The base font names argument is mandatory at creation time, and the output context will not be created unless it is provided. All other output context values can be set later.
_X_C_r_e_a_t_e_O_C returns NULL if no output context could be created. NULL can be returned for any of the following reasons:
The _X_D_e_s_t_r_o_y_O_C function destroys the specified output context.
The _X_S_e_t_O_C_V_a_l_u_e_s function returns NULL if no error occurred; otherwise, it returns the name of the first argument that could not be set. An argument might not be set for any of the following reasons:
Each value to be set must be an appropriate datum, matching the data type imposed by the semantics of the argument.
The _X_G_e_t_O_C_V_a_l_u_e_s function returns NULL if no error occurred; otherwise, it returns the name of the first argument that could not be obtained. An argument might not be obtained for any of the following reasons:
Each argument value following a name must point to a location where the value is to be stored.
The _X_O_M_O_f_O_C function returns the output method associated with the specified output context.