Linux: rounded iconify/maximize/close buttons if using FlatLaf window decorations (issue #821)

flatlaf-core/src/main/java/com/formdev/flatlaf/icons/FlatWindowAbstractIcon.java

@@ -18,44 +18,95 @@ package com.formdev.flatlaf.icons;
 
 import java.awt.Color;
 import java.awt.Component;
+import java.awt.Container;
 import java.awt.Dimension;
 import java.awt.Graphics2D;
-import java.awt.RenderingHints;
+import java.awt.Insets;
+import java.awt.Window;
+import javax.swing.SwingUtilities;
 import com.formdev.flatlaf.ui.FlatButtonUI;
+import com.formdev.flatlaf.ui.FlatTitlePane;
 import com.formdev.flatlaf.ui.FlatUIUtils;
+import com.formdev.flatlaf.util.DerivedColor;
 import com.formdev.flatlaf.util.HiDPIUtils;
+import com.formdev.flatlaf.util.UIScale;
 
 /**
  * Base class for window icons.
  *
  * @uiDefault TitlePane.buttonSize						Dimension
+ * @uiDefault TitlePane.buttonInsets					Insets	optional
+ * @uiDefault TitlePane.buttonArc						int		optional
  * @uiDefault TitlePane.buttonSymbolHeight				int
- * @uiDefault TitlePane.buttonHoverBackground			Color
- * @uiDefault TitlePane.buttonPressedBackground			Color
+ * @uiDefault TitlePane.buttonBackground				Color	optional
+ * @uiDefault TitlePane.buttonForeground				Color	optional
+ * @uiDefault TitlePane.buttonInactiveBackground		Color	optional
+ * @uiDefault TitlePane.buttonInactiveForeground		Color	optional
+ * @uiDefault TitlePane.buttonHoverBackground			Color	optional
+ * @uiDefault TitlePane.buttonHoverForeground			Color	optional
+ * @uiDefault TitlePane.buttonPressedBackground			Color	optional
+ * @uiDefault TitlePane.buttonPressedForeground			Color	optional
  *
  * @author Karl Tauber
  */
 public abstract class FlatWindowAbstractIcon
 	extends FlatAbstractIcon
 {
-	private final int symbolHeight;
-	private final Color hoverBackground;
-	private final Color pressedBackground;
+	/** @since 3.6 */ protected final Insets insets;
+	/** @since 3.6 */ protected final int arc;
+	/** @since 3.6 */ protected final int symbolHeight;
+
+	/** @since 3.6 */ protected final Color background;
+	/** @since 3.6 */ protected final Color foreground;
+	/** @since 3.6 */ protected final Color inactiveBackground;
+	/** @since 3.6 */ protected final Color inactiveForeground;
+	protected final Color hoverBackground;
+	/** @since 3.6 */ protected final Color hoverForeground;
+	protected final Color pressedBackground;
+	/** @since 3.6 */ protected final Color pressedForeground;
 
 	/** @since 3.2 */
 	protected FlatWindowAbstractIcon( String windowStyle ) {
-		this( FlatUIUtils.getSubUIDimension( "TitlePane.buttonSize", windowStyle ),
-			FlatUIUtils.getSubUIInt( "TitlePane.buttonSymbolHeight", windowStyle, 10 ),
-			FlatUIUtils.getSubUIColor( "TitlePane.buttonHoverBackground", windowStyle ),
-			FlatUIUtils.getSubUIColor( "TitlePane.buttonPressedBackground", windowStyle ) );
+		this( windowStyle, null, null, null, null, null, null, null, null );
 	}
 
