Hello Xfce Team,

First of all, thank you very much for Xfce v4.12, it is amazing that it "just works", and it does very well.

However, there would always be ways for improvement, isn't it?

Multiple monitor setup (3x)

01. Settings => Xfce Power Manager => 

General => Laptop lid => Switch off display (both "On battery"/"Plugged in")
General => Buttons => When power button is pressed => Ask
General => Buttons => When hibernate button is pressed => Do nothing
General => Handle display brightness keys
System => System sleep mode => Hibernate / Suspend (On battery / Plugged in)
System => When inactive for => Never / Never
System => On critical battery power => Do nothing
Display => [v] Handle display power management (checked)
Display => Blank after => Never / Never
Display => Put to sleep after => Never / Never
Display => Switch off after => Never / Never
Display => Redduce after => Never / Never
Security => Lock screen when system is going to sleep

02. Closing lid => Only Laptop's monitor goes off === OK.

03. Launching xflock4 by keyboard application shortcuts (Ctrl+Alt+L)

04. All monitors go black screen, but NOT on standby (there is still signal to all 3, just blacked out, resulting in the IPS glow at night) === **NOT OK**

05. After closing Laptop's lid => the system goes into hibernate/suspend mode, Laptop's power button fades out, signal to monitors lost, all 2 remaining monitors go to the standby mode (a highly desirable feature for xflock4, as in https://bugzilla.xfce.org/show_bug.cgi?id=6516). 
=== **NOT OK**.

06. Return from suspend/hibernate on keyboard/mouse event OK (thanks, Debian and Xfce).

System details:

$ xfce4-power-manager -V

Xfce Power Manager 1.4.4

$ uname -a
Linux a 4.9.0-2-amd64 #1 SMP Debian 4.9.18-1 (2017-03-30) x86_64 GNU/Linux
(Debian 9 Stretch RC 03)

$ nvidia-detect
Detected NVIDIA GPUs:
01:00.0 VGA compatible controller [0300]: NVIDIA Corporation GM204M [GeForce GTX 980M] [10de:1617] (rev a1)

$ xrandr
Screen 0: minimum 8 x 8, current 6400 x 1440, maximum 16384 x 16384
DP-0 disconnected (normal left inverted right x axis y axis)
DP-1 disconnected (normal left inverted right x axis y axis)
DP-2 connected 1920x1080+4480+0 (normal left inverted right x axis y axis) 382mm x 215mm
   1920x1080     75.00*+
HDMI-0 connected 1920x1080+2560+0 (normal left inverted right x axis y axis) 527mm x 296mm
   1920x1080     60.00*+  59.94    50.00    60.05    60.00    50.04  

...
DP-3 connected 2560x1440+0+0 (normal left inverted right x axis y axis) 596mm x 335mm
   2560x1440     59.95*+

...
DP-4 disconnected (normal left inverted right x axis y axis)


$ cat /etc/modeprobe.d/blacklists-nouveau.conf

blacklist nouveau
blacklist nouveaufb
blacklist lbm-nouveau
options nouveau modeset=0
alias nouveau off
alias nouveaufb off
alias lbm-nouveau off

$ cat /etc/modprobe.d/blacklist-nouveau-kms.conf

options nouveau modeset=0