(require 'electric)
(defvar electric-help-map ()
"Keymap defining commands available in `electric-help-mode'.")
(defvar electric-help-form-to-execute nil)
(defgroup electric-help ()
"Electric help facility."
:version "21.1"
:group 'help)
(defcustom electric-help-shrink-window t
"If set, adjust help window sizes to buffer sizes when displaying help."
:type 'boolean
:group 'electric-help)
(defcustom electric-help-mode-hook nil
"Hook run by `with-electric-help' after initializing the buffer."
:type 'hook
:group 'electric-help)
(put 'electric-help-undefined 'suppress-keymap t)
(if electric-help-map
()
(let ((map (make-keymap)))
(suppress-keymap map)
(define-key map "\C-u" 'electric-help-undefined)
(define-key map [?\C-0] 'electric-help-undefined)
(define-key map [?\C-1] 'electric-help-undefined)
(define-key map [?\C-2] 'electric-help-undefined)
(define-key map [?\C-3] 'electric-help-undefined)
(define-key map [?\C-4] 'electric-help-undefined)
(define-key map [?\C-5] 'electric-help-undefined)
(define-key map [?\C-6] 'electric-help-undefined)
(define-key map [?\C-7] 'electric-help-undefined)
(define-key map [?\C-8] 'electric-help-undefined)
(define-key map [?\C-9] 'electric-help-undefined)
(define-key map (char-to-string help-char) 'electric-help-help)
(define-key map "?" 'electric-help-help)
(define-key map " " 'scroll-up)
(define-key map "\^?" 'scroll-down)
(define-key map "." 'beginning-of-buffer)
(define-key map "<" 'beginning-of-buffer)
(define-key map ">" 'end-of-buffer)
(define-key map "q" 'electric-help-exit)
(define-key map "Q" 'electric-help-exit)
(define-key map "r" 'electric-help-retain)
(define-key map "R" 'electric-help-retain)
(define-key map "\ex" 'electric-help-execute-extended)
(define-key map "\C-x" 'electric-help-ctrl-x-prefix)
(setq electric-help-map map)))
(defun electric-help-mode ()
"`with-electric-help' temporarily places its buffer in this mode.
\(On exit from `with-electric-help', the buffer is put in `default-major-mode'.)"
(setq buffer-read-only t)
(setq mode-name "Help")
(setq major-mode 'help)
(setq mode-line-buffer-identification '(" Help: %b"))
(use-local-map electric-help-map)
(add-hook 'mouse-leave-buffer-hook 'electric-help-retain)
(view-mode -1)
)
(defun with-electric-help (thunk &optional buffer noerase minheight)
"Pop up an \"electric\" help buffer.
The arguments are THUNK &optional BUFFER NOERASE MINHEIGHT.
THUNK is a function of no arguments which is called to initialize the
contents of BUFFER. BUFFER defaults to `*Help*'. BUFFER will be
erased before THUNK is called unless NOERASE is non-nil. THUNK will
be called while BUFFER is current and with `standard-output' bound to
the buffer specified by BUFFER.
If THUNK returns nil, we display BUFFER starting at the top, and
shrink the window to fit. If THUNK returns non-nil, we don't do those things.
After THUNK has been called, this function \"electrically\" pops up a window
in which BUFFER is displayed and allows the user to scroll through that buffer
in electric-help-mode. The window's height will be at least MINHEIGHT if
this value is non-nil.
If THUNK returns nil, we display BUFFER starting at the top, and
shrink the window to fit if `electric-help-shrink-window' is non-nil.
If THUNK returns non-nil, we don't do those things.
When the user exits (with `electric-help-exit', or otherwise), the help
buffer's window disappears (i.e., we use `save-window-excursion'), and
BUFFER is put into `default-major-mode' (or `fundamental-mode') when we exit."
