Variable: global-display-fill-column-indicator-modes
global-display-fill-column-indicator-modes is a customizable variable
defined in display-fill-column-indicator.el.gz.
Value
((not special-mode)
t)
Documentation
Which major modes display-fill-column-indicator-mode(var)/display-fill-column-indicator-mode(fun) is switched on in.
This variable can be either t (all major modes), nil (no major modes), or a list of modes and (not modes) to switch use this minor mode or not. For instance
(c-mode (not message-mode mail-mode) text-mode)
means "use this mode in all modes derived from `c-mode', don't use in modes derived from `message-mode' or `mail-mode', but do use in other modes derived from `text-mode'". An element with value t means "use" and nil means "don't use". There's an implicit nil at the end of the list.
Probably introduced at or before Emacs version 28.1.
Source Code
;; Defined in /usr/src/emacs/lisp/display-fill-column-indicator.el.gz