macOS fullWindowContent mode:

- added title bar buttons placeholder
- added client property to root pane that contains title bar buttons bounds
- undone toolbar extensions from commit ea2447dcb7

flatlaf-core/src/main/java/com/formdev/flatlaf/FlatClientProperties.java

@@ -270,6 +270,76 @@ public interface FlatClientProperties
 	String COMPONENT_TITLE_BAR_CAPTION = "JComponent.titleBarCaption";
 
 
+	//---- Panel --------------------------------------------------------------
+
+	/**
+	 * Marks the panel as placeholder for the iconfify/maximize/close buttons
+	 * in fullWindowContent mode.
+	 * <p>
+	 * If fullWindowContent mode is enabled, the preferred size of the panel is equal
+	 * to the size of the iconfify/maximize/close buttons. Otherwise is is {@code 0,0}.
+	 * <p>
+	 * You're responsible to layout that panel at the top-left or top-right corner,
+	 * depending on platform, where the iconfify/maximize/close buttons are located.
+	 * <p>
+	 * Syntax of the value string is: {@code "win|mac [horizontal|vertical]"}.
+	 * <p>
+	 * The string must start with {@code "win"} (for Windows or Linux) or
+	 * with {@code "mac"} (for macOS) and specifies the platform where the placeholder
+	 * should be used. On macOS, you need the placeholder in the top-left corner,
+	 * but on Windows/Linux you need it in the top-right corner. So if fullWindowContent mode
+	 * is supported on both platforms, you can add two placeholders to your layout
+	 * and FlatLaf automatically uses only one of them. The other gets size {@code 0,0}.
+	 * <p>
+	 * Optionally, you can append {@code " horizontal"} or {@code " vertical"} to the value string
+	 * to specify that the placeholder preferred size should be limited to one orientation.
+	 * E.g. {@code "win horizontal"} means that the placeholder preferred width is
+	 * equal to iconfify/maximize/close buttons width, but preferred height is zero.
+	 * <p>
+	 * Example for adding placeholder to top-left corner on macOS:
+	 * <pre>{@code
+	 * JPanel placeholder = new JPanel();
+	 * placeholder.putClientProperty( FlatClientProperties.FULL_WINDOW_CONTENT_BUTTONS_PLACEHOLDER, "mac" );
+     *
+     * JToolBar toolBar = new JToolBar();
+     * // add tool bar items
+     *
+	 * JPanel toolBarPanel = new JPanel( new BorderLayout() );
+	 * toolBarPanel.add( placeholder, BorderLayout.WEST );
+	 * toolBarPanel.add( toolBar, BorderLayout.CENTER );
+	 *
+	 * frame.getContentPane().add( toolBarPanel, BorderLayout.NORTH );
+	 * }</pre>
+	 *
+	 * Or add placeholder as first item to the tool bar:
+	 * <pre>{@code
+	 * JPanel placeholder = new JPanel();
+	 * placeholder.putClientProperty( FlatClientProperties.FULL_WINDOW_CONTENT_BUTTONS_PLACEHOLDER, "mac" );
+	 *
+	 * JToolBar toolBar = new JToolBar();
+	 * toolBar.add( placeholder );
+	 * // add tool bar items
+	 *
+	 * frame.getContentPane().add( toolBar, BorderLayout.NORTH );
+	 * }</pre>
+	 *
+	 * If a tabbed pane is located at the top, you can add the placeholder
+	 * as leading component to that tabbed pane:
+	 * <pre>{@code
+	 * JPanel placeholder = new JPanel();
+	 * placeholder.putClientProperty( FlatClientProperties.FULL_WINDOW_CONTENT_BUTTONS_PLACEHOLDER, "mac" );
+	 *
+	 * tabbedPane.putClientProperty( FlatClientProperties.TABBED_PANE_LEADING_COMPONENT, placeholder );
+	 * }</pre>
+	 * <p>
+	 * <strong>Component</strong> {@link javax.swing.JPanel}<br>
+	 * <strong>Value type</strong> {@link java.lang.String}
+	 *
+	 * @since 3.4
+	 */
+	String FULL_WINDOW_CONTENT_BUTTONS_PLACEHOLDER = "FlatLaf.fullWindowContent.buttonsPlaceholder";
+
+
 	//---- Popup --------------------------------------------------------------
 
 	/**
@@ -388,6 +458,20 @@ public interface FlatClientProperties
 	 */
 	String MENU_BAR_EMBEDDED = "JRootPane.menuBarEmbedded";
 
+	/**
+	 * Contains the current bounds of the iconfify/maximize/close buttons
+	 * (in root pane coordinates) if fullWindowContent mode is enabled.
+	 * Otherwise its value is {@code null}.
+	 * <p>
+	 * <b>Note</b>: Do not set this client property. It is set by FlatLaf.
+	 * <p>
+	 * <strong>Component</strong> {@link javax.swing.JRootPane}<br>
+	 * <strong>Value type</strong> {@link java.awt.Rectangle}
+	 *
+	 * @since 3.4
+	 */
+	String FULL_WINDOW_CONTENT_BUTTONS_BOUNDS = "FlatLaf.fullWindowContent.buttonsBounds";
+
 	/**
 	 * Specifies whether the window icon should be shown in the window title bar
 	 * (requires enabled window decorations). Default is UI property {@code TitlePane.showIcon}.

flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatNativeMacLibrary.java

@@ -16,6 +16,7 @@
 
 package com.formdev.flatlaf.ui;
 
+import java.awt.Rectangle;
 import java.awt.Window;
 
 /**
@@ -54,14 +55,14 @@ public class FlatNativeMacLibrary
 
 	public native static boolean setWindowRoundedBorder( Window window, float radius, float borderWidth, int borderColor );
 