-	/** @since 3.2 */
-	protected FlatWindowAbstractIcon( Dimension size, int symbolHeight, Color hoverBackground, Color pressedBackground ) {
+	/** @since 3.6 */
+	protected FlatWindowAbstractIcon( String windowStyle,
+		Color background, Color foreground, Color inactiveBackground, Color inactiveForeground,
+		Color hoverBackground, Color hoverForeground, Color pressedBackground, Color pressedForeground )
+	{
+		this( FlatUIUtils.getSubUIDimension( "TitlePane.buttonSize", windowStyle ),
+			FlatUIUtils.getSubUIInsets( "TitlePane.buttonInsets", windowStyle ),
+			FlatUIUtils.getSubUIInt( "TitlePane.buttonArc", windowStyle, 0 ),
+			FlatUIUtils.getSubUIInt( "TitlePane.buttonSymbolHeight", windowStyle, 10 ),
+			(background != null) ? background : FlatUIUtils.getSubUIColor( "TitlePane.buttonBackground", windowStyle ),
+			(foreground != null) ? foreground : FlatUIUtils.getSubUIColor( "TitlePane.buttonForeground", windowStyle ),
+			(inactiveBackground != null) ? inactiveBackground : FlatUIUtils.getSubUIColor( "TitlePane.buttonInactiveBackground", windowStyle ),
+			(inactiveForeground != null) ? inactiveForeground : FlatUIUtils.getSubUIColor( "TitlePane.buttonInactiveForeground", windowStyle ),
+			(hoverBackground != null) ? hoverBackground : FlatUIUtils.getSubUIColor( "TitlePane.buttonHoverBackground", windowStyle ),
+			(hoverForeground != null) ? hoverForeground : FlatUIUtils.getSubUIColor( "TitlePane.buttonHoverForeground", windowStyle ),
+			(pressedBackground != null) ? pressedBackground : FlatUIUtils.getSubUIColor( "TitlePane.buttonPressedBackground", windowStyle ),
+			(pressedForeground != null) ? pressedForeground : FlatUIUtils.getSubUIColor( "TitlePane.buttonPressedForeground", windowStyle ) );
+	}
+
+	/** @since 3.6 */
+	protected FlatWindowAbstractIcon( Dimension size, Insets insets, int arc, int symbolHeight,
+		Color background, Color foreground, Color inactiveBackground, Color inactiveForeground,
+		Color hoverBackground, Color hoverForeground, Color pressedBackground, Color pressedForeground )
+	{
 		super( size.width, size.height, null );
+		this.insets = (insets != null) ? insets : new Insets( 0, 0, 0, 0 );
+		this.arc = arc;
 		this.symbolHeight = symbolHeight;
+
+		this.background = background;
+		this.foreground = foreground;
+		this.inactiveBackground = inactiveBackground;
+		this.inactiveForeground = inactiveForeground;
 		this.hoverBackground = hoverBackground;
+		this.hoverForeground = hoverForeground;
 		this.pressedBackground = pressedBackground;
+		this.pressedForeground = pressedForeground;
 	}
 
 	@Override
@@ -69,26 +120,39 @@ public abstract class FlatWindowAbstractIcon
 	/** @since 3.5.2 */
 	@Override
 	protected void paintBackground( Component c, Graphics2D g, int x, int y ) {
-		Color background = FlatButtonUI.buttonStateColor( c, null, null, null, hoverBackground, pressedBackground );
+		Color bg = null;
+		if( background != null || inactiveBackground != null ) {
+			Window window = SwingUtilities.windowForComponent( c );
+			bg = (window == null || window.isActive()) ? background : inactiveBackground;
+		}
+
+		Color background = FlatButtonUI.buttonStateColor( c, bg, null, null, hoverBackground, pressedBackground );
 		if( background != null ) {
-			// disable antialiasing for background rectangle painting to avoid blurry edges when scaled (e.g. at 125% or 175%)
-			Object oldHint = g.getRenderingHint( RenderingHints.KEY_ANTIALIASING );
-			g.setRenderingHint( RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_OFF );
+			Insets insets = UIScale.scale( this.insets );
+			float arc = UIScale.scale( (float) this.arc );
 
-			// fill background of whole component
-			g.setColor( FlatUIUtils.deriveColor( background, c.getBackground() ) );
-			g.fillRect( 0, 0, c.getWidth(), c.getHeight() );
+			// derive color from title pane background
+			if( background instanceof DerivedColor ) {
+				Container titlePane = SwingUtilities.getAncestorOfClass( FlatTitlePane.class, c );
+				Component baseComp = (titlePane != null) ? titlePane : c;
+				background = FlatUIUtils.deriveColor( background, baseComp.getBackground() );
+			}
 
-			g.setRenderingHint( RenderingHints.KEY_ANTIALIASING, oldHint );
+			g.setColor( background );
+			FlatUIUtils.paintComponentBackground( g, insets.left, insets.top,
+				c.getWidth() - insets.left - insets.right,
+				c.getHeight() - insets.top - insets.bottom,
+				0, arc );
 		}
 	}
 
 	protected Color getForeground( Component c ) {
-		return c.getForeground();
-	}
-
-	/** @since 3.2 */
-	protected int getSymbolHeight() {
-		return symbolHeight;
+		Color fg = null;
+		if( foreground != null || inactiveForeground != null ) {
+			Window window = SwingUtilities.windowForComponent( c );
+			fg = (window == null || window.isActive()) ? foreground : inactiveForeground;
+		}
+		return FlatButtonUI.buttonStateColor( c, (fg != null) ? fg : c.getForeground(),
+			null, null, hoverForeground, pressedForeground );
 	}
 }

