This page deals with ERC’s mode-line and header-line.

Change header-line face on disconnect

If you’ve ever found yourself reading the backlog of messages in an ERC channel buffer, and only after you’ve made it down to the ERC propmt you see you’ve been disconnected for a while, you might need more than the “ERC: CLOSED” text in the mode-line to give you a clue. The following code makes the header-line face red whenever the connection to the IRC server is closed.

    ;;; change header line face if disconnected
    (defface erc-header-line-disconnected
      '((t (:foreground "black" :background "indianred")))
      "Face to use when ERC has been disconnected.")
    (defun erc-update-header-line-show-disconnected ()
      "Use a different face in the header-line when disconnected."
        (cond ((erc-server-process-alive) 'erc-header-line)
              (t 'erc-header-line-disconnected))))
    (setq erc-header-line-face-method 'erc-update-header-line-show-disconnected)

Number of members in a channel

I have wrapped the below slightly more formally. It’s currently wrapped with my init stuff and not published as a seperate project or gist but may remain findable via gitlab permalink. -Corwin

Add this to your .emacs to see the number of opped/voiced/normal members of the current channel in the modeline:

    (define-minor-mode ncm-mode "" nil
       (let ((ops 0)
             (voices 0)
             (members 0))
         (maphash (lambda (key value)
                    (when (erc-channel-user-op-p key)
                      (setq ops (1+ ops)))
                    (when (erc-channel-user-voice-p key)
                      (setq voices (1+ voices)))
                    (setq members (1+ members)))
         (format " %S/%S/%S" ops voices members))))