emacs/lisp/menu-bar.el

(define-key global-map [menu-bar] (make-sparse-keymap "menu-bar"))
(setq menu-bar-file-menu (make-sparse-keymap "File"))
(define-key global-map [menu-bar file] (cons "File" menu-bar-file-menu))
(setq menu-bar-edit-menu (make-sparse-keymap "Edit"))
(define-key global-map [menu-bar edit] (cons "Edit" menu-bar-edit-menu))
(setq menu-bar-buffer-menu (make-sparse-keymap "Buffers"))
(define-key global-map [menu-bar buffer] (cons "Buffers" menu-bar-buffer-menu))
(setq menu-bar-help-menu (make-sparse-keymap "Help"))
(define-key global-map [menu-bar help] (cons "Help" menu-bar-help-menu))

(define-key menu-bar-file-menu [exit-emacs]
  '("Exit Emacs" . save-buffers-kill-emacs))
(define-key menu-bar-file-menu [kill-buffer]
  '("Kill Buffer" . kill-this-buffer))
(define-key menu-bar-file-menu [delete-frame] '("Delete Frame" . delete-frame))
(define-key menu-bar-file-menu [print-buffer] '("Print Buffer" . print-buffer))
(define-key menu-bar-file-menu [revert-buffer]
  '("Revert Buffer" . revert-buffer))
(define-key menu-bar-file-menu [write-file]
  '("Save Buffer As..." . write-file))
(define-key menu-bar-file-menu [save-buffer] '("Save Buffer" . save-buffer))
(define-key menu-bar-file-menu [open-file] '("Open File..." . find-file))
(define-key menu-bar-file-menu [new-frame] '("New Frame" . new-frame))

(define-key menu-bar-edit-menu [clear] '("Clear" . x-delete-primary-selection))
(define-key menu-bar-edit-menu [paste] '("Paste" . x-yank-clipboard-selection))
(define-key menu-bar-edit-menu [copy] '("Copy" . x-copy-primary-selection))
(define-key menu-bar-edit-menu [cut] '("Cut" . x-kill-primary-selection))
(define-key menu-bar-edit-menu [undo] '("Undo" . advertised-undo))

(define-key menu-bar-help-menu [emacs-tutorial]
  '("Emacs Tutorial" . help-with-tutorial))
(define-key menu-bar-help-menu [man] '("Man..." . manual-entry))
(define-key menu-bar-help-menu [describe-variable]
  '("Describe Variable..." . describe-variable))
(define-key menu-bar-help-menu [describe-function]
  '("Describe Function..." . describe-function))
(define-key menu-bar-help-menu [describe-key]
  '("Describe Key..." . describe-key))
(define-key menu-bar-help-menu [list-keybindings]
  '("List Keybindings" . describe-bindings))
(define-key menu-bar-help-menu [command-apropos]
  '("Command Apropos..." . command-apropos))
(define-key menu-bar-help-menu [describe-mode]
  '("Describe Mode" . describe-mode))
(define-key menu-bar-help-menu [info] '("Info" . info))

(define-key menu-bar-help-menu [emacs-news] '("Emacs News" . view-emacs-news))
(defun kill-this-buffer ()	; for the menubar
  "Kills the current buffer."
  (interactive)
  (kill-buffer (current-buffer)))

(defun kill-this-buffer-enabled-p ()
  (let ((count 0)
	(buffers (buffer-list)))
    (while buffers
      (or (string-match "^ " (buffer-name (car buffers)))
	  (setq count (1+ count)))
      (setq buffers (cdr buffers)))
    (> count 1)))

(put 'save-buffer 'menu-enable '(buffer-modified-p))
(put 'revert-buffer 'menu-enable '(and (buffer-modified-p) (buffer-file-name)))
(put 'delete-frame 'menu-enable '(cdr (visible-frame-list)))
(put 'kill-this-buffer 'menu-enable '(kill-this-buffer-enabled-p))

(put 'x-kill-primary-selection 'menu-enable '(x-selection-owner-p))
(put 'x-copy-primary-selection 'menu-enable '(x-selection-owner-p))
(put 'x-yank-clipboard-selection 'menu-enable '(x-selection-owner-p))
(put 'x-delete-primary-selection 'menu-enable
     '(x-selection-exists-p 'CLIPBOARD))

(put 'advertised-undo 'menu-enable
     '(and (not (eq t buffer-undo-list))
	   (if (eq last-command 'undo)
	       (and (boundp 'pending-undo-list)
		    pending-undo-list)
	     buffer-undo-list)))

(let ((frames (frame-list)))
  (while frames
    (modify-frame-parameters (car frames) '((menu-bar-lines . 1)))
    (setq frames (cdr frames))))
(or (assq 'menu-bar-lines default-frame-alist)
    (setq default-frame-alist
	  (cons '(menu-bar-lines . 1) default-frame-alist)))