static AliasStrength strengthOfFirstAlias(const FcPattern& original)
{
    // Ideally there would exist a call like
    // FcResult FcPatternIsWeak(pattern, object, id, FcBool* isWeak);
    //
    // However, there is no such call and as of Fc 2.11.0 even FcPatternEquals ignores the weak bit.
    // Currently, the only reliable way of finding the weak bit is by its effect on matching.
    // The weak bit only affects the matching of FC_FAMILY and FC_POSTSCRIPT_NAME object values.
    // A element with the weak bit is scored after FC_LANG, without the weak bit is scored before.
    // Note that the weak bit is stored on the element, not on the value it holds.
    FcValue value;
    FcResult result = FcPatternGet(&original, FC_FAMILY, 0, &value);
    if (result != FcResultMatch)
        return AliasStrength::Done;

    RefPtr<FcPattern> pattern = adoptRef(FcPatternDuplicate(&original));
    FcBool hasMultipleFamilies = true;
    while (hasMultipleFamilies)
        hasMultipleFamilies = FcPatternRemove(pattern.get(), FC_FAMILY, 1);

    // Create a font set with two patterns.
    // 1. the same FC_FAMILY as pattern and a lang object with only 'nomatchlang'.
    // 2. a different FC_FAMILY from pattern and a lang object with only 'matchlang'.
    FcUniquePtr<FcFontSet> fontSet(FcFontSetCreate());

    FcUniquePtr<FcLangSet> strongLangSet(FcLangSetCreate());
    FcLangSetAdd(strongLangSet.get(), reinterpret_cast<const FcChar8*>("nomatchlang"));
    // Ownership of this FcPattern will be transferred with FcFontSetAdd.
    FcPattern* strong = FcPatternDuplicate(pattern.get());
    FcPatternAddLangSet(strong, FC_LANG, strongLangSet.get());

    FcUniquePtr<FcLangSet> weakLangSet(FcLangSetCreate());
    FcLangSetAdd(weakLangSet.get(), reinterpret_cast<const FcChar8*>("matchlang"));
    // Ownership of this FcPattern will be transferred via FcFontSetAdd.
    FcPattern* weak = FcPatternCreate();
    FcPatternAddString(weak, FC_FAMILY, reinterpret_cast<const FcChar8*>("nomatchstring"));
    FcPatternAddLangSet(weak, FC_LANG, weakLangSet.get());

    FcFontSetAdd(fontSet.get(), strong);
    FcFontSetAdd(fontSet.get(), weak);

    // Add 'matchlang' to the copy of the pattern.
    FcPatternAddLangSet(pattern.get(), FC_LANG, weakLangSet.get());

    // Run a match against the copy of the pattern.
    // If the first element was weak, then we should match the pattern with 'matchlang'.
    // If the first element was strong, then we should match the pattern with 'nomatchlang'.

    // Note that this config is only used for FcFontRenderPrepare, which we don't even want.
    // However, there appears to be no way to match/sort without it.
    RefPtr<FcConfig> config = adoptRef(FcConfigCreate());
    FcFontSet* fontSets[1] = { fontSet.get() };
    RefPtr<FcPattern> match = adoptRef(FcFontSetMatch(config.get(), fontSets, 1, pattern.get(), &result));

    FcLangSet* matchLangSet;
    FcPatternGetLangSet(match.get(), FC_LANG, 0, &matchLangSet);
    return FcLangEqual == FcLangSetHasLang(matchLangSet, reinterpret_cast<const FcChar8*>("matchlang"))
        ? AliasStrength::Weak : AliasStrength::Strong;
}
Esempio n. 2
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Vector<String> FontCache::systemFontFamilies()
{
    RefPtr<FcPattern> scalablesOnlyPattern = adoptRef(FcPatternCreate());
    FcPatternAddBool(scalablesOnlyPattern.get(), FC_SCALABLE, FcTrue);

    FcUniquePtr<FcObjectSet> familiesOnly(FcObjectSetBuild(FC_FAMILY, nullptr));
    FcUniquePtr<FcFontSet> fontSet(FcFontList(nullptr, scalablesOnlyPattern.get(), familiesOnly.get()));

    Vector<String> fontFamilies;
    for (int i = 0; i < fontSet->nfont; i++) {
        FcPattern* pattern = fontSet->fonts[i];
        FcChar8* family = nullptr;
        FcPatternGetString(pattern, FC_FAMILY, 0, &family);
        if (family)
            fontFamilies.appendVector(patternToFamilies(*pattern));
    }

    return fontFamilies;
}