Native window decorations: show window system menu when left-clicking on application icon, close window on left-double-click on app icon

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

@@ -196,7 +196,9 @@ public class FlatNativeWindowBorder
 		nativeProvider.setHasCustomDecoration( window, hasCustomDecoration );
 	}
 
-	static void setTitleBarHeightAndHitTestSpots( Window window, int titleBarHeight, List<Rectangle> hitTestSpots ) {
+	static void setTitleBarHeightAndHitTestSpots( Window window, int titleBarHeight,
+		List<Rectangle> hitTestSpots, Rectangle appIconBounds )
+	{
 		if( canUseJBRCustomDecorations ) {
 			JBRCustomDecorations.setTitleBarHeightAndHitTestSpots( window, titleBarHeight, hitTestSpots );
 			return;
@@ -207,6 +209,7 @@ public class FlatNativeWindowBorder
 
 		nativeProvider.setTitleBarHeight( window, titleBarHeight );
 		nativeProvider.setTitleBarHitTestSpots( window, hitTestSpots );
+		nativeProvider.setTitleBarAppIconBounds( window, appIconBounds );
 	}
 
 	private static void initialize() {
@@ -240,5 +243,6 @@ public class FlatNativeWindowBorder
 		void setHasCustomDecoration( Window window, boolean hasCustomDecoration );
 		void setTitleBarHeight( Window window, int titleBarHeight );
 		void setTitleBarHitTestSpots( Window window, List<Rectangle> hitTestSpots );
+		void setTitleBarAppIconBounds( Window window, Rectangle appIconBounds );
 	}
 }

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

@@ -453,6 +453,12 @@ public class FlatTitlePane
 			for( Rectangle r : debugHitTestSpots )
 				g.drawRect( r.x - offset.x, r.y - offset.y, r.width - 1, r.height - 1 );
 		}
+		if( debugAppIconBounds != null ) {
+			g.setColor( Color.red );
+			Point offset = SwingUtilities.convertPoint( this, 0, 0, window );
+			Rectangle r = debugAppIconBounds;
+			g.drawRect( r.x - offset.x, r.y - offset.y, r.width - 1, r.height - 1 );
+		}
 	}
 debug*/
 
@@ -632,16 +638,31 @@ debug*/
 			titleBarHeight--;
 
 		List<Rectangle> hitTestSpots = new ArrayList<>();
-		if( iconLabel.isVisible() )
-			addNativeHitTestSpot( iconLabel, false, hitTestSpots );
+		Rectangle appIconBounds = null;
+		if( iconLabel.isVisible() ) {
+			// compute real icon size (without insets)
+			Point location = SwingUtilities.convertPoint( iconLabel, 0, 0, window );
+			Insets iconInsets = iconLabel.getInsets();
+			Rectangle iconBounds = new Rectangle(
+				location.x + iconInsets.left,
+				location.y + iconInsets.top,
+				iconLabel.getWidth() - iconInsets.left - iconInsets.right,
+				iconLabel.getHeight() - iconInsets.top - iconInsets.bottom );
+
+			if( hasJBRCustomDecoration() )
+				hitTestSpots.add( iconBounds );
+			else
+				appIconBounds = iconBounds;
+		}
 		addNativeHitTestSpot( buttonPanel, false, hitTestSpots );
 		addNativeHitTestSpot( menuBarPlaceholder, true, hitTestSpots );
 
-		FlatNativeWindowBorder.setTitleBarHeightAndHitTestSpots( window, titleBarHeight, hitTestSpots );
+		FlatNativeWindowBorder.setTitleBarHeightAndHitTestSpots( window, titleBarHeight, hitTestSpots, appIconBounds );
 
 /*debug
 		debugTitleBarHeight = titleBarHeight;
 		debugHitTestSpots = hitTestSpots;
+		debugAppIconBounds = appIconBounds;
 		repaint();
 debug*/
 	}
@@ -663,6 +684,7 @@ debug*/
 /*debug
 	private int debugTitleBarHeight;
 	private List<Rectangle> debugHitTestSpots;
+	private Rectangle debugAppIconBounds;
 debug*/
 
