update graphic driver to const variable.

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@1460 bbd45198-f89e-11dd-88c7-29a3b14d5316

components/rtgui/include/rtgui/driver.h

@@ -52,8 +52,8 @@ void rtgui_graphic_driver_add(const struct rtgui_graphic_driver* driver);
 struct rtgui_graphic_driver* rtgui_graphic_driver_get_default(void);
 
 void rtgui_graphic_driver_get_rect(const struct rtgui_graphic_driver *driver, rtgui_rect_t *rect);
-void rtgui_graphic_driver_screen_update(struct rtgui_graphic_driver* driver, rtgui_rect_t *rect);
-rt_uint8_t* rtgui_graphic_driver_get_framebuffer(struct rtgui_graphic_driver* driver);
+void rtgui_graphic_driver_screen_update(const struct rtgui_graphic_driver* driver, rtgui_rect_t *rect);
+rt_uint8_t* rtgui_graphic_driver_get_framebuffer(const struct rtgui_graphic_driver* driver);
 
 rt_err_t rtgui_graphic_set_device(rt_device_t device);
 

components/rtgui/server/driver.c

@@ -72,7 +72,7 @@ rt_err_t rtgui_graphic_set_device(rt_device_t device)
 }
 
 /* screen update */
-void rtgui_graphic_driver_screen_update(struct rtgui_graphic_driver* driver, rtgui_rect_t *rect)
+void rtgui_graphic_driver_screen_update(const struct rtgui_graphic_driver* driver, rtgui_rect_t *rect)
 {
 	struct rt_device_rect_info rect_info;
 
@@ -83,7 +83,7 @@ void rtgui_graphic_driver_screen_update(struct rtgui_graphic_driver* driver, rtg
 }
 
 /* get video frame buffer */
-rt_uint8_t* rtgui_graphic_driver_get_framebuffer(struct rtgui_graphic_driver* driver)
+rt_uint8_t* rtgui_graphic_driver_get_framebuffer(const struct rtgui_graphic_driver* driver)
 {
 	return (rt_uint8_t*)driver->framebuffer;
 }