Variable: mh-showing-mode-hook
mh-showing-mode-hook is a customizable variable defined in mh-e.el.gz.
Value
nil
Documentation
Hook run after entering or leaving mh-showing-mode(var)/mh-showing-mode(fun).
No problems result if this variable is not bound.
add-hook automatically binds it. (This is true for all hook variables.)
Source Code
;; Defined in /usr/src/emacs/lisp/mh-e/mh-e.el.gz