--- a/include/mb_backend.h	Mon Nov 22 14:02:01 2010 +0800
+++ b/include/mb_backend.h	Mon Nov 22 15:20:11 2010 +0800
@@ -79,11 +79,48 @@
      * Following two methods are used to integrate a backend to
      * event loop of main application.
      */
-    void (*reg_IO_factory)(mb_IO_factory_t *evman);
-    void (*reg_timer_factory)(mb_timer_factory_t *evman);
+    void (*reg_IO_factory)(mb_IO_factory_t *io_man);
+    void (*reg_timer_factory)(mb_timer_factory_t *tm_man);
 } mb_backend_t;
 
-extern mb_backend_t backend;
+#define mb_runtime_new(disp, w, h)	\
+    mb_dfl_backend.new((disp), (w), (h))
+#define mb_runtime_new_with_win(disp, win)	\
+    mb_dfl_backend.new_with_win((disp), (win))
+#define mb_reg_IO_factory(io_man)	\
+    mb_dfl_backend.reg_IO_factory(io_man)
+#define mb_reg_timer_factory(tm_man)	\
+    mb_dfl_backend.reg_timer_factory(tm_man)
+
+/*
+ * This is defined by backend implementations.  For example, X_supp.c
+ * or dfb_supp.c should defined a backend.
+ */
+extern mb_backend_t mb_dfl_backend;
+
+#define mb_runtime_free(rt)			\
+    mb_dfl_backend.free(rt)
+#define mb_runtime_free_with_win(rt)		\
+    mb_dfl_backend.free_with_win(rt)
+#define mb_runtime_add_event(rt, fd, type, cb, arg)		\
+    mb_dfl_backend.add_event((rt), (fd), (type), (cb), (arg))
+#define mb_runtime_remove_event(hdl)		\
+    mb_dfl_backend.remove_event((rt), (hdl))
+#define mb_runtime_event_loop(rt)		\
+    mb_dfl_backend.event_loop(rt)
+#define mb_runtime_flush(rt)			\
+    mb_dfl_backend.flush(rt)
+#define mb_runtime_kbevents(rt)			\
+    mb_dfl_backend.kbevents(rt)
+#define mb_runtime_rdman(rt)			\
+    mb_dfl_backend.rdman(rt)
+#define mb_runtime_timer_man(rt)		\
+    mb_dfl_backend.timer_man(rt)
+#define mb_runtime_ob_factory(rt)		\
+    mb_dfl_backend.ob_factory(rt)
+#define mb_runtime_loader(rt)			\
+    mb_dfl_backend.loader(rt)
+
 
 /*! \brief Type of IO that registered with an IO manager.
  */

--- a/src/X_supp.c	Mon Nov 22 14:02:01 2010 +0800
+++ b/src/X_supp.c	Mon Nov 22 15:20:11 2010 +0800
@@ -1056,22 +1056,22 @@
     return r == 0? ERR: OK;
 }
 
-mb_backend_t backend = { _x_supp_new,
-			 _x_supp_new_with_win,
-			 
-			 _x_supp_free,
-			 _x_supp_free_keep_win,
-			 _x_supp_add_event,
-			 _x_supp_remove_event,
-			 _x_supp_event_loop,
-			 _x_supp_flush,
-			 
-			 _x_supp_kbevents,
-			 _x_supp_rdman,
-			 _x_supp_timer_man,
-			 _x_supp_ob_factory,
-			 _x_supp_img_ldr
-		};
+mb_backend_t mb_dfl_backend = { _x_supp_new,
+				_x_supp_new_with_win,
+				
+				_x_supp_free,
+				_x_supp_free_keep_win,
+				_x_supp_add_event,
+				_x_supp_remove_event,
+				_x_supp_event_loop,
+				_x_supp_flush,
+				
+				_x_supp_kbevents,
+				_x_supp_rdman,
+				_x_supp_timer_man,
+				_x_supp_ob_factory,
+				_x_supp_img_ldr
+};
 
 #if 0
 /*! \defgroup x_supp_nodejs_sup Export functions for supporting nodejs plugin.

--- a/src/mbaf/mbapp.c	Mon Nov 22 14:02:01 2010 +0800
+++ b/src/mbaf/mbapp.c	Mon Nov 22 15:20:11 2010 +0800
@@ -9,19 +9,19 @@
     mbaf_t *app = (mbaf_t *) malloc(sizeof(mbaf_t));
     mb_rt_t *rt;
 
-    rt = backend.new(":0.0", 800, 600);
+    rt = mb_runtime_new(":0.0", 800, 600);
     if(rt == NULL)
 	return NULL;
 
     sprite_set_search_path(module_dir);
 
     app->rt = rt;
-    app->rdman =  backend.rdman(rt);
-    app->kbevents = backend.kbevents(rt);
+    app->rdman =  mb_runtime_rdman(rt);
+    app->kbevents = mb_runtime_kbevents(rt);
 
     app->rootsprite= sprite_load(module,app->rdman, app->rdman->root_coord);
     if(app->rootsprite == NULL) {
-	backend.free(rt);
+	mb_runtime_free(rt);
 	free(app);
 	return NULL;
     }
@@ -39,7 +39,7 @@
 
 mb_timer_man_t *mbaf_get_timer(mbaf_t *app)
 {
-    return backend.timer_man(app->rt);
+    return mb_runtime_timer_man(app->rt);
 }
 
 void mbaf_loop(mbaf_t *app)
@@ -48,11 +48,11 @@
      * Start handle connections, includes one to X server.
      * User start to interact with the application.
      */
-    backend.event_loop(app->rt);
+    mb_runtime_event_loop(app->rt);
 
     /*
      * Clean
      */
-    backend.free(app->rt);
+    mb_runtime_free(app->rt);
     free(app);
 }