wlroots VS wl-gammactl

>barrier has been unmaintained for a long time.

As if not having new features added for 2 years makes it stop working? barrier is perfectly fine on normal linux desktop installs. I actually use synergy 1.x personally which has been "unmaintained" for much, much longer. Except synergy 1.x will compile and run on anything from windows 98 to ubuntu 5 to debian 12. You can't get a waynergy or inputleap to compile on an OS more than 2 years old. And even then, as you say, it's crapshoot if the particular wayland will have libei; many like sway are actively hostile to it and never will: https://github.com/swaywm/wlroots/issues/2378

It looks like they actually patched it to filter those modes out, so presumably it worked out of the box and was considered undesirable: https://github.com/swaywm/wlroots/issues/3038

I haven't experienced any of those. The video game performance hit may be due to vsync, but I don't play games so I haven't noticed.

You can however use tinywl. It is an example Wayland compositor that can't do more than displaying one application.

Sway/wlroots has implemented this, but I can't find any discussion for KDE.

wlroots is archived on github. Is it abandoned? Just saying, that only means they moved git hosts :-D

A lot of compositors are based no the wlroots lirbary. So they are still sharing the development effort and have a common base, its just in the form of a library rather than a display server.

gamescope use wlroots

I don't know what you mean by color management - is it the calibration of the display with xrite/argyll?

For ICC profiles colormgr can help: https://wiki.archlinux.org/title/ICC_profiles#Wayland

If you just need basic brightness, contrast and gamma, wl-gammactl should do that: https://github.com/mischw/wl-gammactl

BTW Hyprland is not required, it's just the most practical way to have shortcuts key mappings in Wayland

However, this does not work in Wayland since it obviously belongs to the X Window System. I started searching the web for a possible solution and found wl-gammactl, which is a GUI for wlroots (https://github.com/mischw/wl-gammactl) and the gnome-gamma-tool (https://github.com/zb3/gnome-gamma-tool), but neither of them seemed to work because of missing dependencies, which can't be installed or invalid version numbers of required packages (e.g. found 1.20 but need: '>=1.23'). When attempting to build the gnome-gamma-tool, the following error message appears (despite Colord being installed):

It's very much possible with Wayland. Whether Plasma supports it is another question, unfortunately. Great program though, you can control it with commands and set an invert screen colors keybind.

What would be the best way to implement this? I tried wl-gammactl https://github.com/mischw/wl-gammactl with those settings but the screen just goes fully white?

Probably it just support sway as said here on github

Wayland is the protocol applications use to talk to compositors. What you need to control (this kind of-, since I assume you want a software overlay) brightness depends on the compositor/desktop environment you use. For wlroots based compositors (wayfire, sway) wl-gammactl or wlr-brightness could be useful. For Gnome (below version 40) the soft-brightness extension looks like what you need.