Bug 480844

Summary:	On Neon Unstable under Wayland in QEMU, black screen on resolution change.
Product:	[Plasma] kwin	Reporter:	funkybomber
Component:	wayland-generic	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	RESOLVED FIXED
Severity:	normal	CC:	akselmo, kde, nate, tagwerk19, xaver.hugl
Priority:	NOR	Keywords:	qt6, regression, wayland-only
Version First Reported In:	unspecified
Target Milestone:	---
Platform:	Neon
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description funkybomber 2024-02-04 11:40:29 UTC

STEPS TO REPRODUCE
1. Install the latest KDE Neon unstable edition (Plasma 6 RC2) in QEMU
2. Log in with the Wayland session
3. Go to Display configuration and change the Resolution to 1920x1080

OBSERVED RESULT
The user gets a black screen and only the cursor appears. After a few seconds the old resolution is restored and everything is back to normal (in the old resolution).

EXPECTED RESULT
The user gets no black screen and is able to change to his preferred display resolution (the same experience as with the X11 session).

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: 
(available in About System)
KDE Plasma Version: 6.0.80
KDE Frameworks Version: 6.0.0
Qt Version: 6.6.1
Kernel version: 6.5.0-15-generic (64-bit)
Graphics Platform: Wayland

Tested in a Virtual Machine (in QEMU v4.0.0) with the following specs:
Processor: 2 × Intel® Core™ i3-4150 CPU @ 3.50GHz
Memory: 3.8 GiB of RAM
Graphics Processor: llvmpipe
Manufacturer: QEMU
Product name: Standard PC (Q35 + ICH9, 2009)
System version: pc-q35-6.2

Comment 1 funkybomber 2024-02-04 11:46:33 UTC

ADDITIONAL INFO:

This used to work in the previous KDE Neon unstable ISO release, hence the "regression" tag.

The X11 session is not affected by this bug.

Comment 2 Akseli Lahtinen 2024-02-07 15:04:10 UTC

Can reproduce using Virtual Machine Manager and running KDE Neon Unstable on QEMU/KVM

Comment 3 Zamundaaa 2024-02-07 15:42:33 UTC

Can confirm. There's more to this though:
- switching to a higher resolution mode works
- this only happens with legacy modesettings with atomic modesetting it works fine

Comment 4 David Redondo 2024-09-17 11:17:19 UTC

I just tested this and this works now changing resolution up and down