Native window decorations: initial implementation in C++ using JNI

.gitattributes

@@ -15,8 +15,11 @@
 # BINARY FILES:
 #   Disable line ending normalize on checkin.
 
+*.dll binary
+*.dylib binary
 *.gif binary
 *.jar binary
 *.png binary
 *.sketch binary
+*.so binary
 *.zip binary

.github/workflows/natives.yml

@@ -0,0 +1,56 @@
+# https://help.github.com/actions/language-and-framework-guides/building-and-testing-java-with-gradle
+
+name: Native Libraries
+
+on:
+    push:
+        branches:
+            - '*'
+        tags:
+            - '[0-9]*'
+        paths:
+            - '**.cpp'
+            - '**.h'
+    pull_request:
+        branches:
+            - '*'
+        paths:
+            - '**.cpp'
+            - '**.h'
+
+jobs:
+    Windows:
+        runs-on: windows-latest
+
+        steps:
+            - uses: actions/checkout@v2
+
+            - uses: gradle/wrapper-validation-action@v1
+
+            - name: Setup Java 1.8
+              uses: actions/setup-java@v1
+              with:
+                  java-version: 1.8
+
+            - name: Cache Gradle wrapper
+              uses: actions/cache@v1
+              with:
+                  path: ~/.gradle/wrapper
+                  key: ${{ runner.os }}-gradle-wrapper-${{ hashFiles('gradle/wrapper/gradle-wrapper.properties') }}
+
+            - name: Cache Gradle cache
+              uses: actions/cache@v2
+              with:
+                  path: ~/.gradle/caches
+                  key: ${{ runner.os }}-gradle-${{ hashFiles('**/*.gradle.kts') }}
+                  restore-keys: ${{ runner.os }}-gradle
+
+            - name: Build with Gradle
+              run: ./gradlew :flatlaf-natives-windows:build
+
+            - name: Upload artifacts
+              uses: actions/upload-artifact@v2
+              with:
+                  name: FlatLaf-natives-windows-build-artifacts
+                  path: |
+                      flatlaf-natives/flatlaf-natives-windows/build

flatlaf-core/build.gradle.kts

@@ -27,6 +27,16 @@ java {
 }
 
 tasks {
+	compileJava {
+		// generate JNI headers
+		options.headerOutputDirectory.set( buildDir.resolve( "generated/jni-headers" ) )
+	}
+
+	processResources {
+		// build native libraries
+		dependsOn( ":flatlaf-natives-windows:assemble" )
+	}
+
 	jar {
 		archiveBaseName.set( "flatlaf" )
 

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

@@ -165,7 +165,7 @@ public abstract class FlatLaf
 	 * <p>
 	 * Returns also {@code false} on Windows 10 if:
 	 * <ul>
-	 * <li>FlatLaf native window border support is available (requires {@code flatlaf-natives-jna.jar})</li>
+	 * <li>FlatLaf native window border support is available (requires Windows 10 64bit)</li>
 	 * <li>running in
 	 * <a href="https://confluence.jetbrains.com/display/JBR/JetBrains+Runtime">JetBrains Runtime 11 (or later)</a>
 	 * (<a href="https://github.com/JetBrains/JetBrainsRuntime">source code on github</a>)

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

@@ -74,14 +74,13 @@ public interface FlatSystemProperties
 	/**
 	 * Specifies whether FlatLaf native window decorations should be used
 	 * when creating {@code JFrame} or {@code JDialog}.
-	 * Requires that {@code flatlaf-natives-jna.jar} is on classpath/modulepath.
 	 * <p>
 	 * Setting this to {@code true} forces using FlatLaf native window decorations
 	 * even if they are not enabled by the application.
 	 * <p>
 	 * Setting this to {@code false} disables using FlatLaf native window decorations.
 	 * <p>
-	 * (requires Window 10)
+	 * (requires Window 10 64bit)
 	 * <p>
 	 * <strong>Allowed Values</strong> {@code false} and {@code true}<br>
 	 * <strong>Default</strong> none

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

@@ -20,7 +20,6 @@ import java.awt.Color;
 import java.awt.Rectangle;
 import java.awt.Window;
 import java.beans.PropertyChangeListener;
-import java.lang.reflect.Method;
 import java.util.List;
 import javax.swing.JDialog;
 import javax.swing.JFrame;
@@ -228,9 +227,12 @@ public class FlatNativeWindowBorder
 			return;
 
 		try {
+/*
 			Class<?> cls = Class.forName( "com.formdev.flatlaf.natives.jna.windows.FlatWindowsNativeWindowBorder" );
 			Method m = cls.getMethod( "getInstance" );
 			nativeProvider = (Provider) m.invoke( null );
+*/
+			nativeProvider = FlatWindowsNativeWindowBorder.getInstance();
 
