dualscreen / multihead / multi screen

[OlMint]

KDE and other QT based desktops cannot handle multihead (several monitors) correctly. It's been at leat 10 years that the same problem makes QT unusable with several monitors : it is still unable (Mint 20) to consistently display 1 desktop over 2 screens. At least not very long.

In linux Mint 20, on a brand new mini PC with 2 screens attached, I spent an hour configuring task bars and widgets on both screens. I lost my time. After the monitors are supposed to blank (standby), they turn back on after a second, and then the 2nd screen displays another, empty desktop, while the 1st one still displays the left part of the normal desktop.

If the screensaver wants to shut off the screens another time, then the same thing happens again, except that the 2nd monitor now displays the right part of the normal desktop again. Each time the screens are supposed to turn off, they are reactivated and the 2nd screen swaps back and forth between the normal desktop and an unknown one. Really weird !

Anyone has an idea ?

[Moonstone Man]

Anyone has an idea ?

KDE has absolutely no issues multiple monitors.

In linux Mint 20...

In Linux Mint 20, there is no KDE desktop. If you have installed KDE on top of LM20 then it's up to you to sort out any issues with your Frankenstein desktop. If you must have KDE, the better course of action is use a distro designed and released with KDE.

[OlMint]

KDE has absolutely no issues multiple monitors

Oh, so I should not trust my eyes any more. But what if I still encounter problems with multiple monitors in QT based desktops ?

In Linux Mint 20, there is no KDE desktop

Sure, but there indeed is a QT desktop, which you can install from the package managers, including mintinstall. It's called Lxqt. And I have the same problems in 2021 with the Plasma (QT based) desktop than I had years ago with previous QT based desktops.

Anyone would have a helpful idea ? It's important to me because another problem I'm facing with desktops, is that GTK based ones (incuding Cinnamon) are unable to let my computers present a decent and fluid video playback (in whichever application, including VLC, and Firefox), where QT based ones have no problem with it, Of course, the difference is smaller on my new mini PC, but there still is one. Probably a matter of V sync or other internals.

[Hoser Rob]

You have no clues whatsopever, it certainly has nothing to do with GTK v. Qt. I use dual monitors in KDE every day and have for years. You've borked your system somehow and stupidly argued with one of the very few actually genuinely knowledgeable users here. Some people should not run Linux.

[Moonstone Man]

Oh, so I should not trust my eyes any more.

See your doctor about Charles Bonnet syndrome.

But what if I still encounter problems with multiple monitors in QT based desktops ?

Take it up with the distribution you're using that provides a Qt desktop. Linux Mint isn't it.

Sure, but there indeed is a QT desktop, which you can install from the package managers, including mintinstall. It's called Lxqt.

Diesel fuel is sold at the service station but that doesn't mean I can put diesel fuel in my petrol tank, which, when all said and done, is exactly what you have done, and now you're arguing at someone else over your mistakes because you don't want to admit that it was you who blew up your engine.

And I have the same problems in 2021 with the Plasma (QT based) desktop than I had years ago with previous QT based desktops.

More than likely you've been making the same mistakes over and over all those years and not learned from a single one of them. Maybe it's time to listen to the best advice you've got and will ever get on this issue: "If you must have KDE, the better course of action is use a distro designed and released with KDE."

Anyone would have a helpful idea ?

<CRICKETS>

It's important to me because another problem I'm facing with desktops

That you've installed the KDE/Plasma desktop on top of Linux Mint and completely borked it in the bargain is not important to most people here, not even a tyre-kicker has said anything. It's your problem entirely, and you get to clean up all your own mess.

QED

[OlMint]

apart from those frustrated people who refuse to read or understand the question, are there some helpful people who encountered the same problem as me and would have some advice other than "you are wrong and stupid" ? I'm looking for help here.

Reminder : Lxqt is a QT based desktop and available on Linux Mint. And I can believe I did something wrong (maybe installing GTK ?) if you tell me what, since the problem occurs before I do anything else than starting Youtube after a fresh install.

EDIT : reminder : 2 problems :

• GTK is almost fine, but cannot display perfectly fluid video playback on my fresh installs, even though less than 10% of CPU is used

• QT is almost fine, but always has problems (for me) with complex user defined multihead desktop setups, especially keeping a coherent user experience

• both can be installed by any user with normal operation of the system

• both can be customized by any user

• some do present a Vsync option, without effect on my GTK problem

Solutions and constructive comments are welcome. Telling me I'm wrong to believe my problem is a problem is useless. I have a question, if you don't know the answer, you're still a good person, don't tell me I'm stupid, just let other persons give a try.

[SMG]

Reminder : Lxqt is a QT based desktop and available on Linux Mint.

Linux Mint 19 and 20, which are the currently supported versions, are only available in three desktops, Cinnamon, MATE, and Xfce. There is no LXQT available for Mint.

apart from those frustrated people who refuse to read or understand the question, are there some helpful people who encountered the same problem as me and would have some advice other than "you are wrong and stupid" ? I'm looking for help here.

You are using an unsupported desktop, so the likelihood that someone else encountered the same problem you have is very slim because the number of people who may have installed an unsupported desktop on their Linux Mint is quite small.

If you really wanted help, you would supply the information Section 5 of READ: How To Get Help! indicates should be provided so others could help you.

[OlMint]

How can I mark this topic as SOLVED ?

OK, OK, not part of the installation wizard... Lxqt is indeed part of Linux Mint, so is Plasma. Just search them in the package managers. Well, on my current 20.2 installation, Plasma does work well [on a different computer] and has no problem any more, and still has an obvious advantage over GTK desktops, in how it handles video and other heavy graphics tasks.

Sorry to contradict some people. I love and respect all of you.

Honestly, my preferred interface is Cinnamon. But honestly, GTK based interfaces still don't fit in 21St century's low-end computers, because they are still unable to properly sync with the monitor's refresh rate. This is why I want to use QT based interfaces, which have no problem with Vsync.

Anyways ... problem seems to depend on the hardware (graphics card). NVIDIA now behaves correctly, where Intel's integrated graphics card does not, and even refuses to shut off the screens (wakes them up after 2 seconds). This is a known bug, If anybody wants a link, I'll try to find it again.

[SMG]

How can I mark this topic as SOLVED ?

Please go to your first post in this topic, click the pencil icon, add [SOLVED] to the title, and then click the Submit button.

OK, OK, not part of the installation wizard... Lxqt is indeed part of Linux Mint, so is Plasma. Just search them in the package managers.

No, they are not part of Mint. Just because they are in Package Manager does not mean they are part of Mint.

[RollyShed]

Honestly, my preferred interface is Cinnamon. But honestly, GTK based interfaces still don't fit in 21St century's low-end computers, because they are still unable to properly sync with the monitor's refresh rate.

Having been using two monitors for about 3 decades and Mint for at least a decade I've just been having problems with my second monitor on Mint 20.2. It blinks off every now and again and sometimes restarts at a lower resolution and won't admit it should / could be set to a higher one.

Off with the back of the monitor (remove screws, use crowbar) and there in its power supply, immediately obvious, 3 dud capacitors. I think I've fixed it, it is working correctly this morning but there might be more capacitors faulty but not obvious.

So?

Question, do you know if your monitors are OK or going faulty?. And I've never had problems with older hardware AND you don't state what older hardware, low-end hardware is supposedly unable to work.