HowTo force screen backlight off when locking screen, general and Xfce4
Introduction
For months (years?) I have wondered why my ThinkPads fail to turn the backlight off when the screen is locked (blanked).
Solution: xset dpms force off in a Script
Unforunately, I found no way to get the X system to turn the backlight off.
The only way to turn it of is to use xset to switch the screen off.
An according lock script might look like this:
lockscreen.sh
#!/bin/bash
# activate screensaver
xscreensaver-command -lock
# or: gnome-screensaver-command --lock
# or: slock
# or: xlock $*
# let the screen fade out
sleep 4
# switch the screen off
xset dpms force off
Xfce4 integration
The script solution above has one disadvantage: The script needs to be called. Time based screen locking and Xfce's "lock screen" button won'nt use it.
Fortunately, Xfce4 uses a script anyway, in the first place: /usr/bin/xflock4
One can simple edit this file (as root), and insert the xset call right before the final exit:
End of patched /usr/bin/xflock4
#[...]
# begin of change
# let the screen fade out
sleep 4
# switch the screen off
xset dpms force off
# end of change
exit 0Of course this edit has to be re-done after an upgrade that provides a fresh original version of xflock4.