+	/** @since 3.4 */
 	public static final int
 		BUTTON_STYLE_DEFAULT = 0,
 		BUTTON_STYLE_MEDIUM = 1,
 		BUTTON_STYLE_LARGE = 2;
 
-	public native static boolean setWindowButtonStyle( Window window, int buttonStyle );
+	/** @since 3.4 */ public native static boolean setWindowButtonStyle( Window window, int buttonStyle );
-	public native static int getWindowButtonAreaWidth( Window window );
+	/** @since 3.4 */ public native static Rectangle getWindowButtonsBounds( Window window );
-	public native static int getWindowTitleBarHeight( Window window );
+	/** @since 3.4 */ public native static boolean isWindowFullScreen( Window window );
-	public native static boolean isWindowFullScreen( Window window );
+	/** @since 3.4 */ public native static boolean toggleWindowFullScreen( Window window );
-	public native static boolean windowToggleFullScreen( Window window );
 }

flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatPanelUI.java

@@ -16,6 +16,7 @@
 
 package com.formdev.flatlaf.ui;
 
+import java.awt.Dimension;
 import java.awt.Graphics;
 import java.awt.Graphics2D;
 import java.beans.PropertyChangeEvent;
@@ -23,6 +24,7 @@ import java.beans.PropertyChangeListener;
 import java.util.Map;
 import javax.swing.JComponent;
 import javax.swing.JPanel;
+import javax.swing.LookAndFeel;
 import javax.swing.plaf.ComponentUI;
 import javax.swing.plaf.basic.BasicPanelUI;
 import com.formdev.flatlaf.FlatClientProperties;
@@ -69,6 +71,8 @@ public class FlatPanelUI
 		super.installUI( c );
 
 		c.addPropertyChangeListener( this );
+		if( c.getClientProperty( FlatClientProperties.FULL_WINDOW_CONTENT_BUTTONS_PLACEHOLDER ) != null )
+			FullWindowContentSupport.registerPlaceholder( c );
 
 		installStyle( (JPanel) c );
 	}
@@ -78,10 +82,20 @@ public class FlatPanelUI
 		super.uninstallUI( c );
 
 		c.removePropertyChangeListener( this );
+		if( c.getClientProperty( FlatClientProperties.FULL_WINDOW_CONTENT_BUTTONS_PLACEHOLDER ) != null )
+			FullWindowContentSupport.unregisterPlaceholder( c );
 
 		oldStyleValues = null;
 	}
 
+	@Override
+	protected void installDefaults( JPanel p ) {
+		super.installDefaults( p );
+
+		if( p.getClientProperty( FlatClientProperties.FULL_WINDOW_CONTENT_BUTTONS_PLACEHOLDER ) != null )
+			LookAndFeel.installProperty( p, "opaque", false );
+	}
+
 	/** @since 2.0.1 */
 	@Override
 	public void propertyChange( PropertyChangeEvent e ) {
@@ -98,6 +112,17 @@ public class FlatPanelUI
 				c.revalidate();
 				c.repaint();
 				break;
+
+			case FlatClientProperties.FULL_WINDOW_CONTENT_BUTTONS_PLACEHOLDER:
+				JPanel p = (JPanel) e.getSource();
+				if( e.getOldValue() != null )
+					FullWindowContentSupport.unregisterPlaceholder( p );
+				if( e.getNewValue() != null )
+					FullWindowContentSupport.registerPlaceholder( p );
+
+				// make panel non-opaque for placeholders
+				LookAndFeel.installProperty( p, "opaque", e.getNewValue() == null );
+				break;
 		}
 	}
 
@@ -162,4 +187,19 @@ public class FlatPanelUI
 
 		paint( g, c );
 	}
+
+	@Override
+	public Dimension getPreferredSize( JComponent c ) {
+		Object value = c.getClientProperty( FlatClientProperties.FULL_WINDOW_CONTENT_BUTTONS_PLACEHOLDER );
+		if( value != null )
+			return FullWindowContentSupport.getPlaceholderPreferredSize( c, (String) value );
+
+		return super.getPreferredSize( c );
+	}
+
+	@Override
+	public void paint( Graphics g, JComponent c ) {
+		if( c.getClientProperty( FlatClientProperties.FULL_WINDOW_CONTENT_BUTTONS_PLACEHOLDER ) != null )
+			FullWindowContentSupport.debugPaint( g, c );
+	}
 }

flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatRootPaneUI.java

@@ -89,6 +89,7 @@ public class FlatRootPaneUI
 	private LayoutManager oldLayout;
 	private PropertyChangeListener ancestorListener;
 	private ComponentListener componentListener;
+	private ComponentListener macFullWindowContentListener;
 
 	public static ComponentUI createUI( JComponent c ) {
 		return new FlatRootPaneUI();
@@ -207,6 +208,9 @@ public class FlatRootPaneUI
 			};
 			root.addPropertyChangeListener( "ancestor", ancestorListener );
 		}
+
+		if( SystemInfo.isMacFullWindowContentSupported )
+			macFullWindowContentListener = FullWindowContentSupport.macInstallListeners( root );
 	}
 
 	@Override
@@ -223,6 +227,11 @@ public class FlatRootPaneUI
 			root.removePropertyChangeListener( "ancestor", ancestorListener );
 			ancestorListener = null;
 		}
+
+		if( SystemInfo.isMacFullWindowContentSupported ) {
+			FullWindowContentSupport.macUninstallListeners( root, macFullWindowContentListener );
+			macFullWindowContentListener = null;
+		}
 	}
 
