WIP

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

@@ -714,6 +714,12 @@ 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/gtk/GtkApplication.java

@@ -462,6 +462,11 @@ protected boolean _supportsInputMethods() {
         return false;
     }
 
+    @Override
+    protected boolean _supportsExtendedWindows() {
+        return true;
+    }
+
     @Override
     protected native int _getKeyCodeForChar(char c, int hint);
 

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

@@ -228,6 +228,11 @@ protected boolean _supportsTransparentWindows() {
         return false;
     }
 
+    @Override
+    protected boolean _supportsExtendedWindows() {
+        return false;
+    }
+
     /**
      * Hides / Shows iOS status bar.
      * @param hidden

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

@@ -407,6 +407,11 @@ protected boolean _supportsTransparentWindows() {
         return true;
     }
 
+    @Override
+    protected boolean _supportsExtendedWindows() {
+        return true;
+    }
+
     @Override native protected boolean _supportsSystemMenu();
 
     // NOTE: this will not return a valid result until the native _runloop

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

@@ -173,7 +173,6 @@ public NonClientHandler getNonClientHandler() {
                         maximize(!isMaximized());
                     } else if (clickCount == 1) {
                         _performWindowDrag(getRawHandle());
-                        return true;
                     }
                 }
             }
@@ -188,7 +187,7 @@ public NonClientHandler getNonClientHandler() {
     public ObservableValue<WindowOverlayMetrics> windowOverlayMetrics() {
         if (windowOverlayMetrics == null) {
             windowOverlayMetrics = ObjectConstant.valueOf(
-                new WindowOverlayMetrics(HorizontalDirection.LEFT, new Dimension2D(68, 0)));
+                new WindowOverlayMetrics(HorizontalDirection.LEFT, new Dimension2D(78, 38)));
         }
 
         return windowOverlayMetrics;

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

@@ -306,6 +306,11 @@ protected boolean _supportsUnifiedWindows() {
         return false;
     }
 
+    @Override
+    protected boolean _supportsExtendedWindows() {
+        return false;
+    }
+
     @Override
     public boolean hasTwoLevelFocus() {
         return deviceFlags[DEVICE_PC_KEYBOARD] == 0 && deviceFlags[DEVICE_5WAY] > 0;

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

@@ -352,6 +352,11 @@ protected boolean _supportsTransparentWindows() {
 
     @Override native protected boolean _supportsUnifiedWindows();
 
+    @Override
+    protected boolean _supportsExtendedWindows() {
+        return true;
+    }
+
     @Override
     public String getDataDirectory() {
         checkEventThread();

modules/javafx.graphics/src/main/java/com/sun/javafx/tk/quantum/QuantumToolkit.java

@@ -1256,6 +1256,8 @@ public boolean isSupported(ConditionalFeature feature) {
                 return Application.GetApplication().supportsTransparentWindows();
             case UNIFIED_WINDOW:
                 return Application.GetApplication().supportsUnifiedWindows();
+            case EXTENDED_WINDOW:
+                return Application.GetApplication().supportsExtendedWindows();
             case TWO_LEVEL_FOCUS:
                 return Application.GetApplication().hasTwoLevelFocus();
             case VIRTUAL_KEYBOARD:

modules/javafx.graphics/src/main/java/javafx/application/ConditionalFeature.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008, 2016, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2008, 2024, 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
@@ -159,6 +159,15 @@ public enum ConditionalFeature {
      */
     UNIFIED_WINDOW,
 
+    /**
+     * Indicates that a system supports {@link javafx.stage.StageStyle#EXTENDED}.
+     * <p>
+     * This feature is currently supported on Windows, Linux, and macOS.
+     *
+     * @since 24
+     */
+    EXTENDED_WINDOW,
+
     /**
      * Indicates whether or not controls should use two-level focus. Two-level
      * focus is when separate operations are needed in some controls to first

modules/javafx.graphics/src/main/java/javafx/scene/layout/HeaderBar.java

@@ -34,9 +34,46 @@
 import javafx.geometry.Pos;
 import javafx.geometry.VPos;
 import javafx.scene.Node;
+import javafx.stage.StageStyle;
 