flatlaf-core/src/main/java/com/formdev/flatlaf/icons/FlatWindowCloseIcon.java

@@ -17,53 +17,54 @@
 package com.formdev.flatlaf.icons;
 
 import java.awt.BasicStroke;
-import java.awt.Color;
-import java.awt.Component;
 import java.awt.Graphics2D;
 import java.awt.geom.Path2D;
-import com.formdev.flatlaf.ui.FlatButtonUI;
 import com.formdev.flatlaf.ui.FlatUIUtils;
 import com.formdev.flatlaf.util.SystemInfo;
 
 /**
  * "close" icon for windows (frames and dialogs).
  *
- * @uiDefault TitlePane.closeHoverBackground			Color
- * @uiDefault TitlePane.closePressedBackground			Color
- * @uiDefault TitlePane.closeHoverForeground			Color
- * @uiDefault TitlePane.closePressedForeground			Color
+ * @uiDefault TitlePane.closeBackground					Color	optional
+ * @uiDefault TitlePane.closeForeground					Color	optional
+ * @uiDefault TitlePane.closeInactiveBackground			Color	optional
+ * @uiDefault TitlePane.closeInactiveForeground			Color	optional
+ * @uiDefault TitlePane.closeHoverBackground			Color	optional
+ * @uiDefault TitlePane.closeHoverForeground			Color	optional
+ * @uiDefault TitlePane.closePressedBackground			Color	optional
+ * @uiDefault TitlePane.closePressedForeground			Color	optional
  *
  * @author Karl Tauber
  */
 public class FlatWindowCloseIcon
 	extends FlatWindowAbstractIcon
 {
-	private final Color hoverForeground;
-	private final Color pressedForeground;
-
 	public FlatWindowCloseIcon() {
 		this( null );
 	}
 
 	/** @since 3.2 */
 	public FlatWindowCloseIcon( String windowStyle ) {
-		super( FlatUIUtils.getSubUIDimension( "TitlePane.buttonSize", windowStyle ),
-			FlatUIUtils.getSubUIInt( "TitlePane.buttonSymbolHeight", windowStyle, 10 ),
+		super( windowStyle,
+			FlatUIUtils.getSubUIColor( "TitlePane.closeBackground", windowStyle ),
+			FlatUIUtils.getSubUIColor( "TitlePane.closeForeground", windowStyle ),
+			FlatUIUtils.getSubUIColor( "TitlePane.closeInactiveBackground", windowStyle ),
+			FlatUIUtils.getSubUIColor( "TitlePane.closeInactiveForeground", windowStyle ),
 			FlatUIUtils.getSubUIColor( "TitlePane.closeHoverBackground", windowStyle ),
-			FlatUIUtils.getSubUIColor( "TitlePane.closePressedBackground", windowStyle ) );
-
-		hoverForeground = FlatUIUtils.getSubUIColor( "TitlePane.closeHoverForeground", windowStyle );
-		pressedForeground = FlatUIUtils.getSubUIColor( "TitlePane.closePressedForeground", windowStyle );
+			FlatUIUtils.getSubUIColor( "TitlePane.closeHoverForeground", windowStyle ),
+			FlatUIUtils.getSubUIColor( "TitlePane.closePressedBackground", windowStyle ),
+			FlatUIUtils.getSubUIColor( "TitlePane.closePressedForeground", windowStyle ) );
 	}
 
 	@Override
 	protected void paintIconAt1x( Graphics2D g, int x, int y, int width, int height, double scaleFactor ) {
-		int iwh = (int) (getSymbolHeight() * scaleFactor);
+		int iwh = (int) (symbolHeight * scaleFactor);
 		int ix = x + ((width - iwh) / 2);
 		int iy = y + ((height - iwh) / 2);
 		int ix2 = ix + iwh - 1;
 		int iy2 = iy + iwh - 1;
-		float thickness = Math.max( SystemInfo.isWindows_11_orLater ? (float) scaleFactor : (int) scaleFactor, 1 );
+		boolean isWindows10 = SystemInfo.isWindows_10_orLater && !SystemInfo.isWindows_11_orLater;
+		float thickness = Math.max( isWindows10 ? (int) scaleFactor : (float) scaleFactor, 1 );
 
