(menu-bar-update-buffers): Avoid excessive consing.

diff --git a/lisp/menu-bar.el b/lisp/menu-bar.el
index cf0f3b174d52a39b348beab99bd15fe96a75739f..61909e5a2bf3ac7f4f98a3376655c3389d120675 100644 (file)
--- a/lisp/menu-bar.el
+++ b/lisp/menu-bar.el
@@ -258,116 +258,101 @@ A large number or nil slows down menu responsiveness.")
   (raise-frame last-command-event)
   (select-frame last-command-event))
 
-(defvar menu-bar-update-buffers-last-buffers nil)
-(defvar menu-bar-update-buffers-last-frames nil)
-
 (defun menu-bar-update-buffers ()
-  (let ((buffers (buffer-list))
-       (frames (frame-list))
-       buffers-info
-       buffers-menu frames-menu)
-    (setq buffers-info
-         (mapcar (function (lambda (buffer)
-                             (list buffer (buffer-modified-p buffer)
-                                   (save-excursion
-                                     (set-buffer buffer)
-                                     buffer-read-only))))
-                 buffers))
-    (if (and (equal buffers-info menu-bar-update-buffers-last-buffers)
-            (equal frames menu-bar-update-buffers-last-frames))
-       nil
-      (setq menu-bar-update-buffers-last-buffers buffers-info)
-      (setq menu-bar-update-buffers-last-frames frames)
-      ;; If requested, list only the N most recently selected buffers.
-      (if (and (integerp buffers-menu-max-size)
-              (> buffers-menu-max-size 1))
-         (if (> (length buffers) buffers-menu-max-size)
-             (setcdr (nthcdr buffers-menu-max-size buffers) nil)))
-
-      ;; Make the menu of buffers proper.
-      (setq buffers-menu
-           (cons "Select Buffer"
-                 (let ((tail buffers)
-                       (maxbuf 0)
-                       (maxlen 0)
-                       alist
-                       head)
-                   (while tail
-                     (or (eq ?\ (aref (buffer-name (car tail)) 0))
-                         (setq maxbuf
-                               (max maxbuf
-                                    (length (buffer-name (car tail))))))
-                     (setq tail (cdr tail)))
-                   (setq tail buffers)
-                   (while tail
-                     (let ((elt (car tail)))
-                       (or (eq ?\ (aref (buffer-name elt) 0))
-                           (setq alist (cons
-                                        (cons
-                                         (format
-                                          (format "%%%ds  %%s%%s  %%s"
-                                                  maxbuf)
-                                          (buffer-name elt)
-                                          (if (buffer-modified-p elt)
-                                              "*" " ")
-                                          (save-excursion
-                                            (set-buffer elt)
-                                            (if buffer-read-only "%" " "))
-                                          (or (buffer-file-name elt)
-                                              (save-excursion
-                                                (set-buffer elt)
-                                                list-buffers-directory)
-                                              ""))
-                                         elt)
-                                        alist)))
-                       (and alist (> (length (car (car alist))) maxlen)
-                            (setq maxlen (length (car (car alist))))))
-                     (setq tail (cdr tail)))
-                   (setq alist (nreverse alist))
-                   (nconc (mapcar '(lambda (pair)
-                                     ;; This is somewhat risque, to use
-                                     ;; the buffer name itself as the event type
-                                     ;; to define, but it works.
-                                     ;; It would not work to use the buffer
-                                     ;; since a buffer as an event has its
-                                     ;; own meaning.
-                                     (nconc (list (buffer-name (cdr pair))
-                                                  (car pair)
-                                                  (cons nil nil))
-                                            'menu-bar-select-buffer))
-                                  alist)
-                          (list (cons 'list-buffers
-                                      (cons
-                                       (concat (make-string (max (- (/ maxlen
-                                                                       2)
-                                                                    8)
-                                                                 0) ?\ )
-                                               "List All Buffers")
-                                       'list-buffers)))))))
-
-
-      ;; Make a Frames menu if we have more than one frame.
-      (if (cdr frames)
-         (setq frames-menu
-               (cons "Select Frame"
-                     (mapcar '(lambda (frame)
-                                (nconc (list frame
-                                             (cdr (assq 'name
-                                                        (frame-parameters frame)))
-                                             (cons nil nil))
-                                       'menu-bar-select-frame))
-                             frames))))
-      (if buffers-menu
