lubuntu monitor settings touching screens with gap between

Bug #1882411 reported by Chris Guiver
This bug affects 1 person
Affects Status Importance Assigned to Milestone
lxqt-config (Ubuntu)

Bug Description

This is a Lubuntu groovy (20.10) QA-test install first boot on
- dell [optiplex] 755 (c2d-e8300, 8gb, amd/ati radeon rv610/radeon hd2400 pro/xt)

As part of post-install checks, I ensure all disk space is utilized..... and finally adjust displays to match the machines setup. It was at this 'adjust displays to match' that this problem occurred.

My two displays are positioned "landscape + portrait(left-tilt)."
(left display is 1280x1024, right is 1024x768 on this setup)

** Synopsis

There is a 'hidden' gap between my displays which shouldn't be there.

** Description

The Monitor settings have been adjusted to match (see screen.jpg) with APPLY already pressed. I cannot move the displays closer (Keep.monitors.attached is clicked), yet windows disappear as if a gap exists between displays, and I have to keep dragging mouse to left awhile to get from my.right monitor before it appears in my.left monitor .. the gap correctly portrays to the BLACK dark section seen in screen.jpg

** Expected Results

Mouse should move between my.left and my.right monitors as if there is no gap, windows should not disappear (you cannot see left edge of Monitor.Settings window in screen.jpg) in this gap..

** Upstream filing

ProblemType: Bug
DistroRelease: Ubuntu 20.10
Package: lxqt-session 0.15.0-0ubuntu1
ProcVersionSignature: Ubuntu 5.4.0-26.30-generic 5.4.30
Uname: Linux 5.4.0-26-generic x86_64
ApportVersion: 2.20.11-0ubuntu38
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: LXQt
Date: Sun Jun 7 13:38:55 2020
InstallationDate: Installed on 2020-06-07 (0 days ago)
InstallationMedia: Lubuntu 20.10 "Groovy Gorilla" - Alpha amd64 (20200606)
SourcePackage: lxqt-session
UpgradeStatus: No upgrade log present (probably fresh install)

Revision history for this message
Chris Guiver (guiverc) wrote :
Revision history for this message
Chris Guiver (guiverc) wrote :

Lubuntu groovy install & strange behavior with Monitor.Settings

I have Keep.Monitors.Attached clicked.

I experienced strange behavior again today with Lubuntu in *live* session, then tested later on opensuse tumbleweed using LXQt 15.1 ... same if not similar behavior.. (too tired for more today, so recording what I found here)

From QA-test report found at (edited)

i had a play on opensuse with it's LXQt 15.1, got it to respond funny like I report above in this live session, albeit once in 20+ tries.. I've made opensuse also use openbox.. I had opensuse re-create the issue I experienced in lubuntu early on, but then could not re-create it again, in numerous attempts to narrow down description for upstream bug filing...
(edited later & it occurred again, but then once again tried to re-create behavior and couldn't recreate that again)..

two displays, one above the other but not aligned left-right perfectly; one far to left the other far to right.. if they're away from outside of Monitor.Settings corner of window and screen-2 is positioned to left (above or below) of other screen, on dropping the monitor (with Keep Monitors attached) the two screens adjust to the opposite left-right orientation to what you dropped at, ie. the one of the left is now to the right & vice-versa.... but I can't get it to occur very often. (ie. screen-2 which was positioned to the left is now the screen on the right after 'warp' move...)

Revision history for this message
Chris Guiver (guiverc) wrote :

2021-feb-23 QA-test installs

I've experienced this on a QA-test install on d755-8 (same box bug is filed against). I was attempting to explore other 'older' bugs on new LXQt 0.16

Report details can be seen at

Uploaded picture found at

This bug needs more exploration & likely filing upstream.

tags: added: hirsute
Revision history for this message
Chris Guiver (guiverc) wrote :

I just noticed this bug on a QA-test install on same d755-8


during second install (install alongside), whilst logging into the original install I noted a huge gap as I moved the cursor between displays... ie. this issue.

I suspect this bug relates to openbox, and it's one I've failed to continue testing on..

Revision history for this message
Chris Guiver (guiverc) wrote :

Using the QA-test install mentioned in comment #4 (2021-03-20 daily ISO)

I `apt install fluxbox xfwm4` and switched out openbox to

- fluxbox
- xfwm4

after changing the WM, I'd
- logout
- login
- open monitor.settings
- change screen to a different position, apply & save
- change screen to match my setup (landscape + portrait), apply & save
- move a window between monitors (pcmanfm-qt & monitor.settings; was window all visible? nope

there was NO DIFFERENCE when using openbox, fluxbox or xfwm4, so my thought of blaming openbox appears wrong.

note: Keep.monitors.attached as clicked in Monitor.Settings so no gap should have existed; middle of pcmanfm-qt or monitor.settings should have been visible..

