FcFontSetList - List fonts from a set of font sets
#include <fontconfig/fontconfig.h>
FcFontSet * FcFontSetList (FcConfig *config, FcFontSet **sets, intnsets, FcPattern *pattern, FcObjectSet *object_set);
Selects fonts matching pattern from sets, creates patterns from
  those fonts containing only the objects in object_set and returns the
  set of unique such patterns. If config is NULL, the default
  configuration is checked to be up to date, and used.