)
add_subdirectory(data)
-add_subdirectory(doc)
+macro_optional_add_subdirectory(doc)
add_subdirectory(effects)
add_subdirectory(export)
add_subdirectory(icons)
add_subdirectory(lumas)
add_subdirectory(man)
add_subdirectory(plugins)
-add_subdirectory(po)
+macro_optional_add_subdirectory(po)
add_subdirectory(renderer)
add_subdirectory(src)
add_subdirectory(thumbnailer)