 			supported = (nativeProvider != null);
 		} catch( Exception ex ) {

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

@@ -0,0 +1,380 @@
+/*
+ * Copyright 2021 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.Dialog;
+import java.awt.EventQueue;
+import java.awt.Frame;
+import java.awt.GraphicsConfiguration;
+import java.awt.Point;
+import java.awt.Rectangle;
+import java.awt.Window;
+import java.awt.geom.AffineTransform;
+import java.util.Collections;
+import java.util.IdentityHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+import javax.swing.JDialog;
+import javax.swing.JFrame;
+import javax.swing.Timer;
+import javax.swing.event.ChangeEvent;
+import javax.swing.event.ChangeListener;
+import javax.swing.event.EventListenerList;
+import com.formdev.flatlaf.FlatLaf;
+import com.formdev.flatlaf.util.NativeLibrary;
+import com.formdev.flatlaf.util.SystemInfo;
+
+//
+// Interesting resources:
+//     https://github.com/microsoft/terminal/blob/main/src/cascadia/WindowsTerminal/NonClientIslandWindow.cpp
+//     https://docs.microsoft.com/en-us/windows/win32/dwm/customframe
+//     https://github.com/JetBrains/JetBrainsRuntime/blob/master/src/java.desktop/windows/native/libawt/windows/awt_Frame.cpp
+//     https://github.com/JetBrains/JetBrainsRuntime/commit/d2820524a1aa211b1c49b30f659b9b4d07a6f96e
+//     https://github.com/JetBrains/JetBrainsRuntime/pull/18
+//     https://medium.com/swlh/customizing-the-title-bar-of-an-application-window-50a4ac3ed27e
+//     https://github.com/kalbetredev/CustomDecoratedJFrame
+//     https://github.com/Guerra24/NanoUI-win32
+//     https://github.com/oberth/custom-chrome
+//     https://github.com/rossy/borderless-window
+//
+
+/**
+ * Native window border support for Windows 10 when using custom decorations.
+ * <p>
+ * If the application wants to use custom decorations, the Windows 10 title bar is hidden
+ * (including minimize, maximize and close buttons), but not the resize borders (including drop shadow).
+ * Windows 10 window snapping functionality will remain unaffected:
+ * https://support.microsoft.com/en-us/windows/snap-your-windows-885a9b1e-a983-a3b1-16cd-c531795e6241
+ *
+ * @author Karl Tauber
+ */
+class FlatWindowsNativeWindowBorder
+	implements FlatNativeWindowBorder.Provider
+{
+	private final Map<Window, WndProc> windowsMap = Collections.synchronizedMap( new IdentityHashMap<>() );
+	private final EventListenerList listenerList = new EventListenerList();
+	private Timer fireStateChangedTimer;
+
+	private boolean colorizationUpToDate;
+	private boolean colorizationColorAffectsBorders;
+	private Color colorizationColor;
+	private int colorizationColorBalance;
+
+	private static NativeLibrary nativeLibrary;
+	private static FlatWindowsNativeWindowBorder instance;
+
+	static FlatNativeWindowBorder.Provider getInstance() {
+		// requires Windows 10 on x86_64
+		if( !SystemInfo.isWindows_10_orLater || !SystemInfo.isX86_64 )
+			return null;
+
+		// load native library
+		if( nativeLibrary == null ) {
+			if( !SystemInfo.isJava_9_orLater ) {
+				// In Java 8, load jawt.dll (part of JRE) explicitly because it
+				// is not found when running application with <jdk>/bin/java.exe.
+				// When using <jdk>/jre/bin/java.exe, it is found.
+				// jawt.dll is located in <jdk>/jre/bin/.
+				// Java 9 and later does not have this problem.
+				try {
+					System.loadLibrary( "jawt" );
+				} catch( Exception ex ) {
+					Logger.getLogger( FlatLaf.class.getName() ).log( Level.SEVERE, null, ex );
+				}
+			}
+
+			nativeLibrary = new NativeLibrary(
+				"com/formdev/flatlaf/natives/flatlaf-windows-x86_64",
+				FlatWindowsNativeWindowBorder.class.getClassLoader(), true );
+		}
+
+		// check whether native library was successfully loaded
+		if( !nativeLibrary.isLoaded() )
+			return null;
+
+		// create new instance
+		if( instance == null )
+			instance = new FlatWindowsNativeWindowBorder();
+		return instance;
+	}
+
+	private FlatWindowsNativeWindowBorder() {
+	}
+
+	@Override
+	public boolean hasCustomDecoration( Window window ) {
+		return windowsMap.containsKey( window );
+	}
+
+	/**
+	 * Tell the window whether the application wants use custom decorations.
+	 * If {@code true}, the Windows 10 title bar is hidden (including minimize,
+	 * maximize and close buttons), but not the resize borders (including drop shadow).
+	 */
+	@Override
+	public void setHasCustomDecoration( Window window, boolean hasCustomDecoration ) {
+		if( hasCustomDecoration )
+			install( window );
+		else
+			uninstall( window );
+	}
+
+	private void install( Window window ) {
+		// requires Windows 10 on x86_64
+		if( !SystemInfo.isWindows_10_orLater || !SystemInfo.isX86_64 )
+			return;
+
+		// only JFrame and JDialog are supported
+		if( !(window instanceof JFrame) && !(window instanceof JDialog) )
+			return;
+
+		// not supported if frame/dialog is undecorated
+		if( (window instanceof Frame && ((Frame)window).isUndecorated()) ||
+			(window instanceof Dialog && ((Dialog)window).isUndecorated()) )
+		  return;
+
+		// check whether already installed
+		if( windowsMap.containsKey( window ) )
+			return;
+
+		// install
+		WndProc wndProc = new WndProc( window );
+		if( wndProc.hwnd == 0 )
+			return;
+
+		windowsMap.put( window, wndProc );
+	}
+
+	private void uninstall( Window window ) {
+		WndProc wndProc = windowsMap.remove( window );
+		if( wndProc != null )
+			wndProc.uninstall();
+	}
+
+	@Override
+	public void setTitleBarHeight( Window window, int titleBarHeight ) {
+		WndProc wndProc = windowsMap.get( window );
+		if( wndProc == null )
+			return;
+
+		wndProc.titleBarHeight = titleBarHeight;
+	}
+
+	@Override
+	public void setTitleBarHitTestSpots( Window window, List<Rectangle> hitTestSpots ) {
+		WndProc wndProc = windowsMap.get( window );
+		if( wndProc == null )
+			return;
+
+		wndProc.hitTestSpots = hitTestSpots.toArray( new Rectangle[hitTestSpots.size()] );
+	}
+
+	@Override
+	public void setTitleBarAppIconBounds( Window window, Rectangle appIconBounds ) {
+		WndProc wndProc = windowsMap.get( window );
+		if( wndProc == null )
+			return;
+
+		wndProc.appIconBounds = (appIconBounds != null) ? new Rectangle( appIconBounds ) : null;
+	}
+
+	@Override
+	public boolean isColorizationColorAffectsBorders() {
+		updateColorization();
+		return colorizationColorAffectsBorders;
+	}
+
+	@Override
+	public Color getColorizationColor() {
+		updateColorization();
+		return colorizationColor;
+	}
+
+	@Override
+	public int getColorizationColorBalance() {
+		updateColorization();
+		return colorizationColorBalance;
+	}
+
+	private void updateColorization() {
+		if( colorizationUpToDate )
+			return;
+		colorizationUpToDate = true;
+
+		String subKey = "SOFTWARE\\Microsoft\\Windows\\DWM";
+
+		int value = registryGetIntValue( subKey, "ColorPrevalence", -1 );
+		colorizationColorAffectsBorders = (value > 0);
+
+		value = registryGetIntValue( subKey, "ColorizationColor", -1 );
+		colorizationColor = (value != -1) ? new Color( value ) : null;
+
+		colorizationColorBalance = registryGetIntValue( subKey, "ColorizationColorBalance", -1 );
+	}
+
+	private native static int registryGetIntValue( String key, String valueName, int defaultValue );
+
+	@Override
+	public void addChangeListener( ChangeListener l ) {
+		listenerList.add( ChangeListener.class, l );
+	}
+
+	@Override
+	public void removeChangeListener( ChangeListener l ) {
+		listenerList.remove( ChangeListener.class, l );
+	}
+
+	private void fireStateChanged() {
+		Object[] listeners = listenerList.getListenerList();
+		if( listeners.length == 0 )
+			return;
+
+		ChangeEvent e = new ChangeEvent( this );
+		for( int i = 0; i < listeners.length; i += 2 ) {
+			if( listeners[i] == ChangeListener.class )
+				((ChangeListener)listeners[i+1]).stateChanged( e );
+		}
+	}
+
+	/**
+	 * Because there may be sent many WM_DWMCOLORIZATIONCOLORCHANGED messages,
+	 * slightly delay event firing and fire it only once (on the AWT thread).
+	 */
+	void fireStateChangedLaterOnce() {
+		EventQueue.invokeLater( () -> {
+			if( fireStateChangedTimer != null ) {
+				fireStateChangedTimer.restart();
+				return;
+			}
+
+			fireStateChangedTimer = new Timer( 300, e -> {
+				fireStateChangedTimer = null;
+				colorizationUpToDate = false;
+
+				fireStateChanged();
+			} );
+			fireStateChangedTimer.setRepeats( false );
+			fireStateChangedTimer.start();
+		} );
+	}
+
+	//---- class WndProc ------------------------------------------------------
+
+	private class WndProc
+	{
+		// WM_NCHITTEST mouse position codes
+		private static final int
+			HTCLIENT = 1,
+			HTCAPTION = 2,
+			HTSYSMENU = 3,
+			HTTOP = 12;
+
+		private Window window;
+		private final long hwnd;
+
+		private int titleBarHeight;
+		private Rectangle[] hitTestSpots;
+		private Rectangle appIconBounds;
+
+		WndProc( Window window ) {
+			this.window = window;
+
+			hwnd = installImpl( window );
+		}
+
+		void uninstall() {
+			uninstallImpl( hwnd );
+
+			// cleanup
+			window = null;
+		}
+
+		private native long installImpl( Window window );
+		private native void uninstallImpl( long hwnd );
+
+		// invoked from native code
+		private int onNcHitTest( int x, int y, boolean isOnResizeBorder ) {
+			// scale-down mouse x/y
+			Point pt = scaleDown( x, y );
+			int sx = pt.x;
+			int sy = pt.y;
+
+			// return HTSYSMENU if mouse is over application icon
+			//   - left-click on HTSYSMENU area shows system menu
+			//   - double-left-click sends WM_CLOSE
+			if( appIconBounds != null && appIconBounds.contains( sx, sy ) )
+				return HTSYSMENU;
+
+			boolean isOnTitleBar = (sy < titleBarHeight);
+
+			if( isOnTitleBar ) {
+				// use a second reference to the array to avoid that it can be changed
+				// in another thread while processing the array
+				Rectangle[] hitTestSpots2 = hitTestSpots;
+				for( Rectangle spot : hitTestSpots2 ) {
+					if( spot.contains( sx, sy ) )
+						return HTCLIENT;
+				}
+				return isOnResizeBorder ? HTTOP : HTCAPTION;
+			}
+
+			return isOnResizeBorder ? HTTOP : HTCLIENT;
+		}
+
+		/**
+		 * Scales down in the same way as AWT.
+		 * See AwtWin32GraphicsDevice::ScaleDownX() and ::ScaleDownY()
+		 */
+		private Point scaleDown( int x, int y ) {
+			GraphicsConfiguration gc = window.getGraphicsConfiguration();
+			if( gc == null )
+				return new Point( x, y );
+
+			AffineTransform t = gc.getDefaultTransform();
+			return new Point( clipRound( x / t.getScaleX() ), clipRound( y / t.getScaleY() ) );
+		}
+
+		/**
+		 * Rounds in the same way as AWT.
+		 * See AwtWin32GraphicsDevice::ClipRound()
+		 */
+		private int clipRound( double value ) {
+			value -= 0.5;
+			if( value < Integer.MIN_VALUE )
+				return Integer.MIN_VALUE;
+			if( value > Integer.MAX_VALUE )
+				return Integer.MAX_VALUE;
+			return (int) Math.ceil( value );
+		}
+
+		// invoked from native code
+		private boolean isFullscreen() {
+			GraphicsConfiguration gc = window.getGraphicsConfiguration();
+			if( gc == null )
+				return false;
+			return gc.getDevice().getFullScreenWindow() == window;
+		}
+
+		// invoked from native code
+		private void fireStateChangedLaterOnce() {
+			FlatWindowsNativeWindowBorder.this.fireStateChangedLaterOnce();
+		}
+	}
+}

