Bug 502374 - With external screen, "Unify Displays" sets Steam Deck resolution to 800x600, breaking it
Summary: With external screen, "Unify Displays" sets Steam Deck resolution to 800x600,...
Status: RESOLVED DOWNSTREAM
Alias: None
Product: kwin
Classification: Plasma
Component: output configuration (other bugs)
Version First Reported In: 6.3.3
Platform: Other Linux
: NOR normal
Target Milestone: ---
Assignee: KWin default assignee
URL:
Keywords: multiscreen, wayland-only
Depends on:
Blocks:
 
Reported: 2025-04-03 19:33 UTC by Liarus1001
Modified: 2025-04-18 17:08 UTC (History)
4 users (show)

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Description Liarus1001 2025-04-03 19:33:40 UTC
SUMMARY
When KDE detects a new monitor it defaults to 800x600, however this is a problem for the steamdeck, when changing monitor configuration, the steamdeck's own screen might be detected as a new screen, and be set to 800x600, which is a resolution that results in a black screen on the steamdeck, due to it's native resolution being 800x1280.

I encountered this issue while plugging my steamdeck in a DisplayLink hub, and then accidentally selecting a random option in the Meta + P menu, this, broke my steamdeck's built in display, and i had to set the resolution back to 800x1280 on the built in display to get a display output on the steamdeck.

I am not sure this could be considered a KDE Bug, as it's specific to the steamdeck, and i assume the display would need to report it's own resolution instead of KDE setting it to 800x600, but i thought it would be worth reporting.

STEPS TO REPRODUCE
1. Plug an extra screen into a steamdeck compatible dock
2. Use any of the options in the meta + p options

OBSERVED RESULT

The steamdeck's own screen is set to 800x600 and thus doesn't display anything.

EXPECTED RESULT

The steamdeck screen is set to 800x1280

SOFTWARE/OS VERSIONSLinux/KDE Plasma: Bazzite 41
KDE Plasma Version: 6.3.3
KDE Frameworks Version: 6.12.0
Qt Version: 6.8.2
Comment 1 Nate Graham 2025-04-04 14:45:33 UTC
> When KDE detects a new monitor it defaults to 800x600
Does it? This doesn't sound like it's supposed to happen, and it's certainly not what I experience when I connect a new monitor.

Are you using the Wayland session or the X11 session? Does it happen in both, or just one?
Comment 2 Liarus1001 2025-04-04 15:28:34 UTC
(In reply to Nate Graham from comment #1)
> > When KDE detects a new monitor it defaults to 800x600
> Does it? This doesn't sound like it's supposed to happen, and it's certainly
> not what I experience when I connect a new monitor.
> 
> Are you using the Wayland session or the X11 session? Does it happen in
> both, or just one?

I'm using Bazzite on my deck, thus i only have wayland sessions.

After further testing the problematic options seems to be the "unify displays" option, i found weird that you couldn't reproduce it because someone from the bazzite discord also encountered the same issue when doing tests haha.

So yeah turns out "unify displays" is the problematic one, i just tried it on a 49" ultrawide connected to the steamdeck via a display link connection, and i tried at home as well with a 720p 4:3 native projector.

Both seem to set the steamdeck to 800x600 when i choose that option, after that i have to connect to a different display / dock and then set the steamdeck back to it's native resolution.
Comment 3 John Kizer 2025-04-13 04:33:48 UTC
For what it's worth, I'm using the Preview channel on my Steam Deck and Unify Displays, from the widget or Meta+P pop-up, does nothing. Setting it via the Display Configuration page in System Settings doesn't cause this issue, though.

Do you have access to a way to try those steps on something other than Bazzite, just in case something odd is being introduced somewhere in its process of adapting to the Deck hardware?
Comment 4 Liarus1001 2025-04-13 12:55:28 UTC
(In reply to John Kizer from comment #3)
> For what it's worth, I'm using the Preview channel on my Steam Deck and
> Unify Displays, from the widget or Meta+P pop-up, does nothing. Setting it
> via the Display Configuration page in System Settings doesn't cause this
> issue, though.
> 
> Do you have access to a way to try those steps on something other than
> Bazzite, just in case something odd is being introduced somewhere in its
> process of adapting to the Deck hardware?

Well, you're on steam OS right ? so you must be using the official dock i assume ?

I am using a displaylink based dock, which the driver is not there by default in SteamOS but is in Bazzite, the docks i am using are these two: Dell D6000 and a HP USB C/A dock G2

I couuuuld try SteamOS if you'd like me to, but would rather not if possible (i have quite a lot setup on it!), if you happen to own a displaylink dock, there is a tutorial here https://web.archive.org/web/20230531035834/https://steamdecklinux.wiki/wiki/Guide:Setting_up_DisplayLink on how to set up the driver on steamOS
Comment 5 Liarus1001 2025-04-13 12:56:33 UTC
I actually just tried the standard steamdeck dock made by valve and faced the exact same issue, so there is a chance this is a bazzite bug, i will try reporting that to them
Comment 6 Liarus1001 2025-04-13 13:12:02 UTC
(In reply to Liarus1001 from comment #5)
> I actually just tried the standard steamdeck dock made by valve and faced
> the exact same issue, so there is a chance this is a bazzite bug, i will try
> reporting that to them

Reported to the bazzite team as well, turns out while looking at the issues, i saw someone get the exact same issue, but this time on a lenovo legion go, so most likely not a KDE bug, sorry! 

Here's the bug report: https://github.com/ublue-os/bazzite/issues/2476
Comment 7 Nate Graham 2025-04-18 17:08:55 UTC
I can't reproduce this on my Steam Deck OLED with the official dock. It may be an issue with your 3rd-party dock or even the screen itself.