {
             var hScenePeer = scenePeer;
             if (hScenePeer != null) {
                 hScenePeer.setPixelScaleFactors((float) newScaleFactorX,
-                                               (float) newScaleFactorY);
+                                                (float) newScaleFactorY);
             }
             scaleFactorX = newScaleFactorX;
             scaleFactorY = newScaleFactorY;
@@ -680,8 +705,12 @@ private boolean updateScreenLocation() {
     }
 
     private void sendMoveEventToFX() {
-        if (stagePeer != null) {
-            stagePeer.setLocation(screenX, screenY);
+
+        // Called on EDT thread.
+
+        var hStagePeer = stagePeer;
+        if (hStagePeer != null) {
+            hStagePeer.setLocation(screenX, screenY);
         }
     }
 
@@ -696,6 +725,9 @@ private void sendMoveEventToFX() {
      */
     @Override
     protected void processHierarchyBoundsEvent(HierarchyEvent e) {
+
+        // Called on EDT thread.
+
         if (e.getID() == HierarchyEvent.ANCESTOR_MOVED) {
             if (updateScreenLocation()) {
                 sendMoveEventToFX();
@@ -706,6 +738,9 @@ protected void processHierarchyBoundsEvent(HierarchyEvent e) {
 
     @Override
     protected void processHierarchyEvent(HierarchyEvent e) {
+
+        // Called on EDT thread.
+
         if ((e.getChangeFlags() & HierarchyEvent.SHOWING_CHANGED) != 0) {
             if (updateScreenLocation()) {
                 sendMoveEventToFX();
@@ -715,6 +750,9 @@ protected void processHierarchyEvent(HierarchyEvent e) {
     }
 
     private void sendFocusEventToFX(final FocusEvent e) {
+
+        // Called on EDT thread.
+
         var hStagePeer = stagePeer;
         if ((stage == null) || (hStagePeer == null) || !isFxEnabled()) {
             return;
@@ -744,6 +782,9 @@ private void sendFocusEventToFX(final FocusEvent e) {
      */
     @Override
     protected void processFocusEvent(FocusEvent e) {
+
+        // Called on EDT thread.
+
         sendFocusEventToFX(e);
         super.processFocusEvent(e);
     }
@@ -779,6 +820,9 @@ private void createResizePixelBuffer(double newScaleFactorX, double newScaleFact
 
     @Override
     protected void processInputMethodEvent(InputMethodEvent e) {
+
+        // Called on EDT thread.
+
         if (e.getID() == InputMethodEvent.INPUT_METHOD_TEXT_CHANGED) {
             sendInputMethodEventToFX(e);
         }
@@ -786,14 +830,18 @@ protected void processInputMethodEvent(InputMethodEvent e) {
     }
 
     private void sendInputMethodEventToFX(InputMethodEvent e) {
+
+        // Called on EDT thread.
+
         String t = InputMethodSupport.getTextForEvent(e);
 
         int insertionIndex = 0;
         if (e.getCaret() != null) {
             insertionIndex = e.getCaret().getInsertionIndex();
         }
-        if (scenePeer != null) {
-            scenePeer.inputMethodEvent(
+        var hScenePeer = scenePeer;
+        if (hScenePeer != null) {
+            hScenePeer.inputMethodEvent(
                     javafx.scene.input.InputMethodEvent.INPUT_METHOD_TEXT_CHANGED,
                     InputMethodSupport.inputMethodEventComposed(t, e.getCommittedCharacterCount()),
                     t.substring(0, e.getCommittedCharacterCount()),
@@ -812,8 +860,14 @@ private void sendInputMethodEventToFX(InputMethodEvent e) {
      */
     @Override
     protected void paintComponent(Graphics g) {
+
+        // Called on EDT thread.
+
+        // scenePeer, stage set in FX thread and being accessed in EDT
         var hScenePeer = scenePeer;
-        if (hScenePeer == null || stage == null) {
+        var hStage = stage;
+
+        if (hScenePeer == null || hStage == null) {
             return;
         }
         if (pixelsIm == null) {
@@ -833,7 +887,7 @@ protected void paintComponent(Graphics g) {
         try {
             ComponentOrientation cor = this.getComponentOrientation();
             boolean rtl = ComponentOrientation.RIGHT_TO_LEFT.equals(cor);
-            stage.setNodeOrientation(rtl ? NodeOrientation.RIGHT_TO_LEFT :
+            hStage.setNodeOrientation(rtl ? NodeOrientation.RIGHT_TO_LEFT :
                                            NodeOrientation.LEFT_TO_RIGHT);
 
