Creates a new pattern consisting of elements of _f_o_n_t not appearing in _p_a_t, elements of _p_a_t not appearing in _f_o_n_t and the best matching value from _p_a_t for elements appearing in both. The result is passed to FcConfigSubstitute with _k_i_n_d FcMatchFont and then returned.
Fontconfig version 2.6.0