Bug#941461: xfce4: Getting out of lock screen is complicated

[Jiff <lazyvirus@gmx.com>]

Package: xfce4
Version: 4.12.5
Severity: normal

Dear Maintainer,

   * What led up to the situation?

This is on a laptop msi CX61 2PC 8 GB RAM (no RAM problem), with an Optimus
nvidia graphic card that is unused, no packages at all about it ; I only use
the intel one. I have another screen (1920x1080) plugged on the VGA output that
right-extends it's tiny display.

As the Xfce4 fast user switch package disappeared (?), I use the lock screen
trick to open a 2nd session for another user, flipping between both by locking
again and re-login from one to another.

As soon as the screen's locked, the power button goes orange (nvidia card) then
(~10-12s) comes back to blue (intel) and then, both screens are off.
I tried everything, but the only possible outcome is to CTRL-ALT-F1, which
works and revive the laptop screen, then ALT-F7 to come back to Xfce, wait
5-6s, then the padlock appears on both screens, ~12s and the login screen of
lightdm comes to live on both screens.

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

This is the only way I found to get the screens back to live after a lock.
The problem is, it is a long procedure to switch from one user to the other.




-- System Information:
Debian Release: 10.1
  APT prefers stable-updates
  APT policy: (500, 'stable-updates'), (500, 'stable')
Architecture: amd64 (x86_64)

Kernel: Linux 4.19.0-6-amd64 (SMP w/4 CPU cores)
Kernel taint flags: TAINT_OOT_MODULE, TAINT_UNSIGNED_MODULE
Locale: LANG=fr_FR.utf8, LC_CTYPE=fr_FR.utf8 (charmap=UTF-8), LANGUAGE=fr_FR.utf8 (charmap=UTF-8)
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages xfce4 depends on:
ii  gtk2-engines-xfce        3.2.0-4
ii  libxfce4ui-utils         4.12.1-3
ii  thunar                   1.8.4-1
ii  xfce4-appfinder          4.12.0-2
ii  xfce4-panel              4.12.2-1
ii  xfce4-pulseaudio-plugin  0.4.1-1
ii  xfce4-session            4.12.1-6
ii  xfce4-settings           4.12.4-1
ii  xfconf                   4.12.1-1
ii  xfdesktop4               4.12.4-2
ii  xfwm4                    4.12.5-1

Versions of packages xfce4 recommends:
ii  desktop-base      10.0.2
ii  tango-icon-theme  0.8.90-7
ii  thunar-volman     0.9.1-1
ii  xfce4-notifyd     0.4.3-1
ii  xorg              1:7.7+19

Versions of packages xfce4 suggests:
ii  gtk3-engines-xfce    3.2.0-4
ii  xfce4-goodies        4.12.6
ii  xfce4-power-manager  1.6.1-1

-- no debconf information