gtk:gl-area-required-version (area)

area -- a gtk:gl-area object
major -- an integer with the required major version
minor -- an integer with the required minor version

The gtk:gl-area-required-version function retrieves the required version of OpenGL. The (setf gtk:gl-area-required-version) function sets the required version of OpenGL to be used when creating the context for the widget. This function must be called before the area has been realized.