flatlaf-core/src/main/java/com/formdev/flatlaf/util/NativeLibrary.java

@@ -0,0 +1,127 @@
+/*
+ * Copyright 2021 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.util;
+
+import java.io.File;
+import java.io.InputStream;
+import java.net.URL;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.StandardCopyOption;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+import com.formdev.flatlaf.FlatLaf;
+
+/**
+ * Helper class to load native library (.dll, .so or .dylib) stored in Jar.
+ * <p>
+ * Copies native library to users temporary folder before loading it.
+ *
+ * @author Karl Tauber
+ */
+public class NativeLibrary
+{
+	private final boolean loaded;
+
+	/**
+	 * Load native library from given classloader.
+	 *
+	 * @param libraryName resource name of the native library (without "lib" prefix and without extension)
+	 * @param classLoader the classloader used to locate the library
+	 * @param supported whether the native library is supported on the current platform
+	 */
+	public NativeLibrary( String libraryName, ClassLoader classLoader, boolean supported ) {
+		this.loaded = supported
+			? loadLibraryFromJar( libraryName, classLoader )
+			: false;
+	}
+
+	/**
+	 * Returns whether the native library is loaded.
+	 * <p>
+	 * Returns {@code false} if not supported on current platform as specified in constructor
+	 * or if loading failed.
+	 */
+	public boolean isLoaded() {
+		return loaded;
+	}
+
+	private static boolean loadLibraryFromJar( String libraryName, ClassLoader classLoader ) {
+		// add prefix and suffix to library name
+		libraryName = decorateLibraryName( libraryName );
+
+		// find library
+		URL libraryUrl = classLoader.getResource( libraryName );
+		if( libraryUrl == null ) {
+			log( "Library '" + libraryName + "' not found", null );
+			return false;
+		}
+
+		try {
+			// for development environment
+			if( "file".equals( libraryUrl.getProtocol() ) ) {
+				File libraryFile = new File( libraryUrl.getPath() );
+				if( libraryFile.isFile() ) {
+					// load library without copying
+					System.load( libraryFile.getCanonicalPath() );
+					return true;
+				}
+			}
+
+			// create temporary file
+			Path tempPath = Files.createTempFile( "jni", basename( libraryName ) );
+			File tempFile = tempPath.toFile();
+
+			//TODO this does not work on Windows
+			tempFile.deleteOnExit();
+
+			// copy library to temporary file
+			try( InputStream in = libraryUrl.openStream() ) {
+				Files.copy( in, tempPath, StandardCopyOption.REPLACE_EXISTING );
+			}
+
+			// load library
+			System.load( tempFile.getCanonicalPath() );
+
+			return true;
+		} catch( Throwable ex ) {
+			log( null, ex );
+			return false;
+		}
+	}
+
+	private static String decorateLibraryName( String libraryName ) {
+		if( SystemInfo.isWindows )
+			return libraryName.concat( ".dll" );
+
+		String suffix = SystemInfo.isMacOS ? ".dylib" : ".so";
+
+		int sep = libraryName.lastIndexOf( '/' );
+		return (sep >= 0)
+			? libraryName.substring( 0, sep + 1 ) + "lib" + libraryName.substring( sep + 1 ) + suffix
+			: "lib" + libraryName + suffix;
+	}
+
+	private static String basename( String libName ) {
+		int sep = libName.lastIndexOf( '/' );
+		return (sep >= 0) ? libName.substring( sep + 1 ) : libName;
+	}
+
+	private static void log( String msg, Throwable thrown ) {
+		Logger.getLogger( FlatLaf.class.getName() ).log( Level.SEVERE, msg, thrown );
+	}
+}