             gg = g.create();
@@ -855,7 +909,7 @@ protected void paintComponent(Graphics g) {
                 createResizePixelBuffer(newScaleFactorX, newScaleFactorY);
                 // The scene will request repaint.
                 hScenePeer.setPixelScaleFactors((float) newScaleFactorX,
-                                               (float) newScaleFactorY);
+                                                (float) newScaleFactorY);
                 scaleFactorX = newScaleFactorX;
                 scaleFactorY = newScaleFactorY;
             }
@@ -909,13 +963,15 @@ private void setFxEnabled(boolean enabled) {
     }
 
     private transient  AWTEventListener ungrabListener = event -> {
+        var hStagePeer = JFXPanel.this.stagePeer;
+
         if (jfxPanelIOP.isUngrabEvent(event)) {
             SwingNodeHelper.runOnFxThread(() -> {
-                if (JFXPanel.this.stagePeer != null &&
+                if (hStagePeer != null &&
                         getScene() != null &&
                         getScene().getFocusOwner() != null &&
                         getScene().getFocusOwner().isFocused()) {
-                    JFXPanel.this.stagePeer.focusUngrab();
+                    hStagePeer.focusUngrab();
                 }
             });
         }
@@ -929,7 +985,7 @@ private void setFxEnabled(boolean enabled) {
 
                 if (jfxPanelWindow == eventWindow) {
                     SwingNodeHelper.runOnFxThread(() -> {
-                        if (JFXPanel.this.stagePeer != null) {
+                        if (hStagePeer != null) {
                             // No need to check if grab is active or not.
                             // NoAutoHide popups don't request the grab and
                             // ignore the Ungrab event anyway.
@@ -937,7 +993,7 @@ private void setFxEnabled(boolean enabled) {
                             // user clicks some non-FX content, even if for
                             // some reason they didn't install the grab when
                             // they were shown.
-                            JFXPanel.this.stagePeer.focusUngrab();
+                            hStagePeer.focusUngrab();
                         }
                     });
                 }
@@ -1013,6 +1069,8 @@ final BufferedImage test_getPixelsIm() {
 
     private class HostContainer implements HostInterface {
 
+        // These methods are invoked from FX thread
+
         @Override
         public void setEmbeddedStage(EmbeddedStageInterface embeddedStage) {
             stagePeer = embeddedStage;

From 290ed2de0ad76ca2bbaf787c7992f730280e01f6 Mon Sep 17 00:00:00 2001
From: Prasanta Sadhukhan <prasanta.sadhukhan@oracle.com>
Date: Wed, 19 Nov 2025 12:32:34 +0000
Subject: [PATCH 07/10] Review comment

---
 .../src/main/java/javafx/embed/swing/JFXPanel.java   | 12 ++++++------
 .../test/javafx/embed/swing/JFXPanelNPETest.java     |  1 -
 2 files changed, 6 insertions(+), 7 deletions(-)

diff --git a/modules/javafx.swing/src/main/java/javafx/embed/swing/JFXPanel.java b/modules/javafx.swing/src/main/java/javafx/embed/swing/JFXPanel.java
index 6b78e8b973d..3a61b4e0817 100644
--- a/modules/javafx.swing/src/main/java/javafx/embed/swing/JFXPanel.java
+++ b/modules/javafx.swing/src/main/java/javafx/embed/swing/JFXPanel.java
@@ -153,6 +153,7 @@ public class JFXPanel extends JComponent {
     // Set in FX thread and accessed in EDT/FX threads
     private transient volatile EmbeddedWindow stage;
 
+    // Set and accessed in FX thread only
     private transient volatile Scene scene;
 
     // Accessed on EDT only
@@ -963,15 +964,14 @@ private void setFxEnabled(boolean enabled) {
     }
 
     private transient  AWTEventListener ungrabListener = event -> {
-        var hStagePeer = JFXPanel.this.stagePeer;
 
         if (jfxPanelIOP.isUngrabEvent(event)) {
             SwingNodeHelper.runOnFxThread(() -> {
-                if (hStagePeer != null &&
+                if (JFXPanel.this.stagePeer != null &&
                         getScene() != null &&
                         getScene().getFocusOwner() != null &&
                         getScene().getFocusOwner().isFocused()) {
-                    hStagePeer.focusUngrab();
+                    JFXPanel.this.stagePeer.focusUngrab();
                 }
             });
         }
@@ -985,7 +985,7 @@ private void setFxEnabled(boolean enabled) {
 
                 if (jfxPanelWindow == eventWindow) {
                     SwingNodeHelper.runOnFxThread(() -> {
-                        if (hStagePeer != null) {
+                        if (JFXPanel.this.stagePeer != null) {
                             // No need to check if grab is active or not.
                             // NoAutoHide popups don't request the grab and
                             // ignore the Ungrab event anyway.
@@ -993,7 +993,7 @@ private void setFxEnabled(boolean enabled) {
                             // user clicks some non-FX content, even if for
                             // some reason they didn't install the grab when
                             // they were shown.
-                            hStagePeer.focusUngrab();
+                            JFXPanel.this.stagePeer.focusUngrab();
                         }
                     });
                 }
@@ -1019,8 +1019,8 @@ public void addNotify() {
             if ((stage != null) && !stage.isShowing()) {
                 stage.show();
             }
+            SwingNodeHelper.runOnEDT(() -> sendMoveEventToFX());
         });
-        sendMoveEventToFX();
     }
 
