Arcs with rx and ry being different are not considered valid

[moazin]

Inside the SVGParserArcToCurve.cpp on line 109 there is an SVG_ASSERT that ensures that rx and ry are not different. In the event that they are, an assertion is violated, thus the program stops. The comment there says untested and I think that means the code hasn't been tested for cases where they are different. The correct behavior is for such arcs to be rendered properly.

    SVG_ASSERT(angle == 0); // untested

    if (radiusX == 0 || radiusY == 0)
    {
        // this is actually a line
        path.LineTo(endX, endY);
        return;
    }

    SVG_ASSERT(radiusX == radiusY); // untested

    SVG_ASSERT(radiusX != 0 && radiusY != 0);

[moazin]

I did some testing and it seems that there are problems with Arcs that have a non-zero angle.

<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 2000 1000" width="2000" height="1000">
  <path d="M 100,100 a 100 50 -45 0 0 100,0" stroke="red" stroke-width="10" />
  <path d="M 100,200 a 100 50 -45 1 0 100,0" stroke="red" stroke-width="10" />
  <path d="M 250,100 a 100 50 -45 0 1 100,0" stroke="red" stroke-width="10" />
  <path d="M 250,300 a 100 50 -45 1 1 100,0" stroke="red" stroke-width="10" />
  <path d="M 500,100 a 100 50 0 0 0 100,0" stroke="red" stroke-width="10" />
  <path d="M 500,200 a 100 50 0 1 0 100,0" stroke="red" stroke-width="10" />
  <path d="M 650,100 a 100 50 0 0 1 100,0" stroke="red" stroke-width="10" />
  <path d="M 750,300 a 100 50 0 1 1 100,0" stroke="red" stroke-width="10" />
  <path d="M 100,400 a 100 50 90 0 0 100,0" stroke="red" stroke-width="10" />
  <path d="M 100,550 a 100 50 90 1 0 100,0" stroke="red" stroke-width="10" />
  <path d="M 250,450 a 100 50 90 0 1 100,0" stroke="red" stroke-width="10" />
  <path d="M 250,600 a 100 50 90 1 1 100,0" stroke="red" stroke-width="10" />
  <path d="M 740,550 A 100 50 -45 0 0 550,500" stroke="red" stroke-width="10" />
</svg>

Rendering by Librsvg: Rendering by SNV (Cairo):