I wrote a small program (as follows) to print available fonts for FLTK2. The result is correct. I have to do some more test.
Code:
#include <fltk/Window.h>
#include <fltk/Widget.h>
#include <fltk/Font.h>
#include <fltk/run.h>
#include <stdio.h>
using namespace fltk;
int main(int argc, char **argv) {
Font ** arrayp;
int n = list_fonts(arrayp);
printf("Number of font items: %d\n", n);
}