I use Vim and Bash side-by-side in Tmux. I have Vim configured to autosave files as I switch between them, but I'd really like it to autosave when I switch to the Bash pane.
Is there a way to get Tmux to send some kind of code to Vim when its pane loses focus?
This is probably best done using vim's client-server model. There's some good guidance about using it in :help remote.txt.
Firstly, you'll need a vim client compiled with the +clientserver option. If your distribution doesn't package it this way, get the source (through apt-get source, abs, et al) and add that option.
Once that's done, you'll need to rebind your keys in tmux so that when you change windows it also sends something like the following to the active window:
vim --servername foo --remote-send '<C-\><C-N>:w<CR>'
Something like the following should work (not tested):
bind-key 0 run-shell "vim --servername foo --remote-send '<C-\><C-N>:w<CR>'" \; select-window -t :0
select-pane, last-pane, swap-pane, or even click a pane. There are just as many ways to switch to a different window. I can't rebind every possible way to activate a different pane. I'm looking, then, for a way to get commands to run every time I activate a pane. Perhaps that's not possible in tmux.
Someone else has already done this work for you in a vim plugin - https://github.com/sjl/vitality.vim
From the README:
(Vit)ality is a plugin that makes (V)im play nicely with (i)Term 2 and (t)mux.
If you're using vim and tmux together you might also be interested in the vimux plugin.
By default when you call RunVimTmuxCommand vimux will create a 20% tall horizontal pane under your current tmux pane and execute a command in it without losing focus of vim. Once that pane exists whenever you call RunVimTmuxCommand again the command will be executed in that pane.
Think re-running tests frequently.
FocusLost/Gained events, but it doesn't notice if you change tmux windows.