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;;; helper.el --- utility help package supporting help in electric modes
;; Copyright (C) 1985, 2001-2021 Free Software Foundation, Inc.
;; Author: K. Shane Hartman
;; Maintainer: emacs-devel@gnu.org
;; Keywords: help
;; Package: emacs
;; This file is part of GNU Emacs.
;; GNU Emacs is free software: you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.
;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;; GNU General Public License for more details.
;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs. If not, see <https://www.gnu.org/licenses/>.
;;; Commentary:
;;; Code:
;; hey, here's a helping hand.
;; Bind this to a string for <blank> in "... Other keys <blank>".
;; Helper-help uses this to construct help string when scrolling.
;; Defaults to "return"
(defvar Helper-return-blurb nil)
;; Keymap implementation doesn't work too well for non-standard loops.
;; But define it anyway for those who can use it. Non-standard loops
;; will probably have to use Helper-help. You can't autoload the
;; keymap either.
(defvar Helper-help-map nil)
(if Helper-help-map
nil
(setq Helper-help-map (make-keymap))
;(fillarray Helper-help-map 'undefined)
(define-key Helper-help-map "m" 'Helper-describe-mode)
(define-key Helper-help-map "b" 'Helper-describe-bindings)
(define-key Helper-help-map "c" 'Helper-describe-key-briefly)
(define-key Helper-help-map "k" 'Helper-describe-key)
;(define-key Helper-help-map "f" 'Helper-describe-function)
;(define-key Helper-help-map "v" 'Helper-describe-variable)
(define-key Helper-help-map "?" 'Helper-help-options)
(define-key Helper-help-map (char-to-string help-char) 'Helper-help-options)
(fset 'Helper-help-map Helper-help-map))
(defun Helper-help-scroller ()
(let ((blurb (or (and (boundp 'Helper-return-blurb)
Helper-return-blurb)
"return")))
(save-window-excursion
(goto-char (window-start))
(if (get-buffer-window "*Help*")
(pop-to-buffer "*Help*")
(switch-to-buffer "*Help*"))
(goto-char (point-min))
(let ((continue t) state)
(while continue
(setq state (+ (* 2 (if (pos-visible-in-window-p (point-max)) 1 0))
(if (pos-visible-in-window-p (point-min)) 1 0)))
(message
(nth state
'("Space forward, Delete back. Other keys %s"
"Space scrolls forward. Other keys %s"
"Delete scrolls back. Other keys %s"
"Type anything to %s"))
blurb)
(setq continue (read-event))
(cond ((and (memq continue '(?\s ?\C-v)) (< state 2))
(scroll-up))
((= continue ?\C-l)
(recenter))
((and (= continue ?\177) (zerop (% state 2)))
(scroll-down))
(t (setq continue nil))))))))
(defun Helper-help-options ()
"Describe help options."
(interactive)
(message "c (key briefly), m (mode), k (key), b (bindings)")
;(message "c (key briefly), m (mode), k (key), v (variable), f (function)")
(sit-for 4))
(defun Helper-describe-key-briefly (key)
"Briefly describe binding of KEY."
(interactive "kDescribe key briefly: ")
(describe-key-briefly key)
(sit-for 4))
(defun Helper-describe-key (key)
"Describe binding of KEY."
(interactive "kDescribe key: ")
(save-window-excursion (describe-key key))
(Helper-help-scroller))
(defun Helper-describe-function ()
"Describe a function. Name read interactively."
(interactive)
(save-window-excursion (call-interactively 'describe-function))
(Helper-help-scroller))
(defun Helper-describe-variable ()
"Describe a variable. Name read interactively."
(interactive)
(save-window-excursion (call-interactively 'describe-variable))
(Helper-help-scroller))
(defun Helper-describe-mode ()
"Describe the current mode."
(interactive)
(let ((name (format-mode-line mode-name))
(documentation (documentation major-mode)))
(with-current-buffer (get-buffer-create "*Help*")
(setq buffer-read-only nil)
(erase-buffer)
(insert name " Mode\n" documentation)
(help-mode)))
(Helper-help-scroller))
;;;###autoload
(defun Helper-describe-bindings ()
"Describe local key bindings of current mode."
(interactive)
(message "Making binding list...")
(save-window-excursion (describe-bindings))
(Helper-help-scroller))
;;;###autoload
(defun Helper-help ()
"Provide help for current mode."
(interactive)
(let ((continue t) c)
(while continue
(message "Help (Type ? for further options)")
(setq c (read-key-sequence nil))
(setq c (lookup-key Helper-help-map c))
(cond ((eq c 'Helper-help-options)
(Helper-help-options))
((commandp c)
(call-interactively c)
(setq continue nil))
(t
(ding)
(setq continue nil))))))
(provide 'helper)
;;; helper.el ends here
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