flatlaf-demo/build.gradle.kts

@@ -27,19 +27,19 @@ repositories {
 
 dependencies {
 	implementation( project( ":flatlaf-core" ) )
-	implementation( project( ":flatlaf-natives-jna" ) )
 	implementation( project( ":flatlaf-extras" ) )
 	implementation( project( ":flatlaf-intellij-themes" ) )
 	implementation( "com.miglayout:miglayout-swing:5.3-SNAPSHOT" )
 	implementation( "com.jgoodies:jgoodies-forms:1.9.0" )
+//	implementation( project( ":flatlaf-natives-jna" ) )
 }
 
 tasks {
 	jar {
 		dependsOn( ":flatlaf-core:jar" )
-		dependsOn( ":flatlaf-natives-jna:jar" )
 		dependsOn( ":flatlaf-extras:jar" )
 		dependsOn( ":flatlaf-intellij-themes:jar" )
+//		dependsOn( ":flatlaf-natives-jna:jar" )
 
 		manifest {
 			attributes( "Main-Class" to "com.formdev.flatlaf.demo.FlatLafDemo" )

flatlaf-natives/flatlaf-natives-jna/src/main/java/com/formdev/flatlaf/natives/jna/windows/FlatWindowsNativeWindowBorder.java

@@ -207,20 +207,20 @@ public class FlatWindowsNativeWindowBorder
 
 		String subKey = "SOFTWARE\\Microsoft\\Windows\\DWM";
 
-		int value = RegGetDword( HKEY_CURRENT_USER, subKey, "ColorPrevalence" );
+		int value = registryGetIntValue( subKey, "ColorPrevalence", -1 );
 		colorizationColorAffectsBorders = (value > 0);
 
-		value = RegGetDword( HKEY_CURRENT_USER, subKey, "ColorizationColor" );
+		value = registryGetIntValue( subKey, "ColorizationColor", -1 );
 		colorizationColor = (value != -1) ? new Color( value ) : null;
 
-		colorizationColorBalance = RegGetDword( HKEY_CURRENT_USER, subKey, "ColorizationColorBalance" );
+		colorizationColorBalance = registryGetIntValue( subKey, "ColorizationColorBalance", -1 );
 	}
 
-	private static int RegGetDword( HKEY hkey, String lpSubKey, String lpValue ) {
+	private static int registryGetIntValue( String key, String valueName, int defaultValue ) {
 		try {
-			return Advapi32Util.registryGetIntValue( hkey, lpSubKey, lpValue );
+			return Advapi32Util.registryGetIntValue( HKEY_CURRENT_USER, key, valueName );
 		} catch( RuntimeException ex ) {
-			return -1;
+			return defaultValue;
 		}
 	}
 

flatlaf-natives/flatlaf-natives-windows/build.gradle.kts

@@ -0,0 +1,90 @@
+/*
+ * Copyright 2021 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.
+ */
+
+plugins {
+	id( "dev.nokee.jni-library" ) version "0.4.0"
+	id( "dev.nokee.cpp-language" ) version "0.4.0"
+}
+
+library {
+	targetMachines.set( listOf( machines.windows.x86_64 ) )
+
+	variants.configureEach {
+		// depend on :flatlaf-core:compileJava because this task generates the JNI headers
+		tasks.named( "compileCpp" ) {
+			dependsOn( ":flatlaf-core:compileJava" )
+		}
+
+		sharedLibrary {
+			compileTasks.configureEach {
+				doFirst {
+					println( "Used Tool Chain:" )
+					println( "  - ${toolChain.get()}" )
+					println( "Available Tool Chains:" )
+					toolChains.forEach {
+						println( "  - $it" )
+					}
+
+					// copy needed JNI headers
+					copy {
+						from( project( ":flatlaf-core" ).buildDir.resolve( "generated/jni-headers" ) )
+						into( "src/main/headers" )
+						include(
+							"com_formdev_flatlaf_ui_FlatWindowsNativeWindowBorder.h",
+							"com_formdev_flatlaf_ui_FlatWindowsNativeWindowBorder_WndProc.h"
+						)
+						filter<org.apache.tools.ant.filters.FixCrLfFilter>(
+							"eol" to org.apache.tools.ant.filters.FixCrLfFilter.CrLf.newInstance( "lf" )
+						)
+					}
+				}
+
+				compilerArgs.addAll( toolChain.map {
+					when( it ) {
+						is Gcc, is Clang -> listOf( "-O2" )
+						is VisualCpp -> listOf( "/O2" )
+						else -> emptyList()
+					}
+				} )
+			}
+
+			linkTask.configure {
+				val nativesDir = project( ":flatlaf-core" ).projectDir.resolve( "src/main/resources/com/formdev/flatlaf/natives" )
+				val libraryName = "flatlaf-windows-x86_64.dll"
+
+				outputs.file( "$nativesDir/$libraryName" )
+
+				val jawt = "${org.gradle.internal.jvm.Jvm.current().javaHome}/lib/jawt"
+				linkerArgs.addAll( toolChain.map {
+					when( it ) {
+						is Gcc, is Clang -> listOf( "-l${jawt}", "-lUser32", "-lshell32", "-lAdvAPI32" )
+						is VisualCpp -> listOf( "${jawt}.lib", "User32.lib", "shell32.lib", "AdvAPI32.lib" )
+						else -> emptyList()
+					}
+				} )
+
+				doLast {
+					// copy shared library to flatlaf-core resources
+					copy {
+						from( linkedFile )
+						into( nativesDir )
+						rename( "flatlaf-natives-windows.dll", libraryName )
+					}
+				}
+			}
+		}
+	}
+}

