modules/javafx.graphics/src/main/java/com/sun/glass/ui/gtk/GtkWindow.java

@@ -226,6 +226,11 @@
 
     @Override
     protected void _releaseInput(long ptr) {
         throw new UnsupportedOperationException("Not supported yet.");
     }
+
+    @Override
+    public long getRawHandle() {
+        return getNativeWindow();
+    }
 }