lxqt not recognizing hotplugged monitors

[RoydZeller]

It appears that lxqt does not automatically recognize hotplugged monitors.

One way to reproduce:

1. Unplug all monitors
2. Plug them back in
3. Black screen until lxqt session is restarted

Virtual terminal automatically recognizes and starts displaying image just fine on any new monitors plugged in.
Couldn't find a way to tell lxqt to scan for monitors again from the virtual terminal either.
There is a chance that this is also happening due to a multi-GPU setup.

[tsujan]

Not reproducible.

Also, the given info is insufficient. Which version? Under X11 or Wayland? etc.

[stefonarch]

Just tested here too, under Wayland/niri, no issue.

[RoydZeller]

X11

• Archlinux 6.17.9
• qt6 6.10.
• liblxqt 2.3.0-1
• pcmanfm-qt 2.3.0

[isf63]

I can verify that under X11 hotplugging monitors is iffy. It seems that the X.org stack has some glitches/bugs, or perhaps some lxqt-config-monitor X11 codes do.
I have a problem with my setup (monitor) where idle isn't triggered by lxqt-config-powermanagement. The X11 codes are really difficult to parse, and squashing bugs in them is quite the feat.

[Chiitoo]

For amdgpu with X11 things, some oddities may or may not be explained by udev things, to some extent at least:

• lxqt-config-monitor: potential issues with xf86-video-amdgpu-25.0.0 lxqt#2759

As I keep udev and other automagic minimal, I generally use xrandr to re-detect things if need be, so if I, for example, un-plug one of my three monitors right now, it will still remain there as if it was there (which I like), instead of going missing like DisplayPort likes to do just when powered off...

If I execute xrandr, the connected displays will be updated and... just doing that now, I did experience something I haven't seen before. I did kind of expected lxqt-config-monitor to step in, and set the defaults which I think used to happen even with my current set-up, but instead, it was as if the desktop moved to the left from where the monitor went missing, and when I re-connected the display, I could already see my main desktop things were there, however, moving my mouse over the things did nothing... however, if I moved it over where they would be in the middle monitor, they would do things in the left monitor (things went back to normal after running xrandr again with the thing connected).

Pretty wild. :]

Anyway, was just going to mention the amdgpu thing though probably not related here specifically. Will investigate what I just saw at some other point in time.

[isf63]

The fact that DisplayPort is iffy with X11 is indicative of a deeper major problem. I use DisplayPort and that may be why I cannot idle my monitor. In essence this is a Linux problem and not LXQt's, but the fact that X.org is so hard to program in makes it hard to tell.

[Chiitoo]

If I remember right, I have heard-read DisplayPort having similar issues with Windows, too, so not entirely a Linux problem even (like the issue with behaving as if un-plugged when powered off, but I suppose it is really a feature rather than a problem in the end...).

I haven't had any other issues with it, but I don't want anything to do anything special after some idle time either, so I can't say anything about such things.