When I run Vim from inside a tmux session and copy some text to the clipboard, each line gets padded with spaces to the right.

For example, say I have a text file like this:

^some$
^text$

Note: I've used ^ and $ to mark the beginning and end of a line respectively. They are not part of the file content.

I start tmux and open this file in Vim. I press Shift (to prevent Vim from processing the mouse click) and mark the complete text by holding the left mouse button clicked. Then I copy it to the clipboard with Shift+Ctrl+c.

The result in the clipboard is something like:

^some                                                  $
^text                                                  $

Note the extra spaces. (The number of spaces depends on the width of the terminal window.)

If I start Vim without tmux or if I just cat the file content and then copy it, there are no extra spaces. So it must have to do with the combination of Vim + tmux. I've seen this on different Linux flavours, i.e. on Ubuntu and Mint. I use the default terminal (Gnome Terminal 3.6.2) there.

So how can I prevent this?

My tmux.conf

set-option -g prefix C-a
set-option -g mouse-utf8 off
set-option -g status-keys vi
set-window-option -g mode-keys vi
set-window-option -g mode-mouse on
set-option -g terminal-overrides 'xterm*:smcup@:rmcup@'

bind-key C-a last-window
bind-key C-h select-pane -L
bind-key C-l select-pane -R

# colors:
set-option -g status-bg black
set-option -g status-fg white
set-option -g status-left '#[fg=green]#H'
set-window-option -g window-status-current-bg red

I've also tried without the above .tmux.conf, using tmux' default settings - no difference.

Here's my /etc/vim/vimrc.local that I use on Mint (Ubuntu derivative):
https://gist.github.com/mikehaertl/1612035