 		Path2D path = new Path2D.Float( Path2D.WIND_EVEN_ODD, 4 );
 		path.moveTo( ix, iy );
@@ -73,9 +74,4 @@ public class FlatWindowCloseIcon
 		g.setStroke( new BasicStroke( thickness ) );
 		g.draw( path );
 	}
-
-	@Override
-	protected Color getForeground( Component c ) {
-		return FlatButtonUI.buttonStateColor( c, c.getForeground(), null, null, hoverForeground, pressedForeground );
-	}
 }

flatlaf-core/src/main/java/com/formdev/flatlaf/icons/FlatWindowIconifyIcon.java

@@ -37,7 +37,7 @@ public class FlatWindowIconifyIcon
 
 	@Override
 	protected void paintIconAt1x( Graphics2D g, int x, int y, int width, int height, double scaleFactor ) {
-		int iw = (int) (getSymbolHeight() * scaleFactor);
+		int iw = (int) (symbolHeight * scaleFactor);
 		int ih = Math.max( (int) scaleFactor, 1 );
 		int ix = x + ((width - iw) / 2);
 		int iy = y + ((height - ih) / 2);

flatlaf-core/src/main/java/com/formdev/flatlaf/icons/FlatWindowMaximizeIcon.java

@@ -39,10 +39,11 @@ public class FlatWindowMaximizeIcon
 
 	@Override
 	protected void paintIconAt1x( Graphics2D g, int x, int y, int width, int height, double scaleFactor ) {
-		int iwh = (int) (getSymbolHeight() * scaleFactor);
+		int iwh = (int) (symbolHeight * scaleFactor);
 		int ix = x + ((width - iwh) / 2);
 		int iy = y + ((height - iwh) / 2);
-		float thickness = Math.max( SystemInfo.isWindows_11_orLater ? (float) scaleFactor : (int) scaleFactor, 1 );
+		boolean isWindows10 = SystemInfo.isWindows_10_orLater && !SystemInfo.isWindows_11_orLater;
+		float thickness = Math.max( isWindows10 ? (int) scaleFactor : (float) scaleFactor, 1 );
 		int arc = Math.max( (int) (1.5 * scaleFactor), 2 );
 
 		g.fill( SystemInfo.isWindows_11_orLater

flatlaf-core/src/main/java/com/formdev/flatlaf/icons/FlatWindowRestoreIcon.java

@@ -42,14 +42,15 @@ public class FlatWindowRestoreIcon
 
 	@Override
 	protected void paintIconAt1x( Graphics2D g, int x, int y, int width, int height, double scaleFactor ) {
-		int iwh = (int) (getSymbolHeight() * scaleFactor);
+		int iwh = (int) (symbolHeight * scaleFactor);
 		int ix = x + ((width - iwh) / 2);
 		int iy = y + ((height - iwh) / 2);
-		float thickness = Math.max( SystemInfo.isWindows_11_orLater ? (float) scaleFactor : (int) scaleFactor, 1 );
+		boolean isWindows10 = SystemInfo.isWindows_10_orLater && !SystemInfo.isWindows_11_orLater;
+		float thickness = Math.max( isWindows10 ? (int) scaleFactor : (float) scaleFactor, 1 );
 		int arc = Math.max( (int) (1.5 * scaleFactor), 2 );
 		int arcOuter = (int) (arc + (1.5 * scaleFactor));
 
-		int rwh = (int) ((getSymbolHeight() - 2) * scaleFactor);
+		int rwh = (int) ((symbolHeight - 2) * scaleFactor);
 		int ro2 = iwh - rwh;
 
 		// upper-right rectangle

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

@@ -31,6 +31,7 @@ import java.awt.Window;
 import java.awt.event.ComponentListener;
 import java.beans.PropertyChangeEvent;
 import java.beans.PropertyChangeListener;
+import java.util.Objects;
 import java.util.function.Function;
 import javax.swing.JComponent;
 import javax.swing.JDialog;
@@ -485,8 +486,12 @@ public class FlatRootPaneUI
 				break;
 
 			case "ancestor":
-				if( e.getNewValue() instanceof Window )
+				if( e.getNewValue() instanceof Window ) {
+					if( titlePane != null && !Objects.equals( titlePane.windowStyle, FlatTitlePane.getWindowStyle( rootPane ) ) )
+						setTitlePane( createTitlePane() );
+
 					macClearBackgroundForTranslucentWindow( rootPane );
+				}
 
 				macUninstallWindowBackgroundListener( rootPane );
 				macInstallWindowBackgroundListener( rootPane );

