#include <fontconfig.h>
FcBool FcPatternAddInteger (FcPattern *p, const char *object, inti);
FcBool FcPatternAddDouble (FcPattern *p, const char *object, doubled);
FcBool FcPatternAddString (FcPattern *p, const char *object, const char *s);
FcBool FcPatternAddMatrix (FcPattern *p, const char *object, const FcMatrix *m);
FcBool FcPatternAddCharSet (FcPattern *p, const char *object, const FcCharSet *c);
FcBool FcPatternAddBool (FcPattern *p, const char *object, FcBoolb);
These are all convenience functions that insert objects of the specified type into the pattern. Use these in preference to FcPatternAdd as they will provide compile-time typechecking. These all append values to any existing list of values.
Fontconfig version 2.3.2