light-locker is well integrated with the LightDM's greeter for unlocking the session.
light-locker is used by Xubuntu as preferred screen/session locker.

---
 scripts/xflock4 | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/scripts/xflock4 b/scripts/xflock4
index 32770b4..45f0967 100644
--- a/scripts/xflock4
+++ b/scripts/xflock4
@@ -27,9 +27,10 @@ export PATH
 # First test for the command set in the session's xfconf channel
 LOCK_CMD=$(xfconf-query -c xfce4-session -p /general/LockCommand)
 
-# Lock by xscreensaver or gnome-screensaver, if a respective daemon is running
+# Screen lock by light-locker, xscreensaver or gnome-screensaver, if a respective daemon is running
 for lock_cmd in \
     "$LOCK_CMD" \
+    "light-locker-command --lock" \
     "xscreensaver-command -lock" \
     "gnome-screensaver-command --lock"
 do
-- 
2.1.0