Changes of Screens can sometimes disable wrong screen on session restore

[thomas-zimmerman]

Expected behaviour

Removing a secondary screen, disable correct screen in current session. On session restore, leave other screen settings as set.

Actual behaviour

When a secondary screen is removed, the default screen is disabled on next session start

Steps to reproduce the behaviour

Start session, add a secondary display. Pull plug on display and shutdown system. On next start, the primary display is set to "off" and the screen is black.

MATE general version

ubuntu-mate-desktop/focal 1.263

Package version

mate-session-manager: 1.24.0-2ubuntu1

Linux Distribution

This has been seen on Pop!OS 20.04 on Nvidia driver version 440.82. The bug is not seen when switching to the Intel GPU driver

I am working with a customer that is reporting this issue and he does not see it in 18.04 or when running Debian 'buster' (on either GPU version). I am not sure what differences between the Ubuntu and Debian versions would be that would cause this.