Screensaver is invisible when activated by lid close

[Nathan Rennie-Waldock]

My power management settings are set to lock screen when the lid is closed. When this happens, the screensaver activates, but is not visible (desktop can't be interacted with, typing password and pressing enter unlocks it).

I'm running Xubuntu and have tried:

* xscreensaver instead of xfce4-screensaver
* slick-greeter instead of lightdm-gtk-greeter

Which made no difference. I'm now using sddm instead of lightdm and no longer having this problem, so I believe the bug is in lightdm. This is possible a duplicate of #1853709, but I'm unsure as that one is specifically talking about suspend, mine is set to lock, not suspend.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: lightdm 1.30.0-0ubuntu4~20.04.1
ProcVersionSignature: Ubuntu 5.13.0-1012.16-oem 5.13.1
Uname: Linux 5.13.0-1012-oem x86_64
ApportVersion: 2.20.11-0ubuntu27.18
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: XFCE
Date: Tue Sep 14 21:10:01 2021
InstallationDate: Installed on 2021-07-01 (75 days ago)
InstallationMedia: Xubuntu 20.04.2.0 LTS "Focal Fossa" - Release amd64 (20210209.1)
SourcePackage: lightdm
UpgradeStatus: No upgrade log present (probably fresh install)