Is it a bug of opencv RotatedRect?

I wrote the following code:

#include<iostream>
#include<opencv2/core/core.hpp>
using namespace std;
using namespace cv;

int main()
{
    Point2f p[4];
    RotatedRect rr(Point2f(),Size2f(1,2),0);
    rr.points(p);
    for(int i = 0;i < 4;i++) cout<<p[i]<<endl;
    Rect r = rr.boundingRect();
    cout<< r.x << " " << r.y << " " << r.br().x << " " << r.br().y <<endl;
    return 0;
}

The top-left corner of RotatedRect rr is (-0.5,-1),and the bottom-right corner of RotatedRect rr is (0.5,1).So the minminimal up-right rectangle containing the rotated rectangle is [(-1,-1),(1,1)],(-1,-1) is the top-left corner,(1,1) is the bottom-right corner.But the result rect's bottom-right corner is (2,2).

And I read the source:

Rect RotatedRect::boundingRect() const
{
    Point2f pt[4];
    points(pt);
    Rect r(cvFloor(std::min(std::min(std::min(pt[0].x, pt[1].x), pt[2].x), pt[3].x)),
           cvFloor(std::min(std::min(std::min(pt[0].y, pt[1].y), pt[2].y), pt[3].y)),
           cvCeil(std::max(std::max(std::max(pt[0].x, pt[1].x), pt[2].x), pt[3].x)),
           cvCeil(std::max(std::max(std::max(pt[0].y, pt[1].y), pt[2].y), pt[3].y)));
    r.width -= r.x - 1;
    r.height -= r.y - 1;
    return r;
}

I wonder the code r.width -= r.x - 1; and r.height -= r.y - 1; And I think it should be r.width -= r.x; and r.height -= r.y; Who can tell me is it the source wrong?