 	/** @since 1.1.2 */
@@ -359,6 +368,10 @@ public class FlatRootPaneUI
 					titlePane.titleBarColorsChanged();
 				break;
 
+			case FlatClientProperties.FULL_WINDOW_CONTENT_BUTTONS_BOUNDS:
+				FullWindowContentSupport.revalidatePlaceholders( rootPane );
+				break;
+
 			case FlatClientProperties.GLASS_PANE_FULL_HEIGHT:
 				rootPane.revalidate();
 				break;
@@ -371,11 +384,11 @@ public class FlatRootPaneUI
 			case FlatClientProperties.MACOS_WINDOW_BUTTON_STYLE:
 			case "ancestor":
 				if( SystemInfo.isMacFullWindowContentSupported &&
-					SystemInfo.isJava_17_orLater &&
 					rootPane.isDisplayable() &&
-					FlatClientProperties.clientPropertyBoolean( rootPane, "apple.awt.fullWindowContent", false ) &&
+					FlatClientProperties.clientPropertyBoolean( rootPane, "apple.awt.fullWindowContent", false ) )
-					FlatNativeMacLibrary.isLoaded() )
 				{
+					// set window button style
+					if( SystemInfo.isJava_17_orLater && FlatNativeMacLibrary.isLoaded() ) {
 						int buttonStyle = FlatNativeMacLibrary.BUTTON_STYLE_DEFAULT;
 						Object value = rootPane.getClientProperty( FlatClientProperties.MACOS_WINDOW_BUTTON_STYLE );
 						switch( String.valueOf( value ) ) {
@@ -392,6 +405,10 @@ public class FlatRootPaneUI
 						Window window = SwingUtilities.windowForComponent( rootPane );
 						FlatNativeMacLibrary.setWindowButtonStyle( window, buttonStyle );
 					}
+
+					// update buttons bounds client property
+					FullWindowContentSupport.macUpdateFullWindowContentButtonsBoundsProperty( rootPane );
+				}
 				break;
 		}
 	}

flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatToolBarBorder.java

@@ -25,7 +25,6 @@ import java.awt.Rectangle;
 import java.util.function.Function;
 import javax.swing.JToolBar;
 import javax.swing.SwingConstants;
-import javax.swing.SwingUtilities;
 import javax.swing.UIManager;
 import javax.swing.plaf.ToolBarUI;
 import com.formdev.flatlaf.util.UIScale;
@@ -115,18 +114,6 @@ public class FlatToolBarBorder
 				insets.top += gripInset;
 		}
 
-		// on macOS, add some extra space to left side for close/minimize/zoom buttons (if necessary)
-		if( c instanceof JToolBar && FlatToolBarUI.isMacOSMainToolbar( (JToolBar) c ) ) {
-			// get button area width from macOS
-			int buttonBarWidth = FlatNativeMacLibrary.isLoaded()
-				? FlatNativeMacLibrary.getWindowButtonAreaWidth( SwingUtilities.windowForComponent( c ) )
-				: -1;
-			if( buttonBarWidth < 0 )
-				buttonBarWidth = 68; // default width if NSWindow does not have a toolbar
-
-			insets.left += buttonBarWidth;
-		}
-
 		return insets;
 	}
 

flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatToolBarUI.java

@@ -19,45 +19,35 @@ package com.formdev.flatlaf.ui;
 import java.awt.Color;
 import java.awt.Component;
 import java.awt.Container;
-import java.awt.Dimension;
 import java.awt.FocusTraversalPolicy;
 import java.awt.Graphics;
 import java.awt.Graphics2D;
 import java.awt.Insets;
-import java.awt.LayoutManager;
-import java.awt.LayoutManager2;
 import java.awt.Rectangle;
-import java.awt.Window;
 import java.awt.event.ContainerEvent;
 import java.awt.event.ContainerListener;
-import java.beans.PropertyChangeEvent;
 import java.beans.PropertyChangeListener;
 import java.util.ArrayList;
 import java.util.Enumeration;
 import java.util.Map;
 import javax.swing.AbstractButton;
-import javax.swing.BoxLayout;
 import javax.swing.ButtonGroup;
 import javax.swing.ButtonModel;
 import javax.swing.DefaultButtonModel;
 import javax.swing.InputMap;
 import javax.swing.JComboBox;
 import javax.swing.JComponent;
-import javax.swing.JRootPane;
 import javax.swing.JToolBar;
 import javax.swing.LayoutFocusTraversalPolicy;
 import javax.swing.RootPaneContainer;
-import javax.swing.SwingUtilities;
 import javax.swing.UIManager;
 import javax.swing.border.Border;
 import javax.swing.plaf.ComponentUI;
-import javax.swing.plaf.UIResource;
 import javax.swing.plaf.basic.BasicToolBarUI;
 import com.formdev.flatlaf.FlatClientProperties;
 import com.formdev.flatlaf.ui.FlatStylingSupport.Styleable;
 import com.formdev.flatlaf.ui.FlatStylingSupport.StyleableUI;
 import com.formdev.flatlaf.util.LoggingFacade;
-import com.formdev.flatlaf.util.SystemInfo;
 import com.formdev.flatlaf.util.UIScale;
 
 /**
@@ -158,12 +148,6 @@ public class FlatToolBarUI
 			toolBar.setFloatable( false );
 		} else
 			oldFloatable = null;
-
-		// layout manager
-		LayoutManager layout = createLayout();
-		toolBar.setLayout( layout );
-		if( layout instanceof PropertyChangeListener )
-			toolBar.addPropertyChangeListener( (PropertyChangeListener) layout );
 	}
 
