eZ\Publish\Core\MVC\Symfony\Configuration\VersatileScopeInterface::setDefaultScope PHP Method

    public function setDefaultScope($scope);

 public function onConfigScopeChange(ScopeChangeEvent $event)
 {
     $siteAccess = $event->getSiteAccess();
     $this->configResolver->setDefaultScope($siteAccess->name);
     if ($this->viewManager instanceof SiteAccessAware) {
         $this->viewManager->setSiteAccess($siteAccess);
     }
 }