JUCE/modules/juce_graphics/unicode/juce_UnicodeBidi.cpp

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

   This file is part of the JUCE framework.
   Copyright (c) Raw Material Software Limited

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   Or:

   You may also use this code under the terms of the AGPLv3:
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   THE JUCE FRAMEWORK IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL
   WARRANTIES, WHETHER EXPRESSED OR IMPLIED, INCLUDING WARRANTY OF
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  ==============================================================================
*/

namespace juce
{

class BidiLine
{
public:
    using ParagraphPtr = std::unique_ptr<std::remove_pointer_t<SBParagraphRef>, FunctionPointerDestructor<SBParagraphRelease>>;
    using LinePtr = std::unique_ptr<std::remove_pointer_t<SBLineRef>, FunctionPointerDestructor<SBLineRelease>>;

    explicit BidiLine (ParagraphPtr p, LinePtr l) : paragraph (std::move (p)), line (std::move (l)) {}

    Span<const SBRun> getRuns() const
    {
        return { SBLineGetRunsPtr (line.get()), SBLineGetRunCount (line.get()) };
    }

    void computeVisualOrder (std::vector<size_t>& result) const
    {
        result.clear();

        const auto runs = getRuns();

        if (runs.empty())
            return;

        thread_local std::vector<size_t> codepointIndicesInVisualOrder;
        codepointIndicesInVisualOrder.clear();
        codepointIndicesInVisualOrder.reserve ((size_t) SBLineGetLength (line.get()));

        jassert (SBLineGetOffset (line.get()) == 0);

        for (const auto& run : runs)
        {
            const auto ltr = run.level % 2 == 0;
            const auto increment = ltr ? 1 : -1;
            auto start = (int) (ltr ? run.offset : run.offset + run.length - 1);

            for (SBUInteger i = 0; i < run.length; ++i)
            {
                codepointIndicesInVisualOrder.push_back ((size_t) start);
                start += increment;
            }
        }

        result.assign (codepointIndicesInVisualOrder.size(), 0);

        if (std::any_of (codepointIndicesInVisualOrder.begin(),
                         codepointIndicesInVisualOrder.end(),
                         [s = result.size()] (auto i) { return i >= s; }))
        {
            jassertfalse;
            return;
        }

        for (const auto [i, index] : enumerate (codepointIndicesInVisualOrder, size_t{}))
            result[index] = i;
    }

private:
    ParagraphPtr paragraph;
    LinePtr line;
};

class BidiParagraph
{
public:
    using ParagraphPtr = BidiLine::ParagraphPtr;

    explicit BidiParagraph (ParagraphPtr p)
        : paragraph (std::move (p))
    {
    }

    size_t getLength() const
    {
        return SBParagraphGetLength (paragraph.get());
    }

    Span<const SBLevel> getResolvedLevels() const
    {
        return { SBParagraphGetLevelsPtr (paragraph.get()), getLength() };
    }

    BidiLine createLine (size_t length) const
    {
        jassert (SBParagraphGetOffset (paragraph.get()) == 0);
        jassert (length <= getLength());
        return BidiLine { ParagraphPtr { SBParagraphRetain (paragraph.get()) },
                          BidiLine::LinePtr { SBParagraphCreateLine (paragraph.get(), 0, length) } };
    }

private:
    ParagraphPtr paragraph;
};

class BidiAlgorithm
{
public:
    using AlgorithmPtr = std::unique_ptr<std::remove_pointer_t<SBAlgorithmRef>, FunctionPointerDestructor<SBAlgorithmRelease>>;

    explicit BidiAlgorithm (Span<const juce_wchar> t)
        : text (t.begin(), t.end())
    {
    }

    size_t getLength() const
    {
        return text.size();
    }

    BidiParagraph createParagraph (std::optional<detail::TextDirection> d = {}) const
    {
        BidiParagraph::ParagraphPtr result { SBAlgorithmCreateParagraph (algorithm.get(), 0, text.size(), [&]() -> SBLevel
        {
            if (! d.has_value())
                return SBLevelDefaultLTR;
            return *d == detail::TextDirection::rtl ? SBLevelDefaultRTL : SBLevelDefaultLTR;
        }()) };

        jassert (result != nullptr);

        return BidiParagraph { std::move (result) };
    }

private:
    std::vector<juce_wchar> text;
    AlgorithmPtr algorithm { [&]
    {
        SBCodepointSequence sequence { SBStringEncodingUTF32, text.data(), text.size() };
        return SBAlgorithmCreate (&sequence);
    }() };
};

