[nouveau] Top margin of secondary monitor covered with black flickering rectangle

[Jackson Smith]

The system has two monitors. Workspaces are activated on the primary monitor, but not the second. A custom background image is used on both monitor desktops. Windows created on primary monitor then moved to secondary e.g. firefox. Window moved towards top of secondary monitor. However, window is clipped. Background image is also clipped. The clipped area is about one eighth of the monitor, from the top, and spans the full area from left to right.

$ lsb_release -rd
No LSB modules are available.
Description: Ubuntu 24.04 LTS
Release: 24.04

ProblemType: Bug
DistroRelease: Ubuntu 24.04
Package: xorg 1:7.7+23ubuntu3
ProcVersionSignature: Ubuntu 6.8.0-39.39-generic 6.8.8
Uname: Linux 6.8.0-39-generic x86_64
ApportVersion: 2.28.1-0ubuntu3
Architecture: amd64
BootLog: Error: [Errno 13] Permission denied: '/var/log/boot.log'
CasperMD5CheckResult: pass
CompositorRunning: None
CurrentDesktop: ubuntu:GNOME
Date: Mon Jul 29 15:35:05 2024
DistUpgraded: Fresh install
DistroCodename: noble
DistroVariant: ubuntu
ExtraDebuggingInterest: Yes
GraphicsCard:
 NVIDIA Corporation TU116 [GeForce GTX 1660 SUPER] [10de:21c4] (rev a1) (prog-if 00 [VGA controller])
   Subsystem: eVga.com. Corp. TU116 [GeForce GTX 1660 SUPER] [3842:1068]
InstallationDate: Installed on 2024-07-29 (0 days ago)
InstallationMedia: Ubuntu 24.04 LTS "Noble Numbat" - Release amd64 (20240424)
MachineType: To Be Filled By O.E.M. Z590 Phantom Gaming 4
ProcEnviron:
 LANG=en_US.UTF-8
 PATH=(custom, no user)
 SHELL=/bin/bash
 TERM=xterm-256color
 XDG_RUNTIME_DIR=<set>
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-6.8.0-39-generic root=UUID=01105987-3c51-4daa-947e-0b4af195e3a6 ro quiet splash vt.handoff=7
SourcePackage: xorg
Symptom: display
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 10/21/2021
dmi.bios.release: 5.19
dmi.bios.vendor: American Megatrends International, LLC.
dmi.bios.version: P2.10
dmi.board.name: Z590 Phantom Gaming 4
dmi.board.vendor: ASRock
dmi.chassis.asset.tag: To Be Filled By O.E.M.
dmi.chassis.type: 3
dmi.chassis.vendor: To Be Filled By O.E.M.
dmi.chassis.version: To Be Filled By O.E.M.
dmi.modalias: dmi:bvnAmericanMegatrendsInternational,LLC.:bvrP2.10:bd10/21/2021:br5.19:svnToBeFilledByO.E.M.:pnZ590PhantomGaming4:pvrToBeFilledByO.E.M.:rvnASRock:rnZ590PhantomGaming4:rvr:cvnToBeFilledByO.E.M.:ct3:cvrToBeFilledByO.E.M.:skuToBeFilledByO.E.M.:
dmi.product.family: To Be Filled By O.E.M.
dmi.product.name: Z590 Phantom Gaming 4
dmi.product.sku: To Be Filled By O.E.M.
dmi.product.version: To Be Filled By O.E.M.
dmi.sys.vendor: To Be Filled By O.E.M.
version.compiz: compiz N/A
version.libdrm2: libdrm2 2.4.120-2build1
version.libgl1-mesa-dri: libgl1-mesa-dri 24.0.9-0ubuntu0.1
version.libgl1-mesa-glx: libgl1-mesa-glx N/A
version.xserver-xorg-core: xserver-xorg-core 2:21.1.12-1ubuntu1
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev N/A
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:22.0.0-1build1
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.917+git20210115-1build1
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.17-2build1

[Daniel van Vugt (vanvugt)]

Thanks for the bug report. Please try adding this to /etc/environment:

  MUTTER_DEBUG_FORCE_KMS_MODE=simple

and then reboot.

[Jackson Smith (jsdpagsr)]

The issue persists when MUTTER_DEBUG_FORCE_KMS_MODE=simple has been added to /etc/environment. Note that Wayland is enabled; that is, /etc/gdm3/custom.conf has commented out the line reading WaylandEnable=false.

It may be relevant to note how the problem does not appear following a fresh reboot. There is a correlation with the use of SDL2 libraries. In fact, I am tracking down an issue in which a program that was stable in Ubuntu 22.04 is now experiencing segmentation faults when installed on Ubuntu 24.04.

[Jackson Smith (jsdpagsr)]

ps - I should have mentioned that the program faults when using an older version of libSDL2-2.0.so.0.

[Jackson Smith (jsdpagsr)]

pps - there is also a correlation with locking and unlocking the screen via OS_Key + L.

[Daniel van Vugt (vanvugt)]

Sounds like the timings of the current display mode are changing, which controls the placement of the display signal relative to the physical screen. And SDL2 apps might be changing the display mode while they are full screen. Unlocking the screen also involves a display "mode set".

If you set the monitor to a lower resolution or refresh rate, does it prevent the bug at least?

[Daniel van Vugt (vanvugt)]

While the problem is happening, does turning the monitor power off and on again help?