MACRO(USE_ARTOOLKITPLUS)
  FIND_PACKAGE(ARTOOLKITPLUS)
  IF ((NOT ARTOOLKITPLUS_FOUND) AND (${ARGC} LESS 1))
    USING_MESSAGE("Skipping because of missing ARTOOLKITPLUS")
    RETURN()
  ENDIF((NOT ARTOOLKITPLUS_FOUND) AND (${ARGC} LESS 1))
  IF(NOT ARTOOLKITPLUS_USED AND ARTOOLKITPLUS_FOUND)
    SET(ARTOOLKITPLUS_USED TRUE)
    ADD_DEFINITIONS(-DHAVE_AR)
    INCLUDE_DIRECTORIES(SYSTEM ${ARTOOLKITPLUS_INCLUDE_DIR})
    SET(EXTRA_LIBS ${EXTRA_LIBS} ${ARTOOLKITPLUS_LIBRARIES})
  ENDIF()
ENDMACRO(USE_ARTOOLKITPLUS)