can tmux watch a particular pane for keys pressed? (to then issue `send-keys`)

Question

I want to have a pane with asciinema "video" (literally it's animated plain text) playing while in another pane the user can be doing miscellaneous stuff (typing commands, writing scripts, or whatever). The user can switch to the asciinema pane and hit < space > key to pause/play the video. I'd like to watch that pane and when the user pauses/plays the recording to then run tmux send-keys to pause/play an mp3 file that's playing in cmus in another window.

I haven't been able to find anything like tmux watch-pane or tmux listen. Does something like that exist? For this use case it'd need to distinguish between spaces being entered via asciinema and actual button presses by the user.

I'm using tmux 2.1, and don't see anything about watch or listen in the man page. But maybe in a newer version there are commands provided?

Answer 1

There are a few ways you could try to do this, of varying complexity:

• You could bind the Space key in the root table to do what you want if pressed in the pane you want, perhaps something like:

  bind -n Space if -F '#{m:*asciinema*:#{pane_current_command}}' 'send -t:mycmuswindow Space; send Space' 'send Space'
  

  Or pane_title or whatever if pane_current_command won't work.

• You could turn on monitor-silence in the asciinema pane and use the alert-silence hook to similarly send a Space to the cmus pane.

• You could write a script that uses control mode to listen to data from the asciinema pane and send the Space, this is assuming it prints something you can recognise (like "paused") into the pane you can look for.