//==============================================================================
//==============================================================================

#if JUCE_UNIT_TESTS

class BidiTests : public UnitTest
{
public:
    BidiTests() : UnitTest ("Unicode Bidi", UnitTestCategories::text) {}

    void runTest() override
    {
        beginTest ("visual order rtl");
        {
            const CharPointer_UTF8 text ("\xd9\x85\xd9\x85\xd9\x85 colour "
                                         "\xd9\x85\xd9\x85\xd9\x85\xd9\x85\xd9\x85\xd9\x85\xd9\x85\xd9\x85\n");
            const std::vector<size_t> result { 19, 18, 17, 16, 10, 11, 12, 13, 14, 15, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0 };

            expect (computeVisualOrder (text) == result);
        }

        beginTest ("visual order ltr");
        {
            const CharPointer_UTF8 text ("hello \xd9\x85\xd9\x85\xd9\x85 world\n");
            const std::vector<size_t> result { 0, 1, 2, 3, 4, 5, 8, 7, 6, 9, 10, 11, 12, 13, 14, 15 };
            expect (computeVisualOrder (text) == result);
        }

        beginTest ("multi-level bidi text");
        {
            const CharPointer_UTF8 text ("LOOPS 4 \xd7\xa1X \xd7\xa1""4");
            const std::vector<size_t> result { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 11 };
            expect (computeVisualOrder (text) == result);
        }

        beginTest ("bidi text with 5 embedding levels");
        {
            // pop directional formatting
            String PDF { CharPointer_UTF8 { "\xe2\x80\xac" } };

            // left to right override
            String LRO { CharPointer_UTF8 { "\xe2\x80\xad" } };

            // right to left override
            String RLO { CharPointer_UTF8 { "\xe2\x80\xae" } };

            const auto replacements = std::array {
                std::make_pair (String { "[PDF]" }, PDF),
                std::make_pair (String { "[LRO]" }, LRO),
                std::make_pair (String { "[RLO]" }, RLO),
            };

            auto getText = [&] (StringRef templateText)
            {
                String text = templateText;

                for (const auto& [placeholder, replacement] : replacements)
                    text = text.replace (placeholder, replacement);

                return text;
            };

            const CharPointer_UTF8 templ { "[RLO]DID YOU SAY '[LRO]he said \"[RLO][LRO]car[PDF] MEANS CAR[PDF]\"[PDF]'?[PDF]" };
            const auto text = getText (templ);
            const auto lookup = computeVisualOrder (text);

            std::vector<juce_wchar> reorderedText ((size_t) text.length());

            for (const auto [i, c] : enumerate (text, size_t{}))
                reorderedText[lookup[i]] = c;

            // The visual order of the control characters is not defined, so we can only compare the
            // ascii part.
            std::vector<juce_wchar> asciiPartOfReorderedText;

            for (const auto c : reorderedText)
            {
                if (c >= 0x20 && c <= 0x7e)
                    asciiPartOfReorderedText.push_back (c);
            }

            const String expected { "?'he said \"RAC SNAEM car\"' YAS UOY DID" };
            const String result { CharPointer_UTF32 { asciiPartOfReorderedText.data() }, asciiPartOfReorderedText.size() };

            expect (result == expected);
        }
    }

    static std::vector<size_t> computeVisualOrder (const String& text)
    {
        std::vector<juce_wchar> chars;

        for (const auto t : text)
            chars.push_back (t);

        BidiAlgorithm algorithm { chars };
        auto paragraph = algorithm.createParagraph();
        auto line = paragraph.createLine (paragraph.getLength());

        std::vector<size_t> order;
        line.computeVisualOrder (order);
        return order;
    }
};

static BidiTests bidiTests;

#endif

} // namespace juce