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.
XCreateOC returns NULL if no output context could be created. NULL can be returned for any of the following reasons:
The XDestroyOC function destroys the specified output context.
The XSetOCValues 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 XGetOCValues 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 XOMOfOC function returns the output method associated with the specified output context.