(require 'backquote)
(defcustom three-step-help nil
"*Non-nil means give more info about Help command in three steps.
The three steps are simple prompt, prompt with all options,
and window listing and describing the options.
A value of nil means skip the middle step, so that
\\[help-command] \\[help-command] gives the window that lists the options."
:type 'boolean
:group 'help)
(defmacro make-help-screen (fname help-line help-text helped-map)
"Construct help-menu function name FNAME.
When invoked, FNAME shows HELP-LINE and reads a command using HELPED-MAP.
If the command is the help character, FNAME displays HELP-TEXT
and continues trying to read a command using HELPED-MAP.
If HELP-TEXT contains the sequence `%THIS-KEY%', that is replaced
with the key sequence that invoked FNAME.
When FNAME finally does get a command, it executes that command
and then returns."
(let ((doc-fn (intern (concat (symbol-name fname) "-doc"))))
`(progn
(defun ,doc-fn () ,help-text)
(defun ,fname ()
"Help command."
(interactive)
(let ((line-prompt
(substitute-command-keys ,help-line)))
(if three-step-help
(message "%s" line-prompt))
(let* ((help-screen (documentation (quote ,doc-fn)))
(local-map (make-sparse-keymap))
(minor-mode-map-alist nil)
(prev-frame (selected-frame))
config new-frame key char)
(if (string-match "%THIS-KEY%" help-screen)
(setq help-screen
(replace-match (key-description (substring (this-command-keys) 0 -1))
t t help-screen)))
(unwind-protect
(progn
(setcdr local-map ,helped-map)
(define-key local-map [t] 'undefined)
(define-key local-map [vertical-scroll-bar]
(lookup-key global-map [vertical-scroll-bar]))
(if three-step-help
(progn
(setq key (let ((overriding-local-map local-map))
(read-key-sequence nil)))
(if (lookup-key function-key-map key)
(setq key (lookup-key function-key-map key)))
(setq char (aref key 0)))
(setq char ??))
(if (or (eq char ??) (eq char help-char)
(memq char help-event-list))
(progn
(setq config (current-window-configuration))
(switch-to-buffer-other-window "*Help*")
(and (fboundp 'make-frame)
(not (eq (window-frame (selected-window))
prev-frame))
(setq new-frame (window-frame (selected-window))
config nil))
(setq buffer-read-only nil)
(let ((inhibit-read-only t))
(erase-buffer)
(insert help-screen))
(help-mode)
(goto-char (point-min))
(while (or (memq char (append help-event-list
(cons help-char '(?? ?\C-v ?\s ?\177 delete backspace vertical-scroll-bar ?\M-v))))
(eq (car-safe char) 'switch-frame)
(equal key "\M-v"))
(condition-case nil
(progn
(if (eq (car-safe char) 'switch-frame)
(handle-switch-frame char))
(if (memq char '(?\C-v ?\s))
(scroll-up))
(if (or (memq char '(?\177 ?\M-v
delete backspace))
(equal key "\M-v"))
(scroll-down)))
(error nil))
(let ((cursor-in-echo-area t)
(overriding-local-map local-map))
(setq key (read-key-sequence
(format "Type one of the options listed%s: "
(if (pos-visible-in-window-p
(point-max))
"" ", or SPACE or DEL to scroll")))
char (aref key 0)))
(when (eq char 'vertical-scroll-bar)
(command-execute (lookup-key local-map key) nil key)))))
(message "")
(if (listp char)
(setq unread-command-events
(cons char unread-command-events)
config nil)
(let ((defn (lookup-key local-map key)))
(if defn
(progn
(if config
(progn
(set-window-configuration config)
(setq config nil)))
(if new-frame
(progn (iconify-frame new-frame)
(setq new-frame nil)))
(call-interactively defn))
(ding)))))
(if new-frame (iconify-frame new-frame))
(if config
(set-window-configuration config))))))
)))
(provide 'help-macro)