Wayland display server porblem?

[joneall]

I took a break for lunch and a siesta and when I got back, my screen was set on 640pixels and insisted that it was the only resolution allowed for this screen. I had to reboot to get back to normal.

In syslog, I see messages like these:

2026-07-16T12:24:34.443502+02:00 jon-desktop strawberry[2294]: 12:24:34.435 DEBUG unknown Creating a fake screen in order for Qt not to crash
...
thunderbird[3381]: [Parent 3381, Main Thread] WARNING: Couldn't map window 0x7db21075e5c0 as subsurface because its parent is not mapped.: 'glib warning',
file /build/thunderbird-VCZ2OF/thunderbird-140.12.1+build1/toolkit/xre/nsSigHandlers.cpp:201 [several hundred times]
...
2026-07-16T12:24:45.306289+02:00 jon-desktop org_kde_powerdevil: [ 9923] Emitting DDCA_Display_Status_Event[15156.935: DDCA_EVENT_DISPLAY_CONNECTED, card1-DP-1, dref: DDCA_Display_Ref[24], io_path:
/dev/i2c-9, ddc working: true]
2026-07-16T12:24:45.306402+02:00 jon-desktop org_kde_powerdevil: [ 9923] libddcutil callback thread 0x76434800f070 started
2026-07-16T12:24:45.306443+02:00 jon-desktop org_kde_powerdevil: [ 9923] Started 1 event callback thread(s)
2026-07-16T12:24:45.306734+02:00 jon-desktop org_kde_powerdevil: [ 1982] Quiescing libddcutil API...
2026-07-16T12:24:45.306795+02:00 jon-desktop org_kde_powerdevil: [ 1982] Quiesce libddcutil API complete
2026-07-16T12:24:45.306821+02:00 jon-desktop org_kde_powerdevil: [ 1982] Display redetection starting.

The AI assistant of duckduckgo tells me:

The message "Creating a fake screen in order for Qt not to crash" is related to problems with the Wayland display server in KDE environments. This occurs when Qt detects issues with the actual display, prompting it to simulate a screen to avoid crashing.

I'm at

Operating System: KDE neon User Edition
KDE Plasma Version: 6.7.2
KDE Frameworks Version: 6.28.0
Qt Version: 6.11.1
Kernel Version: 6.17.0-35-generic (64-bit)
Graphics Platform: Wayland

[claydoh]

Wayland is not a display server, it is a protocol that is implemented by the compositor (aka Kwin for us in Plasma) so the AI might be a little suspect in its response

But:
My AI says something a tiny bit different, and makes a little more sense, maybe?

The error message qt.qpa.wayland: Creating a fake screen in order for Qt not to crash typically appears on Linux systems running Wayland (like KDE Plasma, Sway, or wlroots-based compositors). It happens when the display server cuts the connection to the physical monitor (e.g., during screen timeout, monitor power-off, or sleep), causing Qt to lose its active display output. To prevent an immediate crash, Qt creates an invisible, fallback "fake screen"

Note that this is specific to Strawberry here, not to the whole screen, but is obviously related.

Was this after waking from sleep or hibernation, or the screen powering off? This probably points to power management (hardware) fun, or maybe driver shenanigans when something powers off.

Is this your new system? Which motherboard? Which GPU?