[Bug 1759950] Re: Lid-close suspend: blank screen when switching to user session

[TJ]

Turns out this *is* systemd-logind and xfce4-power-manager fighting over
the lid close event.

It can be solved with:

echo "HandleLidSwitch=ignore" | sudo tee -a /etc/systemd/logind.conf
echo "HandleLidSwitchExternalPower=ignore" | sudo tee -a /etc/systemd/logind.conf

If you're doing this change from a TTY console whilst the GUI session
has gone dark, then simply:

$ sudo systemctl restart lightdm

** Also affects: systemd (Ubuntu)
   Importance: Undecided
       Status: New

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https://bugs.launchpad.net/bugs/1759950

Title:
  Lid-close suspend: blank screen when switching to user session

Status in Light-Locker:
  New
Status in Xfce4 Power Manager:
  Unknown
Status in light-locker package in Ubuntu:
  Invalid
Status in systemd package in Ubuntu:
  New
Status in xfce4-power-manager package in Ubuntu:
  Confirmed

Bug description:
  I'm currently testing Xubuntu 18.04 after a do-release-upgrade from
  16.04.

  I discovered a very weird issue. When doing S3 sleep via closing the
  lid, on resume the lock screen appears, I authenticate, but as soon as
  it switches to the user session the screen goes blank - not even a
  backlight.

  Switching to other ttys works and they display correctly but the GUI
  user session remains blank.

  If the system is manually suspended (not using the lid), then resumed
  either by opening the lid or pressing the power button, the GUI user
  session is fine.

  I narrowed it down to xfce4-power-manager and discovered disabling the
  lock-screen cured the issue.

  I cloned the repository and reviewed commits between 1.7 and 1.8.
  Fortunately there aren't many. Looking at 6365683 "Proper exit status
  for light-locker-command" I suspected the change in the SetActive
  return value, and reverted it.

  After a build/install cycle I've found the system now behaves
  correctly so I think the change should be reverted.

  I've created an issue upstream for this at

  https://github.com/the-cavalry/light-locker/issues/108

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