+void blit(unsigned char *src_img, const Rect &src_rect, unsigned char* dest_img,
+ const Rect &dest_rect, int dest_x, int dest_y);
+
+void blit_key(unsigned char *src_img, const Rect &src_rect, unsigned char* dest_img,
+ const Rect &dest_rect, int dest_x, int dest_y, int key_r, int key_g, int key_b);
+
+void gfx_update();
+
+void wait_vsync(); // vertical synchronization
+