 	//---- class TitlePaneBorder ----------------------------------------------

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

@@ -157,6 +157,15 @@ public class FlatWindowsNativeWindowBorder
 		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;
+	}
+
 	//---- class WndProc ------------------------------------------------------
 
 	private class WndProc
@@ -164,14 +173,16 @@ public class FlatWindowsNativeWindowBorder
 	{
 		private static final int GWLP_WNDPROC = -4;
 
-		private static final int WM_NCCALCSIZE = 0x0083;
-		private static final int WM_NCHITTEST = 0x0084;
-		private static final int WM_NCRBUTTONUP = 0x00A5;
+		private static final int
+			WM_NCCALCSIZE = 0x0083,
+			WM_NCHITTEST = 0x0084,
+			WM_NCRBUTTONUP = 0x00A5;
 
 		// WM_NCHITTEST mouse position codes
 		private static final int
 			HTCLIENT = 1,
 			HTCAPTION = 2,
+			HTSYSMENU = 3,
 			HTTOP = 12;
 
 		private static final int ABS_AUTOHIDE = 0x0000001;
@@ -198,6 +209,7 @@ public class FlatWindowsNativeWindowBorder
 
 		private int titleBarHeight;
 		private Rectangle[] hitTestSpots;
+		private Rectangle appIconBounds;
 
 		WndProc( Window window ) {
 			this.window = window;
@@ -242,7 +254,7 @@ public class FlatWindowsNativeWindowBorder
 					return WmNcHitTest( hwnd, uMsg, wParam, lParam );
 
 				case WM_NCRBUTTONUP:
-					if( wParam.longValue() == HTCAPTION )
+					if( wParam.longValue() == HTCAPTION || wParam.longValue() == HTSYSMENU )
 						openSystemMenu( hwnd, GET_X_LPARAM( lParam ), GET_Y_LPARAM( lParam ) );
 					break;
 
@@ -367,6 +379,12 @@ public class FlatWindowsNativeWindowBorder
 			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 new LRESULT( HTSYSMENU );
+
 			int resizeBorderHeight = getResizeHandleHeight();
 			boolean isOnResizeBorder = (y < resizeBorderHeight) &&
 				(User32.INSTANCE.GetWindowLong( hwnd, GWL_STYLE ) & WS_THICKFRAME) != 0;
@@ -415,7 +433,7 @@ public class FlatWindowsNativeWindowBorder
 
 		/**
 		 * Scales down in the same way as AWT.
-		 * See AwtWin32GraphicsDevice::ScaleDownX()
+		 * See AwtWin32GraphicsDevice::ScaleDownX() and ::ScaleDownY()
 		 */
 		private Point scaleDown( int x, int y ) {
 			GraphicsConfiguration gc = window.getGraphicsConfiguration();

flatlaf-testing/src/main/java/com/formdev/flatlaf/testing/FlatNativeWindowBorderTest.java

@@ -28,8 +28,8 @@ import java.util.WeakHashMap;
 import javax.swing.*;
 import com.formdev.flatlaf.FlatLightLaf;
 import com.formdev.flatlaf.extras.FlatInspector;
-import com.formdev.flatlaf.nativejna.windows.FlatWindowsNativeWindowBorder;
 import com.formdev.flatlaf.ui.FlatLineBorder;
+import com.formdev.flatlaf.ui.FlatNativeWindowBorder;
 import net.miginfocom.swing.*;
 
 /**
@@ -258,7 +258,7 @@ public class FlatNativeWindowBorderTest
 	}
 
 	private void nativeChanged() {
-		FlatWindowsNativeWindowBorder.getInstance().setHasCustomDecoration( window, nativeCheckBox.isSelected() );
+		FlatNativeWindowBorder.setHasCustomDecoration( window, nativeCheckBox.isSelected() );
 	}
 
 	private void revalidateLayout() {