docs: public static double[] getRelativeCoordinates(Event evt, Element reference) {
      if(evt instanceof DOMMouseEvent && reference instanceof SVGLocatable && reference instanceof SVGElement) {
        // Get the screen (pixel!) coordinates
        DOMMouseEvent gnme = (DOMMouseEvent) evt;
        SVGMatrix mat = ((SVGLocatable) reference).getScreenCTM();
        SVGMatrix imat = mat.inverse();
        SVGPoint cPt = ((SVGElement) reference).getOwnerSVGElement().createSVGPoint();
        cPt.setX(gnme.getClientX());
        cPt.setY(gnme.getClientY());
        // Have Batik transform the screen (pixel!) coordinates into SVG element
        // coordinates
        cPt = cPt.matrixTransform(imat);
  
        return new double[] { cPt.getX(), cPt.getY() };
      }
      return null;
    }