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

@@ -89,13 +89,16 @@ import com.formdev.flatlaf.util.UIScale;
  * @uiDefault TitlePane.iconSize							Dimension
  * @uiDefault TitlePane.iconMargins							Insets
  * @uiDefault TitlePane.titleMargins						Insets
- * @uiDefault TitlePane.menuBarEmbedded						boolean
  * @uiDefault TitlePane.titleMinimumWidth					int
  * @uiDefault TitlePane.buttonMinimumWidth					int
  * @uiDefault TitlePane.buttonMaximizedHeight				int
+ * @uiDefault TitlePane.buttonsGap							int
+ * @uiDefault TitlePane.buttonsMargins						Insets
+ * @uiDefault TitlePane.buttonsFillVertically				boolean
  * @uiDefault TitlePane.centerTitle							boolean
  * @uiDefault TitlePane.centerTitleIfMenuBarEmbedded		boolean
  * @uiDefault TitlePane.showIconBesideTitle					boolean
+ * @uiDefault TitlePane.menuBarEmbedded						boolean
  * @uiDefault TitlePane.menuBarTitleGap						int
  * @uiDefault TitlePane.menuBarTitleMinimumGap				int
  * @uiDefault TitlePane.closeIcon							Icon
@@ -123,9 +126,14 @@ public class FlatTitlePane
 	/** @since 2.5 */ protected final boolean showIconInDialogs;
 	/** @since 2 */ protected final int noIconLeftGap;
 	protected final Dimension iconSize;
+	/** @since 3.6 */ protected final Insets iconMargins;
+	/** @since 3.6 */ protected final Insets titleMargins;
 	/** @since 2.4 */ protected final int titleMinimumWidth;
 	/** @since 2.4 */ protected final int buttonMinimumWidth;
 	protected final int buttonMaximizedHeight;
+	/** @since 3.6 */ protected final int buttonsGap;
+	/** @since 3.6 */ protected final Insets buttonsMargins;
+	/** @since 3.6 */ protected final boolean buttonsFillVertically;
 	protected final boolean centerTitle;
 	protected final boolean centerTitleIfMenuBarEmbedded;
 	/** @since 2.4 */ protected final boolean showIconBesideTitle;
@@ -145,6 +153,9 @@ public class FlatTitlePane
 	protected JButton restoreButton;
 	protected JButton closeButton;
 
+	private JComponent iconifyMaximizeGapComp;
+	private JComponent maximizeCloseGapComp;
+
 	protected Window window;
 
 	private final Handler handler;
@@ -179,9 +190,7 @@ public class FlatTitlePane
 	public FlatTitlePane( JRootPane rootPane ) {
 		this.rootPane = rootPane;
 
-		Window w = SwingUtilities.getWindowAncestor( rootPane );
-		String defaultWindowStyle = (w != null && w.getType() == Window.Type.UTILITY) ? WINDOW_STYLE_SMALL : null;
-		windowStyle = clientProperty( rootPane, WINDOW_STYLE, defaultWindowStyle, String.class );
+		windowStyle = getWindowStyle( rootPane );
 
 		titleFont = FlatUIUtils.getSubUIFont( "TitlePane.font", windowStyle );
 		activeBackground = FlatUIUtils.getSubUIColor( "TitlePane.background", windowStyle );
@@ -196,9 +205,14 @@ public class FlatTitlePane
 		showIconInDialogs = FlatUIUtils.getSubUIBoolean( "TitlePane.showIconInDialogs", windowStyle, true );
 		noIconLeftGap = FlatUIUtils.getSubUIInt( "TitlePane.noIconLeftGap", windowStyle, 8 );
 		iconSize = FlatUIUtils.getSubUIDimension( "TitlePane.iconSize", windowStyle );
+		iconMargins = FlatUIUtils.getSubUIInsets( "TitlePane.iconMargins", windowStyle );
+		titleMargins = FlatUIUtils.getSubUIInsets( "TitlePane.titleMargins", windowStyle );
 		titleMinimumWidth = FlatUIUtils.getSubUIInt( "TitlePane.titleMinimumWidth", windowStyle, 60 );
 		buttonMinimumWidth = FlatUIUtils.getSubUIInt( "TitlePane.buttonMinimumWidth", windowStyle, 30 );
 		buttonMaximizedHeight = FlatUIUtils.getSubUIInt( "TitlePane.buttonMaximizedHeight", windowStyle, 0 );
+		buttonsGap = FlatUIUtils.getSubUIInt( "TitlePane.buttonsGap", windowStyle, 0 );
+		buttonsMargins = FlatUIUtils.getSubUIInsets( "TitlePane.buttonsMargins", windowStyle );
+		buttonsFillVertically = FlatUIUtils.getSubUIBoolean( "TitlePane.buttonsFillVertically", windowStyle, true );
 		centerTitle = FlatUIUtils.getSubUIBoolean( "TitlePane.centerTitle", windowStyle, false );
 		centerTitleIfMenuBarEmbedded = FlatUIUtils.getSubUIBoolean( "TitlePane.centerTitleIfMenuBarEmbedded", windowStyle, true );
 		showIconBesideTitle = FlatUIUtils.getSubUIBoolean( "TitlePane.showIconBesideTitle", windowStyle, false );
@@ -228,6 +242,12 @@ public class FlatTitlePane
 		applyComponentOrientation( rootPane.getComponentOrientation() );
 	}
 
