sig
  type req_attribute =
      GLX_FBCONFIG_ID
    | GLX_BUFFER_SIZE
    | GLX_LEVEL
    | GLX_DOUBLEBUFFER
    | GLX_STEREO
    | GLX_AUX_BUFFERS
    | GLX_RED_SIZE
    | GLX_GREEN_SIZE
    | GLX_BLUE_SIZE
    | GLX_ALPHA_SIZE
    | GLX_DEPTH_SIZE
    | GLX_STENCIL_SIZE
    | GLX_ACCUM_RED_SIZE
    | GLX_ACCUM_GREEN_SIZE
    | GLX_ACCUM_BLUE_SIZE
    | GLX_ACCUM_ALPHA_SIZE
    | GLX_RENDER_TYPE
    | GLX_DRAWABLE_TYPE
    | GLX_X_RENDERABLE
    | GLX_VISUAL_ID
    | GLX_X_VISUAL_TYPE
    | GLX_CONFIG_CAVEAT
    | GLX_TRANSPARENT_TYPE
    | GLX_TRANSPARENT_INDEX_VALUE
    | GLX_TRANSPARENT_RED_VALUE
    | GLX_TRANSPARENT_GREEN_VALUE
    | GLX_TRANSPARENT_BLUE_VALUE
    | GLX_TRANSPARENT_ALPHA_VALUE
    | GLX_MAX_PBUFFER_WIDTH
    | GLX_MAX_PBUFFER_HEIGHT
    | GLX_MAX_PBUFFER_PIXELS
end