blank screen does not turn off display backlight

[Robert Blair]

I updated a system from 21.10 to 22.04 and noticed that when the screen is blanked by no keyboard or mouse activity that the backlight in the VGA monitor is still on. The "settings->Displays" has "Unknown Display" which I assume means the system does not know what commands to send to the monitor to shut it off. I booted a live DVD of 21.10 and the settings has the VGA display as 'AOC 22" ' which is correct and the screen blanking works correctly. So it seems that the definition for the AOC displays have been removed from 22.04.

This behavior is different on Ubuntu 21.10, the VGA display is blank and the backlight is off. A minor nit is on 21.10 the "settings->Displays" shows the VGA display manufacture name, on 22.04 the
VGA display manufacture name is "Unknown Display".

I have discovered that the settings have the following options

"settings->Power->Screen Blank" with a time value to be selected and the
following text on the next line "Turns the screen off after a period of
inactivity"

"settings->Privacy->Screen->Blank Screen Display" with a time value to be
selected and the following text on the next line "Period of inactivity after
which the screen will go blank"

The two options have different actions but seem to be connected because
changing the time on one changes the time on the other.

My guess is that the update changed the action for Ubuntu 22.04. I would like the 21.10 behavior, that is to turn off the VGA display not just blank the display when selecting the "settings->Power->Screen Blank" for 22.04.

[Ubuntu Foundations Team Bug Bot (crichton)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. It seems that your bug report is not filed about a specific source package though, rather it is just filed against Ubuntu in general. It is important that bug reports be filed about source packages so that people interested in the package can find the bugs about it. You can find some hints about determining what package your bug might be about at https://wiki.ubuntu.com/Bugs/FindRightPackage. You might also ask for help in the #ubuntu-bugs irc channel on Libera.chat.

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[This is an automated message. I apologize if it reached you inappropriately; please just reply to this message indicating so.]

[Daniel van Vugt (vanvugt)]

The difference between 21.10 and 22.04 might just be that we now default to Wayland instead of Xorg. So the display subsystems are different.

Please run this command to gather more information:

  apport-collect 1975557

And to save time in future please use the 'ubuntu-bug' command to report new bugs.

[Robert Blair (ubuntu-qygzanxc)]

** Reply to message from Daniel van Vugt <email address hidden> on Wed,
25 May 2022 06:15:35 -0000

I get an error running apport-collect. I am beginning to think that the last
update to this system went wrong. There are other problems comming up which I
did not have before.

I have now tried the display with another 22.04 install and that works OK.

So I think this problem report should be closed.

bob1@Juptier:~$ apport-collect 1975557
ERROR: connecting to Launchpad failed: Unable to find the server at
launchpad.net
You can reset the credentials by removing the file
"/home/bob1/.cache/apport/launchpad.credentials"
bob1@Juptier:~$

> The difference between 21.10 and 22.04 might just be that we now default
> to Wayland instead of Xorg. So the display subsystems are different.
>
> Please run this command to gather more information:
>
> apport-collect 1975557
>
> And to save time in future please use the 'ubuntu-bug' command to report
> new bugs.
>
> ** Tags added: jammy
>
> ** Package changed: xorg (Ubuntu) => gnome-shell (Ubuntu)
>
> ** Changed in: gnome-shell (Ubuntu)
> Status: New => Incomplete
>
> --
> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/1975557
>
> Title:
> blank screen does not turn off display backlight
>
> Status in gnome-shell package in Ubuntu:
> Incomplete
>
> Bug description:
> I updated a system from 21.10 to 22.04 and noticed that when the
> screen is blanked by no keyboard or mouse activity that the backlight
> in the VGA monitor is still on. The "settings->Displays" has "Unknown
> Display" which I assume means the system does not know what commands
> to send to the monitor to shut it off. I booted a live DVD of 21.10
> and the settings has the VGA display as 'AOC 22" ' which is correct
> and the screen blanking works correctly. So it seems that the
> definition for the AOC displays have been removed from 22.04.
>
> This behavior is different on Ubuntu 21.10, the VGA display is blank and the
> backlight is off. A minor nit is on 21.10 the "settings->Displays" shows the
> VGA display manufacture name, on 22.04 the
> VGA display manufacture name is "Unknown Display".
>
> I have discovered that the settings have the following options
>
> "settings->Power->Screen Blank" with a time value to be selected and the
> following text on the next line "Turns the screen off after a period of
> inactivity"
>
> "settings->Privacy->Screen->Blank Screen Display" with a time value to be
> selected and the following text on the next line "Period of inactivity after
> which the screen will go blank"
>
> The two options have different actions but seem to be connected because
> changing the time on one changes the time on the other.
>
> My guess is that the update changed the action for Ubuntu 22.04. I
> would like the 21.10 behavior, that is to turn off the VGA display not
> just blank the display when selecting the "settings->Power->Screen
> Blank" for 22.04.
>
> To manage notifications about this bug go to:
> https://bugs.launchpad.net/ubuntu/+source/gnome-shell/+bug/1975557/+s...

[Daniel van Vugt (vanvugt)]

Please try:

  cd /home/bob1/.cache/
  rm -rf apport
  apport-collect 1975557

If that doesn't work then maybe consider opening a new bug with the same info:

  ubuntu-bug gnome-shell

[Launchpad Janitor (janitor)]

[Expired for gnome-shell (Ubuntu) because there has been no activity for 60 days.]

[Sadaharu Wakisaka (psw1747)]

I confirmed this bug occurs when the gnome-shell-extension-dash-to-dock is on.
Turn it off and restart computer, the display shuts off after blank.

[T (reguluss)]

Still have the same problem on my Ubuntu 22.04.
The monitor backlight isn't off after lock or after 5 minutes with Screen Blank power saving options selcted.
I didn't install gnome-shell-extension-dash-to-dock as #7 said.

And there are other similar reports on this issue:
https://bugs.launchpad.net/ubuntu/+source/mutter/+bug/1998716
https://bugs.launchpad.net/gnome-settings-daemon/+bug/1971434

This is not a big deal but really annoying. TT

[Daniel van Vugt (vanvugt)]

In that case please try:

  gnome-extensions disable <email address hidden>

[Sam Vervaeck (samvv)]

Just wanted to link to the following to comments I made for reference:

 - https://bugs.launchpad.net/ubuntu/+source/linux-raspi/+bug/1998716/comments/19
 - https://bugs.launchpad.net/ubuntu/+source/gnome-settings-daemon/+bug/1971434/comments/42

I believe that for some people the KMS module may be the culprit. If I connect an external monitor, this bug appears, but on my laptop monitor everything works fine.

If anyone could share how to dig deeper into this I'd be grateful.