FcFontSetMatch - Return the best font from a set of font sets
#include <fontconfig/fontconfig.h>
FcPattern * FcFontSetMatch (FcConfig *config, FcFontSet **sets, intnsets, FcPattern *pattern, FcResult *result);
Finds the font in sets most closely matching pattern and returns
  the result of FcFontRenderPrepare for that font and the provided
  pattern. This function should be called only after FcConfigSubstitute
  and FcDefaultSubstitute have been called for pattern; otherwise
  the results will not be correct. If config is NULL, the current
  configuration is used. Returns NULL if an error occurs during this process.