flatlaf-natives/flatlaf-natives-windows/src/main/cpp/FlatWndProc.cpp

@@ -0,0 +1,399 @@
+/*
+ * Copyright 2021 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.
+ */
+
+#include <windows.h>
+#include <windowsx.h>
+#include <shellapi.h>
+#include <jawt.h>
+#include <jawt_md.h>
+#include <map>
+#include "FlatWndProc.h"
+#include "com_formdev_flatlaf_ui_FlatWindowsNativeWindowBorder_WndProc.h"
+
+/**
+ * @author Karl Tauber
+ */
+
+//---- JNI methods ------------------------------------------------------------
+
+extern "C"
+JNIEXPORT jlong JNICALL Java_com_formdev_flatlaf_ui_FlatWindowsNativeWindowBorder_00024WndProc_installImpl
+	( JNIEnv *env, jobject obj, jobject window )
+{
+	return reinterpret_cast<jlong>( FlatWndProc::install( env, obj, window ) );
+}
+
+extern "C"
+JNIEXPORT void JNICALL Java_com_formdev_flatlaf_ui_FlatWindowsNativeWindowBorder_00024WndProc_uninstallImpl
+	( JNIEnv* env, jobject obj, jlong hwnd )
+{
+	FlatWndProc::uninstall( env, obj, reinterpret_cast<HWND>( hwnd ) );
+}
+
+//---- class FlatWndProc fields -----------------------------------------------
+
+int FlatWndProc::initialized = 0;
+jmethodID FlatWndProc::onNcHitTestMID;
+jmethodID FlatWndProc::isFullscreenMID;
+jmethodID FlatWndProc::fireStateChangedLaterOnceMID;
+
+std::map<HWND, FlatWndProc*> FlatWndProc::hwndMap = std::map<HWND, FlatWndProc*>();
+
+//---- class FlatWndProc methods ----------------------------------------------
+
+FlatWndProc::FlatWndProc() {
+	jvm = NULL;
+	env = NULL;
+	obj = NULL;
+	hwnd = NULL;
+	defaultWndProc = NULL;
+}
+
+HWND FlatWndProc::install( JNIEnv *env, jobject obj, jobject window ) {
+    initIDs( env, obj );
+
+    if( initialized < 0 )
+    		return 0;
+
+	// get window handle
+	HWND hwnd = getWindowHandle( env, window );
+	if( hwnd == NULL || hwndMap.count( hwnd ) > 0 )
+		return 0;
+
+	FlatWndProc* fwp = new FlatWndProc();
+	env->GetJavaVM( &fwp->jvm );
+	fwp->obj = env->NewGlobalRef( obj );
+	fwp->hwnd = hwnd;
+	hwndMap[hwnd] = fwp;
+
+	// replace window procedure
+	fwp->defaultWndProc = reinterpret_cast<WNDPROC>(
+		::SetWindowLongPtr( hwnd, GWLP_WNDPROC, (LONG_PTR) FlatWndProc::StaticWindowProc ) );
+
+	// remove the OS window title bar
+	fwp->updateFrame();
+
+	return hwnd;
+}
+
+void FlatWndProc::uninstall( JNIEnv *env, jobject obj, HWND hwnd ) {
+    if( hwnd == NULL || hwndMap.count( hwnd ) == 0 )
+    		return;
+
+    FlatWndProc* fwp = hwndMap[hwnd];
+	hwndMap.erase( hwnd );
+
+	// restore original window procedure
+	::SetWindowLongPtr( hwnd, GWLP_WNDPROC, (LONG_PTR) fwp->defaultWndProc );
+
+	// show the OS window title bar
+	fwp->updateFrame();
+
+	// cleanup
+	env->DeleteGlobalRef( fwp->obj );
+	delete fwp;
+}
+
+void FlatWndProc::initIDs( JNIEnv *env, jobject obj ) {
+	if( initialized )
+		return;
+
+	initialized = -1;
+
+	jclass cls = env->GetObjectClass( obj );
+	onNcHitTestMID = env->GetMethodID( cls, "onNcHitTest", "(IIZ)I" );
+	isFullscreenMID = env->GetMethodID( cls, "isFullscreen", "()Z" );
+	fireStateChangedLaterOnceMID = env->GetMethodID( cls, "fireStateChangedLaterOnce", "()V" );
+
+	// check whether all IDs were found
+	if( onNcHitTestMID != NULL &&
+		isFullscreenMID != NULL &&
+		fireStateChangedLaterOnceMID != NULL )
+	  initialized = 1;
+}
+
+void FlatWndProc::updateFrame() {
+	// this sends WM_NCCALCSIZE and removes/shows the window title bar
+	::SetWindowPos( hwnd, hwnd, 0, 0, 0, 0,
+		SWP_FRAMECHANGED | SWP_NOMOVE | SWP_NOSIZE | SWP_NOZORDER );
+}
+
+LRESULT CALLBACK FlatWndProc::StaticWindowProc( HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam ) {
+	FlatWndProc* fwp = hwndMap[hwnd];
+	return fwp->WindowProc( hwnd, uMsg, wParam, lParam );
+}
+
+/**
+ * NOTE: This method is invoked on the AWT-Windows thread (not the AWT-EventQueue thread).
+ */
+LRESULT CALLBACK FlatWndProc::WindowProc( HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam ) {
+	switch( uMsg ) {
+		case WM_NCCALCSIZE:
+			return WmNcCalcSize( hwnd, uMsg, wParam, lParam );
+
+		case WM_NCHITTEST:
+			return WmNcHitTest( hwnd, uMsg, wParam, lParam );
+
+		case WM_NCRBUTTONUP:
+			if( wParam == HTCAPTION || wParam == HTSYSMENU )
+				openSystemMenu( hwnd, GET_X_LPARAM( lParam ), GET_Y_LPARAM( lParam ) );
+			break;
+
+		case WM_DWMCOLORIZATIONCOLORCHANGED:
+			fireStateChangedLaterOnce();
+			break;
+
+		case WM_DESTROY:
+			return WmDestroy( hwnd, uMsg, wParam, lParam );
+	}
+
+	return ::CallWindowProc( defaultWndProc, hwnd, uMsg, wParam, lParam );
+}
+/**
+ * Handle WM_DESTROY
+ *
+ * https://docs.microsoft.com/en-us/windows/win32/winmsg/wm-destroy
+ */
+LRESULT FlatWndProc::WmDestroy( HWND hwnd, int uMsg, WPARAM wParam, LPARAM lParam ) {
+	// restore original window procedure
+	::SetWindowLongPtr( hwnd, GWLP_WNDPROC, (LONG_PTR) defaultWndProc );
+
+	WNDPROC defaultWndProc2 = defaultWndProc;
+
+	// cleanup
+	getEnv()->DeleteGlobalRef( obj );
+	hwndMap.erase( hwnd );
+	delete this;
+
+	// call original AWT window procedure because it may fire window closed event in AwtWindow::WmDestroy()
+	return ::CallWindowProc( defaultWndProc2, hwnd, uMsg, wParam, lParam );
+}
+
+/**
+ * Handle WM_NCCALCSIZE
+ *
+ * https://docs.microsoft.com/en-us/windows/win32/winmsg/wm-nccalcsize
+ *
+ * See also NonClientIslandWindow::_OnNcCalcSize() here:
+ * https://github.com/microsoft/terminal/blob/main/src/cascadia/WindowsTerminal/NonClientIslandWindow.cpp
+ */
+LRESULT FlatWndProc::WmNcCalcSize( HWND hwnd, int uMsg, WPARAM wParam, LPARAM lParam ) {
+	if( wParam != TRUE )
+		return ::CallWindowProc( defaultWndProc, hwnd, uMsg, wParam, lParam );
+
+	NCCALCSIZE_PARAMS* params = reinterpret_cast<NCCALCSIZE_PARAMS*>( lParam );
+
+	// store the original top before the default window proc applies the default frame
+	int originalTop = params->rgrc[0].top;
+
+	// apply the default frame
+	LRESULT lResult = ::CallWindowProc( defaultWndProc, hwnd, uMsg, wParam, lParam );
+	if( lResult != 0 )
+		return lResult;
+
+	// re-apply the original top from before the size of the default frame was applied
+	params->rgrc[0].top = originalTop;
+
+	bool isMaximized = ::IsZoomed( hwnd );
+	if( isMaximized && !isFullscreen() ) {
+		// When a window is maximized, its size is actually a little bit more
