8313424: JavaFX controls in the title bar (Preview)

build.gradle

@@ -2182,6 +2182,8 @@ allprojects {
         systemProperty 'unstable.test', IS_UNSTABLE_TEST
         systemProperty 'junit.jupiter.execution.timeout.test.method.default', JUNIT_TEST_TIMEOUT
         systemProperty 'junit.jupiter.execution.timeout.lifecycle.method.default', JUNIT_LIFECYCLE_TIMEOUT
+        systemProperty 'javafx.enablePreview', 'true'
+        systemProperty 'javafx.suppressPreviewWarning', 'true'
     }
 
     compileTestJava {

modules/javafx.base/src/main/java/com/sun/javafx/PreviewFeature.java

@@ -38,7 +38,8 @@ public enum PreviewFeature {
 
     // Add preview feature constants here:
     // TEST_FEATURE("Test Feature")
-    ;
+    STAGE_STYLE_EXTENDED("StageStyle.EXTENDED"),
+    HEADER_BAR("HeaderBar");
 
     PreviewFeature(String featureName) {
         this.featureName = featureName;

modules/javafx.base/src/test/java/test/util/ReflectionUtils.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2024, Oracle and/or its affiliates. All rights reserved.
+ * 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
@@ -26,15 +26,20 @@
 package test.util;
 
 import java.lang.reflect.Field;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
 import java.util.function.Function;
 
 public final class ReflectionUtils {
 
+    private ReflectionUtils() {}
+
     /**
      * Returns the value of a potentially private field of the specified object.
      * The field can be declared on any of the object's inherited classes.
      */
-    public static Object getFieldValue(Object object, String fieldName) {
+    @SuppressWarnings("unchecked")
+    public static <T> T getFieldValue(Object object, String fieldName) {
         Function<Class<?>, Field> getField = cls -> {
             try {
                 var field = cls.getDeclaredField(fieldName);
@@ -50,7 +55,7 @@ public static Object getFieldValue(Object object, String fieldName) {
             Field field = getField.apply(cls);
             if (field != null) {
                 try {
-                    return field.get(object);
+                    return (T)field.get(object);
                 } catch (IllegalAccessException e) {
                     throw new AssertionError(e);
                 }
@@ -61,4 +66,41 @@ public static Object getFieldValue(Object object, String fieldName) {
 
         throw new AssertionError("Field not found: " + fieldName);
     }
+
+    /**
+     * Invokes the specified method on the object, and returns a value.
+     * The method can be declared on any of the object's inherited classes.
+     *
+     * @param object the object on which the method will be invoked
+     * @param methodName the method name
+     * @param args the arguments
+     * @return the return value
+     */
+    public static Object invokeMethod(Object object, String methodName, Class<?>[] parameterTypes, Object... args) {
+        Function<Class<?>, Method> getMethod = cls -> {
+            try {
+                var method = cls.getDeclaredMethod(methodName, parameterTypes);
+                method.setAccessible(true);
+                return method;
+            } catch (NoSuchMethodException e) {
+                return null;
+            }
+        };
+
+        Class<?> cls = object.getClass();
+        while (cls != null) {
+            Method method = getMethod.apply(cls);
+            if (method != null) {
+                try {
+                    return method.invoke(object, args);
+                } catch (IllegalAccessException | InvocationTargetException e) {
+                    throw new AssertionError(e);
+                }
+            }
+
+            cls = cls.getSuperclass();
+        }
+
+        throw new AssertionError("Method not found: " + methodName);
+    }
 }

modules/javafx.graphics/src/main/java/com/sun/glass/ui/Application.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2010, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2010, 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
@@ -711,6 +711,12 @@ public final boolean supportsUnifiedWindows() {
         return _supportsUnifiedWindows();
     }
 
+    protected abstract boolean _supportsExtendedWindows();
+    public final boolean supportsExtendedWindows() {
+        checkEventThread();
+        return _supportsExtendedWindows();
+    }
+
     protected boolean _supportsSystemMenu() {
         // Overridden in subclasses
         return false;

modules/javafx.graphics/src/main/java/com/sun/glass/ui/HeaderButtonMetrics.java

@@ -0,0 +1,62 @@
+/*
+ * 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 com.sun.glass.ui;
+
+import javafx.geometry.Dimension2D;
+import javafx.scene.layout.HeaderBar;
+import javafx.stage.StageStyle;
+import java.util.Objects;
+
+/**
+ * Provides metrics about the header buttons of {@link StageStyle#EXTENDED} windows.
+ *
+ * @param leftInset the size of the left inset
+ * @param rightInset the size of the right inset
+ * @param minHeight the minimum height of the window buttons
+ * @see HeaderButtonOverlay
+ * @see HeaderBar
+ */
+public record HeaderButtonMetrics(Dimension2D leftInset, Dimension2D rightInset, double minHeight) {
+
+    public static HeaderButtonMetrics EMPTY = new HeaderButtonMetrics(new Dimension2D(0, 0), new Dimension2D(0, 0), 0);
+
+    public HeaderButtonMetrics {
+        Objects.requireNonNull(leftInset);
+        Objects.requireNonNull(rightInset);
+
+        if (minHeight < 0) {
+            throw new IllegalArgumentException("minHeight cannot be negative");
+        }
+    }
+
+    public double totalInsetWidth() {
+        return leftInset.getWidth() + rightInset.getWidth();
+    }
+
+    public double maxInsetHeight() {
+        return Math.max(leftInset.getHeight(), rightInset.getHeight());
+    }
+}