     @Override
diff --git a/tests/system/src/test/java/test/javafx/embed/swing/JFXPanelNPETest.java b/tests/system/src/test/java/test/javafx/embed/swing/JFXPanelNPETest.java
index e451a09deee..ccb67cefafe 100644
--- a/tests/system/src/test/java/test/javafx/embed/swing/JFXPanelNPETest.java
+++ b/tests/system/src/test/java/test/javafx/embed/swing/JFXPanelNPETest.java
@@ -102,7 +102,6 @@ public void uncaughtException(Thread t, Throwable e) {
             Platform.runLater(() -> contentPane.setScene(webView.getScene()));
             Thread.sleep(100);
         }
-        System.out.println("failure = " + failure.get());
         Assertions.assertFalse(failure.get());
     }
 

From 4049ad67ae86b81b37874a43a717b778a57a2cec Mon Sep 17 00:00:00 2001
From: Prasanta Sadhukhan <prasanta.sadhukhan@oracle.com>
Date: Wed, 19 Nov 2025 12:50:16 +0000
Subject: [PATCH 08/10] Review comment

---
 .../javafx.swing/src/main/java/javafx/embed/swing/JFXPanel.java | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/modules/javafx.swing/src/main/java/javafx/embed/swing/JFXPanel.java b/modules/javafx.swing/src/main/java/javafx/embed/swing/JFXPanel.java
index 3a61b4e0817..5aada2bfcb3 100644
--- a/modules/javafx.swing/src/main/java/javafx/embed/swing/JFXPanel.java
+++ b/modules/javafx.swing/src/main/java/javafx/embed/swing/JFXPanel.java
@@ -1018,8 +1018,8 @@ public void addNotify() {
         SwingNodeHelper.runOnFxThread(() -> {
             if ((stage != null) && !stage.isShowing()) {
                 stage.show();
+                SwingNodeHelper.runOnEDT(() -> sendMoveEventToFX());
             }
-            SwingNodeHelper.runOnEDT(() -> sendMoveEventToFX());
         });
     }
 

From f08b74171ae9dad8b732fb0c247b980f18c67a55 Mon Sep 17 00:00:00 2001
From: Prasanta Sadhukhan <prasanta.sadhukhan@oracle.com>
Date: Wed, 19 Nov 2025 16:23:50 +0000
Subject: [PATCH 09/10] Review comment

---
 .../main/java/com/sun/javafx/tk/quantum/EmbeddedScene.java    | 4 +---
 .../src/main/java/com/sun/javafx/tk/quantum/GlassScene.java   | 4 +++-
 .../test/java/test/javafx/embed/swing/JFXPanelNPETest.java    | 4 ++--
 3 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/modules/javafx.graphics/src/main/java/com/sun/javafx/tk/quantum/EmbeddedScene.java b/modules/javafx.graphics/src/main/java/com/sun/javafx/tk/quantum/EmbeddedScene.java
index 8455b059f4b..a84d6b736e2 100644
--- a/modules/javafx.graphics/src/main/java/com/sun/javafx/tk/quantum/EmbeddedScene.java
+++ b/modules/javafx.graphics/src/main/java/com/sun/javafx/tk/quantum/EmbeddedScene.java
@@ -155,9 +155,7 @@ public void setPixelScaleFactors(float scalex, float scaley) {
         entireSceneNeedsRepaint();
         Platform.runLater(() -> {
             QuantumToolkit.runWithRenderLock(() -> {
-                if (getSceneState() != null) {
-                    updateSceneState();
-                }
+                updateSceneState();
                 return null;
             });
         });
diff --git a/modules/javafx.graphics/src/main/java/com/sun/javafx/tk/quantum/GlassScene.java b/modules/javafx.graphics/src/main/java/com/sun/javafx/tk/quantum/GlassScene.java
index e623060b306..12dc090e80f 100644
--- a/modules/javafx.graphics/src/main/java/com/sun/javafx/tk/quantum/GlassScene.java
+++ b/modules/javafx.graphics/src/main/java/com/sun/javafx/tk/quantum/GlassScene.java
@@ -250,7 +250,9 @@ final SceneState getSceneState() {
 
