Bug 393223 - DisplayPort detection issues after standby/resume
Summary: DisplayPort detection issues after standby/resume
Alias: None
Product: KScreen
Classification: Unclassified
Component: common (show other bugs)
Version: 5.12.4
Platform: Other Linux
: NOR normal
Target Milestone: ---
Assignee: Sebastian Kügler
Depends on:
Reported: 2018-04-17 13:01 UTC by Christian Muehlhaeuser
Modified: 2021-11-09 17:11 UTC (History)
3 users (show)

See Also:
Latest Commit:
Version Fixed In:

kscreen log (54.81 KB, text/x-log)
2018-04-17 13:01 UTC, Christian Muehlhaeuser

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Description Christian Muehlhaeuser 2018-04-17 13:01:53 UTC
Created attachment 112071 [details]
kscreen log

Note: I'm not sure if this is a kscreen bug or kwin bug, but I'm leaning towards the former.

I have two monitors connected to my system, one 1080p per HDMI, one 4k per DisplayPort. When putting my system to sleep (RAM), the DisplayPort connection seems to be shutdown in a weird way. Upon resuming from sleep, kscreen detects the DisplayPort monitor multiple times, which confuses kwin and a bunch of other applications (like latte-dock). Usually this manifests in the following ways:

- Only the HDMI monitor shows the lock-screen, the 4k/DP monitor only shows a black background (no lock-screen controls), but does show a mouse cursor when moving it to the screen.

- kwin loses window positioning and moves my windows from the HDMI monitor to the DP monitor.

- latte-dock sets an incorrect screen mask, making the right half of the dock disappear (see https://github.com/psifidotos/Latte-Dock/issues/941 for the upstream issue)

This is not happening every time I resume, but more often than not. It makes me assume this is a timing issues. Maybe the screen first gets initialized with 1080p, then quickly switches over to 4k?

Debug output from kscreen attached!
Comment 1 phrxmd 2021-11-09 16:19:41 UTC
I also have this issue when my monitor goes to Deep Sleep, upon wakeup the login screen appears on only one screen and my windows are a jumbled mess. This is with KDE 5.23.2