Add support to hotplug_mode_update

[trixpan]

Expected Behavior

Screen resize should occur automatically

Current Behavior

Screen resize does not occur. User must change resolutions manually.

Possible Solution

N/A

Steps to Reproduce (for bugs)

1. Deploy KVM VM using QXL / Spice
2. Connect to VM using a Spice Client like remote-viewer
3. Resize screen

Context

A few CPU cycles back, Spice/QXL decided to change the way they resize screens and seem to have forgotten to coordinate this with desktop manager developers.

As consequence a number of developers have been playing catch with the change

e.g.
https://phabricator.kde.org/D15789
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=935896

• Distribution & Version: Lubuntu 19.*
• Kernel: Linux 5.3.x Linux 5.0.x
• Qt Version: 0.14.x
• liblxqt Version:
• Package version:

[agaida]

Why is this a LXQt problem - and for which WM we should support hotplugging? - I guess it's a WM thing?

[trixpan]

@agaida good question.

As you can see in the above issue, KDE addressed this via Plasma, which as far as I understand their architecture seems to be a Desktop environment (I may be wrong.)

I also note #239 seems to address similar issues of display management.

To your point, the gnome fix happened in mutter, which, again, as far as I understand is their WM.
https://gitlab.gnome.org/GNOME/mutter/commit/957513242c26be458be7a101b83180e3f59f6a44

I suspect this may being fixed differently according to architectural discrepancies between each of the environments?

[agaida]

My point is: We have no fixed ŴM - a few users use kwin, others xfwm4, others openbox :D

[tsujan]

We get the screen info by using QScreen, not KScreen, I don't think we can do anything about this until QScreen supports it.

#239 is a totally different topic; it's about showing Monitor Settings automatically.

[1ras]

I'm running Debian Bookworm and lxqt-config-monitor seems to use KScreen now. However, this issue is still valid since lxqt-config-monitor switches to a wrong resolution. It looks like lxqt-config-monitor switches to a saved resolution, even if the user never saved one.

However, when deleting /usr/bin/lxqt-config-monitor and replacing it with

#!/bin/sh
xrandr -s 0

then everything works as expected. The resolution is changed as intended when the Spice window is resized. "xrandr -s 0" is explained here: https://github.com/seife/spice-autorandr (no, spice-autorandr is not a possible workaround since lxqt-config-monitor is immediately reverting the change).

It seems that the events are in the meantime received, but handled incorrectly.