+	static String getWindowStyle( JRootPane rootPane ) {
+		Window w = SwingUtilities.getWindowAncestor( rootPane );
+		String defaultWindowStyle = (w != null && w.getType() == Window.Type.UTILITY) ? WINDOW_STYLE_SMALL : null;
+		return clientProperty( rootPane, WINDOW_STYLE, defaultWindowStyle, String.class );
+	}
+
 	protected FlatTitlePaneBorder createTitlePaneBorder() {
 		return new FlatTitlePaneBorder();
 	}
@@ -245,8 +265,8 @@ public class FlatTitlePane
 				setUI( new FlatTitleLabelUI() );
 			}
 		};
-		iconLabel.setBorder( new FlatEmptyBorder( FlatUIUtils.getSubUIInsets( "TitlePane.iconMargins", windowStyle ) ) );
-		titleLabel.setBorder( new FlatEmptyBorder( FlatUIUtils.getSubUIInsets( "TitlePane.titleMargins", windowStyle ) ) );
+		iconLabel.setBorder( new FlatEmptyBorder( iconMargins ) );
+		titleLabel.setBorder( new FlatEmptyBorder( titleMargins ) );
 
 		leftPanel.setLayout( new BoxLayout( leftPanel, BoxLayout.LINE_AXIS ) );
 		leftPanel.setOpaque( false );
@@ -349,10 +369,15 @@ public class FlatTitlePane
 		restoreButton = createButton( "TitlePane.restoreIcon", "Restore", e -> restore() );
 		closeButton = createButton( "TitlePane.closeIcon", "Close", e -> close() );
 
+		iconifyMaximizeGapComp = createButtonsGapComp();
+		maximizeCloseGapComp = createButtonsGapComp();
+
 		// initially hide buttons that are only supported in frames
 		iconifyButton.setVisible( false );
 		maximizeButton.setVisible( false );
 		restoreButton.setVisible( false );
+		iconifyMaximizeGapComp.setVisible( false );
+		maximizeCloseGapComp.setVisible( false );
 
 		buttonPanel = new JPanel() {
 			@Override
@@ -364,12 +389,13 @@ public class FlatTitlePane
 
 				if( buttonMaximizedHeight > 0 && isWindowMaximized() && !hasVisibleEmbeddedMenuBar( rootPane.getJMenuBar() ) ) {
 					// make title pane height smaller when frame is maximized
-					size = new Dimension( size.width, Math.min( size.height, UIScale.scale( buttonMaximizedHeight ) ) );
+					size = new Dimension( size.width, Math.min( size.height, UIScale.scale( buttonMaximizedHeight + buttonsMargins.top + buttonsMargins.bottom ) ) );
 				}
 				return size;
 			}
 		};
 		buttonPanel.setOpaque( false );
+		buttonPanel.setBorder( FlatUIUtils.nonUIResource( new FlatEmptyBorder( buttonsMargins ) ) );
 		buttonPanel.setLayout( new BoxLayout( buttonPanel, BoxLayout.LINE_AXIS ) );
 		if( rootPane.getWindowDecorationStyle() == JRootPane.FRAME ) {
 			// JRootPane.FRAME works only for frames (and not for dialogs)
@@ -378,8 +404,10 @@ public class FlatTitlePane
 			// later in frameStateChanged(), which is invoked from addNotify()
 
 			buttonPanel.add( iconifyButton );
+			buttonPanel.add( iconifyMaximizeGapComp );
 			buttonPanel.add( maximizeButton );
 			buttonPanel.add( restoreButton );
+			buttonPanel.add( maximizeCloseGapComp );
 		}
 		buttonPanel.add( closeButton );
 
