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."
      (erc-with-server-buffer
        (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
[https://gitlab.com/mplscorwin/dotfiles/-/blob/09135326920b2dc19a6cbf606defe2852255a406/elisp/site-lisp/erc-count-users-mode.el 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
      (:eval
       (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)))
                  erc-channel-users)
         (format " %S/%S/%S" ops voices members))))

-- RomainFrancoise

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[[ERC]]