Window decorations: fixed missing window top border on Windows 10 in "full window content" mode (issue #809)

CHANGELOG.md

@@ -8,6 +8,8 @@ FlatLaf Change Log
 - TabbedPane: Fixed swapped back and forward scroll buttons when using
   `TabbedPane.scrollButtonsPlacement = trailing` (regression in FlatLaf 3.3).
 - Extras: `FlatSVGIcon` color filters now support linear gradients. (PR #817)
+- Fixed missing window top border on Windows 10 in "full window content" mode.
+  (issue 809)
 
 
 ## 3.4

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

@@ -270,6 +270,7 @@ public class FlatRootPaneUI
 	// layer title pane under frame content layer to allow placing menu bar over title pane
 	protected final static Integer TITLE_PANE_LAYER = JLayeredPane.FRAME_CONTENT_LAYER - 1;
 	private final static Integer TITLE_PANE_MOUSE_LAYER = JLayeredPane.FRAME_CONTENT_LAYER - 2;
+	private final static Integer WINDOW_TOP_BORDER_LAYER = Integer.MAX_VALUE;
 
 	// for fullWindowContent mode, layer title pane over frame content layer to allow placing title bar buttons over content
 	/** @since 3.4 */
@@ -285,11 +286,15 @@ public class FlatRootPaneUI
 		if( titlePane != null ) {
 			layeredPane.remove( titlePane );
 			layeredPane.remove( titlePane.mouseLayer );
+			if( titlePane.windowTopBorderLayer != null )
+				layeredPane.remove( titlePane.windowTopBorderLayer );
 		}
 
 		if( newTitlePane != null ) {
 			layeredPane.add( newTitlePane, getLayerForTitlePane() );
 			layeredPane.add( newTitlePane.mouseLayer, TITLE_PANE_MOUSE_LAYER );
+			if( newTitlePane.windowTopBorderLayer != null && newTitlePane.isWindowTopBorderNeeded() && isFullWindowContent( rootPane ) )
+				layeredPane.add( newTitlePane.windowTopBorderLayer, WINDOW_TOP_BORDER_LAYER );
 		}
 
 		titlePane = newTitlePane;
@@ -446,6 +451,13 @@ public class FlatRootPaneUI
 			case FlatClientProperties.FULL_WINDOW_CONTENT:
 				if( titlePane != null ) {
 					rootPane.getLayeredPane().setLayer( titlePane, getLayerForTitlePane() );
+					if( titlePane.windowTopBorderLayer != null ) {
+						JLayeredPane layeredPane = rootPane.getLayeredPane();
+						if( titlePane.isWindowTopBorderNeeded() && isFullWindowContent( rootPane ) )
+							layeredPane.add( titlePane.windowTopBorderLayer, WINDOW_TOP_BORDER_LAYER );
+						else
+							layeredPane.remove( titlePane.windowTopBorderLayer );
+					}
 					titlePane.updateIcon();
 					titlePane.updateVisibility();
 					titlePane.updateFullWindowContentButtonsBoundsProperty();
@@ -591,6 +603,12 @@ public class FlatRootPaneUI
 					titlePane.setBounds( 0, 0, width, prefHeight );
 
 				titlePane.mouseLayer.setBounds( 0, 0, width, prefHeight );
+				if( titlePane.windowTopBorderLayer != null ) {
+					boolean show = isFullWindowContent && !titlePane.isWindowMaximized() && !isFullScreen;
+					if( show )
+						titlePane.windowTopBorderLayer.setBounds( 0, 0, width, 1 );
+					titlePane.windowTopBorderLayer.setVisible( show );
+				}
 
 				if( !isFullWindowContent )
 					nextY += prefHeight;

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

@@ -110,6 +110,7 @@ public class FlatTitlePane
 	extends JComponent
 {
 	static final String KEY_DEBUG_SHOW_RECTANGLES = "FlatLaf.debug.titlebar.showRectangles";
+	private static final boolean isWindows_10 = SystemInfo.isWindows_10_orLater && !SystemInfo.isWindows_11_orLater;
 
