The value of @code{auto-fill-function} is @code{do-auto-fill} when
Auto-Fill mode is enabled. That is a function whose sole purpose is to
implement the usual strategy for breaking a line.
-
-@quotation
-In older Emacs versions, this variable was named @code{auto-fill-hook},
-but since it is not called with the standard convention for hooks, it
-was renamed to @code{auto-fill-function} in version 19.
-@end quotation
@end defvar
@defvar normal-auto-fill-function