 /**
+ * A client-area header bar that is used as a replacement for the system-provided header bar in stages
+ * with the {@link StageStyle#EXTENDED} style. This class enables the <em>drag to move</em> and
+ * <em>double-click to maximize</em> behaviors that are usually afforded by system-provided header bars.
+ * <p>
+ * {@code HeaderBar} is also a layout container that allows applications to lay out scene graph nodes
+ * in three areas: left, center, and right. {@code HeaderBar} ensures that the left and right areas
+ * account for the default window buttons (minimize, maximize, close). The center area is laid out
+ * with respect to the window, so that nodes will appear centered in the window regardless of the
+ * platform-specific placement of default window buttons.
  *
+ * <h2>Optional layout constraints</h2>
+ * An application may set constraints on individual children to customize their layout.
+ * For each constraint, {@code HeaderBar} provides static getter and setter methods.
+ * <table style="white-space: nowrap">
+ *     <caption>Layout constraints of {@code HeaderBar}</caption>
+ *     <thead>
+ *         <tr><th>Constraint</th><th>Type</th><th>Description</th></tr>
+ *     </thead>
+ *     <tbody>
+ *         <tr><th>alignment</th><td>{@link Pos}</td>
+ *             <td>The alignment of the child within its area of the {@code HeaderBar}.</td>
+ *         </tr>
+ *         <tr><th>margin</th>
+ *             <td>{@link Insets}</td><td>Margin space around the outside of the child.</td>
+ *         </tr>
+ *     </tbody>
+ * </table>
+ *
+ * <h2>Example</h2>
+ * <pre>{@code
+ *     var button = new Button("My button");
+ *     HeaderBar.setAlignment(button, Pos.CENTER_LEFT);
+ *     HeaderBar.setMargin(button, new Insets(5));
+ *     myHeaderBar.setCenter(button);
+ * }</pre>
+ *
+ * @since 24
  */
 public class HeaderBar extends HeaderBarBase {
 

modules/javafx.graphics/src/main/java/javafx/scene/layout/HeaderBarBase.java

@@ -43,7 +43,7 @@
  * point for custom header bar implementations. This class enables the <em>drag to move</em> and
  * <em>double-click to maximize</em> behaviors that are usually afforded by system-provided header bars.
  * <p>
- * Client-area header bars are used as a replacement for system-provided header bars in stages
+ * Client-area header bars are used as a replacement for the system-provided header bar in stages
  * with the {@link StageStyle#EXTENDED} style.
  * <p>
  * Most application developers should use the {@link HeaderBar} implementation instead of

modules/javafx.graphics/src/main/java/javafx/stage/StageStyle.java

@@ -25,6 +25,9 @@
 
 package javafx.stage;
 
+import javafx.scene.layout.BorderPane;
+import javafx.scene.layout.HeaderBar;
+
 /**
  * This enum defines the possible styles for a {@code Stage}.
  * @since JavaFX 2.0
@@ -69,8 +72,27 @@ public enum StageStyle {
     UNIFIED,
 
     /**
-     * Defines a {@code Stage} style in which the client area is extended into the non-client area,
-     * allowing applications to place scene graph nodes in the title bar area of the stage.
+     * Defines a {@code Stage} style in which the client area is extended into the header bar area, removing
+     * the separation between the two areas and allowing applications to place scene graph nodes in the header
+     * bar area of the stage.
+     * <p>
+     * An extended window has the default window buttons (minimize, maximize, close), but no system-provided
+     * draggable header bar. Applications need to provide their own header bar by placing the {@link HeaderBar}
+     * control in the scene graph. Usually, this is combined with a {@link BorderPane} root container:
+     * <pre>{@code
+     * public class MyApp extends Application {
+     *     @Override
+     *     public void start(Stage stage) {
+     *         var headerBar = new HeaderBar();
+     *         var root = new BorderPane();
+     *         root.setTop(headerBar);
+     *
+     *         stage.setScene(new Scene(root));
+     *         stage.initStyle(StageStyle.EXTENDED);
+     *         stage.show();
+     *     }
+     * }
+     * }</pre>
      *
      * @since 24
      */

modules/javafx.graphics/src/main/native-glass/mac/GlassWindow.m

@@ -460,6 +460,8 @@ static jlong _createWindowCommonDo(JNIEnv *env, jobject jWindow, jlong jOwnerPtr
 
         if ((jStyleMask & com_sun_glass_ui_Window_EXTENDED) != 0) {
             [window->nsWindow setTitlebarAppearsTransparent:YES];
+            [window->nsWindow setToolbar:[NSToolbar new]];
+            [window->nsWindow setToolbarStyle:NSWindowToolbarStyleUnifiedCompact];
         }
 
         if ((jStyleMask & com_sun_glass_ui_Window_UNIFIED) != 0) {