[PATCH] nested imenu support for which-func

[Daniel Colascione <danc@merrillpress.com>]

As it is in 22.1, which-func only looks one level down the imenu tree. This 
patch has it look down all branches. In addition, there's a new variable, 
which-func-imenu-joiner-function. It's called with the names of all
the levels of imenu that which-func had to traverse to reach the given 
function. By default, which-func just uses the deepest name; that matches 
existing behavior.

--- /dev/stdin	2008-09-25 17:00:50.305409082 -0400
+++ which-func.el	2008-09-25 16:03:41.000000000 -0400
@@ -153,6 +153,12 @@
   :type 'sexp)
 ;;;###autoload (put 'which-func-format 'risky-local-variable t)
 
+(defvar which-func-imenu-joiner-function #'last
+  "Function to call when using imenu to join together multiple
+levels of nomenclature. Called with a single argument, a list of
+strings giving the names of the menus we had to traverse to get
+to the item. Return a single string, the new name of the item.")
+
 (defvar which-func-cleanup-function nil
   "Function to transform a string before displaying it in the mode line.
 The function is called with one argument, the string to display.
@@ -282,25 +288,38 @@
 	       (boundp 'imenu--index-alist) imenu--index-alist)
       (let ((alist imenu--index-alist)
             (minoffset (point-max))
-            offset elem pair mark)
-        (while alist
-          (setq elem  (car-safe alist)
-                alist (cdr-safe alist))
-          ;; Elements of alist are either ("name" . marker), or
-          ;; ("submenu" ("name" . marker) ... ).
-          (unless (listp (cdr elem))
-              (setq elem (list elem)))
-          (while elem
-            (setq pair (car elem)
-                  elem (cdr elem))
-            (and (consp pair)
-                 (number-or-marker-p (setq mark (cdr pair)))
-                 (if (>= (setq offset (- (point) mark)) 0)
-                     (if (< offset minoffset) ; find the closest item
-                         (setq minoffset offset
-                               name (car pair)))
-                   ;; Entries in order, so can skip all those after point.
-                   (setq elem nil)))))))
+            offset pair mark imstack namestack)
+        ;; Elements of alist are either ("name" . marker), or
+        ;; ("submenu" ("name" . marker) ... ). The list can be
+        ;; arbitrarily nested.
+        (while (or alist imstack)
+          (if alist
+              (progn
+                (setq pair (car-safe alist)
+                      alist (cdr-safe alist))
+
+                (cond ((atom pair))     ; skip anything not a cons
+
+                      ((imenu--subalist-p pair)
+                       (setq imstack   (cons alist imstack)
+                             namestack (cons (car pair) namestack)
+                             alist     (cdr pair)))
+
+                      ((number-or-marker-p (setq mark (cdr pair)))
+                       (if (>= (setq offset (- (point) mark)) 0)
+                           (if (< offset minoffset) ; find the closest item
+                               (setq minoffset offset
+                                     name (funcall
+                                           which-func-imenu-joiner-function
+                                           (reverse (cons (car pair) 
namestack)))))
+                         ;; Entries in order, so can skip all those after 
point.
+                         (setq alist nil
+                               imstack nil)))))
+
+            (setq alist     (car imstack)
+                  namestack (cdr namestack)
+                  imstack   (cdr imstack))))))
+
     ;; Try using add-log support.
     (when (and (null name) (boundp 'add-log-current-defun-function)
 	       add-log-current-defun-function)