[SOLVED-ish] KDE detecting monitor changes: start/stop/pause

[netjiro]

Hi. I run a 3 monitor setup from an intel nuc NUC6i7KYK. KDE plasma ca v5.8 detects and handles all monitors nicely.
How to make kde stop/pause detecting changes in the monitor setup? E.g. if I temporarily turn off one or more of the monitors I don't want it to rearrange my desktop. I don't mind that all windows on the "off" monitors will be unavailable while it's off. How to turn the automatic detection back on or unpause?

monitor 1: 1600x1200 via hdmi > dvi converter cable
monitor 2: 2160x3840 via mdp (portrait)
monitor 3: 1024x768 via thunderbolt 3 usb-c > dvi converter plug

The thunderbolt 3 > dvi converter plug actually already fools the detection system to report the 1024x768 projector as always "on". But if I turn off either of the other two monitors the change will be detected and KDE will try to rearrange the desktop leading to all kinds of things I don't like. I usually keep most windows strictly to one monitor or the other and it would be good to be able to simply turn off the monitor I don't need for a while (often hours or days depending on work tasks).

[Roman_Gruber]

My opinion:

You should set up a xorg.conf with a static setup of the screens.

with these contents:

left of main, resolution @ VFREQ
main screen, resolution @ VFREQ
right of main, resolution @ VFREQ

--

Not sure how KDE influences the behaviour of X.

[netjiro]

Thanks for the tip, seems like a straight forward solution :)

Will that stop kscreen / kded / xrandr or whatnot other stuff from fiddling with the settings though?

[Roman_Gruber]

For i3wm with nvidia-drivers, I can keep the external screen active when I have set them up temporarily with nvidia-settings, regardless of the power turned on or off for my external screens.

Its just plain xorg syntax. nvidia binary driver manual has a decent intro how to set it up

I doubt xrandr will cause fuss.

[netjiro]

An alternative solution, very quick and simple, though not as robust:

Turn off the KDE background service "KScreen 2", seems to not trigger the serious problems.
But it has some bugs where it will for example crash the task bar: https://bbs.archlinux.org/viewtopic.php?id=210439

[netjiro]

I've been fiddling with this on and off. The setup that works best for me under current circumstances are what Roman suggested:
a very simple xorg.conf.d setup with basic monitor, device, serverlayout sections.
BUT: the "KScreen 2" service must be turned off, otherwise it will come back to fiddle around with the settings with a somewhat random behaviour.

A few things still get screwed up when the monitor marked as "primary" is manually switched off, but it's easy enough to fix and doesn't usually create any serious crashes.