Bug 426323

Summary:	Switch user and log back in as same creates blank screen
Product:	[Plasma] plasmashell	Reporter:	T <tejaswi.popuri>
Component:	general	Assignee:	David Edmundson <kde>
Status:	RESOLVED DOWNSTREAM
Severity:	normal	CC:	nalvarez, nate, plasma-bugs-null, sheedy
Priority:	NOR
Version First Reported In:	5.18.5
Target Milestone:	1.0
Platform:	Ubuntu
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description T 2020-09-09 00:47:10 UTC

SUMMARY
When I click switch user in session to change user but log back into the same account, I get a blank screen and the UI does not load. 


STEPS TO REPRODUCE
1. Log into machine/VM with account "x"
2. Switch user to log in with a different account through login screen. 
3. Log back into machine/VM with account "x"

OBSERVED RESULT
It looks like the system tries to actually create another session. 
I have to wait a few seconds and then am presented with a blank screen. 
The mouse cursor is active but click actions do not yield any results (including context menus). 

EXPECTED RESULT
The machine should simply unlock the computer for user "x" and take the user back to the session that was logged into originally. In effect, in this scenario, the login screen is expected to act as a screen lock. 

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Kubuntu 20.04 x64 
KDE Plasma Version: 5.18.5
KDE Frameworks Version: 5.68.0
Qt Version: 5.12.8
Kernel version: 5.4.0.47-generic


ADDITIONAL INFORMATION
Using SSDM from https://store.kde.org/p/1312658/

Comment 1 Nicolás Alvarez 2020-09-09 01:31:02 UTC

Reassigning to plasmashell for a start, but it seems this could be an SDDM issue.

Comment 2 Nate Graham 2020-09-09 04:01:43 UTC

> It looks like the system tries to actually create another session. 

Yeah, it probably is. However SDDM supports re-logging-in to the existing session, and in fact does it by default if you have a relatively recent version. See https://github.com/sddm/sddm/blob/develop/src/common/Configuration.h#L94

If this is isn't happening in Kubuntu, it's a distro bug for either not using a recent enough version of SDDM, or not explicitly adding ReuseSession=True to the config file to trigger that behavior in the old version. See https://phabricator.kde.org/T9034

Comment 3 T 2020-09-10 03:38:30 UTC

Thank you Nicolas and Nate. 

It is indeed happening in Kubuntu focal fossa. 
So, it is a distro bug. OK.
I'll see if I can raise it as an issue on a Kubuntu related tracker and reference your comments.

T