(setq buffer (get-buffer-create (or buffer "*Help*")))
(let ((one (one-window-p t))
(config (current-window-configuration))
(bury nil)
(electric-help-form-to-execute nil))
(unwind-protect
(save-excursion
(when one
(goto-char (window-start (selected-window))))
(let ((pop-up-windows t))
(pop-to-buffer buffer))
(save-excursion
(set-buffer buffer)
(when (and minheight (< (window-height) minheight))
(enlarge-window (- minheight (window-height))))
(electric-help-mode)
(setq buffer-read-only nil)
(unless noerase
(erase-buffer)))
(let ((standard-output buffer))
(unless (funcall thunk)
(set-buffer buffer)
(set-buffer-modified-p nil)
(goto-char (point-min))
(when (and one electric-help-shrink-window)
(shrink-window-if-larger-than-buffer))))
(set-buffer buffer)
(run-hooks 'electric-help-mode-hook)
(setq buffer-read-only t)
(if (eq (car-safe (electric-help-command-loop)) 'retain)
(setq config (current-window-configuration))
(setq bury t))
(when (memq 'electric-help-retain mouse-leave-buffer-hook)
(remove-hook 'mouse-leave-buffer-hook 'electric-help-retain)))
(message "")
(set-buffer buffer)
(setq buffer-read-only nil)
(condition-case ()
(funcall (or default-major-mode 'fundamental-mode))
(error nil))
(set-window-configuration config)
(when bury
(replace-buffer-in-windows buffer)
(bury-buffer buffer))
(eval electric-help-form-to-execute))))
(defun electric-help-command-loop ()
(catch 'exit
(if (pos-visible-in-window-p (point-max))
(progn (message "%s" (substitute-command-keys "<<< Press Space to bury the help buffer, Press \\[electric-help-retain] to retain it >>>"))
(if (equal (setq unread-command-events (list (read-event)))
'(?\ ))
(progn (setq unread-command-events nil)
(throw 'exit t)))))
(let (up down both neither
(standard (and (eq (key-binding " ")
'scroll-up)
(eq (key-binding "\^?")
'scroll-down)
(eq (key-binding "q")
'electric-help-exit)
(eq (key-binding "r")
'electric-help-retain))))
(Electric-command-loop
'exit
(function (lambda ()
(sit-for 0) (let ((min (pos-visible-in-window-p (point-min)))
(max (pos-visible-in-window-p (point-max))))
(cond (isearch-mode 'noprompt)
((and min max)
(cond (standard "Press q to exit, r to retain ")
(neither)
(t (setq neither (substitute-command-keys "Press \\[electric-help-exit] to exit, \\[electric-help-retain] to retain ")))))
(min
(cond (standard "Press SPC to scroll, q to exit, r to retain ")
(up)
(t (setq up (substitute-command-keys "Press \\[scroll-up] to scroll, \\[electric-help-exit] to exit, \\[electric-help-retain] to retain ")))))
(max
(cond (standard "Press DEL to scroll back, q to exit, r to retain ")
(down)
(t (setq down (substitute-command-keys "Press \\[scroll-down] to scroll back, \\[electric-help-exit] to exit, \\[electric-help-retain] to retain ")))))
(t
(cond (standard "Press SPC to scroll, DEL to scroll back, q to exit, r to retain ")
(both)
(t (setq both (substitute-command-keys "Press \\[scroll-up] to scroll, \\[scroll-down] to scroll back, \\[electric-help-exit] to exit, \\[electric-help-retain] to retain ")))))))))
t))))
(defun electric-help-exit ()
"Exit `electric-help', restoring the previous window/buffer configuration.
\(The *Help* buffer will be buried.)"
(interactive)
(if (memq 'electric-help-retain mouse-leave-buffer-hook)
(progn
(remove-hook 'mouse-leave-buffer-hook 'electric-help-retain)
(throw 'exit t))))
(defun electric-help-retain ()
"Exit `electric-help', retaining the current window/buffer configuration.
\(The *Help* buffer will not be selected, but \\[switch-to-buffer-other-window] RET
will select it.)"
