Window decorations: allow enabling/disabling custom window decorations via system properties "flatlaf.useWindowDecorations", "flatlaf.useJetBrainsCustomDecorations" and "flatlaf.menuBarEmbedded" (all boolean)

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

@@ -88,6 +88,9 @@ public abstract class FlatLaf
 
 	private Consumer<UIDefaults> postInitialization;
 
+	private Boolean oldFrameWindowDecorated;
+	private Boolean oldDialogWindowDecorated;
+
 	public static boolean install( LookAndFeel newLookAndFeel ) {
 		try {
 			UIManager.setLookAndFeel( newLookAndFeel );
@@ -242,6 +245,16 @@ public abstract class FlatLaf
 					String.format( "a { color: #%06x; }", linkColor.getRGB() & 0xffffff ) );
 			}
 		};
+
+		// enable/disable window decorations, but only if system property is either
+		// "true" or "false"; in other cases it is not changed
+		Boolean useWindowDecorations = FlatSystemProperties.getBooleanStrict( FlatSystemProperties.USE_WINDOW_DECORATIONS, null );
+		if( useWindowDecorations != null ) {
+			oldFrameWindowDecorated = JFrame.isDefaultLookAndFeelDecorated();
+			oldDialogWindowDecorated = JDialog.isDefaultLookAndFeelDecorated();
+			JFrame.setDefaultLookAndFeelDecorated( useWindowDecorations );
+			JDialog.setDefaultLookAndFeelDecorated( useWindowDecorations );
+		}
 	}
 
 	@Override
@@ -274,6 +287,14 @@ public abstract class FlatLaf
 		new HTMLEditorKit().getStyleSheet().addRule( "a { color: blue; }" );
 		postInitialization = null;
 
+		// restore enable/disable window decorations
+		if( oldFrameWindowDecorated != null ) {
+			JFrame.setDefaultLookAndFeelDecorated( oldFrameWindowDecorated );
+			JDialog.setDefaultLookAndFeelDecorated( oldDialogWindowDecorated );
+			oldFrameWindowDecorated = null;
+			oldDialogWindowDecorated = null;
+		}
+
 		super.uninitialize();
 	}
 

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

@@ -16,6 +16,9 @@
 
 package com.formdev.flatlaf;
 
+import javax.swing.JDialog;
+import javax.swing.JFrame;
+
 /**
  * Defines/documents own system properties used in FlatLaf.
  *
@@ -46,6 +49,41 @@ public interface FlatSystemProperties
 	 */
 	String USE_UBUNTU_FONT = "flatlaf.useUbuntuFont";
 
+	/**
+	 * Specifies whether custom look and feel window decorations should be used
+	 * when creating {@code JFrame} or {@code JDialog}.
+	 * <p>
+	 * If this system property is set, FlatLaf invokes {@link JFrame#setDefaultLookAndFeelDecorated(boolean)}
+	 * and {@link JDialog#setDefaultLookAndFeelDecorated(boolean)} on LaF initialization.
+	 * <p>
+	 * <strong>Allowed Values</strong> {@code false} and {@code true}<br>
+	 * <strong>Default</strong> none
+	 */
+	String USE_WINDOW_DECORATIONS = "flatlaf.useWindowDecorations";
+
+	/**
+	 * Specifies whether JetBrains Runtime custom window decorations should be used
+	 * when creating {@code JFrame} or {@code JDialog}.
+	 * Requires that the application runs in a
+	 * <a href="https://confluence.jetbrains.com/display/JBR/JetBrains+Runtime">JetBrains Runtime</a>
+	 * (based on OpenJDK).
+	 * <p>
+	 * Setting this to {@code true} forces using JetBrains Runtime custom window decorations
+	 * even if they are not enabled by the application.
+	 * <p>
+	 * <strong>Allowed Values</strong> {@code false} and {@code true}<br>
+	 * <strong>Default</strong> {@code true}
+	 */
+	String USE_JETBRAINS_CUSTOM_DECORATIONS = "flatlaf.useJetBrainsCustomDecorations";
+
+	/**
+	 * Specifies whether menubar is embedded into custom window decorations.
+	 * <p>
+	 * <strong>Allowed Values</strong> {@code false} and {@code true}<br>
+	 * <strong>Default</strong> {@code true}
+	 */
+	String MENUBAR_EMBEDDED = "flatlaf.menuBarEmbedded";
+
 	/**
 	 * Specifies whether vertical text position is corrected when UI is scaled on HiDPI screens.
 	 * <p>
@@ -63,4 +101,18 @@ public interface FlatSystemProperties
 		String value = System.getProperty( key );
 		return (value != null) ? Boolean.parseBoolean( value ) : defaultValue;
 	}
+
+	/**
+	 * Checks whether a system property is set and returns {@code Boolean.TRUE} if its value
+	 * is {@code "true"} (case-insensitive) or returns {@code Boolean.FALSE} if its value
+	 * is {@code "false"} (case-insensitive). Otherwise {@code defaultValue} is returned.
+	 */
+	static Boolean getBooleanStrict( String key, Boolean defaultValue ) {
+		String value = System.getProperty( key );
+		if( "true".equalsIgnoreCase( value ) )
+			return Boolean.TRUE;
+		if( "false".equalsIgnoreCase( value ) )
+			return Boolean.FALSE;
+		return defaultValue;
+	}
 }