 	@Override
@@ -176,8 +160,6 @@ public class FlatToolBarUI
 			toolBar.setFloatable( oldFloatable );
 			oldFloatable = null;
 		}
-
-		toolBar.setLayout( null );
 	}
 
 	@Override
@@ -471,137 +453,6 @@ public class FlatToolBarUI
 			: null;
 	}
 
-	/** @since 3.3 */
-	protected LayoutManager createLayout() {
-		return new FlatToolBarLayoutManager();
-	}
-
-	/**
-	 * Returns whether the given toolbar is used in window titlebar on macOS.
-	 * <p>
-	 * Returns {@code true} if:
-	 * <ul>
-	 *   <li>running on macOS
-	 *   <li>Java supports "full window content"
-	 *   <li>"full window content" is enabled for window
-	 *   <li>toolbar orientation is horizontal
-	 *   <li>toolbar is located at {@code 0,0} in window
-	 * </ul>
-	 *
-	 * @since 3.3
-	 */
-	public static boolean isMacOSMainToolbar( JToolBar toolBar ) {
-		if( !SystemInfo.isMacFullWindowContentSupported ||
-			toolBar.getOrientation() != JToolBar.HORIZONTAL ||
-			toolBar.getX() != 0 ||
-			toolBar.getY() != 0 )
-		  return false;
-
-		JRootPane rootPane = SwingUtilities.getRootPane( toolBar );
-		if( rootPane == null )
-			return false;
-
-		if( !FlatClientProperties.clientPropertyBoolean( rootPane, "apple.awt.fullWindowContent", false ) )
-			return false;
-
-		for( Component p = toolBar.getParent(); p != null && !(p instanceof Window); p = p.getParent() ) {
-			if( p.getX() != 0 || p.getY() != 0 )
-				return false;
-		}
-
-		return true;
-	}
-
-	//---- class FlatToolBarLayoutManager -------------------------------------
-
-	/**
-	 * @since 3.3
-	 */
-	protected class FlatToolBarLayoutManager
-		implements LayoutManager2, PropertyChangeListener, UIResource
-	{
-		private BoxLayout delegate;
-
-		FlatToolBarLayoutManager() {
-			initBoxLayout();
-		}
-
-		private void initBoxLayout() {
-			delegate = new BoxLayout( toolBar, (toolBar.getOrientation() == JToolBar.HORIZONTAL)
-				? BoxLayout.LINE_AXIS : BoxLayout.PAGE_AXIS );
-		}
-
-		@Override
-		public void addLayoutComponent( Component comp, Object constraints ) {
-			delegate.addLayoutComponent( comp, constraints );
-		}
-
-		@Override
-		public void addLayoutComponent( String name, Component comp ) {
-			delegate.addLayoutComponent( name, comp );
-		}
-
-		@Override
-		public void removeLayoutComponent( Component comp ) {
-			delegate.removeLayoutComponent( comp );
-		}
-
-		@Override
-		public Dimension preferredLayoutSize( Container parent ) {
-			return minimumHeightOnMacOS( delegate.preferredLayoutSize( parent ) );
-		}
-
-		@Override
-		public Dimension minimumLayoutSize( Container parent ) {
-			return minimumHeightOnMacOS( delegate.minimumLayoutSize( parent ) );
-		}
-
-		@Override
-		public Dimension maximumLayoutSize( Container target ) {
-			return minimumHeightOnMacOS( delegate.maximumLayoutSize( target ) );
-		}
-
-		private Dimension minimumHeightOnMacOS( Dimension size ) {
-			if( isMacOSMainToolbar( toolBar ) ) {
-				// get title bar height from macOS
-				int titleBarHeight = FlatNativeMacLibrary.isLoaded()
-					? FlatNativeMacLibrary.getWindowTitleBarHeight( SwingUtilities.windowForComponent( toolBar ) )
-					: -1;
-				if( titleBarHeight < 0 )
-					titleBarHeight = 28; // default height if NSWindow does not have a toolbar
-
-				size.height = Math.max( size.height, titleBarHeight );
-			}
-			return size;
-		}
-
-		@Override
-		public void layoutContainer( Container parent ) {
-			delegate.layoutContainer( parent );
-		}
-
-		@Override
-		public void invalidateLayout( Container target ) {
-			delegate.invalidateLayout( target );
-		}
-
-		@Override
-		public float getLayoutAlignmentX( Container target ) {
-			return delegate.getLayoutAlignmentX( target );
-		}
-
-		@Override
-		public float getLayoutAlignmentY( Container target ) {
-			return delegate.getLayoutAlignmentY( target );
-		}
-
-		@Override
-		public void propertyChange( PropertyChangeEvent e ) {
-			if( "orientation".equals( e.getPropertyName() ) )
-				initBoxLayout();
-		}
-	}
-
 	//---- class FlatToolBarFocusTraversalPolicy ------------------------------
 
 	/**

flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FullWindowContentSupport.java

