+void
+Diamond::move_by (double dx, double dy)
+{
+ points->coords[0] += dx;
+ points->coords[1] += dy;
+
+ points->coords[2] += dx;
+ points->coords[3] += dy;
+
+ points->coords[4] += dx;
+ points->coords[5] += dy;
+
+ points->coords[6] += dx;
+ points->coords[7] += dy;
+
+ g_object_set (gobj(), "points", points, NULL);
+}