changing screen positions (mate-control-center.displays) caused one display to become unreadable/unusable

[Chris Guiver]

Ubuntu MATE live QA-test on
- hp 8200 elite sff (i5-2400, 8gb, nvidia quadro 600)
another check for

My display setup is strange (one monitor above the other), so using the Displays area of Ubuntu-MATE Control Center to adjust, I drag the location of one relative to the other to where it should be for my setup.

** Expected results

I expect the Monitor.Preferences to show show ghost-images, and clicking APPLY I expect the display orientation to adjust to the changed setup, and both displays to be readable, static & usable.

** Actual results

On dragging one relative to the other, the Monitor.Preferences image is showing a trail of where it was dragged like solitaire years ago (on another OS) when you 'won'.. Not expected

On clicking Apply
- my.top monitor is perfectly clear & usable
- the displays are orientated correctly relative to one another
- my.bottom display is now unusable/unreadable as it's a constant changing/flashing mess

Dragging windows on my.lower display now leave trails (on desktop), the flashing/changing (strobe-like) could be a problem for some health conditions possibly (seizure?), but it's very annoying (it's occurring on what I consider my primary monitor when I'm seated as I am currently).

** More detail/testing

Strange - on closing Monitor.Preferences window, and re-opening it again.. my.lower monitor stopped it's flashing/changing images & became fully readable & usable.

Adjusting the screen.location in Control.Centre.Displays again still leave trails in the "Monitor Preferences" window, but that is easily ignored as it's only used once (or a few times) as its operation was effective anyway.

ProblemType: Bug
DistroRelease: Ubuntu 21.10
Package: mate-control-center 1.26.0-0ubuntu1
ProcVersionSignature: Ubuntu 5.13.0-16.16-generic 5.13.13
Uname: Linux 5.13.0-16-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
ApportVersion: 2.20.11-0ubuntu69
Architecture: amd64
CasperMD5CheckResult: pass
CasperVersion: 1.465
CurrentDesktop: MATE
Date: Thu Sep 23 02:44:52 2021
LiveMediaBuild: Ubuntu-MATE 21.10 "Impish Indri" - Beta amd64 (20210922)
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: mate-control-center
UpgradeStatus: No upgrade log present (probably fresh install)

[Chris Guiver (guiverc)]

You'll note the lower display has a mess of windows..

What the picture does not show is that the whole screen is flashing/strobe like; it appears a messy-clear image on the picture; but the image is not actually static but flashing...

I've since further tested & adjusted display position again (when the flashing stopped) so I can't describe what it was like that well; but it was very irritating & made it difficult to concentrate even on the one display that was perfectly normal

FYI: I'm still convinced I've experienced this before; but I can't find bug reports on it, and these actual screens are shared with other boxes; so I maybe thinking of the hp dc7700 (another box that uses same screens/keyboard/mouse etc)

[Chris Guiver (guiverc)]

another pic..

the top screens with terminal is perfectly calm & useable.

bottom screen (where window trails exist) is flashing/strobe-like

It's mostly the background that strobes; the windows themselves are somewhat usable/readable - caja is shown here and were it not for the flashing of wallpaper & background-stuff, it's likely 100% usable.

[Chris Guiver (guiverc)]

at this time I've re-opened the Control.Centre.Displays option (top display), and altered the relative position of each other..

Please NOTICE the SHADOW/TRAILS of the movement I made of the 'green' or originally 'right' monitor which was dragged to be below the left one.

Also NOTICE all trails on the lower-display are now gone; so has all FLASHING/STROBING on that display (it's now static). It's now 100% usable & readable.

The trails being left on

PS: I wonder if this issue is nouveau related, and NOT a Ubuntu-MATE issue; but again whilst I'm convinced I've had this issue before, I didn't find bug reports about it.

