Darktile – GPU rendered terminal emulator designed for tiling window managers

What could they do instead? There's so many trivial solutions. A clipboard named pipe for instance, or at least something that operates like one. Read is paste, write is copy. That's a very 1970 style fix that could have been done 35 years ago. Then anything that can read and write from a file can interface the clipboard, opening up a whole new array of applications without setting aside "highlighting text" as having some special magical power.

Also having multiple clipboards is trivial, just have more of these special files. You can even set one aside if say some crazy old Xt application someone is still running only works with copy-on-select for some reason

A clipboard history is super trivial as well, just set up a pipe...

There's so many more unixy ways this could have been done. It's so dumb how it works. Heck dbus would be a less insane fix

Keep in mind that the terminal app is what reads keyboard events and passes them on to what it runs, and the terminal app reads the output back from the attached application (or tmux session) to render them to the screen. It has full control to monitor what you do, and to inject additional commands (and hide the responses) to whatever you connect it to.

Anything you can do in the terminal, the terminal can also do without your permission unless you do far more complicated filtering.

EDIT: I think what might not be clear here is how a terminal operates. It'll differ by operating system and winding system, but on Linux what you have is this:

    X server ----[keyboard events]----------> terminal ------[pty w/keyboard events]----> [app/shell/tmux session]
                  <---[rendering instructions]----/               <----[pty w/output]------------------/

You could conceivably still lock this down, but it would involve writing something that either replicates the keyboard event pipeline of the terminal to verify that what is sent over the pty matches the inbound keyboard events, or applying heuristics to what is sent to block things that seems odd, so it's potentially possible to do "something" useful here. E.g. something that blocks and pops up a warning if the pty "keyboard events" suddently contains the string "curl" when that string hasn't been seen in the keyboard events from the X server for example could be useful, but bubblewrap certainly can't do anything like that.

It'd be quite interesting to write a tool that wraps an app and allows you to script monitoring and/or munging of what goes over its sockets, though...