sig
  type attrib_bit =
      GL_ACCUM_BUFFER_BIT
    | GL_COLOR_BUFFER_BIT
    | GL_CURRENT_BIT
    | GL_DEPTH_BUFFER_BIT
    | GL_ENABLE_BIT
    | GL_EVAL_BIT
    | GL_FOG_BIT
    | GL_HINT_BIT
    | GL_LIGHTING_BIT
    | GL_LINE_BIT
    | GL_LIST_BIT
    | GL_MULTISAMPLE_BIT
    | GL_PIXEL_MODE_BIT
    | GL_POINT_BIT
    | GL_POLYGON_BIT
    | GL_POLYGON_STIPPLE_BIT
    | GL_SCISSOR_BIT
    | GL_STENCIL_BUFFER_BIT
    | GL_TEXTURE_BIT
    | GL_TRANSFORM_BIT
    | GL_VIEWPORT_BIT
end