Don't paint titlebar border when it isn't opaque

macos/src/main/java/com/github/weisj/darklaf/platform/macos/ui/MacOSTitlePane.java

@@ -101,10 +101,11 @@ public class MacOSTitlePane extends CustomTitlePane {
 
     @Override
     public void paintComponent(final Graphics g) {
+        if (!isOpaque()) return;
+        
         int width = getWidth();
         int height = getHeight();
 
-        if (isOpaque()) {
         Window window = getWindow();
         boolean active = window == null || window.isActive();
 
@@ -112,7 +113,6 @@ public class MacOSTitlePane extends CustomTitlePane {
 
         g.setColor(background);
         g.fillRect(0, 0, width, height);
-        }
 
         if (!hideTitleBar()) {
             g.setColor(border);

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

@@ -486,12 +486,12 @@ public class WindowsTitlePane extends CustomTitlePane {
 
             g.setColor(background);
             g.fillRect(0, 0, width, height);
-        }
 
             if (isDrawBorder()) {
                 g.setColor(border);
                 g.fillRect(0, height - 1, width, 1);
             }
+        }
 
         GraphicsConfiguration currentGC = getGraphicsConfiguration();
         if (currentGC != null && currentGC != gc) {