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+;;; which-func.el -- Print current function in mode line
+
+;; Copyright (C) 1994, 1997 Free Software Foundation, Inc.
+
+;; Author:   Alex Rezinsky <[email protected]>
+;; Keywords: mode-line imenu
+
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs is free software; you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation; either version 2, or (at your option)
+;; any later version.
+
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs; see the file COPYING.  If not, write to the
+;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+;; Boston, MA 02111-1307, USA.
+
+;;; COMMENTARY
+;;; ----------
+;;; This package prints name of function where  your current point is
+;;; located in mode line. It assumes that you work with imenu package
+;;; and imenu--index-alist is up to date.
+
+;;; KNOWN BUGS
+;;; ----------
+;;; Really this package shows not  "function where the current  point
+;;; is located now", but "nearest   function which defined above  the
+;;; current point". So if your current point is  located after end of
+;;; function  FOO but before   begin  of function  BAR,  FOO  will be
+;;; displayed in mode line.
+
+;;; TODO LIST
+;;; ---------
+;;;     1. Dependence on imenu package should be removed.  Separate
+;;; function determination mechanism should be used to determine the end
+;;; of a function as well as the beginning of a function.
+;;;     2. This package should be realized with the help of overlay
+;;; properties instead of imenu--index-alist variable.
+
+;;; THANKS TO
+;;; ---------
+;;; Per Abrahamsen   <[email protected]>
+;;;     Some ideas (inserting  in mode-line,  using of post-command  hook
+;;;     and toggling this  mode) have  been   borrowed from  his  package
+;;;     column.el
+;;; Peter Eisenhauer <[email protected]>
+;;;     Bug fixing in case nested indexes.
+;;; Terry Tateyama   <[email protected]>
+;;;     Suggestion to use find-file-hooks for first imenu
+;;;     index building.
+
+;;; Variables for customization
+;;; ---------------------------
+;;;  
+(defvar which-func-unknown "???"
+  "String to display in the mode line when current function is unknown.")
+
+(defcustom which-func-modes 
+  '(emacs-lisp-mode c-mode c++-mode perl-mode makefile-mode sh-mode)
+  "List of major modes for which `which-func-mode' should be used.
+For other modes it is disabled.  If this is equal to t,
+then current-function recognition is enabled in any mode."
+  :group 'which-func
+  :type '(choice (const :tag "All modes" t)
+		 (list (symbol :tag "Major mode"))))
+
+(defcustom which-func-amodes '(emacs-lisp-mode c-mode c++-mode)
+  "List of major modes for which the Imenu menu should be computed automatically.
+It is computed when you visit a file in one of these major modes.
+If the variable's value is nil, then the Imenu menu is not computed
+automatically in any mode.  Note that the menu is never computed
+automatically if the buffer size exceeds `which-func-maxout'."
+  :group 'which-func
+  :type '(list (symbol :tag "Major mode")))
+
+(defcustom which-func-maxout 100000
+  "Don't automatically compute the Imenu menu if buffer is this big or bigger.
+Zero means compute the Imenu menu regardless of size."
+  :group 'which-func
+  :type 'integer)
+
+(defcustom which-func-format '(" [" which-func-current "]")
+  "Format for displaying the function in the mode line."
+  :group 'which-func
+  :type 'sexp)
+
+;;; Code, nothing to customize below here
+;;; -------------------------------------
+;;;
+(require 'imenu)
+
+(defvar which-func-current  which-func-unknown)
+(defvar which-func-previous which-func-unknown)
+(make-variable-buffer-local 'which-func-current)
+(make-variable-buffer-local 'which-func-previous)
+
+(defvar which-func-mode-global nil
+  "Non-nil means display current function name in mode line.")
+
+(defvar which-func-mode nil
+  "Non-nil means display current function name in mode line.
+This makes a difference only if which-func-mode-global is non-nil")
+(make-variable-buffer-local 'which-func-mode)
+(put 'which-func-mode 'permanent-local t)
+
+(add-hook 'find-file-hooks 'which-func-ff-hook t)
+
+(defun which-func-ff-hook ()
+  "File find hook for Which Function mode.
+It creates the Imenu index for the buffer, if necessary."
+  (if (or (eq which-func-modes t) (member major-mode which-func-modes))
+      (setq which-func-mode which-func-mode-global)
+    (setq which-func-mode nil))
+
+  (if (and which-func-mode
+           (member major-mode which-func-amodes)
+           (or (< buffer-saved-size which-func-maxout)
+               (= which-func-maxout 0)))
+      (setq imenu--index-alist
+	    (save-excursion (funcall imenu-create-index-function)))))
+
+(defun which-func-update ()
+  ;; Update the string containing the current function.
+  (condition-case info
+    (progn
+      (if (not (setq which-func-current (which-function)))
+          (setq which-func-current which-func-unknown))
+      (if (not (string= which-func-current which-func-previous))
+        (progn
+          (force-mode-line-update)
+          (setq which-func-previous which-func-current))))
+    (error
+     (ding)
+     (remove-hook 'post-command-hook 'which-func-update)
+     (which-func-mode -1)   ; Function mode off
+     (message "Error in which-func-update: %s" info)))
+
+(defun which-func-mode (&optional arg)
+  "Toggle Which Function mode, globally.
+When Which Function mode is enabled, the current function name is
+continuously displayed in the mode line, in certain major modes.
+
+With prefix arg, turn Which Function mode on iff arg is positive,
+and off otherwise."
+  (interactive "P")
+  (if (or (and (null arg) which-func-mode-global)
+          (<= (prefix-numeric-value arg) 0))
+      ;; Turn it off
+      (if which-func-mode-global
+          (progn
+            (remove-hook 'post-command-hook 'which-func-update)
+            (setq which-func-mode-global nil)
+            (setq which-func-mode nil)
+            (force-mode-line-update)))
+    ;;Turn it on
+    (if which-func-mode-global
+        ()
+      (add-hook 'post-command-hook 'which-func-update)
+      (setq which-func-mode-global t)
+      (setq which-func-mode
+	    (or (eq which-func-modes t)
+		(member major-mode which-func-modes))))))
+
+(defun which-function ()
+  "Returns current function name based on point.
+If imenu--index-alist does not exist, or is empty  or if point
+is located before first function, returns nil."
+  (and
+   (boundp 'imenu--index-alist)
+   imenu--index-alist
+   (let ((pair (car-safe imenu--index-alist))
+         (rest (cdr-safe imenu--index-alist))
+         (name nil))
+     (while (and pair (or (not (number-or-marker-p (cdr pair)))
+			  (> (point) (cdr pair))))
+       (setq name (car pair))
+       (setq pair (car-safe rest))
+       (setq rest (cdr-safe rest)))
+     name)))
+
+(provide 'which-func)
+
+;; which-func.el ends here