+		// than the monitor's work area. The window is positioned and sized in
+		// such a way that the resize handles are outside of the monitor and
+		// then the window is clipped to the monitor so that the resize handle
+		// do not appear because you don't need them (because you can't resize
+		// a window when it's maximized unless you restore it).
+		params->rgrc[0].top += getResizeHandleHeight();
+
+		// check whether taskbar is in the autohide state
+		APPBARDATA autohide{ 0 };
+		autohide.cbSize = sizeof( autohide );
+		UINT state = (UINT) ::SHAppBarMessage( ABM_GETSTATE, &autohide );
+		if( (state & ABS_AUTOHIDE) != 0 ) {
+			// get monitor info
+			// (using MONITOR_DEFAULTTONEAREST finds right monitor when restoring from minimized)
+			HMONITOR hMonitor = ::MonitorFromWindow( hwnd, MONITOR_DEFAULTTONEAREST );
+			MONITORINFO monitorInfo{ 0 };
+			::GetMonitorInfo( hMonitor, &monitorInfo );
+
+			// If there's a taskbar on any side of the monitor, reduce our size
+			// a little bit on that edge.
+			if( hasAutohideTaskbar( ABE_TOP, monitorInfo.rcMonitor ) )
+				params->rgrc[0].top++;
+			if( hasAutohideTaskbar( ABE_BOTTOM, monitorInfo.rcMonitor ) )
+				params->rgrc[0].bottom--;
+			if( hasAutohideTaskbar( ABE_LEFT, monitorInfo.rcMonitor ) )
+				params->rgrc[0].left++;
+			if( hasAutohideTaskbar( ABE_RIGHT, monitorInfo.rcMonitor ) )
+				params->rgrc[0].right--;
+		}
+	}
+
+	return lResult;
+}
+
+/**
+ * Handle WM_NCHITTEST
+ *
+ * https://docs.microsoft.com/en-us/windows/win32/inputdev/wm-nchittest
+ *
+ * See also NonClientIslandWindow::_OnNcHitTest() here:
+ * https://github.com/microsoft/terminal/blob/main/src/cascadia/WindowsTerminal/NonClientIslandWindow.cpp
+ */
+LRESULT FlatWndProc::WmNcHitTest( HWND hwnd, int uMsg, WPARAM wParam, LPARAM lParam ) {
+	// this will handle the left, right and bottom parts of the frame because we didn't change them
+	LRESULT lResult = ::CallWindowProc( defaultWndProc, hwnd, uMsg, wParam, lParam );
+	if( lResult != HTCLIENT )
+		return lResult;
+
+	// get window rectangle needed to convert mouse x/y from screen to window coordinates
+	RECT rcWindow;
+	::GetWindowRect( hwnd, &rcWindow );
+
+	// get mouse x/y in window coordinates
+	int x = GET_X_LPARAM( lParam ) - rcWindow.left;
+	int y = GET_Y_LPARAM( lParam ) - rcWindow.top;
+
+	int resizeBorderHeight = getResizeHandleHeight();
+	bool isOnResizeBorder = (y < resizeBorderHeight) &&
+		(::GetWindowLong( hwnd, GWL_STYLE ) & WS_THICKFRAME) != 0;
+
+	return onNcHitTest( x, y, isOnResizeBorder );
+}
+
+/**
+ * Returns the height of the little space at the top of the window used to
+ * resize the window.
+ *
+ * See also NonClientIslandWindow::_GetResizeHandleHeight() here:
+ * https://github.com/microsoft/terminal/blob/main/src/cascadia/WindowsTerminal/NonClientIslandWindow.cpp
+ */
+int FlatWndProc::getResizeHandleHeight() {
+	int dpi = ::GetDpiForWindow( hwnd );
+
+	// there isn't a SM_CYPADDEDBORDER for the Y axis
+	return ::GetSystemMetricsForDpi( SM_CXPADDEDBORDER, dpi )
+		 + ::GetSystemMetricsForDpi( SM_CYSIZEFRAME, dpi );
+}
+
+/**
+ * Returns whether there is an autohide taskbar on the given edge.
+ */
+bool FlatWndProc::hasAutohideTaskbar( UINT edge, RECT rcMonitor ) {
+	APPBARDATA data{ 0 };
+	data.cbSize = sizeof( data );
+	data.uEdge = edge;
+	data.rc = rcMonitor;
+	HWND hTaskbar = (HWND) ::SHAppBarMessage( ABM_GETAUTOHIDEBAREX, &data );
+	return hTaskbar != nullptr;
+}
+
+BOOL FlatWndProc::isFullscreen() {
+	JNIEnv* env = getEnv();
+	if( env == NULL )
+		return FALSE;
+
+	return env->CallBooleanMethod( obj, isFullscreenMID );
+}
+
+int FlatWndProc::onNcHitTest( int x, int y, boolean isOnResizeBorder ) {
+	JNIEnv* env = getEnv();
+	if( env == NULL )
+		return isOnResizeBorder ? HTTOP : HTCLIENT;
+
+	return env->CallIntMethod( obj, onNcHitTestMID, (jint) x, (jint) y, (jboolean) isOnResizeBorder );
+}
+
+void FlatWndProc::fireStateChangedLaterOnce() {
+	JNIEnv* env = getEnv();
+	if( env == NULL )
+		return;
+
+	env->CallVoidMethod( obj, fireStateChangedLaterOnceMID );
+}
+
+// similar to JNU_GetEnv() in jni_util.c
+JNIEnv* FlatWndProc::getEnv() {
+	if( env != NULL )
+		return env;
+
+	jvm->GetEnv( (void **) &env, JNI_VERSION_1_2 );
+	return env;
+}
+
+/**
+ * Opens the window's system menu.
+ * The system menu is the menu that opens when the user presses Alt+Space or
+ * right clicks on the title bar
+ */
+void FlatWndProc::openSystemMenu( HWND hwnd, int x, int y ) {
+	// get system menu
+	HMENU systemMenu = ::GetSystemMenu( hwnd, false );
+
+	// update system menu
+	bool isMaximized = ::IsZoomed( hwnd );
+	setMenuItemState( systemMenu, SC_RESTORE, isMaximized );
+	setMenuItemState( systemMenu, SC_MOVE, !isMaximized );
+	setMenuItemState( systemMenu, SC_SIZE, !isMaximized );
+	setMenuItemState( systemMenu, SC_MINIMIZE, true );
+	setMenuItemState( systemMenu, SC_MAXIMIZE, !isMaximized );
+	setMenuItemState( systemMenu, SC_CLOSE, true );
+
+	// make "Close" item the default to be consistent with the system menu shown
+	// when pressing Alt+Space
+	::SetMenuDefaultItem( systemMenu, SC_CLOSE, 0 );
+
+	// show system menu
+	int ret = ::TrackPopupMenu( systemMenu, TPM_RETURNCMD, x, y, 0, hwnd, nullptr );
+	if( ret != 0 )
+		::PostMessage( hwnd, WM_SYSCOMMAND, ret, 0 );
+}
+
+void FlatWndProc::setMenuItemState( HMENU systemMenu, int item, bool enabled ) {
+	MENUITEMINFO mii{ 0 };
+	mii.cbSize = sizeof( mii );
+	mii.fMask = MIIM_STATE;
+	mii.fType = MFT_STRING;
+	mii.fState = enabled ? MF_ENABLED : MF_DISABLED;
+	::SetMenuItemInfo( systemMenu, item, FALSE, &mii );
+}
+
+HWND FlatWndProc::getWindowHandle( JNIEnv* env, jobject window ) {
+	JAWT awt;
+	awt.version = JAWT_VERSION_1_4;
+	if( !JAWT_GetAWT( env, &awt ) )
+		return 0;
+
+	jawt_DrawingSurface* ds = awt.GetDrawingSurface( env, window );
+	if( ds == NULL )
+		return 0;
+
+	jint lock = ds->Lock( ds );
+	if( (lock & JAWT_LOCK_ERROR) != 0 ) {
+		awt.FreeDrawingSurface( ds );
+		return 0;
+	}
+
+	JAWT_DrawingSurfaceInfo* dsi = ds->GetDrawingSurfaceInfo( ds );
+	JAWT_Win32DrawingSurfaceInfo* wdsi = (JAWT_Win32DrawingSurfaceInfo*) dsi->platformInfo;
+
+	HWND hwnd = wdsi->hwnd;
+
+	ds->FreeDrawingSurfaceInfo( dsi );
+	ds->Unlock( ds );
+	awt.FreeDrawingSurface( ds );
+
+	return hwnd;
+}

