How to activate bracketed paste mode in GNOME Terminal for Vim inside tmux

Question

Edit this issue happens inside a tmux session. The original value of $TERM before starting vim is:

echo $TERM
screen

The issue appears for example when pasting this kind of indented code:

def function(condition):
    if condition:
        print("Hi")
    if not condition:
        print("Bye")

When I press Ctrl+Shift+V in vim's insert mode, auto indentation messes-up the output and this is what appears:

I have to set vim to paste mode :set paste to have the pasted text indented correctly:

I then have to remember to deactivate it with :set nopaste.

This SO answer says that vim can enter and exit automatically from paste mode with bracketed paste mode. It is even supposed to be by default in Vim 8. I have vim 8, how to enable bracketed paste mode for gnome terminal?

Answer 1

It is even supposed to be by default in Vim 8.

Only if Vim thinks the terminal is xterm-compatible, which is the case if TERM is xterm or some derivative. If TERM is gnome, Vim won't enable the bracketed paste mode automatically; you have to configure it.

I have vim 8, how to enable bracketed paste mode for gnome terminal?

Try this:

if &t_BE == ''
    let &t_BE = "\e[?2004h"
    let &t_BD = "\e[?2004l"
    let &t_PS = "\e[200~"
    let &t_PE = "\e[201~"
endif

t_BE, t_BD, t_PS and t_PE are all terminal options. The first two are sent automatically to the terminal whenever it enters/leaves raw mode; they must be set correctly so that they enable/disable the bracketed paste mode.

The sequences \e?2004h and \e?2004l are documented in xterm's documentation. Look for CSI ? Pm h (or CSI ? Pm l), then for Ps = 2 0 0 4.

Ps = 2 0 0 4 ⇒ Set bracketed paste mode, xterm.
...
Ps = 2 0 0 4 ⇒ Reset bracketed paste mode, xterm.

t_PS and t_PE tell Vim which sequences the terminal will use to surround the pasted text. The values are documented here.

---

To test the code, start Vim like this:

vim +'let @+ = "clipboard\e:echom \"malicious code injected\"\ri"' +startinsert

Then press C-S-v to insert the contents of the clipboard in the Vim buffer. If the only text which is inserted is clipboard and :mess has logged malicious code injected, then it doesn't work.

---

Note that the bracketed paste mode can be bypassed if the pasted text contains \e[201~; the latter sequence may end the bracketed mode prematurely. See the second example on this page. It doesn't work on all terminals though; see this answer for more info.

Also, the bracketed paste mode does not prevent Vim from auto-indenting the text when inserting the contents of a register with C-r.

$ vim -Nu NONE +'set ai' +':let @a = "Level 1\n    Level 2\n    Level 2\nLevel 1"'
" press:  i C-r a

If 'paste' is reset, you'll get:

Level 1
    Level 2
        Level 2
        Level 1

If 'paste' is set, you'll get:

Level 1
    Level 2
    Level 2
Level 1

You can avoid this issue by pasting from normal mode ("ap), or inserting with C-r C-o or C-r C-p.

FWIW, for this reason, I use these mappings:

ino <expr> <c-r> getregtype(v:register) =~# '<c-v>' ? '<c-r>' : '<c-r><c-o>'
ino <c-r><c-p> <c-r><c-p>
ino <c-r><c-o> <c-r><c-o>
ino <c-r><c-r> <c-r><c-r>

---

If you use tmux, be aware that the latter supports the bracketed paste mode since version 1.7, but it doesn't use it by default. In the key bindings table, ] is bound to the paste-buffer command:

bind-key    -T prefix       ]                     paste-buffer

If you want paste bracket control codes to be inserted around the buffer, you need to pass the -p flag to paste-buffer. FWIW, I use it in these 3 key bindings:

bind C-p paste-buffer -p
bind p choose-buffer -Z -F "#{buffer_sample}" "paste-buffer -p -b '%%'"
bind -T copy-mode-vi p send -X copy-selection-and-cancel \; paste-buffer -p \; delete-buffer

Update: This was changed in 3f6af41.

---

For more info, see :h xterm-bracketed-paste.

Answer 2

This was because I was calling vim inside a tmux session and the $TERM environment variable is equal to "screen" in tmux.

Recommended way

As explained in :h xterm-bracketed-paste and in the other answer above, you can add this to your ~/.vimrc:

" Activate bracketed paste in tmux
if &term =~ "screen"
  let &t_BE = "\e[?2004h"
  let &t_BD = "\e[?2004l"
  exec "set t_PS=\e[200~"
  exec "set t_PE=\e[201~"
endif

After that vim bracketed paste mode becomes enabled also when vim is inside tmux.

Not recommended way

According to this answer and the tmux FAQ.

Provided the underlying terminal supports 256 colours, it is usually sufficient to add one of the following to ~/.tmux.conf:

  set -g default-terminal "screen-256color" 

By default, vim doesn't recognize "screen-256color" as a terminal compatible with bracketed paste, so I changed the setting to

set -g default-terminal "xterm-256color"

After that vim recognized the terminal as compatible with bracketed paste mode.