IF(WITH_LIB_GLAD)
    message(STATUS "Included lib_glad.cmake.")
    ###################
    ## first example ##
    ###################
    set(OpenGL_GL_PREFERENCE CACHE STRING "LEGACY")


    find_package(OpenGL REQUIRED)
    find_package(glfw3 REQUIRED)
    find_package(X11 REQUIRED)
    find_package(Threads REQUIRED)

    set(THREADS_PREFER_PTHREAD_FLAG ON)
    find_package(Threads REQUIRED)

    set(LIB_GLAD_INC_PATH
        ${PLATFORM_INC_PATH}
        ${X11_INCLUDE_DIR}
        ${OPENGL_INCLUDE_DIR}
        ${OUTPUT_PATH}/lib/glad/include
        ${CMAKE_SYSTEM_INCLUDE_PATH}
    )

    set(LIB_GLAD_LIB_PATH
        ${PLATFORM_LIB_PATH}
        ${X11_LIBRARIES}
        ${OPENGL_LIBRARIES}
        ${OUTPUT_PATH}/lib/glad/lib
        ${CMAKE_SYSTEM_LIBRARY_PATH}
    )

    cmake_print_variables(${CMAKE_SYSTEM_LIBRARY_PATH})

    set(LIB_GLAD_STATIC_LIBS
        ${PLATFORM_STATIC_LIBS}
        ${CMAKE_DL_LIBS}
        glut
        glad
        OpenGL::GL
        Threads::Threads
        X11::X11
        X11::Xxf86vm
        X11::Xi
        X11::Xrandr
        X11::Xcursor
        X11::Xinerama
    )

    set(LIB_GLAD_DEPS "external_glad")


    ExternalProject_Add(external_glad
        PREFIX ${CMAKE_BINARY_DIR}/glad
        GIT_REPOSITORY ${GLAD_REPO}
        GIT_TAG ${GLAD_TAG}
        GIT_PROGRESS TRUE
        GIT_SHALLOW TRUE
        SOURCE_DIR ${CMAKE_BINARY_DIR}/glad-src
        INSTALL_DIR ${CMAKE_BINARY_DIR}/glad-download
        CMAKE_ARGS -DCMAKE_BUILD_TYPE:String=${CMAKE_BUILD_TYPE} -DGLAD_INSTALL=ON -DCMAKE_INSTALL_PREFIX=${OUTPUT_PATH}/lib/glad
        INSTALL_COMMAND COMMAND make -j${CPU_COUNT} install
    )
ENDIF()