FcPatternAdd (3) - Linux Manuals
FcPatternAdd: Add a value to a pattern
FcPatternAdd - Add a value to a pattern
Adds a single value to the list of values associated with the property named `object. If `append is FcTrue, the value is added at the end of any existing list, otherwise it is inserted at the beginning. `value' is saved (with FcValueSave) when inserted into the pattern so that the library retains no reference to any application-supplied data structure.