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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. This section explains how to customize how Imenu finds the definitions or buffer portions for a particular major mode.
The usual and simplest way is to set the variable
imenu-generic-expression:
nil, specifies regular expressions for
finding definitions for Imenu. In the simplest case, elements should
look like this:
(menu-title regexp subexp) |
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 section 34.2 Regular Expressions); anything in the buffer that it matches is considered a definition, something to mention in the buffer index. The third item, subexp, indicates which subexpression in regexp matches the definition's name.
An element can also look like this:
(menu-title regexp index function arguments...) |
Each match for this element creates a special index item which, if selected by the user, calls function with arguments consisting of the item name, the buffer position, and arguments.
For Emacs Lisp mode, pattern could look like this:
((nil "^\\s-*(def\\(un\\|subst\\|macro\\|advice\\)\
\\s-+\\([-A-Za-z0-9+]+\\)" 2)
("*Vars*" "^\\s-*(def\\(var\\|const\\)\
\\s-+\\([-A-Za-z0-9+]+\\)" 2)
("*Types*"
"^\\s-*\
(def\\(type\\|struct\\|class\\|ine-condition\\)\
\\s-+\\([-A-Za-z0-9+]+\\)" 2))
|
Setting this variable makes it buffer-local in the current buffer.
t, the default,
means matching should ignore case.
Setting this variable makes it buffer-local in the current buffer.
imenu-generic-expression, to override the syntax table
of the current buffer. Each element should have this form:
(characters . syntax-description) |
The CAR, characters, can be either a character or a string.
The element says to give that character or characters the syntax
specified by syntax-description, which is passed to
modify-syntax-entry (see section 35.3 Syntax Table Functions).
This feature is typically used to give word syntax to characters which
normally have symbol syntax, and thus to simplify
imenu-generic-expression and speed up matching.
For example, Fortran mode uses it this way:
(setq imenu-syntax-alist '(("_$" . "w")))
|
The imenu-generic-expression patterns can then use `\\sw+'
instead of `\\(\\sw\\|\\s_\\)+'. Note that this technique may be
inconvenient when the mode needs to limit the initial character
of a name to a smaller set of characters than are allowed in the rest
of a name.
Setting this variable makes it buffer-local in the current buffer.
Another way to customize Imenu for a major mode is to set the
variables imenu-prev-index-position-function and
imenu-extract-index-name-function:
nil, its value should be a function that
finds the next "definition" to put in the buffer index, scanning
backward in the buffer from point. It should return nil if it
doesn't find another "definition" before point. Otherwise it shuould
leave point at the place it finds a "definition," and return any
non-nil value.
Setting this variable makes it buffer-local in the current buffer.
nil, its value should be a function to
return the name for a definition, assuming point is in that definition
as the imenu-prev-index-position-function function would leave
it.
Setting this variable makes it buffer-local in the current buffer.
The last way to customize Imenu for a major mode is to set the
variable imenu-create-index-function:
save-excursion, so where it
leaves point makes no difference.
The default value is a function that uses
imenu-generic-expression to produce the index alist. If you
specify a different function, then imenu-generic-expression is
not used.
Setting this variable makes it buffer-local in the current buffer.
Simple elements in the alist look like (index-name
. index-position). Selecting a simple element has the effect of
moving to position index-position in the buffer.
Special elements look like (index-name position
function arguments...). Selecting a special element
performs
(funcall function index-name position arguments...) |
A nested sub-alist element looks like (index-name
sub-alist).
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