@@ -0,0 +1,183 @@
+/*
+ * Copyright 2024 FormDev Software GmbH
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.formdev.flatlaf.ui;
+
+import java.awt.Color;
+import java.awt.Component;
+import java.awt.Dimension;
+import java.awt.Graphics;
+import java.awt.Rectangle;
+import java.awt.Window;
+import java.awt.event.ComponentAdapter;
+import java.awt.event.ComponentEvent;
+import java.awt.event.ComponentListener;
+import java.lang.ref.WeakReference;
+import java.util.ArrayList;
+import java.util.Iterator;
+import javax.swing.JComponent;
+import javax.swing.JRootPane;
+import javax.swing.SwingUtilities;
+import javax.swing.UIManager;
+import com.formdev.flatlaf.FlatClientProperties;
+import com.formdev.flatlaf.util.SystemInfo;
+
+/**
+ * @author Karl Tauber
+ */
+class FullWindowContentSupport
+{
+	private static final String KEY_DEBUG_SHOW_PLACEHOLDERS = "FlatLaf.debug.panel.showPlaceholders";
+
+	private static ArrayList<WeakReference<JComponent>> placeholders = new ArrayList<>();
+
+	static Dimension getPlaceholderPreferredSize( JComponent c, String options ) {
+		JRootPane rootPane;
+		Rectangle bounds;
+
+		if( options.startsWith( SystemInfo.isMacOS ? "mac" : "win" ) &&
+			c.isDisplayable() &&
+			(rootPane = SwingUtilities.getRootPane( c )) != null &&
+			(bounds = (Rectangle) rootPane.getClientProperty( FlatClientProperties.FULL_WINDOW_CONTENT_BUTTONS_BOUNDS )) != null )
+		{
+			// On macOS, the client property is updated very late when toggling full screen,
+			// which results in "jumping" layout after full screen toggle finished.
+			// To avoid that, get up-to-date buttons bounds from macOS.
+			if( SystemInfo.isMacFullWindowContentSupported && FlatNativeMacLibrary.isLoaded() ) {
+				Rectangle r = FlatNativeMacLibrary.getWindowButtonsBounds( SwingUtilities.windowForComponent( c ) );
+				if( r != null )
+					bounds = r;
+			}
+
+			if( options.length() > 3 ) {
+				if( options.contains( "horizontal" ) )
+					return new Dimension( bounds.width, 0 );
+				if( options.contains( "vertical" ) )
+					return new Dimension( 0, bounds.height );
+			}
+
+			return bounds.getSize();
+		}
+
+		// default to 0,0
+		return new Dimension();
+	}
+
+	static void registerPlaceholder( JComponent c ) {
+		synchronized( placeholders ) {
+			if( indexOfPlaceholder( c ) < 0 )
+				placeholders.add( new WeakReference<>( c ) );
+		}
+	}
+
+	static void unregisterPlaceholder( JComponent c ) {
+		synchronized( placeholders ) {
+			int index = indexOfPlaceholder( c );
+			if( index >= 0 )
+				placeholders.remove( index );
+		}
+	}
+
+	private static int indexOfPlaceholder( JComponent c ) {
+		int size = placeholders.size();
+		for( int i = 0; i < size; i++ ) {
+			if( placeholders.get( i ).get() == c )
+				return i;
+		}
+		return -1;
+	}
+
+	static void revalidatePlaceholders( Component container ) {
+		synchronized( placeholders ) {
+			if( placeholders.isEmpty() )
+				return;
+
+			for( Iterator<WeakReference<JComponent>> it = placeholders.iterator(); it.hasNext(); ) {
+				WeakReference<JComponent> ref = it.next();
+				JComponent c = ref.get();
+
+				// remove already released placeholder
+				if( c == null ) {
+					it.remove();
+					continue;
+				}
+
+				// revalidate placeholder if is in given container
+				if( SwingUtilities.isDescendingFrom( c, container ) )
+					c.revalidate();
+			}
+		}
+	}
+
+	static ComponentListener macInstallListeners( JRootPane rootPane ) {
+		ComponentListener l = new ComponentAdapter() {
+			boolean lastFullScreen;
+
+			@Override
+			public void componentResized( ComponentEvent e ) {
+				Window window = SwingUtilities.windowForComponent( rootPane );
+				if( window == null )
+					return;
+
+				boolean fullScreen = FlatNativeMacLibrary.isLoaded() && FlatNativeMacLibrary.isWindowFullScreen( window );
+				if( fullScreen == lastFullScreen )
+					return;
+
+				lastFullScreen = fullScreen;
+				macUpdateFullWindowContentButtonsBoundsProperty( rootPane );
+			}
+		};
+
+		rootPane.addComponentListener( l );
+		return l;
+	}
+
+	static void macUninstallListeners( JRootPane rootPane, ComponentListener l ) {
+		if( l != null )
+			rootPane.removeComponentListener( l );
+	}
+
+	static void macUpdateFullWindowContentButtonsBoundsProperty( JRootPane rootPane ) {
+		if( !SystemInfo.isMacFullWindowContentSupported ||
+			!rootPane.isDisplayable() ||
+			!FlatClientProperties.clientPropertyBoolean( rootPane, "apple.awt.fullWindowContent", false ) )
+		  return;
+
+		Rectangle bounds = FlatNativeMacLibrary.isLoaded()
+			? FlatNativeMacLibrary.getWindowButtonsBounds( SwingUtilities.windowForComponent( rootPane ) )
+			: new Rectangle( 68, 28 ); // default size
+		rootPane.putClientProperty( FlatClientProperties.FULL_WINDOW_CONTENT_BUTTONS_BOUNDS, bounds );
+	}
+
+	static void debugPaint( Graphics g, JComponent c ) {
+		if( !UIManager.getBoolean( KEY_DEBUG_SHOW_PLACEHOLDERS ) )
+			return;
+
+		int width = c.getWidth() - 1;
+		int height = c.getHeight() - 1;
+		if( width <= 0 || height <= 0 )
+			return;
+
+		g.setColor( Color.red );
+		g.drawRect( 0, 0, width, height );
+
+		// draw diagonal cross
+		Object[] oldRenderingHints = FlatUIUtils.setRenderingHints( g );
+		g.drawLine( 0, 0, width, height );
+		g.drawLine( 0, height, width, 0 );
+		FlatUIUtils.resetRenderingHints( g, oldRenderingHints );
+	}
+}

flatlaf-demo/src/main/java/com/formdev/flatlaf/demo/DemoFrame.java

@@ -102,6 +102,9 @@ class DemoFrame
 					rootPane.putClientProperty( "apple.awt.windowTitleVisible", false );
 				else
 					setTitle( null );
+
+				// uncomment this line to see title bar buttons placeholders in fullWindowContent mode
+//				UIManager.put( "FlatLaf.debug.panel.showPlaceholders", true );
 			}
 
