canvas: Fix single header inclusion guard

diff --git a/clutter/clutter-canvas.h b/clutter/clutter-canvas.h
index 26cc8d3..c37d947 100644 (file)
--- a/clutter/clutter-canvas.h
+++ b/clutter/clutter-canvas.h
@@ -22,6 +22,10 @@
  *   Emmanuele Bassi <ebassi@linux.intel.com>
  */
 
+#if !defined(__CLUTTER_H_INSIDE__) && !defined(CLUTTER_COMPILATION)
+#error "Only <clutter/clutter.h> can be included directly."
+#endif
+
 #ifndef __CLUTTER_CANVAS_H__
 #define __CLUTTER_CANVAS_H__