@@ -396,13 +424,17 @@ public class FlatTitlePane
 			@Override
 			public Dimension getMinimumSize() {
 				// allow the button to shrink if space is rare
-				return new Dimension( UIScale.scale( buttonMinimumWidth ), super.getMinimumSize().height );
+				return new Dimension(
+					Math.min( UIScale.scale( buttonMinimumWidth ), super.getPreferredSize().width ),
+					super.getMinimumSize().height );
 			}
 			@Override
 			public Dimension getMaximumSize() {
 				// allow the button to fill whole button area height
 				// see also BasicMenuUI.getMaximumSize()
-				return new Dimension( super.getMaximumSize().width, Short.MAX_VALUE );
+				return buttonsFillVertically
+					? new Dimension( super.getMaximumSize().width, Short.MAX_VALUE )
+					: super.getMaximumSize();
 			}
 		};
 		button.setFocusable( false );
@@ -413,6 +445,14 @@ public class FlatTitlePane
 		return button;
 	}
 
+	private JComponent createButtonsGapComp() {
+		JComponent gapComp = new JPanel();
+		gapComp.setOpaque( false );
+		gapComp.setMinimumSize( new Dimension( 0, 0 ) );
+		gapComp.setPreferredSize( new Dimension( UIScale.scale( buttonsGap ), 0 ) );
+		return gapComp;
+	}
+
 	protected void activeChanged( boolean active ) {
 		Color background = clientPropertyColor( rootPane, TITLE_BAR_BACKGROUND, null );
 		Color foreground = clientPropertyColor( rootPane, TITLE_BAR_FOREGROUND, null );
@@ -434,6 +474,9 @@ public class FlatTitlePane
 		closeButton.setForeground( foreground );
 
 		// this is necessary because hover/pressed colors are derived from background color
+		// (since FlatWindowAbstractIcon now invokes FlatTitlePane.getBackground()
+		//  to get base color, this is no longer necessary, but keep it for compatibility;
+		//  e.g. for custom window icons)
 		iconifyButton.setBackground( background );
 		maximizeButton.setBackground( background );
 		restoreButton.setBackground( background );
@@ -493,6 +536,13 @@ public class FlatTitlePane
 			maximizeButton.setVisible( false );
 			restoreButton.setVisible( false );
 		}
+
+		boolean iconifyVisible = iconifyButton.isVisible();
+		boolean maximizeVisible = maximizeButton.isVisible();
+		boolean restoreVisible = restoreButton.isVisible();
+		boolean closeVisible = closeButton.isVisible();
+		iconifyMaximizeGapComp.setVisible( iconifyVisible && (maximizeVisible || restoreVisible || closeVisible) );
+		maximizeCloseGapComp.setVisible( closeVisible && (maximizeVisible || restoreVisible) );
 	}
 
 	protected void updateIcon() {
@@ -746,12 +796,17 @@ public class FlatTitlePane
 		if( isFullWindowContent() )
 			return;
 
+		g.setColor( getBackground() );
+		g.fillRect( 0, 0, getWidth(), getHeight() );
+	}
+
+	@Override
+	public Color getBackground() {
 		// not storing value of "TitlePane.unifiedBackground" in class to allow changing at runtime
-		g.setColor( (UIManager.getBoolean( "TitlePane.unifiedBackground" ) &&
+		return (UIManager.getBoolean( "TitlePane.unifiedBackground" ) &&
 				clientPropertyColor( rootPane, TITLE_BAR_BACKGROUND, null ) == null)
 			? FlatUIUtils.getParentBackground( this )
-			: getBackground() );
-		g.fillRect( 0, 0, getWidth(), getHeight() );
+			: super.getBackground();
 	}
 
 	/**
@@ -1093,6 +1148,7 @@ public class FlatTitlePane
 		if( !c.isDisplayable() || !c.isVisible() || !contains( c, x, y ) || c == mouseLayer )
 			return true; // continue checking with next component
 
+		// check enabled component that has mouse listeners
 		if( c.isEnabled() &&
 			(c.getMouseListeners().length > 0 ||
 			 c.getMouseMotionListeners().length > 0) )

flatlaf-core/src/main/resources/com/formdev/flatlaf/FlatDarkLaf.properties

@@ -341,8 +341,13 @@ TableHeader.bottomSeparatorColor = $TableHeader.separatorColor
 #---- TitlePane ----
 