 			// enable full screen mode for this window (for Java 8 - 10; not necessary for Java 11+)
@@ -509,6 +512,8 @@ class DemoFrame
 		JMenuItem showUIDefaultsInspectorMenuItem = new JMenuItem();
 		JMenu helpMenu = new JMenu();
 		aboutMenuItem = new JMenuItem();
+		JPanel toolBarPanel = new JPanel();
+		JPanel macFullWindowContentButtonsPlaceholder = new JPanel();
 		toolBar = new JToolBar();
 		JButton backButton = new JButton();
 		JButton forwardButton = new JButton();
@@ -825,6 +830,16 @@ class DemoFrame
 		}
 		setJMenuBar(menuBar1);
 
+		//======== toolBarPanel ========
+		{
+			toolBarPanel.setLayout(new BorderLayout());
+
+			//======== macFullWindowContentButtonsPlaceholder ========
+			{
+				macFullWindowContentButtonsPlaceholder.setLayout(new FlowLayout());
+			}
+			toolBarPanel.add(macFullWindowContentButtonsPlaceholder, BorderLayout.WEST);
+
 			//======== toolBar ========
 			{
 				toolBar.setMargin(new Insets(3, 3, 3, 3));
@@ -868,7 +883,9 @@ class DemoFrame
 				showToggleButton.setIcon(new FlatSVGIcon("com/formdev/flatlaf/demo/icons/show.svg"));
 				toolBar.add(showToggleButton);
 			}
-		contentPane.add(toolBar, BorderLayout.NORTH);
+			toolBarPanel.add(toolBar, BorderLayout.CENTER);
+		}
+		contentPane.add(toolBarPanel, BorderLayout.NORTH);
 
 		//======== contentPanel ========
 		{
@@ -963,7 +980,7 @@ class DemoFrame
 		} );
 		if( SystemInfo.isMacOS && FlatNativeMacLibrary.isLoaded() ) {
 			showToggleButton.addActionListener( e -> {
-				FlatNativeMacLibrary.windowToggleFullScreen( this );
+				FlatNativeMacLibrary.toggleWindowFullScreen( this );
 			} );
 		}
 
@@ -1007,6 +1024,9 @@ class DemoFrame
 		if( "false".equals( System.getProperty( "flatlaf.animatedLafChange" ) ) )
 			animatedLafChangeMenuItem.setSelected( false );
 
+		// on macOS, panel left to toolBar is a placeholder for title bar buttons in fullWindowContent mode
+		macFullWindowContentButtonsPlaceholder.putClientProperty( FlatClientProperties.FULL_WINDOW_CONTENT_BUTTONS_PLACEHOLDER, "mac" );
+
 		// remove contentPanel bottom insets
 		MigLayout layout = (MigLayout) contentPanel.getLayout();
 		LC lc = ConstraintParser.parseLayoutConstraint( (String) layout.getLayoutConstraints() );

flatlaf-demo/src/main/java/com/formdev/flatlaf/demo/DemoFrame.jfd

@@ -1,4 +1,4 @@
-JFDML JFormDesigner: "8.1.0.0.283" Java: "19.0.2" encoding: "UTF-8"
+JFDML JFormDesigner: "8.2.1.0.348" Java: "21.0.1" encoding: "UTF-8"
 
 new FormModel {
 	contentType: "form/swing"
@@ -12,6 +12,13 @@ new FormModel {
 			"defaultCloseOperation": 2
 			"$locationPolicy": 2
 			"$sizePolicy": 2
+			add( new FormContainer( "javax.swing.JPanel", new FormLayoutManager( class java.awt.BorderLayout ) ) {
+				name: "toolBarPanel"
+				add( new FormContainer( "javax.swing.JPanel", new FormLayoutManager( class java.awt.FlowLayout ) ) {
+					name: "macFullWindowContentButtonsPlaceholder"
+				}, new FormLayoutConstraints( class java.lang.String ) {
+					"value": "West"
+				} )
 				add( new FormContainer( "javax.swing.JToolBar", new FormLayoutManager( class javax.swing.JToolBar ) ) {
 					name: "toolBar"
 					"margin": new java.awt.Insets( 3, 3, 3, 3 )
@@ -63,6 +70,9 @@ new FormModel {
 						"toolTipText": "Show Details"
 						"icon": new com.jformdesigner.model.SwingIcon( 0, "/com/formdev/flatlaf/demo/icons/show.svg" )
 					} )
+				}, new FormLayoutConstraints( class java.lang.String ) {
+					"value": "Center"
+				} )
 			}, new FormLayoutConstraints( class java.lang.String ) {
 				"value": "North"
 			} )

flatlaf-natives/flatlaf-natives-macos/src/main/headers/JNIUtils.h

@@ -41,4 +41,6 @@
 	}
 
 
-jfieldID getFieldID( JNIEnv *env, const char* className, const char* fieldName, const char* fieldSignature );
+jclass findClass( JNIEnv *env, const char* className, bool globalRef );
+jfieldID getFieldID( JNIEnv *env, const char* className, const char* fieldName, const char* fieldSignature, bool staticField );
+jmethodID getMethodID( JNIEnv *env, jclass cls, const char* methodName, const char* methodSignature, bool staticMethod );

flatlaf-natives/flatlaf-natives-macos/src/main/headers/com_formdev_flatlaf_ui_FlatNativeMacLibrary.h

