terminal-focus-reporting.el

Minor mode for terminal focus reporting.

This plugin restores focus-in-hook, focus-out-hook functionality. Now Emacs can, for example, save when the terminal loses a focus, even if it's inside the tmux.

You don't need this plugin for latest Emacs. Since Emacs 27 it now requests and recognizes focus-change notifications from TTYs. You would rather need to hook the after focus change:

(add-function :after after-focus-change-function (lambda () (save-some-buffers t)))

Usage

1. Install it from Melpa

2. Add code to the Emacs config file:

(unless (display-graphic-p)
  (terminal-focus-reporting-mode))

How it works

Emacs and terminal communicate by sending and receiving special string sequences.

For example, if the program (emacs) sends to the terminal the text <Esc>[?1004h, terminal enables "focus reporting" feature and sends special sequences to the program when focus lost or restored.

This can be tested directly in the terminal executing this command:

$ echo -e "\e[?1004h" && read

and if we let terminal lose a focus and then restore it, we will see these commands sent back by the terminal:

^[[O^[[I

This plugin is able to enable and disable terminal focus reporting and can read special commands from the terminal and execute needed hooks (focus-in, focus-out) when the terminal fires focus lost or focus restored events respectively.