macro(add_sources)
    get_property(tmp GLOBAL PROPERTY SRCS)
    file(RELATIVE_PATH _relPath "${PROJECT_SOURCE_DIR}" "${CMAKE_CURRENT_SOURCE_DIR}")
    foreach (_src ${ARGN})
        if (_relPath)
            list(APPEND tmp "${_relPath}/${_src}")
        else ()
            list(APPEND tmp "${_src}")
        endif ()
    endforeach ()
    set_property(GLOBAL PROPERTY SRCS ${tmp})
endmacro()

macro(add_headers)
    get_property(tmp GLOBAL PROPERTY Headers)
    file(RELATIVE_PATH _relPath "${PROJECT_SOURCE_DIR}" "${CMAKE_CURRENT_SOURCE_DIR}")
    foreach (_src ${ARGN})
        if (_relPath)
            list(APPEND tmp "${_relPath}/${_src}")
        else ()
            list(APPEND tmp "${_src}")
        endif ()
    endforeach ()
    set_property(GLOBAL PROPERTY Headers ${tmp})
endmacro()