public function get_logo_url($maxwidth = null, $maxheight = 200) {
        global $CFG;
        $logo = get_config('core_admin', 'logo');
        if (empty($logo)) {
            return false;
        }

        // 200px high is the default image size which should be displayed at 100px in the page to account for retina displays.
        // It's not worth the overhead of detecting and serving 2 different images based on the device.

        // Hide the requested size in the file path.
        $filepath = ((int) $maxwidth . 'x' . (int) $maxheight) . '/';

        // Use $CFG->themerev to prevent browser caching when the file changes.
        return moodle_url::make_pluginfile_url(context_system::instance()->id, 'core_admin', 'logo', $filepath,
            theme_get_revision(), $logo);
    }