through InitCurrentFlashLevelScanlineEffect

include/field_camera.h

@@ -33,5 +33,6 @@ void InstallCameraPanAheadCallback(void);
 void DrawDoorMetatileAt(int x, int y, const u16 *data);
 void move_tilemap_camera_to_upper_left_corner(void);
 void CameraUpdate(void);
+void FieldUpdateBgTilemapScroll(void);
 
 #endif //GUARD_FIELD_CAMERA_H