-         (setq buffers-menu (cons 'keymap buffers-menu)))
-      (if frames-menu
-         (setq frames-menu (cons 'keymap frames-menu)))
-      (define-key global-map [menu-bar buffer]
-       (cons "Buffers"
-             (if (and buffers-menu frames-menu)
-                 (list 'keymap "Buffers and Frames"
-                       (cons 'buffers (cons "Buffers" buffers-menu))
-                       (cons 'frames (cons "Frames" frames-menu)))
-               (or buffers-menu frames-menu 'undefined)))))))
+  (if (frame-or-buffer-changed-p)
+      (let ((buffers (buffer-list))
+           (frames (frame-list))
+           buffers-menu frames-menu)
+       ;; If requested, list only the N most recently selected buffers.
+       (if (and (integerp buffers-menu-max-size)
+                (> buffers-menu-max-size 1))
+           (if (> (length buffers) buffers-menu-max-size)
+               (setcdr (nthcdr buffers-menu-max-size buffers) nil)))
+
+       ;; Make the menu of buffers proper.
+       (setq buffers-menu
+             (cons "Select Buffer"
+                   (let ((tail buffers)
+                         (maxbuf 0)
+                         (maxlen 0)
+                         alist
+                         head)
+                     (while tail
+                       (or (eq ?\ (aref (buffer-name (car tail)) 0))
+                           (setq maxbuf
+                                 (max maxbuf
+                                      (length (buffer-name (car tail))))))
+                       (setq tail (cdr tail)))
+                     (setq tail buffers)
+                     (while tail
+                       (let ((elt (car tail)))
+                         (or (eq ?\ (aref (buffer-name elt) 0))
+                             (setq alist (cons
+                                          (cons
+                                           (format
+                                            (format "%%%ds  %%s%%s  %%s"
+                                                    maxbuf)
+                                            (buffer-name elt)
+                                            (if (buffer-modified-p elt)
+                                                "*" " ")
+                                            (save-excursion
+                                              (set-buffer elt)
+                                              (if buffer-read-only "%" " "))
+                                            (or (buffer-file-name elt)
+                                                (save-excursion
+                                                  (set-buffer elt)
+                                                  list-buffers-directory)
+                                                ""))
+                                           elt)
+                                          alist)))
+                         (and alist (> (length (car (car alist))) maxlen)
+                              (setq maxlen (length (car (car alist))))))
+                       (setq tail (cdr tail)))
+                     (setq alist (nreverse alist))
+                     (nconc (mapcar '(lambda (pair)
+                                       ;; This is somewhat risque, to use
+                                       ;; the buffer name itself as the event
+                                       ;; type to define, but it works.
+                                       ;; It would not work to use the buffer
+                                       ;; since a buffer as an event has its
+                                       ;; own meaning.
+                                       (nconc (list (buffer-name (cdr pair))
+                                                    (car pair)
+                                                    (cons nil nil))
+                                              'menu-bar-select-buffer))
+                                    alist)
+                            (list
+                             (cons
+                              'list-buffers
+                              (cons
+                               (concat (make-string (max (- (/ maxlen 2) 8) 0)
+                                                    ?\ )
+                                       "List All Buffers")
+                               'list-buffers)))))))
+
+
+       ;; Make a Frames menu if we have more than one frame.
+       (if (cdr frames)
+           (setq frames-menu
+                 (cons "Select Frame"
+                       (mapcar '(lambda (frame)
+                                  (nconc (list frame
+                                               (cdr (assq 'name
+                                                          (frame-parameters frame)))
+                                               (cons nil nil))
+                                         'menu-bar-select-frame))
+                               frames))))
+       (if buffers-menu
+           (setq buffers-menu (cons 'keymap buffers-menu)))
+       (if frames-menu
+           (setq frames-menu (cons 'keymap frames-menu)))
+       (define-key global-map [menu-bar buffer]
+         (cons "Buffers"
+               (if (and buffers-menu frames-menu)
+                   (list 'keymap "Buffers and Frames"
+                         (cons 'buffers (cons "Buffers" buffers-menu))
+                         (cons 'frames (cons "Frames" frames-menu)))
+                 (or buffers-menu frames-menu 'undefined)))))))
 
 (add-hook 'menu-bar-update-hook 'menu-bar-update-buffers)