 TitlePane.embeddedForeground = darken($TitlePane.foreground,15%)
-TitlePane.buttonHoverBackground = lighten($TitlePane.background,15%,derived)
-TitlePane.buttonPressedBackground = lighten($TitlePane.background,10%,derived)
+TitlePane.buttonHoverBackground = lighten($TitlePane.background,10%,derived)
+TitlePane.buttonPressedBackground = lighten($TitlePane.background,6%,derived)
+
+# Linux
+[linux]TitlePane.buttonBackground = lighten($TitlePane.background,5%,derived)
+[linux]TitlePane.buttonHoverBackground = lighten($TitlePane.background,10%,derived)
+[linux]TitlePane.buttonPressedBackground = lighten($TitlePane.background,15%,derived)
 
 
 #---- ToggleButton ----

flatlaf-core/src/main/resources/com/formdev/flatlaf/FlatLaf.properties

@@ -823,9 +823,14 @@ TitlePane.iconMargins = 3,8,3,8
 TitlePane.titleMargins = 3,0,3,0
 TitlePane.titleMinimumWidth = 60
 TitlePane.buttonSize = 44,30
+TitlePane.buttonInsets = 0,0,0,0
+TitlePane.buttonArc = 0
 TitlePane.buttonMinimumWidth = 30
 TitlePane.buttonMaximizedHeight = 22
 TitlePane.buttonSymbolHeight = 10
+TitlePane.buttonsGap = 0
+TitlePane.buttonsMargins = 0,0,0,0
+TitlePane.buttonsFillVertically = true
 TitlePane.centerTitle = false
 TitlePane.centerTitleIfMenuBarEmbedded = true
 TitlePane.showIconBesideTitle = false
@@ -856,6 +861,27 @@ TitlePane.small.iconifyIcon = com.formdev.flatlaf.icons.FlatWindowIconifyIcon, s
 TitlePane.small.maximizeIcon = com.formdev.flatlaf.icons.FlatWindowMaximizeIcon, small
 TitlePane.small.restoreIcon = com.formdev.flatlaf.icons.FlatWindowRestoreIcon, small
 
+# Linux
+[linux]TitlePane.buttonSize = 26,26
+[linux]TitlePane.buttonInsets = 2,2,2,2
+[linux]TitlePane.buttonArc = 999
+[linux]TitlePane.buttonMaximizedHeight = -1
+[linux]TitlePane.buttonSymbolHeight = 8
+[linux]TitlePane.buttonsGap = 8
+[linux]TitlePane.buttonsMargins = 4,4,4,4
+[linux]TitlePane.buttonsFillVertically = false
+[linux]TitlePane.small.buttonSize = 20,20
+[linux]TitlePane.small.buttonInsets = 1,1,1,1
+[linux]TitlePane.small.buttonSymbolHeight = 6
+[linux]TitlePane.small.buttonsGap = 4
+[linux]TitlePane.small.buttonsMargins = 2,2,2,2
+[linux]TitlePane.closeBackground = $?TitlePane.buttonBackground
+[linux]TitlePane.closeInactiveBackground = $?TitlePane.buttonInactiveBackground
+[linux]TitlePane.closeHoverBackground = $?TitlePane.buttonHoverBackground
+[linux]TitlePane.closePressedBackground = $?TitlePane.buttonPressedBackground
+[linux]TitlePane.closeHoverForeground = $?TitlePane.foreground
+[linux]TitlePane.closePressedForeground = $?TitlePane.foreground
+
 
 #---- ToggleButton ----
 

flatlaf-core/src/main/resources/com/formdev/flatlaf/FlatLightLaf.properties

@@ -347,8 +347,13 @@ TableHeader.bottomSeparatorColor = $TableHeader.separatorColor
 #---- TitlePane ----
 
 TitlePane.embeddedForeground = lighten($TitlePane.foreground,35%)
-TitlePane.buttonHoverBackground = darken($TitlePane.background,10%,derived)
-TitlePane.buttonPressedBackground = darken($TitlePane.background,8%,derived)
+TitlePane.buttonHoverBackground = darken($TitlePane.background,5%,derived)
+TitlePane.buttonPressedBackground = darken($TitlePane.background,3%,derived)
+
+# Linux
+[linux]TitlePane.buttonBackground = darken($TitlePane.background,5%,derived)
+[linux]TitlePane.buttonHoverBackground = darken($TitlePane.background,10%,derived)
+[linux]TitlePane.buttonPressedBackground = darken($TitlePane.background,15%,derived)
 
 
 #---- ToggleButton ----