Monitors can't exit from power-saving-mode.

[fortuna at c4k3.space]

Hello All,

First:
I know at first sight, this doesn't look like a xfce-problem,
but the strange thing is I can't reproduce it when I use gnome or mate.

This is my first post ever, so forgive me when I don't supply enough 
info. Please teach me courtesy- and other rules. If the solution was in 
the wiki and I overlooked it, feel free to just post me a pointer.


Background info:

# cat /etc/centos-release
CentOS Linux release 7.2.1511 (Core)

# rpm -qa|grep -i xfce
xfce4-settings-4.12.0-7.el7.x86_64
xfce4-session-engines-4.12.1-8.el7.x86_64
xfce-polkit-0.2-5.el7.x86_64
xfce4-panel-4.12.0-4.el7.x86_64
xfce4-power-manager-1.6.0-2.el7.x86_64
xfce4-terminal-0.6.3-4.el7.x86_64
xfce4-session-4.12.1-8.el7.x86_64
libxfce4ui-4.12.1-3.el7.x86_64
xfce4-appfinder-4.12.0-4.el7.x86_64
libxfce4util-4.12.1-2.el7.x86_64
xfce4-pulseaudio-plugin-0.2.4-4.el7.x86_64

# cat /proc/cmdline |grep -o BOOT_IMAGE=.*pw
BOOT_IMAGE=vmlinuz-4.6.2-1.el7.elrepo.x86_64

# lsmod |grep video
video                  40960  2 i915,dell_wmi



2 monitors are connected to the onboard intel videocard ( 2x Display 
port )


Problem:

When I'm logged in and use the desktop environment, and I power off the 
monitor (or I unplug the power of the monitor), I feel happy because 
it's good for the environment.

But when I power the monitor back on, it goes immediately in 
power-saving-mode.
(which is good for the environment, but bad for my productivity).

There is no problem when I choose gnome or mate instead of xfce when 
loggin in (gdm).

I found a little workaround:
I can power off the monitor, and when before powering it back on, I go 
to console (CTRL+ALT+F2),
the monitor comes up, and I can go back to X and work where I was.

But nevertheless I'm eagerly to find the cause of this problem.
Does anyone have an idea? Or an idea why I only have this problem when 
using xfce?


dmesg is not showing anything useful.
/var/log/messages neither
a .xfce4-session.verbose-log attached (nothing useful I guess)
"xset q" attached (DPMS disabled with xfce4-power-manager-settings)


I'm very grateful if someone could help me out or show me the way to the 
solution!
No offence, but please spare me the "don't power off your monitor" 
solution.







-------------- next part --------------
An embedded and charset-unspecified text was scrubbed...
Name: xfce4-session.verbose-log
URL: <https://mail.xfce.org/pipermail/xfce/attachments/20160719/7eb423f8/attachment-0002.ksh>
-------------- next part --------------
An embedded and charset-unspecified text was scrubbed...
Name: xset-q
URL: <https://mail.xfce.org/pipermail/xfce/attachments/20160719/7eb423f8/attachment-0003.ksh>