Variable: imenu-prev-index-position-function
imenu-prev-index-position-function is a buffer-local variable defined
in imenu.el.gz.
Documentation
Function for finding the next index position.
If imenu-create-index-function is set to
imenu-default-create-index-function, then you must set this variable
to a function that will find the next index, looking backwards in the
file.
The function should leave point at the place to be connected to the index and it should return nil when it doesn't find another index.
Source Code
;; Defined in /usr/src/emacs/lisp/imenu.el.gz
;;;###autoload
(defvar-local imenu-prev-index-position-function 'beginning-of-defun
"Function for finding the next index position.
If `imenu-create-index-function' is set to
`imenu-default-create-index-function', then you must set this variable
to a function that will find the next index, looking backwards in the
file.
The function should leave point at the place to be connected to the
index and it should return nil when it doesn't find another index.")