     final void updateSceneState() {
         // should only be called on the event thread
-        sceneState.update();
+        if (getSceneState() != null) {
+            sceneState.update();
+        }
     }
 
     protected View getPlatformView() {
diff --git a/tests/system/src/test/java/test/javafx/embed/swing/JFXPanelNPETest.java b/tests/system/src/test/java/test/javafx/embed/swing/JFXPanelNPETest.java
index ccb67cefafe..220033e80a8 100644
--- a/tests/system/src/test/java/test/javafx/embed/swing/JFXPanelNPETest.java
+++ b/tests/system/src/test/java/test/javafx/embed/swing/JFXPanelNPETest.java
@@ -98,9 +98,9 @@ public void uncaughtException(Thread t, Throwable e) {
         for (int i = 0; i < 300; i++) {
             SwingUtilities.invokeLater(contentPane::repaint);
             Platform.runLater(() -> contentPane.setScene(null));
-            Thread.sleep(100);
+            Thread.sleep(1);
             Platform.runLater(() -> contentPane.setScene(webView.getScene()));
-            Thread.sleep(100);
+            Thread.sleep(1);
         }
         Assertions.assertFalse(failure.get());
     }

From f66fff5c5914a800bb2ecd52e5704281b3a23922 Mon Sep 17 00:00:00 2001
From: Prasanta Sadhukhan <prasanta.sadhukhan@oracle.com>
Date: Wed, 19 Nov 2025 17:09:47 +0000
Subject: [PATCH 10/10] Review comment + OutputRedirect

---
 .../com/sun/javafx/tk/quantum/GlassScene.java |  2 +-
 .../javafx/embed/swing/JFXPanelNPETest.java   | 28 ++++++++-----------
 2 files changed, 13 insertions(+), 17 deletions(-)

diff --git a/modules/javafx.graphics/src/main/java/com/sun/javafx/tk/quantum/GlassScene.java b/modules/javafx.graphics/src/main/java/com/sun/javafx/tk/quantum/GlassScene.java
index 12dc090e80f..e888730b2fc 100644
--- a/modules/javafx.graphics/src/main/java/com/sun/javafx/tk/quantum/GlassScene.java
+++ b/modules/javafx.graphics/src/main/java/com/sun/javafx/tk/quantum/GlassScene.java
@@ -250,7 +250,7 @@ final SceneState getSceneState() {
 
     final void updateSceneState() {
         // should only be called on the event thread
-        if (getSceneState() != null) {
+        if (sceneState != null) {
             sceneState.update();
         }
     }
diff --git a/tests/system/src/test/java/test/javafx/embed/swing/JFXPanelNPETest.java b/tests/system/src/test/java/test/javafx/embed/swing/JFXPanelNPETest.java
index 220033e80a8..4a58dd2eb28 100644
--- a/tests/system/src/test/java/test/javafx/embed/swing/JFXPanelNPETest.java
+++ b/tests/system/src/test/java/test/javafx/embed/swing/JFXPanelNPETest.java
@@ -43,6 +43,7 @@
 import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.Test;
 
+import test.javafx.util.OutputRedirect;
 import test.util.Util;
 
 public class JFXPanelNPETest {
@@ -86,23 +87,19 @@ public void doCleanup() {
 
     @Test
     public void testSceneNPE() throws Exception {
-        failure = new AtomicBoolean(false);
-        Thread.setDefaultUncaughtExceptionHandler(new Thread.UncaughtExceptionHandler() {
-            @Override
-            public void uncaughtException(Thread t, Throwable e) {
-                e.printStackTrace();
-                failure.set(true);
+        OutputRedirect.suppressStderr();
+        try {
+            SwingUtilities.invokeAndWait(JFXPanelNPETest::createUI);
+            for (int i = 0; i < 300; i++) {
+                SwingUtilities.invokeLater(contentPane::repaint);
+                Platform.runLater(() -> contentPane.setScene(null));
+                Thread.sleep(1);
+                Platform.runLater(() -> contentPane.setScene(webView.getScene()));
+                Thread.sleep(1);
             }
-        });
-        SwingUtilities.invokeAndWait(JFXPanelNPETest::createUI);
-        for (int i = 0; i < 300; i++) {
-            SwingUtilities.invokeLater(contentPane::repaint);
-            Platform.runLater(() -> contentPane.setScene(null));
-            Thread.sleep(1);
-            Platform.runLater(() -> contentPane.setScene(webView.getScene()));
-            Thread.sleep(1);
+        } finally {
+            OutputRedirect.checkAndRestoreStderr();
         }
-        Assertions.assertFalse(failure.get());
     }
 
     protected static void createUI() {
@@ -122,4 +119,3 @@ private static void fx(final JFXPanel contentPane) {
         contentPane.setScene(new Scene(webView));
     }
 }
-