Bug#929834: lightdm-gtk-greeter: After locking screen, display is turned off and unlock prompt is not visible.

[Raj Kiran Grandhi <grajkiran@gmail.com>]

Package: lightdm-gtk-greeter
Version: 2.0.6-1
Severity: important

Dear Maintainer,

   * What led up to the situation?

Perform a clean install of testing using the RC1 netinst CD and selected XFCE desktop environment. 

   * What exactly did you do (or not do) that was effective (or
     ineffective)?

Log into the system from the lightdm login window, and lock the screen.

   * What was the outcome of this action?

Screen got locked and the disply got turned off (monitor entered power save). No unlock prompt was displayed, but typing the password blindly unlocked the session.

   * What outcome did you expect instead?

Screen gets locked, and an unlock prompt is displayed.

Additional info:

After locking the screen, when the display gets turned off, switching to a different VT and back displays the unlock prompt as usual and everything works as expected. This problem does not occur when switching the greeter from lightdm-gtk-greeter to slick-greeter.

References:
1. https://lists.debian.org/debian-user/2019/05/msg01477.html
2. https://lists.debian.org/debian-devel/2019/06/msg00000.html

Thanks,
Raj Kiran

-- System Information:
Debian Release: 10.0
  APT prefers testing
  APT policy: (500, 'testing')
Architecture: amd64 (x86_64)

Kernel: Linux 4.19.0-5-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_IN, LC_CTYPE=en_IN (charmap=UTF-8), LANGUAGE=en_IN:en (charmap=UTF-8)
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages lightdm-gtk-greeter depends on:
ii  libc6                   2.28-10
ii  libcairo2               1.16.0-4
ii  libgdk-pixbuf2.0-0      2.38.1+dfsg-1
ii  libglib2.0-0            2.58.3-1
ii  libgtk-3-0              3.24.5-1
ii  libindicator3-7         0.5.0-4
ii  liblightdm-gobject-1-0  1.26.0-4
ii  libx11-6                2:1.6.7-1

Versions of packages lightdm-gtk-greeter recommends:
ii  adwaita-icon-theme  3.30.1-1
ii  desktop-base        10.0.2
ii  gnome-themes-extra  3.28-1
ii  policykit-1         0.105-25

lightdm-gtk-greeter suggests no packages.

-- no debconf information