(interactive)
(if (memq 'electric-help-retain mouse-leave-buffer-hook)
(progn
(remove-hook 'mouse-leave-buffer-hook 'electric-help-retain)
(throw 'exit '(retain)))))
(defun electric-help-undefined ()
(interactive)
(error "%s is undefined -- Press %s to exit"
(mapconcat 'single-key-description (this-command-keys) " ")
(if (eq (key-binding "q") 'electric-help-exit)
"q"
(substitute-command-keys "\\[electric-help-exit]"))))
(defun electric-help-help ()
(interactive)
(if (and (eq (key-binding "q") 'electric-help-exit)
(eq (key-binding " ") 'scroll-up)
(eq (key-binding "\^?") 'scroll-down)
(eq (key-binding "r") 'electric-help-retain))
(message "SPC scrolls up, DEL scrolls down, q exits burying help buffer, r exits")
(message "%s" (substitute-command-keys "\\[scroll-up] scrolls up, \\[scroll-down] scrolls down, \\[electric-help-exit] exits burying help buffer, \\[electric-help-retain] exits")))
(sit-for 2))
(defun electric-helpify (fun &optional name)
(let ((name (or name "*Help*")))
(if (save-window-excursion
(let* ((p (symbol-function 'print-help-return-message))
(b (get-buffer name))
(m (buffer-modified-p b)))
(and b (not (get-buffer-window b))
(setq b nil))
(unwind-protect
(progn
(message "%s..." (capitalize (symbol-name fun)))
(and b
(save-excursion
(set-buffer b)
(set-buffer-modified-p t)))
(fset 'print-help-return-message 'ignore)
(call-interactively fun)
(and (get-buffer name)
(get-buffer-window (get-buffer name))
(or (not b)
(not (eq b (get-buffer name)))
(not (buffer-modified-p b)))))
(fset 'print-help-return-message p)
(and b (buffer-name b)
(save-excursion
(set-buffer b)
(set-buffer-modified-p m))))))
(with-electric-help 'ignore name t))))
(defun electric-help-execute-extended (prefixarg)
(interactive "p")
(setq electric-help-form-to-execute '(execute-extended-command nil))
(electric-help-retain))
(defun electric-help-ctrl-x-prefix (prefixarg)
(interactive "p")
(setq electric-help-form-to-execute '(progn (message nil) (setq unread-command-char ?\C-x)))
(electric-help-retain))
(defun electric-describe-key ()
(interactive)
(electric-helpify 'describe-key))
(defun electric-describe-mode ()
(interactive)
(electric-helpify 'describe-mode))
(defun electric-view-lossage ()
(interactive)
(electric-helpify 'view-lossage))
(defun electric-describe-function ()
(interactive)
(electric-helpify 'describe-function))
(defun electric-describe-variable ()
(interactive)
(electric-helpify 'describe-variable))
(defun electric-describe-bindings ()
(interactive)
(electric-helpify 'describe-bindings))
(defun electric-describe-syntax ()
(interactive)
(electric-helpify 'describe-syntax))
(defun electric-command-apropos ()
(interactive)
(electric-helpify 'command-apropos "*Apropos*"))
(defun electric-apropos ()
(interactive)
(electric-helpify 'apropos))
(defvar ehelp-map ())
(if ehelp-map
nil
(let ((map (copy-keymap help-map)))
(substitute-key-definition 'apropos 'electric-apropos map)
(substitute-key-definition 'command-apropos 'electric-command-apropos map)
(substitute-key-definition 'describe-key 'electric-describe-key map)
(substitute-key-definition 'describe-mode 'electric-describe-mode map)
(substitute-key-definition 'view-lossage 'electric-view-lossage map)
(substitute-key-definition 'describe-function 'electric-describe-function map)
(substitute-key-definition 'describe-variable 'electric-describe-variable map)
(substitute-key-definition 'describe-bindings 'electric-describe-bindings map)
(substitute-key-definition 'describe-syntax 'electric-describe-syntax map)
(setq ehelp-map map)
(fset 'ehelp-command map)))
(provide 'ehelp)