JUCE/modules/juce_graphics/unicode/juce_UnicodeLine.cpp

/*
  ==============================================================================

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   Copyright (c) Raw Material Software Limited

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  ==============================================================================
*/

namespace juce::tr14
{

using EAWType    = EastAsianWidthType;
using BreakClass = LineBreakType;

// This compiles down to the same machine code as an array matrix and
// gives us enum value compile time safety. This way we dont need to worry
// about the enum being modified and the table being out of sync.
template <size_t Size, typename ValueType, typename ResultType>
struct LookUpTable
{
    inline constexpr void set (ValueType v1, ValueType v2, ResultType result)
    {
        cols[index (v1)][index (v2)] = result;
    }

    inline constexpr ResultType get (ValueType v1, ValueType v2) const
    {
        return cols[index (v1)][index (v2)];
    }

private:
    static inline constexpr size_t index (ValueType value)
    {
        return (size_t) value;
    }

    ResultType cols[Size][Size];
};

enum class BreakOppurtunity
{
    direct,
    indirect,
    prohibited,
    combinedProhibited,
    combinedIndirect
};

struct BreakAtom final : public UnicodeAnalysisPoint
{
    constexpr bool operator== (BreakClass type) const { return data.bt == type; }
    constexpr bool operator== (EAWType type)    const { return data.asian == type; }

    constexpr auto getBreakClass()              const { return data.bt; }
    constexpr auto getEastAsianWidthType()      const { return data.asian; }
};

static_assert (sizeof (BreakAtom) == sizeof (UnicodeAnalysisPoint), "BreakAtom - UnicodeAnalysisPoint size mismatch");

struct BreakPairTable final : LookUpTable<42, BreakClass, BreakOppurtunity>
{
    BreakPairTable()
    {
        #include "juce_LineBreakTable.inl"
    }
};

static inline BreakClass resolve (BreakClass bc, [[maybe_unused]] bool mnMc = false)
{
    JUCE_BEGIN_IGNORE_WARNINGS_GCC_LIKE ("-Wswitch-enum")
    switch (bc)
    {
        case BreakClass::ai:
        case BreakClass::sg:
        case BreakClass::xx:
            return BreakClass::al;

        case BreakClass::sa:
            return BreakClass::al;

        case BreakClass::cj:
            return BreakClass::ns;

        default: break;
    }
    JUCE_END_IGNORE_WARNINGS_GCC_LIKE

    return bc;
}

static inline BreakClass resolveSOT (BreakClass bc)
{
    JUCE_BEGIN_IGNORE_WARNINGS_GCC_LIKE ("-Wswitch-enum")
    switch (bc)
    {
        case BreakClass::lf:
        case BreakClass::nl:
            return BreakClass::bk;

        case BreakClass::sp:
            return BreakClass::wj;

        default: break;
    }
    JUCE_END_IGNORE_WARNINGS_GCC_LIKE

    return bc;
}

static const BreakPairTable pairTable;

template <typename Callback>
size_t analyseLineBreaks (Span<const UnicodeAnalysisPoint> span, Callback&& callback)
{
    uint32_t resultIndex     = 0;
    uint32_t regionalCounter = 0;
    std::optional<BreakClass> lb9;
    bool lb21a{};

    const auto data = (const BreakAtom*) span.data();
    const auto len  = span.size();

    const auto emit = [&] (auto op) { callback ((int) resultIndex++, op); };

    #define step()   i++; continue

    for (size_t i = 0; i < len;)
    {
        const auto isSOT = i == 0;
        const auto isEOT = i == len - 1;

        const auto prev = isSOT ? resolveSOT (resolve (data[i].getBreakClass()))
                                : lb9.value_or (resolve (data[i].getBreakClass()));
        const auto next = isEOT ? BreakClass::cm
                                : resolve (data[i + 1].getBreakClass());

        lb9.reset();

        if (prev == BreakClass::cr && next == BreakClass::lf)
        {
            emit (TextBreakType::none);
            step();
        }

        // LB4
        if (any (prev, BreakClass::bk, BreakClass::lf, BreakClass::nl))
        {
            emit (TextBreakType::hard);
            step();
        }

        // LB6
        if (any (next, BreakClass::bk, BreakClass::lf, BreakClass::nl))
        {
            emit (TextBreakType::none);
            step();
        }

        // LB7
        if (any (next, BreakClass::sp, BreakClass::zw))
        {
            emit (TextBreakType::none);
            step();
        }

        // LB13
        if (any (next, BreakClass::cl, BreakClass::cp, BreakClass::ex, BreakClass::is, BreakClass::sy))
        {
            emit (TextBreakType::none);
            step();
        }

        // lb21a
        if (lb21a && any (prev, BreakClass::hy, BreakClass::ba))
        {
            emit (TextBreakType::none);
            step();
        }

        lb21a = prev == BreakClass::hl;

        // LB30a
        if (prev == BreakClass::ri)
        {
            regionalCounter++;

            if (next == BreakClass::ri && regionalCounter % 2 == 0)
            {
                regionalCounter = 0;
                emit (TextBreakType::soft);
                step();
            }
        }
        else
        {
            regionalCounter = 0;
        }

        const auto bt = pairTable.get (prev, next);

        switch (bt)
        {
            case BreakOppurtunity::direct:
            {
                emit (TextBreakType::soft);
                step();
            } break;

            case BreakOppurtunity::prohibited:
            {
                emit (TextBreakType::none);
                step();
            } break;

            case BreakOppurtunity::indirect:
            {
                while (i < len)
                {
                    emit (TextBreakType::none);

                    if (resolve (data[i].getBreakClass()) != BreakClass::sp)
                        break;

                    i++;
                }

                step();
            } break;

            case BreakOppurtunity::combinedIndirect:
            {
                lb9 = std::make_optional (prev);

                while (i < len)
                {
                    emit (TextBreakType::none);

                    if (! any (resolve (data[i].getBreakClass()), BreakClass::cm, BreakClass::zwj))
                        break;

                    i++;
                }

                step();
            } break;

            case BreakOppurtunity::combinedProhibited:
            {
                emit (TextBreakType::none);
                step();
            } break;
        }

        step();
    }

    //emit (TextBreakType::soft);

    #undef emit
    #undef step

    return resultIndex;
}

}