include/rive/math/aabb.hpp

#ifndef _RIVE_AABB_HPP_
#define _RIVE_AABB_HPP_

#include "rive/span.hpp"
#include "rive/math/mat2d.hpp"
#include "rive/math/vec2d.hpp"
#include <cstddef>
#include <limits>

namespace rive
{
struct IAABB
{
    int32_t left, top, right, bottom;

    constexpr int width() const { return right - left; }
    constexpr int height() const { return bottom - top; }
    constexpr bool empty() const { return width() <= 0 || height() <= 0; }

    IAABB inset(int dx, int dy) const { return {left + dx, top + dy, right - dx, bottom - dy}; }
    IAABB offset(int dx, int dy) const { return {left + dx, top + dy, right + dx, bottom + dy}; }
};

class AABB
{
public:
    float minX, minY, maxX, maxY;

    AABB() : minX(0), minY(0), maxX(0), maxY(0) {}
    AABB(const AABB& o) : minX(o.minX), minY(o.minY), maxX(o.maxX), maxY(o.maxY) {}
    static AABB fromLTWH(float x, float y, float width, float height)
    {
        return {x, y, x + width, y + height};
    }

    AABB(float minX, float minY, float maxX, float maxY) :
        minX(minX), minY(minY), maxX(maxX), maxY(maxY)
    {}

    AABB(const IAABB& o) : AABB((float)o.left, (float)o.top, (float)o.right, (float)o.bottom) {}

    AABB(Span<Vec2D>); // computes the union of all points, or 0,0,0,0

    bool operator==(const AABB& o) const
    {
        return minX == o.minX && minY == o.minY && maxX == o.maxX && maxY == o.maxY;
    }
    bool operator!=(const AABB& o) const { return !(*this == o); }

    float left() const { return minX; }
    float top() const { return minY; }
    float right() const { return maxX; }
    float bottom() const { return maxY; }

    float width() const { return maxX - minX; }
    float height() const { return maxY - minY; }
    Vec2D size() const { return {width(), height()}; }
    Vec2D center() const { return {(minX + maxX) * 0.5f, (minY + maxY) * 0.5f}; }

    AABB inset(float dx, float dy) const
    {
        AABB r = {minX + dx, minY + dy, maxX - dx, maxY - dy};
        assert(r.width() >= 0);
        assert(r.height() >= 0);
        return r;
    }
    AABB offset(float dx, float dy) const { return {minX + dx, minY + dy, maxX + dx, maxY + dy}; }

    IAABB round() const;

    ///
    /// Initialize an AABB to values that represent an invalid/collapsed
    /// AABB that can then expand to points that are added to it.
    ///
    inline static AABB forExpansion()
    {
        return AABB(std::numeric_limits<float>::max(),
                    std::numeric_limits<float>::max(),
                    -std::numeric_limits<float>::max(),
                    -std::numeric_limits<float>::max());
    }

    ///
    /// Grow the AABB to fit the point.
    ///
    static void expandTo(AABB& out, const Vec2D& point);
    static void expandTo(AABB& out, float x, float y);

    /// Join two AABBs.
    static void join(AABB& out, const AABB& a, const AABB& b);

    void expand(const AABB& other) { join(*this, *this, other); }
};

} // namespace rive
#endif