Windows: Don't hardcode menubar layout adjustment

core/src/main/java/com/github/weisj/darklaf/ui/menu/DarkMenuBarBorder.java

@@ -27,8 +27,10 @@ import javax.swing.border.Border;
 import javax.swing.plaf.InsetsUIResource;
 import javax.swing.plaf.UIResource;
 
+import com.github.weisj.darklaf.platform.CustomTitlePane;
+
 /** @author Jannis Weis */
-public class DarkMenuBarBorder implements Border, UIResource {
+public class DarkMenuBarBorder implements Border, UIResource, CustomTitlePane.BorderCollapseHint {
 
     protected final Color borderColor;
 
@@ -51,4 +53,9 @@ public class DarkMenuBarBorder implements Border, UIResource {
     public boolean isBorderOpaque() {
         return true;
     }
+
+    @Override
+    public int getBottomCollapse() {
+        return 1;
+    }
 }

platform-base/src/main/java/com/github/weisj/darklaf/platform/CustomTitlePane.java

@@ -1,7 +1,7 @@
 /*
  * MIT License
  *
- * Copyright (c) 2019-2022 Jannis Weis
+ * Copyright (c) 2019-2023 Jannis Weis
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
  * associated documentation files (the "Software"), to deal in the Software without restriction,
@@ -24,6 +24,10 @@ import javax.swing.*;
 
 public abstract class CustomTitlePane extends JComponent {
 
+    public interface BorderCollapseHint {
+        int getBottomCollapse();
+    }
+
     protected int decorationStyle;
 
     public abstract void uninstall(final boolean removeDecorations);

windows/src/main/java/com/github/weisj/darklaf/platform/windows/ui/WindowsTitlePane.java

@@ -1,7 +1,7 @@
 /*
  * MIT License
  *
- * Copyright (c) 2019-2022 Jannis Weis
+ * Copyright (c) 2019-2023 Jannis Weis
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
  * associated documentation files (the "Software"), to deal in the Software without restriction,
@@ -865,7 +865,7 @@ public class WindowsTitlePane extends CustomTitlePane {
             int w = getWidth();
             int x;
             int start = 0;
-            int y = 0;
+            final int y = 0;
             height = computeHeight();
             left = 0;
             right = 0;
@@ -881,8 +881,13 @@ public class WindowsTitlePane extends CustomTitlePane {
 
             if (menuBarStealer.hasMenuBar()) {
                 int menuWidth = getPreferredMenuSize().width;
-                Insets menuInsets = menuBarStealer.getMenuBar().getInsets();
+                JMenuBar menuBar = menuBarStealer.getMenuBar();
-                menuBarStealer.getMenuBar().setBounds(start, y, menuWidth, height + menuInsets.bottom);
+                Border b = menuBar.getBorder();
+                int menuHeight = height;
+                if (b instanceof BorderCollapseHint) {
+                    menuHeight += ((BorderCollapseHint) b).getBottomCollapse();
+                }
+                menuBarStealer.getMenuBar().setBounds(start, y, menuWidth, menuHeight);
                 start += menuWidth + PAD;
                 left += menuWidth;
             }