flatlaf-natives/flatlaf-natives-windows/src/main/cpp/FlatWndProc.h

@@ -0,0 +1,63 @@
+/*
+ * Copyright 2021 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.
+ */
+
+#include <windows.h>
+
+/**
+ * @author Karl Tauber
+ */
+class FlatWndProc
+{
+public:
+	static HWND install( JNIEnv *env, jobject obj, jobject window );
+	static void uninstall( JNIEnv *env, jobject obj, HWND hwnd );
+
+private:
+	static int initialized;
+	static jmethodID onNcHitTestMID;
+	static jmethodID isFullscreenMID;
+	static jmethodID fireStateChangedLaterOnceMID;
+
+	static std::map<HWND, FlatWndProc*> hwndMap;
+
+	JavaVM* jvm;
+	JNIEnv* env; // attached to AWT-Windows/Win32 thread
+	jobject obj;
+	HWND hwnd;
+	WNDPROC defaultWndProc;
+
+	FlatWndProc();
+	static void initIDs( JNIEnv *env, jobject obj );
+	void updateFrame();
+
+	static LRESULT CALLBACK StaticWindowProc( HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam );
+	LRESULT CALLBACK WindowProc( HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam );
+	LRESULT WmDestroy( HWND hwnd, int uMsg, WPARAM wParam, LPARAM lParam );
+	LRESULT WmNcCalcSize( HWND hwnd, int uMsg, WPARAM wParam, LPARAM lParam );
+	LRESULT WmNcHitTest( HWND hwnd, int uMsg, WPARAM wParam, LPARAM lParam );
+
+	int getResizeHandleHeight();
+	bool hasAutohideTaskbar( UINT edge, RECT rcMonitor );
+	BOOL isFullscreen();
+	int onNcHitTest( int x, int y, boolean isOnResizeBorder );
+	void fireStateChangedLaterOnce();
+	JNIEnv* getEnv();
+
+	void openSystemMenu( HWND hwnd, int x, int y );
+	void setMenuItemState( HMENU systemMenu, int item, bool enabled );
+
+	static HWND getWindowHandle( JNIEnv* env, jobject window );
+};