Revision history for this message
Chris Guiver (guiverc) wrote :

the QA-test install (install alongside mentioned in comments #4 & #5) was logged in and also has the same issue. Same box, but subsequent install.

Picture is reason for comment (this is the other install to #4-5 but effect is identical). pcmanfm-qt is on left monitor, monitor.settings is on right (portrait) monitor, and pcmanfm-qt's ABOUT page is mostly hidden in 'gap' between left & right not-touching monitors.

Revision history for this message
Ubuntu QA Website (ubuntuqa) wrote :

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

A list of all reports related to this bug can be found here:

tags: added: iso-testing
Revision history for this message
Chris Guiver (guiverc) wrote :

I've been successful in re-creating this now in Debian Bullseye/sid on
- dell [optiplex] 780 (c2q-q9400, 8gb, amd/ati cedar radeon hd 5000/6000/7350/8350)

(research aimed at filing upstream; versions of LXQt is identical to hirsute I believe)

HOWEVER it took a lot of play before I could get this to occur. (on this regularly used system, I wasn't able to get it to occur like I have difficulty on my main Lubuntu hirsute install; it appears to be easier to produce on freshly installed systems; I had issues getting it to occur the first time on opensuse too. fear here is upstream may have trouble proving it). A theory for other like bugs has been it's a value not being set/initialized; that maybe at play however I got it to occur by changing LXQt's Monitor.Settings.Fast.Menu.Fast.Option so no openbox connection??

In the end I went into Monitor.Settings and used the Fast.Menu to to select Fast.Options and selecting Extended.View (which wasn't the in-use option at the time) and it appeared easily.

This uploaded picture is print screen showing the just being selected... Two displays, the panel on the bottom-left shows the position of the left.monitor the qterminal however is maximized on the right.monitor (portrait), and a GAP has opened up??

As Monitor.Settings reflects this; at this stage it's only a nuisance, however I'd not expect the gap to occur on selecting Extended.View in Fast.Menu->Fast.Options

Revision history for this message
Chris Guiver (guiverc) wrote :

Continuing from last comment (#8) I've decided to skip the remaining pictures I took.

1. it's difficult to re-create (on installed systems, thus to be found by upstream devs)
2. it's easily worked around
3. the gap in this (comment #8 & #9) case isn't "hidden" as I describe it in the initial bug report... likely the same issue, but my description doesn't fit that... if one bug is found, likely a few (this 'non-hidden' gap) may also be fixed

I'll only continue with another issue, the picture in Monitor.Settings->Set.Position can get mis-placed on repeated moves & testing...

On this picture the prior screenshot is still visible in the Spectacle window, window positions haven't been changed but on the Monitor.Settings window I've changed instead to the HDMI-0 tab so the "Rotation: Left" can be seen; the effect is still present & working, but it's no longer reflected in the Set.Position display.

A minor cosmetic issue this one, easily ignored & doesn't even need working around.. I think it's proof there is a bug or two in Monitor.Settings, but is this worth filing upstream?

Describing again: In testing with constant moving of monitor positions relative to one-another in Monitor.Settings->Set.Position the picture of the 'portrait' display gets forgotten and replaced by a 'landscape' display. (easy description for upstream, but is it easy to re-create?)

Note: this comment & last were on Debian Bullseye/sid not Lubuntu.

Revision history for this message
Chris Guiver (guiverc) wrote :

Lubuntu hirsute live QA-test on
- dell [optiplex] 755 (c2d-e8300, 8gb, amd/ati radeon rv610/radeon hd2400 pro/xt)

box originally filed with. During my actual QA-test I didn't notice any issues, and I left the box sitting idle still running..

a (ask ubu) support question (related to 1366x768 displays) had me go to this box (as it has a 1024x768) and perform various setting tasks... those caused this issue to re-occur.

left-monitor is landscape & right-monitor is portrait as normal, and show as connected in monitor.settings, but there is a obvious gap (delay when you move pointer between two displays), or if you drag a window so it appears on both displays the middle of the window is not seen...

I added xfwm4 & switched out openbox; logged out & logged in many times using both openbox & xfwm4 & issue still occurred (no changes to monitor.position which look perfect within that setting).

as I've experienced this issue before, and have worked around it I'll ignore..still occurring :(

Revision history for this message
Chris Guiver (guiverc) wrote :

Lubuntu impish daily QA-test (live) on
- dell [optiplex] 755 (c2d-e8300, 8gb, amd/ati radeon rv610/radeon hd2400 pro/xt)

adjusted monitors to match setup (landscape+portrait) & a gap appears between them on moving windows around - YET none show in monitor.settings... ie.

no picture taken, but it resembles the one on comment #8 except for different wallpaper

tags: added: impish
Revision history for this message
Chris Guiver (guiverc) wrote :

Lubuntu impish daily QA-test (live) on
- dell [optiplex] 755 (c2d-e8300, 8gb, amd/ati radeon rv610/radeon hd2400 pro/xt)

adjusted monitors to match setup (landscape+portrait) & a gap appears between them on moving windows around - YET none show in monitor.settings...

