README.tmp-imenu-notes

major modes:

The mode should specify how Imenu should find the definitions or
sections of a buffer, by setting up a buffer-local value for the
variable imenu-generic-expression, for the two variables
imenu-prev-index-position-function and
imenu-extract-index-name-function, or for the variable
imenu-create-index-function (see Imenu).

Macro: defvar-local variable value &optional docstring

  This macro defines variable as a variable with initial value value
  and docstring, and marks it as automatically buffer-local. It is
  equivalent to calling defvar followed by
  make-variable-buffer-local. variable should be an unquoted symbol.

22.5 Imenu

Imenu is a feature that lets users select a definition or section in
the buffer, from a menu which lists all of them, to go directly to
that location in the buffer. Imenu works by constructing a buffer
index which lists the names and buffer positions of the definitions,
or other named portions of the buffer; then the user can choose one of
them and move point to it. Major modes can add a menu bar item to use
Imenu using imenu-add-to-menubar.

Command: imenu-add-to-menubar name

  This function defines a local menu bar item named name to run Imenu.

The usual and simplest way is to set the variable imenu-generic-expression:

Variable: imenu-generic-expression

  This variable, if non-nil, is a list that specifies regular
  expressions for finding definitions for Imenu. Simple elements of
  imenu-generic-expression look like this:

    (menu-title regexp index)

  Here, if menu-title is non-nil, it says that the matches for this
  element should go in a submenu of the buffer index; menu-title
  itself specifies the name for the submenu. If menu-title is nil, the
  matches for this element go directly in the top level of the buffer
  index.

  The second item in the list, regexp, is a regular expression (see
  Regular Expressions); anything in the buffer that it matches is
  considered a definition, something to mention in the buffer
  index.

  The third item, index, is a non-negative integer that indicates
  which subexpression in regexp matches the definition’s name.