docs: public static SVGPoint elementCoordinatesFromEvent(Document doc, Element tag, Event evt) {
      try {
        DOMMouseEvent gnme = (DOMMouseEvent) evt;
        SVGMatrix mat = ((SVGLocatable) tag).getScreenCTM();
        SVGMatrix imat = mat.inverse();
        SVGPoint cPt = ((SVGDocument) doc).getRootElement().createSVGPoint();
        cPt.setX(gnme.getClientX());
        cPt.setY(gnme.getClientY());
        return cPt.matrixTransform(imat);
      }
      catch(Exception e) {
        LoggingUtil.warning("Error getting coordinates from SVG event.", e);
        return null;
      }
    }