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

@@ -58,6 +58,7 @@ import javax.swing.UIManager;
 import javax.swing.border.AbstractBorder;
 import javax.swing.border.Border;
 import com.formdev.flatlaf.FlatClientProperties;
+import com.formdev.flatlaf.FlatSystemProperties;
 import com.formdev.flatlaf.ui.JBRCustomDecorations.JBRWindowTopBorder;
 import com.formdev.flatlaf.util.SystemInfo;
 import com.formdev.flatlaf.util.UIScale;
@@ -320,8 +321,9 @@ class FlatTitlePane
 	}
 
 	boolean isMenuBarEmbedded() {
-		return menuBarEmbedded && FlatClientProperties.clientPropertyBoolean(
-			rootPane, FlatClientProperties.MENU_BAR_EMBEDDED, true );
+		return menuBarEmbedded &&
+			FlatClientProperties.clientPropertyBoolean( rootPane, FlatClientProperties.MENU_BAR_EMBEDDED, true ) &&
+			FlatSystemProperties.getBoolean( FlatSystemProperties.MENUBAR_EMBEDDED, true );
 	}
 
 	Rectangle getMenuBarBounds() {
@@ -376,7 +378,7 @@ class FlatTitlePane
 		// (if not running in JBR and if not modified from the application)
 		if( !hasJBRCustomDecoration() &&
 			(frame.getMaximizedBounds() == null ||
-			 Objects.equals( frame.getMaximizedBounds(), rootPane.getClientProperty( "flatlaf.maximizedBounds" ) )) )
+			 Objects.equals( frame.getMaximizedBounds(), rootPane.getClientProperty( "_flatlaf.maximizedBounds" ) )) )
 		{
 			GraphicsConfiguration gc = window.getGraphicsConfiguration();
 
@@ -428,7 +430,7 @@ class FlatTitlePane
 
 			// remember maximized bounds in client property to be able to detect
 			// whether maximized bounds are modified from the application
-			rootPane.putClientProperty( "flatlaf.maximizedBounds", maximizedBounds );
+			rootPane.putClientProperty( "_flatlaf.maximizedBounds", maximizedBounds );
 		}
 
 		// maximize window

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

@@ -39,6 +39,7 @@ import javax.swing.SwingUtilities;
 import javax.swing.UIManager;
 import javax.swing.plaf.BorderUIResource;
 import com.formdev.flatlaf.FlatLaf;
+import com.formdev.flatlaf.FlatSystemProperties;
 import com.formdev.flatlaf.util.HiDPIUtils;
 import com.formdev.flatlaf.util.SystemInfo;
 
@@ -111,8 +112,10 @@ public class JBRCustomDecorations
 			JFrame frame = (JFrame) window;
 
 			// do not enable JBR decorations if JFrame should use system window decorations
-			if( !JFrame.isDefaultLookAndFeelDecorated()  )
-				return;
+			// and if not forced to use JBR decorations
+			if( !JFrame.isDefaultLookAndFeelDecorated() &&
+				!FlatSystemProperties.getBoolean( FlatSystemProperties.USE_JETBRAINS_CUSTOM_DECORATIONS, false ))
+			  return;
 
 			// do not enable JBR decorations if frame is undecorated
 			if( frame.isUndecorated() )
@@ -128,8 +131,10 @@ public class JBRCustomDecorations
 			JDialog dialog = (JDialog) window;
 
 			// do not enable JBR decorations if JDialog should use system window decorations
-			if( !JDialog.isDefaultLookAndFeelDecorated() )
-				return;
+			// and if not forced to use JBR decorations
+			if( !JDialog.isDefaultLookAndFeelDecorated() &&
+				!FlatSystemProperties.getBoolean( FlatSystemProperties.USE_JETBRAINS_CUSTOM_DECORATIONS, false ))
+			  return;
 
 			// do not enable JBR decorations if dialog is undecorated
 			if( dialog.isUndecorated() )
@@ -189,6 +194,9 @@ public class JBRCustomDecorations
 		if( !SystemInfo.IS_JETBRAINS_JVM_11_OR_LATER || !SystemInfo.IS_WINDOWS_10_OR_LATER )
 			return;
 
+		if( !FlatSystemProperties.getBoolean( FlatSystemProperties.USE_JETBRAINS_CUSTOM_DECORATIONS, true ) )
+			return;
+
 		try {
 			Class<?> awtAcessorClass = Class.forName( "sun.awt.AWTAccessor" );
 			Class<?> compAccessorClass = Class.forName( "sun.awt.AWTAccessor$ComponentAccessor" );