[19.10] Tri-screen hell


As I have mentioned it on more than 1 occasion and into previous posts, my main system consists of a dual-head (2x monitors) in portrait mode and 1x in reverse portrait mode. That means that I am using 2x wide screen monitors that are both physically tilted 90 degrees(and the other 270 degrees, being a reverse portrait display) as I enjoy my MATE windows to be open into the vertical mode instead of the "regular" horizontal mode.

In my quest for "portrait perfection" I have now added a 3rd screen on my system via the DVI plug of my ATI video card. (My first 2 screens were already hooked up via the display port and HDMI port).

But silly me, allow me to present you with my system's specs first:

0a:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Baffin [Radeon RX 460/560D / Pro 450/455/460/555/555X/560/560X] (rev e5)

Linux T-2031 5.3.0-29-generic #31-Ubuntu SMP Fri Jan 17 17:27:26 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux



So I added a 3rd monitor: a NEC MultiSync EA241WM and that's when the fun began...

Picture yourself running a fully patched UM 19.10 and, all of a sudden, having the urge to plug in a 3rd monitor into your EYEFINITY capable ATI video card. But Linux refusing to cooperate.

First off, my 3rd monitor has been properly detected without a reboot, and it also fully messed up the resolution of my 2 portrait screens by "resetting" them to regular view format.

So I figured out I might as well reboot. After rebooting, both of my Dell screens that were NOT configured in portrait mode again and had their resolution resetted to "regular" horizontal display. Annoying to say the least.

Fearing things NOT, I headed into "Displays" and my first reflex was to reconfigure screen sizes and displays but, oh boy, was I wrong/naïve in terms of the outcome.

First off, even tho "Displays" did poped up, I was UNABLE to click on the rotation drop down menu so I could NOT reconfigure my newly added 3rd screen. So I had once again needed to reboot and there I was facing the exact same problem.

Afterwards I simply unplugged the DVI cable from my newly added 3rd screen from my video card. Doing so (and rebooting) actually brought back my 2 previously configured screens back into the same portrait mode that I had been using before first plugging in that 3rd screen . So, "victory", but not really because this 3rd screen of mine is still useless.

So, once again, oh so great Community, here I am posting this rather unique situation onto you and hoping that somebody else can corroberate on what I think is another great/unique/stubborn situation that is going on with "our" almighty video drivers/layout in Linux in 2020.

I am therefore encouraging (once more) everybody from this community who is having issues with dual/triple/quadruple video head/screens to bonnify this thread and help our community reach new heights of software maturity.

Rest assure that I will be back posting more updates as I get them.

Best regards,

Merely a suggestion to help diagnose. Have you tried narrowing things down a bit?

I would plug in the NEC by itself using first the DVI cable and then either or both the DP and HDMI cables. If that works fine and the monitor can be controlled, I would then try different combinations of the monitors and cables. That way you can eliminate the hardware as the problem source.

Been there, done that :wink:

That issue will be there - potentially - if you had simply rotated 1 of your screens!

If you look at the config file monitors.xml in ~/.config, you see there is an entry in there for EACH monitor combination that you use - or have used! So when you boot up, it compares the set of monitors it has currently found connected - including the orientations I believe - then uses that config entry to set which is Left/Right/Center, which is Primary, etc.

Seems like a great idea, and it would be except ... when it doesn't find an entry for that combo, it CREATES one! Now clearly that's necessary on the very first boot of a newly installed OS (else you'd never have a display to use ), but in all other cases it has the potential to make an entry that you don't want, because you were, say, just connecting to see if it worked ... And on top of that, when you close down the OS it saves the current settings regardless of how messed up they may be, if you have entered the Displays applet!

I use 2 Dell's (next size up to yours), with 1 each in portrait and landscape, plus the laptop's own monitor. [It's a re-purposed Gaming laptop, so has a nVidia card.]

What I had to do in the end was make a copy of ~/.config/monitors.xml and then work my way through identifying the ones I wanted and deleting the others/rest. Non-trivial, but can be done. [It may be better to save a copy and blow away the .config version and build a new one, if you have lots of 'bad' configurations to sift through as I had.]