flatlaf-natives/flatlaf-natives-windows/src/main/cpp/Registry.cpp

@@ -0,0 +1,44 @@
+/*
+ * Copyright 2021 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.
+ */
+
+#include <windows.h>
+#include <winreg.h>
+#include <winerror.h>
+#include <jni.h>
+#include "com_formdev_flatlaf_ui_FlatWindowsNativeWindowBorder.h"
+
+/**
+ * @author Karl Tauber
+ */
+
+//---- JNI methods ------------------------------------------------------------
+
+extern "C"
+JNIEXPORT jint JNICALL Java_com_formdev_flatlaf_ui_FlatWindowsNativeWindowBorder_registryGetIntValue
+	( JNIEnv* env, jclass cls, jstring key, jstring valueName, jint defaultValue )
+{
+	const char* skey = env->GetStringUTFChars( key, NULL );
+	const char* svalueName = env->GetStringUTFChars( valueName, NULL );
+
+	DWORD data = 0;
+	DWORD cbData = sizeof( data );
+	int rc = ::RegGetValueA( HKEY_CURRENT_USER, skey, svalueName, RRF_RT_DWORD, NULL, &data, &cbData );
+
+	env->ReleaseStringUTFChars( key, skey );
+	env->ReleaseStringUTFChars( valueName, svalueName );
+
+	return (rc == ERROR_SUCCESS) ? data : defaultValue;
+}

flatlaf-natives/flatlaf-natives-windows/src/main/headers/com_formdev_flatlaf_ui_FlatWindowsNativeWindowBorder.h

@@ -0,0 +1,21 @@
+/* DO NOT EDIT THIS FILE - it is machine generated */
+#include <jni.h>
+/* Header for class com_formdev_flatlaf_ui_FlatWindowsNativeWindowBorder */
+
+#ifndef _Included_com_formdev_flatlaf_ui_FlatWindowsNativeWindowBorder
+#define _Included_com_formdev_flatlaf_ui_FlatWindowsNativeWindowBorder
+#ifdef __cplusplus
+extern "C" {
+#endif
+/*
+ * Class:     com_formdev_flatlaf_ui_FlatWindowsNativeWindowBorder
+ * Method:    registryGetIntValue
+ * Signature: (Ljava/lang/String;Ljava/lang/String;I)I
+ */
+JNIEXPORT jint JNICALL Java_com_formdev_flatlaf_ui_FlatWindowsNativeWindowBorder_registryGetIntValue
+  (JNIEnv *, jclass, jstring, jstring, jint);
+
+#ifdef __cplusplus
+}
+#endif
+#endif

flatlaf-natives/flatlaf-natives-windows/src/main/headers/com_formdev_flatlaf_ui_FlatWindowsNativeWindowBorder_WndProc.h

@@ -0,0 +1,37 @@
+/* DO NOT EDIT THIS FILE - it is machine generated */
+#include <jni.h>
+/* Header for class com_formdev_flatlaf_ui_FlatWindowsNativeWindowBorder_WndProc */
+
+#ifndef _Included_com_formdev_flatlaf_ui_FlatWindowsNativeWindowBorder_WndProc
+#define _Included_com_formdev_flatlaf_ui_FlatWindowsNativeWindowBorder_WndProc
+#ifdef __cplusplus
+extern "C" {
+#endif
+#undef com_formdev_flatlaf_ui_FlatWindowsNativeWindowBorder_WndProc_HTCLIENT
+#define com_formdev_flatlaf_ui_FlatWindowsNativeWindowBorder_WndProc_HTCLIENT 1L
+#undef com_formdev_flatlaf_ui_FlatWindowsNativeWindowBorder_WndProc_HTCAPTION
+#define com_formdev_flatlaf_ui_FlatWindowsNativeWindowBorder_WndProc_HTCAPTION 2L
+#undef com_formdev_flatlaf_ui_FlatWindowsNativeWindowBorder_WndProc_HTSYSMENU
+#define com_formdev_flatlaf_ui_FlatWindowsNativeWindowBorder_WndProc_HTSYSMENU 3L
+#undef com_formdev_flatlaf_ui_FlatWindowsNativeWindowBorder_WndProc_HTTOP
+#define com_formdev_flatlaf_ui_FlatWindowsNativeWindowBorder_WndProc_HTTOP 12L
+/*
+ * Class:     com_formdev_flatlaf_ui_FlatWindowsNativeWindowBorder_WndProc
+ * Method:    installImpl
+ * Signature: (Ljava/awt/Window;)J
+ */
+JNIEXPORT jlong JNICALL Java_com_formdev_flatlaf_ui_FlatWindowsNativeWindowBorder_00024WndProc_installImpl
+  (JNIEnv *, jobject, jobject);
+
+/*
+ * Class:     com_formdev_flatlaf_ui_FlatWindowsNativeWindowBorder_WndProc
+ * Method:    uninstallImpl
+ * Signature: (J)V
+ */
+JNIEXPORT void JNICALL Java_com_formdev_flatlaf_ui_FlatWindowsNativeWindowBorder_00024WndProc_uninstallImpl
+  (JNIEnv *, jobject, jlong);
+
+#ifdef __cplusplus
+}
+#endif
+#endif

flatlaf-testing/build.gradle.kts

@@ -27,12 +27,12 @@ repositories {
 
 dependencies {
 	implementation( project( ":flatlaf-core" ) )
-	implementation( project( ":flatlaf-natives-jna" ) )
 	implementation( project( ":flatlaf-extras" ) )
 	implementation( project( ":flatlaf-swingx" ) )
 	implementation( project( ":flatlaf-jide-oss" ) )
 	implementation( project( ":flatlaf-intellij-themes" ) )
 	implementation( project( ":flatlaf-demo" ) )
+//	implementation( project( ":flatlaf-natives-jna" ) )
 
 	implementation( "com.miglayout:miglayout-swing:5.3-SNAPSHOT" )
 	implementation( "com.jgoodies:jgoodies-forms:1.9.0" )

settings.gradle.kts

@@ -25,6 +25,7 @@ include( "flatlaf-demo" )
 include( "flatlaf-testing" )
 include( "flatlaf-theme-editor" )
 
+includeProject( "flatlaf-natives-windows", "flatlaf-natives/flatlaf-natives-windows" )
 includeProject( "flatlaf-natives-jna",     "flatlaf-natives/flatlaf-natives-jna" )
 
 fun includeProject( projectPath: String, projectDir: String ) {