I've never thought of xxd as being anything but a "Vim thing".
That it had its own history (1990-1998) before being pulled into Vim is a TIL for me.
Here you go:
https://github.com/vim/vim/tree/master/src/xxd
There might still be other versions of this out there, but I suspect most OS distros pick up xxd by way of packaging Vim.
So if you work on some other xxd, you're probably in a dead fork.
The man page is also from Vim:
https://github.com/vim/vim/blob/master/runtime/doc/xxd.1
My first patch to xxd, if I were to work on it, would be to fix the man page to indicate clearly that it's the xxd bundled with Vim.
This also solves the problem of moving the cursor and drawing a screen in general.
If anything, I've found doing this works better then trying to muck around with ncurses, which often gets actively mislead by incorrect terminfo entries.
I get the idea behind your question, but it irks me a bit since it implies a sort of responsibility to contribute to an existing piece of software. This is a net positive of course, but the beauty of open source is the freedom to work on the things you want to work on.
