+#else
+ /*
+ * GTK 3 has decided that there's no such thing as a 'default
+ * background colour' any more, because widget styles might set
+ * the background to something more complicated like a background
+ * image. We don't want to get into overlaying our entire puzzle
+ * on an arbitrary background image, so we'll just make up a
+ * reasonable shade of grey.
+ */
+ output[0] = output[1] = output[2] = 0.9F;
+#endif