@@ -31,18 +31,10 @@ JNIEXPORT jboolean JNICALL Java_com_formdev_flatlaf_ui_FlatNativeMacLibrary_setW
 
 /*
  * Class:     com_formdev_flatlaf_ui_FlatNativeMacLibrary
- * Method:    getWindowButtonAreaWidth
+ * Method:    getWindowButtonsBounds
- * Signature: (Ljava/awt/Window;)I
+ * Signature: (Ljava/awt/Window;)Ljava/awt/Rectangle;
  */
-JNIEXPORT jint JNICALL Java_com_formdev_flatlaf_ui_FlatNativeMacLibrary_getWindowButtonAreaWidth
+JNIEXPORT jobject JNICALL Java_com_formdev_flatlaf_ui_FlatNativeMacLibrary_getWindowButtonsBounds
-  (JNIEnv *, jclass, jobject);
-
-/*
- * Class:     com_formdev_flatlaf_ui_FlatNativeMacLibrary
- * Method:    getWindowTitleBarHeight
- * Signature: (Ljava/awt/Window;)I
- */
-JNIEXPORT jint JNICALL Java_com_formdev_flatlaf_ui_FlatNativeMacLibrary_getWindowTitleBarHeight
   (JNIEnv *, jclass, jobject);
 
 /*
@@ -55,10 +47,10 @@ JNIEXPORT jboolean JNICALL Java_com_formdev_flatlaf_ui_FlatNativeMacLibrary_isWi
 
 /*
  * Class:     com_formdev_flatlaf_ui_FlatNativeMacLibrary
- * Method:    windowToggleFullScreen
+ * Method:    toggleWindowFullScreen
  * Signature: (Ljava/awt/Window;)Z
  */
-JNIEXPORT jboolean JNICALL Java_com_formdev_flatlaf_ui_FlatNativeMacLibrary_windowToggleFullScreen
+JNIEXPORT jboolean JNICALL Java_com_formdev_flatlaf_ui_FlatNativeMacLibrary_toggleWindowFullScreen
   (JNIEnv *, jclass, jobject);
 
 #ifdef __cplusplus

flatlaf-natives/flatlaf-natives-macos/src/main/objcpp/JNIUtils.mm

@@ -21,8 +21,8 @@
  * @author Karl Tauber
  */
 
-jfieldID getFieldID( JNIEnv *env, const char* className, const char* fieldName, const char* fieldSignature ) {
+jclass findClass( JNIEnv *env, const char* className, bool globalRef ) {
-//	NSLog( @"getFieldID %s %s %s", className, fieldName, fieldSignature );
+//	NSLog( @"findClass %s", className );
 
 	jclass cls = env->FindClass( className );
 	if( cls == NULL ) {
@@ -32,7 +32,22 @@ jfieldID getFieldID( JNIEnv *env, const char* className, const char* fieldName,
 		return NULL;
 	}
 
-	jfieldID fieldID = env->GetFieldID( cls, fieldName, fieldSignature );
+	if( globalRef )
+		cls = reinterpret_cast<jclass>( env->NewGlobalRef( cls ) );
+
+	return cls;
+}
+
+jfieldID getFieldID( JNIEnv *env, const char* className, const char* fieldName, const char* fieldSignature, bool staticField ) {
+//	NSLog( @"getFieldID %s %s %s", className, fieldName, fieldSignature );
+
+	jclass cls = findClass( env, className, false );
+	if( cls == NULL )
+		return NULL;
+
+	jfieldID fieldID = staticField
+		? env->GetStaticFieldID( cls, fieldName, fieldSignature )
+		: env->GetFieldID( cls, fieldName, fieldSignature );
 	if( fieldID == NULL ) {
 		NSLog( @"FlatLaf: failed to lookup field '%s' of type '%s' in class '%s'", fieldName, fieldSignature, className );
 		env->ExceptionDescribe(); // print stack trace
@@ -42,3 +57,22 @@ jfieldID getFieldID( JNIEnv *env, const char* className, const char* fieldName,
 
 	return fieldID;
 }
+
+jmethodID getMethodID( JNIEnv *env, jclass cls, const char* methodName, const char* methodSignature, bool staticMethod ) {
+//	NSLog( @"getMethodID %s %s", methodName, methodSignature );
+
+	if( cls == NULL )
+		return NULL;
+
+	jmethodID methodID = staticMethod
+		? env->GetStaticMethodID( cls, methodName, methodSignature )
+		: env->GetMethodID( cls, methodName, methodSignature );
+	if( methodID == NULL ) {
+		NSLog( @"FlatLaf: failed to lookup method '%s' of type '%s'", methodName, methodSignature );
+		env->ExceptionDescribe(); // print stack trace
+		env->ExceptionClear();
+		return NULL;
+	}
+
+	return methodID;
+}

flatlaf-natives/flatlaf-natives-macos/src/main/objcpp/MacWindow.mm

@@ -51,9 +51,9 @@ NSWindow* getNSWindow( JNIEnv* env, jclass cls, jobject window ) {
 		return NULL;
 
