XSetFontPath man page
XSetFontPath, XGetFontPath, XFreeFontPath — set, get, or free the font search path
int XSetFontPath(Display *display, char **directories, int ndirs);
char **XGetFontPath(Display *display, int *npaths_return);
int XFreeFontPath(char **list);
Specifies the directory path used to look for a font. Setting the path to the empty list restores the default path defined for the X server.
Specifies the connection to the X server.
Specifies the array of strings you want to free.
Specifies the number of directories in the path.
Returns the number of strings in the font path array.
The XSetFontPath function defines the directory search path for font lookup. There is only one search path per X server, not one per client. The encoding and interpretation of the strings are implementation-dependent, but typically they specify directories or font servers to be searched in the order listed. An X server is permitted to cache font information internally; for example, it might cache an entire font from a file and not check on subsequent opens of that font to see if the underlying font file has changed. However, when the font path is changed, the X server is guaranteed to flush all cached information about fonts for which there currently are no explicit resource IDs allocated. The meaning of an error from this request is implementation-dependent.
XSetFontPath can generate a BadValue error.
The XGetFontPath function allocates and returns an array of strings containing the search path. The contents of these strings are implementation-dependent and are not intended to be interpreted by client applications. When it is no longer needed, the data in the font path should be freed by using XFreeFontPath.
The XFreeFontPath function frees the data allocated by XGetFontPath.
Some numeric value falls outside the range of values accepted by the request. Unless a specific range is specified for an argument, the full range defined by the argument's type is accepted. Any argument defined as a set of alternatives can generate this error.
Xlib - C Language X Interface
The man pages XFreeFontPath(3) and XGetFontPath(3) are aliases of XSetFontPath(3).