src/java.desktop/macosx/classes/sun/lwawt/macosx/LWCToolkit.java

@@ -100,11 +100,10 @@
 import javax.swing.UIManager;
 
 import com.apple.laf.AquaMenuBarUI;
 import sun.awt.AWTAccessor;
 import sun.awt.AppContext;
-import sun.awt.CGraphicsConfig;
 import sun.awt.CGraphicsDevice;
 import sun.awt.LightweightFrame;
 import sun.awt.PlatformGraphicsInfo;
 import sun.awt.SunToolkit;
 import sun.awt.datatransfer.DataTransferer;

@@ -477,11 +476,15 @@
                 .getXResolution();
     }
 
     @Override
     public Insets getScreenInsets(final GraphicsConfiguration gc) {
-        return ((CGraphicsConfig) gc).getDevice().getScreenInsets();
+        GraphicsDevice gd = gc.getDevice();
+        if (!(gd instanceof CGraphicsDevice)) {
+            return super.getScreenInsets(gc);
+        }
+        return ((CGraphicsDevice)gd).getScreenInsets();
     }
 
     @Override
     public void sync() {
         // flush the OGL pipeline (this is a no-op if OGL is not enabled)