That’s true from a technical perspective. But in reality devs (especially ones who aren’t making “Linux apps” but are doing things like porting a previously Windows-only game to Linux) will occasionally ship a broken Wayland client. The compositor could then still give that a basic titlebar with window buttons like KDE and Cosmic do, or alternatively it can refuse to do it and make the novice user annoyed at the system as a whole.

I’m not really convinced that requiring all Wayland clients to draw their own decorations was the correct decision in the first place, but even if we accept it, I think there’s still a convincing case for fallback SSDs.

Now if there was just an official API from all window managers that can check this configuration

This actually does exist. Reasonable Wayland Compositors will negotiate with their clients on whether they should use CSDs or SSDs. To an extent Qt does this: It prefers SSDs but it can draw CSDs if the compositor can’t draw SSDs (or signals that it doesn’t want to), which is why proper Qt apps are perfectly usable on GNOME Wayland despite missing SSDs.

It would be possible to go even further and make apps that display menu and tool bars on compositors that prefer SSDs (like Plasma/KWin) and nice GTK-style decorations on others. It just happens that most apps either really want to draw their CSDs (mostly because they’re made for GNOME, a.k.a. anything using Libadwaita) or they don’t really have a use for them (like regular Qt apps).

The biggest drawback of not providing any SSDs even as a fallback is obviously… what if the app just doesn’t draw CSDs? ~~There are many new Linux users who try to get something like DaVinci Resolve running and then can’t maximize it because it doesn’t have CSDs. For these users it just makes using Linux feel broken for basically no reason.~~¹

This is also a burden for application developers. Maybe the DaVinci Resolve devs should just fix their app (from what I heard it’s a massive PITA in all aspects imaginable), but is it really reasonable to also expect e.g game devs to add dependencies on libdecor or whatever solely to unbreak window mode on GNOME Wayland?

¹ Edit: I have since learned that Resolve actually does draw CSDs, it just doesn’t draw the window buttons. That’s certainly a choice… I think the overall point isn’t too affected but this specific app isn’t a good example since it would still be broken if GNOME had fallback SSDs.

That’s a largely unrelated topic… You can have theming without SSDs (as seen in most standalone compositors and also kind of Cosmic) and you can have SSDs without theming (at least in theory, I’m not aware of a project actually taking this stance).

There’s apparently a ZSH plugin for this with a quite a few stars, though I haven’t used it and can’t speak for how well it works. In other shells what you want just doesn’t exist to my knowledge, though it should be possible to script it with enough effort.

The problem is that in the terminal you always have at least two layers of input handling in the terminal emulator and the shell. And these layers talk to each other by emulating a 70s VT100. This leads to some issues, in no particular order:

• Terminal emulator keybindings will step on shell keybindings, and the shell will never know about it because it can’t actually see the keys being pressed.
• Even if the terminal doesn’t care about a key, it might be impossible or error-prone to detect anyway. This applies to surprisingly regular keys like Tab.
• As you’ve noticed some terminals try to get clever and do things like making Ctrl-C copy if you’ve selected text. The shell doesn’t know about this either.
• Most shells and TUI apps have selection modes. These are independent from terminal selections.
• There’s no standard way of using the clipboard in Linux, but multiple different ones that may or may not work.

All of these problems gets worse if you add multiplexers like tmux by the way.

Now it would be possible to write a bespoke terminal emulator and shell combination that unifies selection and makes all the reasonable keybindings actually work. There are attempts at this, such as the Emacs Eshell. Unfortunately Emacs people don’t quite share your idea of what reasonable keybindings look like (and it’s also a little bit broken, though for mostly unrelated reason).

Ultimately though the main reason this is an unsolved problem is that most Linux users just get used to the regular Readline line editor that all commonly used shells ship with. Complex edits can always be done in your $EDITOR (via C-X C-E in Bash).

I’m not a btrfs expert but AFAIK high unreachable space usage is usually a result of fragmentation. You might want to defragment the filesystem and see if that helps.

I will note that btrfs makes estimations of used/available space very difficult by design, and you especially can not trust what standard UNIX tools like df and du tell you about btrfs volumes. Scripting around du or using ncdu will not help here in any way. You might want to read this kernel.org wiki article as well as the man pages for the btrfs tools (btrfs(8) and particularly btrfs-filesystem(8)), which among other things provide versions of df and du that actually work, or at least they do most of the time instead of never.