Method updateRainbowText

examples/text/Text.cpp:541–592

    }

    void updateRainbowText(float delta)
    {
        rainbowColorHue += delta;
        while (rainbowColorHue >= 360.0f)
            rainbowColorHue -= 360.0f;

        const auto&   shapedGlyphs = text.getShapedGlyphs();
        auto&         vertices     = text.getVertexData();
        const auto    hueStep      = 360.0f / static_cast<float>(text.getString().getSize());
        float         currentHue   = rainbowColorHue;
        std::uint32_t previousCluster{};

        auto getColor = [&currentHue]()
        {
            // Convert hue to RGB using the textbook method
            const auto h = currentHue / 60.f;
            const auto x = static_cast<std::uint8_t>(std::round((1.0f - std::abs(std::fmod(h, 2.0f) - 1.0f)) * 255.0f));

            if (h < 1.0f)
                return sf::Color(255, x, 0);
            if (h < 2.0f)
                return sf::Color(x, 255, 0);
            if (h < 3.0f)
                return sf::Color(0, 255, x);
            if (h < 4.0f)
                return sf::Color(0, x, 255);
            if (h < 5.0f)
                return sf::Color(x, 0, 255);
            return sf::Color(255, 0, x);
        };

        for (const auto& shapedGlyph : shapedGlyphs)
        {
            // Increment hue per cluster
            if (shapedGlyph.cluster != previousCluster)
            {
                currentHue += hueStep;
                previousCluster = shapedGlyph.cluster;
            }

            while (currentHue >= 360.0f)
                currentHue -= 360.0f;

            // Update vertex colors and y position
            for (auto index = shapedGlyph.vertexOffset; index < shapedGlyph.vertexOffset + shapedGlyph.vertexCount; ++index)
            {
                vertices[index].color      = getColor();
                vertices[index].position.y = rainbowYPositions[index] +
                                             std::sin(sf::degrees(currentHue * 2.0f).asRadians()) * 2.0f;
            }
        }
    }

    static inline auto        currentYPosition = 140.0f;
    std::unique_ptr<sf::Font> font;