Once you have a clean'ish file then you can make your final edits and SAVE A COPY. Oh, and remember to preserve it somewhere else when you do a clean OS install, 'cos you're going there again. :slight_smile:

FYI, the problem is upstream of MATE. I know because on 17.04 there was a further issue that the combined display size is incorrectly calculated if the portrait monitor is in any position other than the far right. This was corrected on a later release subsequent to my bug report (1723238). The fix had to be done upstream. I believed that it was fixed in 18.04 - not sure as my test systems only have 1 monitor. But it sounds like you are still experiencing the same problem as I was in 17.04. :frowning: Perhaps there is a further problem with >1 portrait monitor? You may have to: put all monitors in landscape, get a auto-generated monitors.xml, then manually edit to change them to portrait, along with the required arithmetic changes to reflect that a rotated HD monitor is 1024 x 1920 not the other way round.

I feel your pain, but have done it twice (that's how I know you need to save a copy elsewhere before a clean OS install! :slight_smile: ) and it's not too hard once you can see what is confusing it.

However, once done, NEVER, ever re-enter Displays unless you are sure the bug is fixed, as you'll have a high probability of a incorrect monitors.xml file.

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Guys, thanks a lot for your fast replies.

@layingback that fixed it! There were indeed 3 iterations of my monitor setup in there and all I did was removed all of the entries that made no sense alongside simply keep the ones into the right angle.

Then, I had to head back into "Displays" to configure the X/Y position and that works like a charm.


Now that I am using the following monitor configuration:


  <output name="DisplayPort-0">
  <output name="HDMI-A-0">
  <output name="DVI-D-0">

Can anybody help me understand why is it that when I open a screen on "HDMI-A-0" and that it prompts me with an extra pop-up (such as a login window), does this newly poped-up window displays in "DVI-D-0" which is set as neither primary NOR is it the screen onto which my window was first opened into?

Another logic that I do not seem to get (from a desktop perspective) is how come my primary monitor as the MATE menu and opened window task bar (which is defaults) but my icons are displayed on my "DVI-D-0" screen. From my desktop usage perspective that dates a couple of full moons ago, I thought desktop icons were a "primary desktop thing" if you get what I mean? :wink:

See you next time for some more "tri-screen hell" folks!

I can tell you what happens, but not why. OK? :wink:

Last first - icons on left screen: Xserver desktops in general work as 1 single desktop which spans as many physical monitors as you tell it to. So if you icons are set to display on the left (the default - I don't know if that is configurable in your setup) they will display on the leftmost monitor. Been that way since I don't know when.

From the above it's a reasonable assumption that the dialog mini windows open relative to the whole xserver desktop. So if it is programmed to open in the center, that'll be somewhere around your middle monitor, if it is programmed to open at x,y pixels then that will be from upper left on your leftmost monitor. Personally I use Compiz so that I can set Placement Mode: Pointer in the Place Windows plug-in, which means most new windows open in the same monitor as my current mouse pointer - most of the time. :wink:

And exception is initial MATE login: the password input field appears on the same monitor as the mouse, if and only if the monitor in question is NOT rotated. The issue must be with the rotation, because the login background image on a rotated monitor is not only NOT rotated, it is not even the image for that monitor.

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@layingback Thanks a bunch. As usual, you've made me a more intelligent person and I thank you for that <3.

So even though I wasn't actively "supporting this thread" lately I felt like I needed to report something else that I felt could be related to using several monitors but that I am yet too dumb to conclude on this.

(And/or maybe this also relates to one of my previous posts @ [19.10] Why doesn't my text cursor stays in CAJA? but am counting on you fine folks to tell me)

So you be the judge:

Earlier today (and every now and then) it happens to me that my resolutions gets TOTALLY fsck'ed up on TTY7. And what I mean by that is that some of my windows are cut or simply missing parts (like 1/2 or 3/4 of them) when 1. everything has been working fine for a couple of days and that 2. I powered off 1 monitor and repowered it on a very short time after.

But this problem doesn't happen all of the time. More like once every 20 tries.

So, I had Firefox opened on my left screen (and a bunch more of opened windows mind you) and powered off my left monitor thinking I would be stepping away for sometime. But immediately after I had to rejump in the Matrix so I powered my left screen back on and the half bottom of FF was displayed but the first half part of my screen was only showing my background (And my icons were now displayed on my right monitor which is NOT set as my primary monitor).

I also need to mention that the MATE menu had just dissapeared from the top of my screen alongside the status bar at the bottom (with my currently opened windows). Per my previous community experience, I switched to TTY1 and killed marco thinking that was it.

