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On 2015-01-31T13:03:53+00:00 Chris Bainbridge wrote:

As noted at http://www.shallowsky.com/linux/x-screen-blanking.html calls
to "xset dpms" need to be prefixed with "sleep 1":

    will blank the screen (or activate the screensaver program, if you're using
    one) after a delay of one second. You need the delay because X gets a little
    confused about the order of events; it will blank the screen but immediate
    un-blank it, thinking the activity of your typing the command happened
    recently enough to come out of screensaver mode.

    sleep 1; xset dpms force off

    will turn the screen OFF after a delay of one second. You can also use
    standby, suspend, or on instead of off.

Downstream bug report: https://bugs.debian.org/cgi-
bin/bugreport.cgi?bug=776674

Reply at:
https://bugs.launchpad.net/ubuntu/+source/xfce4-session/+bug/1802138/comments/0

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On 2015-02-08T12:50:49+00:00 Chris Bainbridge wrote:

Created attachment 5915
xflock4-sleep.patch

Reply at:
https://bugs.launchpad.net/ubuntu/+source/xfce4-session/+bug/1802138/comments/1

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On 2015-02-08T17:07:02+00:00 Steve Dodier-Lazaro wrote:

I can reproduce the issue, but the patch does not work for me (Xfce
4.11, ArchLinux 64 bits, xscreensaver 5.32).

@OP, what screensaver do you use, and does the patch work for you?

@Other triagers, could you please test the patch?

Reply at:
https://bugs.launchpad.net/ubuntu/+source/xfce4-session/+bug/1802138/comments/2

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On 2015-02-08T20:27:28+00:00 Chris Bainbridge wrote:

@Steve Yes the patch works for me using slock. 
What exactly fails for you?
Does "sleep 1; xset dpms force off" successfully turn off the monitors on your 
system?
Do you have one of 
{xscreensaver-command,light-locker-command,gnome-screensaver-command} 
installed? If so, the xset dpms line in xflock4 is never executed.

(can't seem to change bug status back from needinfo..)

Reply at:
https://bugs.launchpad.net/ubuntu/+source/xfce4-session/+bug/1802138/comments/3

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On 2015-02-08T20:36:33+00:00 Steve Dodier-Lazaro wrote:

Hi Chris,

When I type xset dpms force off in a terminal, my screen is turned off.
Xflock4, with or without delay, always fails to turn my screen off. I
believe the screensaver is the culprit, it probably talks to the X11
server and causes it to wake up.

Reply at:
https://bugs.launchpad.net/ubuntu/+source/xfce4-session/+bug/1802138/comments/4

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On 2015-02-08T20:38:11+00:00 Steve Dodier-Lazaro wrote:

Errata; after uninstalling xscreensaver, the patch still does not work.

Reply at:
https://bugs.launchpad.net/ubuntu/+source/xfce4-session/+bug/1802138/comments/5

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On 2015-02-08T21:15:53+00:00 Chris Bainbridge wrote:

Can you try "slock & sleep 1; xset dpms force off"

Also try "sh -x /usr/bin/xflock4" and see if the xset line is actually
being executed. It won't be if you have xscreensaver, light-locker or
gnome-screensaver installed.

Reply at:
https://bugs.launchpad.net/ubuntu/+source/xfce4-session/+bug/1802138/comments/6

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On 2015-02-12T02:20:22+00:00 Steve Dodier-Lazaro wrote:

Ok, I've been a bit silly on that one. So, when having slock installed I
reach this code path.

With the patch: 1 second delay, then a black screen
Without the patch: black screen immediately

Now, on desktops, when using a mouse, it's quite easy to trigger the
mouse after the screen has been forced off. Still, a whole second is a
bit excessive.

I'd like more developers to weight in before applying the patch.

Reply at:
https://bugs.launchpad.net/ubuntu/+source/xfce4-session/+bug/1802138/comments/7

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On 2015-02-12T02:21:19+00:00 Steve Dodier-Lazaro wrote:

Chris, thanks for writing the patch and bearing with me though. Of
course if you can link to others complaining about the issue, and to
more precise reasons why it is systematically happening for you, it'll
increase the odds of people weighing in favour of your patch.

