Font family matching with FontConfig demo

fctest.cpp

// c++ -lfontconfig fctest.cpp
// ./a.out 'DejaVu Sans Mono' monospace 'Andale Mono' 'Ubuntu Mono' Lato

#include <cstdio>
#include <fontconfig/fontconfig.h>

class FontConfig {
public:
  FontConfig() : m_config(FcInitLoadConfigAndFonts()) {}
  FontConfig(const FontConfig &) = delete;
  ~FontConfig() { FcConfigDestroy(m_config); }

  operator FcConfig *() { return m_config; }

private:
  FcConfig *m_config;
};

class FontPattern {
public:
  FontPattern(FcPattern *p = FcPatternCreate()) : m_pattern(p) {}
  FontPattern(const FontPattern &) = delete;
  ~FontPattern() { FcPatternDestroy(m_pattern); }

  operator bool() const { return m_pattern; }
  template<typename T> T get(const char *object, int n = 0) const;
  template<typename T> bool add(const char *object, T val);

  FontPattern bestMatch(FcConfig * = nullptr);

private:
  FcPattern *m_pattern;
};

template<>
const char *FontPattern::get(const char *object, const int n) const {
  FcChar8 *value;
  if(FcPatternGetString(m_pattern, object, n, &value) == FcResultMatch)
    return reinterpret_cast<const char *>(value);
  return nullptr;
}

template<>
bool FontPattern::add(const char *object, const char *val) {
  return FcPatternAddString(m_pattern, object, reinterpret_cast<const FcChar8 *>(val));
}

template<>
bool FontPattern::add(const char *object, const int val) {
  return FcPatternAddInteger(m_pattern, object, val);
}

FontPattern FontPattern::bestMatch(FcConfig *cfg) {
  FcConfigSubstitute(cfg, m_pattern, FcMatchPattern);
  FcDefaultSubstitute(m_pattern);

  FcResult result;
  return {FcFontMatch(cfg, m_pattern, &result)};
}

int main(const int argc, const char *argv[]) {
  FontConfig fc;

  for(int i = 1; i < argc; ++i) {
    FontPattern query;
    query.add(FC_FAMILY, argv[i]);
    // query.add(FC_WEIGHT, FC_WEIGHT_BOLD);
    // query.add(FC_SLANT, FC_SLANT_ITALIC);
    // ...

    const FontPattern &font = query.bestMatch(fc);

    if(font) {
      printf("found font matching '%s': '%s' in '%s'\n", argv[i],
        font.get<const char *>(FC_FAMILY), font.get<const char *>(FC_FILE));
    }
    else
      printf("no font matching '%s' found\n", argv[i]);
  }

  return 0;
}