From this point on the system experience was GREAT
(making it both easier for me to type in the problem, but now I need to describe a condition I saw in the past - no longer occurring)

[Chris Guiver (guiverc)]

Nothing really new in this picture to the last.

it's identical to prior uploaded.photo except I adjusted the bottom monitor to be slightly-left (askew) of the top display (thus the black borders shown in the picture).

EXCEPT for the TRAILS in the Monitor.Preferences window

no issue here at all. Clicking apply & no flashing, system remained usable/readable & perfectly matches what the change I made.

This was reflected in subsequent changes I tested/tried

[Chris Guiver (guiverc)]

/var/crash/ is empty

[Chris Guiver (guiverc)]

Another QA-test on different hardware
- dell [optiplex] 780 (c2q-q9400, 8gb, amd/ati cedar radeon hd 5000/6000/7350/8350)

the moment I adjusted screens... same behavior as hp.8200; TRAILS appear in the Monitor.Preferences window, and flashing.background on one display. this box has very different GPU so I didn't expect the issue here - but this looks the same (not as annoying on these displays).

screen change this box is swap left-right and my-right display is portrait-left-tilt.

TRAILS & FLASHY single-display occurring here too

[Chris Guiver (guiverc)]

On this machine - the flashing appears to be only at the bottom of my.right (the portrait-left tilted display).. ie. the section that is below the other display.

effect is it's less annoying than the prior box (which was the whole background strobe-like flashing).

I've now adjusted the display a few times; all flashing has now ALL GONE but it wasn't the multiple changes that caused it to stop, but my clicking on the SHOW.DESKTOP (which hid all windows) that caused it to stop.

dell d780 box - very different GPU to hp (see prior comment)

[Ubuntu QA Website (ubuntuqa)]

This bug has been reported on the Ubuntu ISO testing tracker.

A list of all reports related to this bug can be found here:
http://iso.qa.ubuntu.com/qatracker/reports/bugs/1944661

[Chris Guiver (guiverc)]

just another screenshot on d780.

the bottom-right of the portrait-left display (my right.display but was default-left on boot) or the area that is BELOW the other screen is where it's flashing (stopped awhile back now; when I clicked the SHOW.DESKTOP type button in error thinking it was a menu)

/var/crash/ is also empty on this box
and again I see nothing useful in dmesg or journalctl

[Chris Guiver (guiverc)]

experiencing this today with Ubuntu MATE jammy daily
- hp 8200 elite sff (i5-2400, 8gb, nvidia quadro 600)

(note the real effect of the screenshot is far worse in real life; on movement of the mouse the image on the bottom display changes & it's mostly white-flashes; esp. the trails left by the terminal I dragged a little down onto the lower screen.. see next bug comment for picture after it was moved to lower screen)

[Chris Guiver (guiverc)]

another picture...

if the terminal window visible on the 'lower' screen is maximized; the wrong-background gets covered & flashing effect is gone.. if the terminal is dragged around, it leaves trails (which is why some can be seen as it was opened on the top screen & dragged to the bottom for picture shot).

[Norbert (nrbrtx)]

Dear Chris, could you please collect all the info from this bug and post new issue at upstream - https://github.com/mate-desktop/mate-control-center/issues .

[Chris Guiver (guiverc)]

Testing Ubuntu-MATE 22.04.2 daily (20230217.1) on
- hp prodesk 400 g1 sff (i5-4570, 8gb, amd/ati cedar radeon hd 5000/6000/7350/8350)

on adjusting displays to match my setup (one monitor above the other), my bottom monitor became unreadable with wallpaper & windows just a visual mess... Matches screenshots & description on https://bugs.launchpad.net/ubuntu/+source/mate-control-center/+bug/1944661

On changing the wallpaper though (on top monitor that I could use), both wallpapers changed & everything on the lower monitor was suddenly usable/viewable... The tagged bug was marked duplicate; but the image perfectly matched what I tagged.

NOTE: This box now shares monitors with the hp8200 this bug was initially filed against, so it's the identical setup display wise; though this box doesn't use nvidia.

Alas, I don't see where I filed upstream as per request on comment 14