Variable: adaptive-fill-mode
adaptive-fill-mode is a customizable variable defined in fill.el.gz.
Value
t
Documentation
Non-nil means determine a paragraph's fill prefix from its text.
Probably introduced at or before Emacs version 19.23.
Source Code
;; Defined in /usr/src/emacs/lisp/textmodes/fill.el.gz
(defcustom adaptive-fill-mode t
"Non-nil means determine a paragraph's fill prefix from its text."
:type 'boolean)