Note: The Monitor.Settings window was opened with no changes made..

** Expected result

I can move the cursor between one window to the other given relative position to each other (ie. monitors are touching in Monitor.Settings)

** Actual result

Mouse pointer movements take time to move from one screen to another; if I move windows so they exist with left & right sides of window on different displays; the middle of the window cannot be seen.

Revision history for this message
Chris Guiver (guiverc) wrote (last edit ):

Same session as prior comment... (firefox & prior comment can be seen on firefox)

Key in this picture is the Monitor.Settings window was moved between displays. The middle of the window cannot be viewed.


- `sudo apt install xfwm4 --no-install-recommends`
- use session-settings to replace `openbox` with `xfwm4`
- logout & login... (somewhat repeat of comment #5)
- still looks the same; monitor.settings when opened shows no space, but space between monitors exists & windows are disappearing..

- tried moving displays around using Monitor.Settings..

kept misbehaving... HOWEVER

- on swapping/reversing the LEFT-RIGHT monitor positions, the issue disappeared.

- on swapping/reversing the LEFT-RIGHT monitor positions the issue re-appeared

Issue only occurs when DVI-0 (my left landscape monitor) is on left, and DVI-1 or portrait-left-tilted monitor is on the right

Is my package filing correct? Are we up-to-date with upstream?
As this needs to be taken upstream..
Can I re-create this in opensuse tumbleweed? (comment #2 implies I could, it just took awhile to re-create & I know what I'm looking for!)

Chris Guiver (guiverc)
affects: lxqt-session (Ubuntu) → lxqt-config (Ubuntu)
Revision history for this message
Chris Guiver (guiverc) wrote (last edit ):

package change ^ was suggested by Dan/kc2bez

I just confirmed the issue still occurs on opensuse tumbleweed.
- hp 8200 elite sff (i5-2400, 8gb, nvidia quadro 600)
Tumbleweed wasn't fully updated (packages updating now), however

VERSION = 2021.06.20 (tumbleweed package level)
lxqt 0.17.0
liblxqt 0.17.0
Qt 5.15.2

I see some Qt5 libs being updated... some are LXQt it turns out, so I'll let it complete.. logout, login & test again.

WM being used is openbox. One screen set to portrait-left, the other landscape. After first change no issue was noted; however swapping the left-right to right-left and issue was evident.

I've flipped WM to `xfwm4` so post-update re-test will be with `xfwm4` instead of `openbox`.

Issue still occurs with XFWM4 (gap feels wider but subjective).
Only change in version details being (I'm adding '.'s for readability)
opensuse VERSION_ID = 2021.06.28

Chris Guiver (guiverc)
description: updated
Revision history for this message
Chris Guiver (guiverc) wrote :

Lubuntu 20.04.3 QA-test install to
- dell [optiplex] 755 (c2d-e8300, 8gb, amd/ati radeon rv610/radeon hd2400 pro/xt)
testcase: full disk, encryption, BIOS, internet

in setup of box (monitor is portrait-left); a gap opened between monitors... updated to include focal.

tags: added: focal
Revision history for this message
Chris Guiver (guiverc) wrote :

Lubuntu 22.04.2 daily (RC?) QA-test install to dc7700

first boot; adjusted displays to match setup (side by side; this video card has the system mirror displays on new install) and a 'gap' appears between the display despite lxqt-config-monitor having the monitors touching...

I've positioned the monitor-settings window so it should appear on both monitors.. you'll note the picture of settings shows the monitors actually touching HOWEVER there is a huge gap between them in what is displayed & I cannot see anything in that gap...

If i move the mouse cursor from one window to another, there is a long delay (I have to keep moving mouse) before it re-appears...

I may have filed more on this issue on another bug report; but this is what I saw on search & don't have time to explore further currently.. It's NOT a major issue for me, as I've learnt how to mitigate this (by replacing openbox, or just re-adjusting displays a few times & it'll stop occurring)

alas this has occurred on a QA RC install.

(this comment was originally filed on as its the closest I saw.. this bug report applies much better

tags: added: jammy
Revision history for this message
Chris Guiver (guiverc) wrote :

Lubuntu lunar QA-test on
- hp dc7700 (c2d-e6320, 8gb amd/ati rv610/radeon hd2400 pro/xt)

and on adjusting monitor alignment (how screens touch each other), a GAP has opened up between them even though in settings the displays are touching...

(I created screenshot, but largest change over prior screenshot added is just different wallpaper - nothing new would be gained)

tags: added: lunar
removed: groovy hirsute impish
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