But I was wrong.

Back in TTY7: I couldn't select anything, nor make sense of anything that was going(ALT+TAB=failed, ALT+F4=failed) on as it seemed that half of my "forefront" pixels were flushed into The Twightlight Zone.

Since this wasn't the first time that I experienced this(possibly been having this for 2-3 years but w/out consistency), I just logged off and relogged back in and, of course, that "fixed" it.

So, here I am yet again asking you, oh dear Community, if anyone ever had this issue (or something similar) going and if so you can help narrow it down so we can squash this once and for all?


I may have increased your knowledge ... :slight_smile:

That'll do it. All bets have to be off when you - effectively - resize the desktop - twice.

The details of what happened I cannot comment on, as I exclusively use Compiz. Different things happen with Compiz in same situation: all windows move to the remaining part of the desktop (although not every modal panel), and stays there even after the other monitor comes back on. But what else could it do really, in the generalised case?

Unless your monitors are from The Arc they should have a very efficient standby mode - so set the screensaver to Off and let the monitors power down into standby state instead.

You are awesome :slight_smile:

That being said, my last reply attempted to only talk about windows on TTY7 that were (literely) cut in half or with spots/portions missing in them after having powered off 1 monitor and repowered it on.

Is that also happening in Compiz? I understand about those windows and icons moving around but what about them being cut? Did you also experienced that?

No, but my point was (intended to be) that some things will go wrong in unexpected ways in that scenario - most of desktop becoming unavailable) pretty much regardless of DE.

Compiz is usable but unpleasant after cycling 1 or more monitors, so I avoid doing it. If I do do it, I simply close (or minimise) all open windows and re-open.

Hello again!

Given that I was silent all that time was because I had nothing of major interest to report back in this thread however today I believe that I have found a very interesting video behaviour that, hopefully, will help our tri-screens Crusade!

First off, I would like you to consider that my desk is big enough to hold 3x wide-screen screens, 2x of those being in portrait mode while the other being used to watch videos. When facing my monitors, I have the video one on the left and the other 2x in front and to my right.

When all of them are enabled and physically plugged in, here is what "Displays" tells me:

Not sure why now but I am totally incapable for dragging that monitor from the bottom to it's physical position: being to the left-most right.

Also, as there is no physical gap in between those 2x Dells in portrait mode, yet I am incapable of narrowing them down to being side by side. Displays will not allow that.

So my first course of action was to simply disable that video monitor since I do not always watch videos. Here's how "Displays" interpretates that:

Again, I cannot move those 2x screens closer, it will not work. As for that disable screen, who knows why it moved to the up-right corner but, for now, it is the least of my care.

At this point I am pretty sure this as something to do with the physical ports being handled by "the software". As you can tell from my 2x pictures: all 3 screens are each using a different video port/input, being HDMI, DisplayPort and DVI.

So I remember that, even though I had issues when ONLY using 2 screens in portrait mode, that it wasn't that bad. So what comes next? Let's simply unplug the DVI cable from the disabled screen. And that results with the following:

I am not certain which other technical information I should be supplying out in this thread because I think that I have already provided everything if we take the time to analyze all my posts since day 1 but if I should, please ask.

Lastly, the only thing that I will add is that I keep religiously patching my systems and while having this experience/posting this I was running latest versions of everything in 19.10.


That problem, not being able to move a rotated monitor adjacent to any monitor TO ITS RIGHT, is a manfiestation of the original problem, that the s/w is calculating the width of a rotated monitor based on its LANDSCAPE width not its PORTRAIT width. That is supposed to have been fixed long ago. I've tested with 2 monitors on the 20.04 Beta and it seemed fine. I will have to test on 20.04 sometime fairly soon, but as I only have 1 monitor that will even kinda interface with my test laptop, that (3 of) will have to wait until my main system gets upgraded to 20.04 with it's 3 monitors (incl. the laptop's).

In meantime, the original solution is probably your only choice. Eradicate the "bad" configuration in monitor.xml and you can then make a good one, but until then it'll keep using the bad one!

Before the fix it was impossibble to position any rotated monitor to the left via the Displays applet, corruption was guarenteed. Seems it's still possible either by accident - or by adding a 3rd monitor. My hunch is that 2 vertical monitors is still iffy (I have only 1 vertical).

[ Sorry for spelling/typos but for some reason this site never shows my cursor position! ]