public function use_svg_icons() {
        global $CFG;
        if ($this->usesvg === null) {

            if (!isset($CFG->svgicons)) {
                $this->usesvg = core_useragent::supports_svg();
            } else {
                // Force them on/off depending upon the setting.
                $this->usesvg = (bool)$CFG->svgicons;
            }
        }
        return $this->usesvg;
    }