Annoying Alt as Meta setting

Annoying alt key and meta behave on different OS and applications.

GUI emacs on Windows:

alt works as meta key, didn’t do much test on msys2 or something.

ArchLinux tty:

alt can be recognised as meta key in some applications(like emacs), in some others it can’t.

application	work as meta
tmux	works as meta and also work with a number like ‘M-1’
emacs	works as meta, also work with number.
vim	alt won’t work as meta, alt-h won’t trigger M-h. you have to use execute "set <M-h>=\eh", then map nnoremap <M-h> <C-w>h
	besides, number related binding like execute "set <M-h>=\e1 won’t give you the M-1 binding, it’s just not work in vim.

MacOS

GUI emacs application: you use Command key as meta key, there is nothing to worry about.
iterm2: you can set the way terminal treat alt in preference, and the following is what it acts like.

set as	work as meta	behaviour
normal	no	alt-specificKey will input a specific char, which could be used to do keybinding( even work with number related keybinding:
		map ¡ <M-1> noremap <C-1> 1gt ) in vim. If you want to use number binding in vim this is the choice.
meta	no respon in terminal	/
esc (current)	yes	aligned with archlinux tty, works fine except number key binding in vim.