Is it possible to get unicode scripts supported by font?

Question

I have set of libraries: fontconfig, freetype, harfbuzz. Is it possible to get scripts list supported by the font?

The task is to create a map of fonts for different unicode scripts.

HarfBuzz, for example, has enum that contains scripts. But I don't understand, is it possible to extract this info from hb_font_t or hb_face_t.

Or maybe it's possible to get this info from fontconfig or freetype?

Answer 1

It's possible, but is't very comfortable. I have found this solution:

#include <hb.h>
#include <magic-deps.h>

struct TInstalledFont {
    std::string FilePath{};
    int FaceIndex{};

    std::shared_ptr<hb_face_t> HbFontFace{nullptr};
    std::unordered_set<char32_t> Unicodes{};
    std::unordered_set<int> HbScripts{};
};

const auto hbUniFuncs = hb_unicode_funcs_get_default();

for (TInstalledFont& font : Fonts) {
  auto blob = hb_blob_create_from_file(font.FilePath.c_str());
  if (!blob) {
    throw std::runtime_error("Failed to load font");
  }
  DEFER(&blob) {
    hb_blob_destroy(blob);
  };

  const auto face = hb_face_create(blob, font.FaceIndex);
  if (!face) {
    throw std::runtime_error("Failed to load face");
  }
  hb_face_make_immutable(face);

  font.HbFontFace = std::shared_ptr<hb_face_t>(face, hb_face_destroy);

  auto unicodes = hb_set_create();
  DEFER(&unicodes) {
    hb_set_destroy(unicodes);
  };
  hb_face_collect_unicodes(face, unicodes);

  hb_codepoint_t val{};
  while (hb_set_next(unicodes, &val)) {
    font.Unicodes.insert(val);

    const hb_script_t tagScript = hb_unicode_script(hbUniFuncs, val);
    // int because hb_script_t doesn't support hashing
    font.HbScripts.insert(static_cast<int>(tagScript));
  }
}