screen saver and locker that is integrated with the xfce4 desktop

 Xfce Screensaver is a screen saver and locker that aims to have simple,
 sane, secure defaults and be well integrated with the Xfce desktop.
 .
 It is a port of MATE Screensaver, itself a port of GNOME Screensaver.
 It has been tightly integrated with the Xfce desktop, utilizing Xfce
 libraries and the Xfconf configuration backend.