Reply at:
https://bugs.launchpad.net/ubuntu/+source/xfce4-session/+bug/1802138/comments/8

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On 2015-02-12T10:47:11+00:00 Chris Bainbridge wrote:

> With the patch: 1 second delay, then a black screen
> Without the patch: black screen immediately

slock will always show a black screen but is the monitor actually turned
off with DPMS - my monitor shows "Entering power save mode" when this
happens and turns off the back light.

Try this: in a terminal type "xset dpms force off" and press and hold
the enter key for one second before releasing it. The key press event
will cause the execution of the xset command, but then the release event
will wake the monitor back up. The same happens with the ctrl-alt-delete
shortcut.


> Of course if you can link to others complaining about the issue

http://www.shallowsky.com/linux/x-screen-blanking.html
http://askubuntu.com/questions/38776/trigger-screensaver-off-monitor
https://wiki.archlinux.org/index.php/Display_Power_Management_Signaling
http://ubuntuforums.org/showthread.php?t=1317747&page=4
http://unix.stackexchange.com/questions/4466/screen-turns-on-automatically-xset-dpms-force-off


The explanation:

"You're using it manually from command line or xset is binded to some
keyboard shortcut? On my brother laptop this command was binded to some
keys and after that monitor was turned off and on again, because when he
was releasing key next event was emitted. Turning it off after quick
sleep solved problem: perl -e 'select(undef,undef,undef,.1)' && xset
dpms force off - this perl expression do sleep for 0.1 sec."

The timeout has to be longer than the delay between a person pressing
the enter key and then releasing it.

Reply at:
https://bugs.launchpad.net/ubuntu/+source/xfce4-session/+bug/1802138/comments/9

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On 2015-02-12T17:37:48+00:00 Rgm-b wrote:

Also see:

https://bugzilla.redhat.com/show_bug.cgi?id=1175015

This is a real pain with my notebook screen not going off when locked.
In a hotel room at night, I have to put a towel over the screen to get
to sleep myself!  When at my desk at home, the external monitor is
brightly lit when locked, lighting up the whole room at night.

I am concerned about long-term effects on the backlight feature failing
if not corrected.

Since I am running Fedora 21, please let me know what I have to do to
test a patch.

thank you

Reply at:
https://bugs.launchpad.net/ubuntu/+source/xfce4-session/+bug/1802138/comments/10

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On 2015-02-24T04:05:05+00:00 Rgm-b wrote:

Same problem with:

Fedora-Xfce-armhfp-22-20150223-sda.raw.xz

On my Cubietruck through its VGA adapter.  I probably will get around to
testing with HDMI tomorrow as well as testing on my Cubieboard2.

The usual:  You set screensaver to use a blank screen, and lock the
screen.

Screen blanks, but backlight stays on.

Reply at:
https://bugs.launchpad.net/ubuntu/+source/xfce4-session/+bug/1802138/comments/11

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On 2018-11-07T20:12:31+00:00 Chris Rainey wrote:

Still happening in Xubuntu 18.10. I vote for adding the patch!

$ hostnamectl 
   Static hostname: CKR-2
         Icon name: computer-laptop
           Chassis: laptop
        Machine ID: 5c61c71187fa4ba4aa26bdd89516ee5a
           Boot ID: 9a2e3fb61f6d461d9b423cdeebaa4c57
  Operating System: Ubuntu 18.10
            Kernel: Linux 4.18.0-10-generic
      Architecture: x86-64

Reply at:
https://bugs.launchpad.net/ubuntu/+source/xfce4-session/+bug/1802138/comments/14


** Changed in: xfce4-session
       Status: Unknown => In Progress

** Changed in: xfce4-session
   Importance: Unknown => Medium

** Bug watch added: Debian Bug tracker #776674
   https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=776674

** Bug watch added: Red Hat Bugzilla #1175015
   https://bugzilla.redhat.com/show_bug.cgi?id=1175015

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https://bugs.launchpad.net/bugs/1802138

Title:
  xflock4 needs a 'sleep 1' before 'xset dpms force off' to prevent
  backlight from immediately reactivating

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