 	// initialize field IDs (done only once because variables are static)
-	static jfieldID peerID = getFieldID( env, "java/awt/Component", "peer", "Ljava/awt/peer/ComponentPeer;" );
+	static jfieldID peerID = getFieldID( env, "java/awt/Component", "peer", "Ljava/awt/peer/ComponentPeer;", false );
-	static jfieldID platformWindowID = getFieldID( env, "sun/lwawt/LWWindowPeer", "platformWindow", "Lsun/lwawt/PlatformWindow;" );
+	static jfieldID platformWindowID = getFieldID( env, "sun/lwawt/LWWindowPeer", "platformWindow", "Lsun/lwawt/PlatformWindow;", false );
-	static jfieldID ptrID = getFieldID( env, "sun/lwawt/macosx/CFRetainedResource", "ptr", "J" );
+	static jfieldID ptrID = getFieldID( env, "sun/lwawt/macosx/CFRetainedResource", "ptr", "J", false );
 	if( peerID == NULL || platformWindowID == NULL || ptrID == NULL )
 		return NULL;
 
@@ -148,7 +148,7 @@ JNIEXPORT jboolean JNICALL Java_com_formdev_flatlaf_ui_FlatNativeMacLibrary_setW
 
 	WindowData* windowData = getWindowData( nsWindow, true );
 
-	[FlatJNFRunLoop performOnMainThreadWaiting:NO withBlock:^(){
+	[FlatJNFRunLoop performOnMainThreadWaiting:YES withBlock:^(){
 //		NSLog( @"\n%@\n\n", [nsWindow.contentView.superview _subtreeDescription] );
 
 		// add/remove toolbar
@@ -222,29 +222,48 @@ JNIEXPORT jboolean JNICALL Java_com_formdev_flatlaf_ui_FlatNativeMacLibrary_setW
 }
 
 extern "C"
-JNIEXPORT jint JNICALL Java_com_formdev_flatlaf_ui_FlatNativeMacLibrary_getWindowButtonAreaWidth
+JNIEXPORT jobject JNICALL Java_com_formdev_flatlaf_ui_FlatNativeMacLibrary_getWindowButtonsBounds
 	( JNIEnv* env, jclass cls, jobject window )
 {
 	JNI_COCOA_ENTER()
 
 	NSWindow* nsWindow = getNSWindow( env, cls, window );
 	if( nsWindow == NULL )
-		return -1;
+		return NULL;
 
-	// return zero if window is full screen because close/minimize/zoom buttons are hidden
+	WindowData* windowData = getWindowData( nsWindow, false );
-	if( isWindowFullScreen( nsWindow ) )
+	int width = 0;
-		return 0;
+	int height = 0;
 
+	// get width
+	if( isWindowFullScreen( nsWindow ) ) {
+		// use zero if window is full screen because close/minimize/zoom buttons are hidden
+		width = 0;
+	} else if( windowData != NULL && windowData.lastWindowButtonAreaWidth > 0 ) {
 		// use remembered value if window is in transition from full screen to non-full screen
 		// because NSToolbar is not yet visible
-	WindowData* windowData = getWindowData( nsWindow, false );
+		width = windowData.lastWindowButtonAreaWidth;
-	if( windowData != NULL && windowData.lastWindowButtonAreaWidth > 0 )
+	} else
-		return windowData.lastWindowButtonAreaWidth;
+		width = getWindowButtonAreaWidth( nsWindow );
 
-	return getWindowButtonAreaWidth( nsWindow );
+	// get height
+	if( windowData != NULL && windowData.lastWindowTitleBarHeight > 0 ) {
+		// use remembered value if window is full screen because NSToolbar is hidden
+		height = windowData.lastWindowTitleBarHeight;
+	} else
+		height = getWindowTitleBarHeight( nsWindow );
+
+	// initialize class and method ID (done only once because variables are static)
+	static jclass cls = findClass( env, "java/awt/Rectangle", true );
+	static jmethodID methodID = getMethodID( env, cls, "<init>", "(IIII)V", false );
+	if( cls == NULL || methodID == NULL )
+		return NULL;
+
+	// create and return Rectangle
+	return env->NewObject( cls, methodID, 0, 0, width, height );
 
 	JNI_COCOA_EXIT()
-	return -1;
+	return NULL;
 }
 
 int getWindowButtonAreaWidth( NSWindow* nsWindow ) {
@@ -279,27 +298,6 @@ int getWindowButtonAreaWidth( NSWindow* nsWindow ) {
 	return right + left;
 }
 
-extern "C"
-JNIEXPORT jint JNICALL Java_com_formdev_flatlaf_ui_FlatNativeMacLibrary_getWindowTitleBarHeight
-	( JNIEnv* env, jclass cls, jobject window )
-{
-	JNI_COCOA_ENTER()
-
-	NSWindow* nsWindow = getNSWindow( env, cls, window );
-	if( nsWindow == NULL )
-		return -1;
-
-	// use remembered value if window is full screen because NSToolbar is hidden
-	WindowData* windowData = getWindowData( nsWindow, false );
-	if( windowData != NULL && windowData.lastWindowTitleBarHeight > 0 )
-		return windowData.lastWindowTitleBarHeight;
-
-	return getWindowTitleBarHeight( nsWindow );
-
-	JNI_COCOA_EXIT()
-	return -1;
-}
-
 int getWindowTitleBarHeight( NSWindow* nsWindow ) {
 	NSView* closeButton = [nsWindow standardWindowButton:NSWindowCloseButton];
 	if( closeButton == NULL )
@@ -330,7 +328,7 @@ bool isWindowFullScreen( NSWindow* nsWindow ) {
 }
 
 extern "C"
-JNIEXPORT jboolean JNICALL Java_com_formdev_flatlaf_ui_FlatNativeMacLibrary_windowToggleFullScreen
+JNIEXPORT jboolean JNICALL Java_com_formdev_flatlaf_ui_FlatNativeMacLibrary_toggleWindowFullScreen
 	( JNIEnv* env, jclass cls, jobject window )
 {
 	JNI_COCOA_ENTER()