 	/** @since 2.5 */ protected final Font titleFont;
 	protected final Color activeBackground;
@@ -166,6 +167,16 @@ public class FlatTitlePane
 	 */
 	final JPanel mouseLayer;
 
+	/**
+	 * This panel paint a border at the top of the window in fullWindowContent mode,
+	 * if FlatLaf window decorations are enabled.
+	 * Only used on Windows 10.
+	 * <p>
+	 * This panel is not a child of the title pane.
+	 * Instead it is added by FlatRootPaneUI to the layered pane at a layer over all other layers.
+	 */
+	final JPanel windowTopBorderLayer;
+
 	public FlatTitlePane( JRootPane rootPane ) {
 		this.rootPane = rootPane;
 
@@ -207,6 +218,14 @@ public class FlatTitlePane
 		mouseLayer.addMouseListener( handler );
 		mouseLayer.addMouseMotionListener( handler );
 
+		if( isWindows_10 && FlatNativeWindowBorder.isSupported() ) {
+			windowTopBorderLayer = new JPanel();
+			windowTopBorderLayer.setVisible( false );
+			windowTopBorderLayer.setOpaque( false );
+			windowTopBorderLayer.setBorder( FlatUIUtils.nonUIResource( FlatNativeWindowBorder.WindowTopBorder.getInstance() ) );
+		} else
+			windowTopBorderLayer = null;
+
 		applyComponentOrientation( rootPane.getComponentOrientation() );
 	}
 
@@ -919,6 +938,10 @@ public class FlatTitlePane
 		return window != null && FlatNativeWindowBorder.hasCustomDecoration( window );
 	}
 
+	boolean isWindowTopBorderNeeded() {
+		return isWindows_10 && hasNativeCustomDecoration();
+	}
+
 	// used to invoke updateNativeTitleBarHeightAndHitTestSpots() only once from latest invokeLater()
 	private int laterCounter;
 
@@ -1146,7 +1169,7 @@ public class FlatTitlePane
 			} else if( borderColor != null && (rootPane.getJMenuBar() == null || !rootPane.getJMenuBar().isVisible()) )
 				insets.bottom += UIScale.scale( 1 );
 
-			if( !SystemInfo.isWindows_11_orLater && hasNativeCustomDecoration() && !isWindowMaximized() )
+			if( isWindowTopBorderNeeded() && !isWindowMaximized() )
 				insets = FlatUIUtils.addInsets( insets, WindowTopBorder.getInstance().getBorderInsets() );
 
 			return insets;
@@ -1165,7 +1188,7 @@ public class FlatTitlePane
 				FlatUIUtils.paintFilledRectangle( g, borderColor, x, y + height - lineHeight, width, lineHeight );
 			}
 
-			if( !SystemInfo.isWindows_11_orLater && hasNativeCustomDecoration() && !isWindowMaximized() )
+			if( isWindowTopBorderNeeded() && !isWindowMaximized() && !isFullWindowContent() )
 				WindowTopBorder.getInstance().paintBorder( c, g, x, y, width, height );
 		}
 
@@ -1329,7 +1352,7 @@ public class FlatTitlePane
 			activeChanged( true );
 			updateNativeTitleBarHeightAndHitTestSpots();
 
-			if( !SystemInfo.isWindows_11_orLater && hasNativeCustomDecoration() )
+			if( isWindowTopBorderNeeded() )
 				WindowTopBorder.getInstance().repaintBorder( FlatTitlePane.this );
 
 			repaintWindowBorder();
@@ -1340,7 +1363,7 @@ public class FlatTitlePane
 			activeChanged( false );
 			updateNativeTitleBarHeightAndHitTestSpots();
 
-			if( !SystemInfo.isWindows_11_orLater && hasNativeCustomDecoration() )
+			if( isWindowTopBorderNeeded() )
 				WindowTopBorder.getInstance().repaintBorder( FlatTitlePane.this );
 
 			repaintWindowBorder();