RectPack.cpp

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#include "RectPack.hpp"
 
namespace galaxy
{
    RectPack::RectPack() noexcept
        : m_width {0}
        , m_height {0}
    {
    }
 
    RectPack::~RectPack() noexcept
    {
        m_free_rects.clear();
    }
 
    void RectPack::init(const int width, const int height) noexcept
    {
        m_width  = width;
        m_height = height;
 
        m_free_rects.emplace_back(0, 0, m_width, m_height);
    }
 
    std::optional<iRect> RectPack::pack(const int width, const int height)
    {
        // Result.
        std::optional<iRect> result = std::nullopt;
 
        // Go over each space in the rectangle, in reverse order (i.e. smallest -> largest).
        for (auto rit = m_free_rects.rbegin(); rit != m_free_rects.rend();)
        {
            auto& space = *rit;
 
            // Check if rect can fit into space.
            if (width <= space.width && height <= space.height)
            {
                // Make the packed area rectangle.
                result = std::make_optional<iRect>(space.x, space.y, width, height);
 
                // Check to see if shape fills completely.
                if (width == space.width && height == space.height)
                {
                    // Destroy since not free space anymore.
                    std::advance(rit, 1);
                    m_free_rects.erase(rit.base());
                }
                else if (width == space.width)
                {
                    // If just width fits, shrink new space.
                    space.y      += height;
                    space.height -= height;
                }
                else if (height == space.height)
                {
                    // Same as width, for height.
                    space.x     += width;
                    space.width -= width;
                }
                else
                {
                    // Otherwise, split up existing space.
                    iRect temp = {space.x + width, space.y, space.width - width, height};
 
                    space.y      += height;
                    space.height -= height;
 
                    m_free_rects.emplace_back(temp);
                }
 
                // If it can fit, no longer need to keep iterating through.
                break;
            }
            else
            {
                // Try next space.
                ++rit;
            }
        }
 
        return result;
    }
 
    void RectPack::clear() noexcept
    {
        m_free_rects.clear();
        m_free_rects.emplace_back(0, 0, m_width, m_height);
    }
 
    int RectPack::get_width() const noexcept
    {
        return m_width;
    }
 
    int RectPack::get_height() const noexcept
    {
        return m_height;
    }
 
    const std::vector<iRect>& RectPack::get_free_space() const noexcept
    {
        return m_free_rects;
    }
} // namespace galaxy