lisp/emacs-lisp/helper.el

   1 ;;; helper.el --- utility help package supporting help in electric modes
   2
   3 ;; Copyright (C) 1985 Free Software Foundation, Inc.
   4
   5 ;; Author: K. Shane Hartman
   6 ;; Maintainer: FSF
   7 ;; Keywords: help
   8
   9 ;; This file is part of GNU Emacs.
  10
  11 ;; GNU Emacs is free software; you can redistribute it and/or modify
  12 ;; it under the terms of the GNU General Public License as published by
  13 ;; the Free Software Foundation; either version 2, or (at your option)
  14 ;; any later version.
  15
  16 ;; GNU Emacs is distributed in the hope that it will be useful,
  17 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  18 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19 ;; GNU General Public License for more details.
  20
  21 ;; You should have received a copy of the GNU General Public License
  22 ;; along with GNU Emacs; see the file COPYING.  If not, write to the
  23 ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  24 ;; Boston, MA 02111-1307, USA.
  25
  26 ;;; Commentary:
  27
  28 ;;; Code:
  29
  30 ;; hey, here's a helping hand.
  31
  32 ;; Bind this to a string for <blank> in "... Other keys <blank>".
  33 ;; Helper-help uses this to construct help string when scrolling.
  34 ;; Defaults to "return"
  35 (defvar Helper-return-blurb nil)
  36
  37 ;; Keymap implementation doesn't work too well for non-standard loops.
  38 ;; But define it anyway for those who can use it.  Non-standard loops
  39 ;; will probably have to use Helper-help.  You can't autoload the
  40 ;; keymap either.
  41
  42
  43 (defvar Helper-help-map nil)
  44 (if Helper-help-map
  45     nil
  46   (setq Helper-help-map (make-keymap))
  47   ;(fillarray Helper-help-map 'undefined)
  48   (define-key Helper-help-map "m" 'Helper-describe-mode)
  49   (define-key Helper-help-map "b" 'Helper-describe-bindings)
  50   (define-key Helper-help-map "c" 'Helper-describe-key-briefly)
  51   (define-key Helper-help-map "k" 'Helper-describe-key)
  52   ;(define-key Helper-help-map "f" 'Helper-describe-function)
  53   ;(define-key Helper-help-map "v" 'Helper-describe-variable)
  54   (define-key Helper-help-map "?" 'Helper-help-options)
  55   (define-key Helper-help-map (char-to-string help-char) 'Helper-help-options)
  56   (fset 'Helper-help-map Helper-help-map))
  57
  58 (defun Helper-help-scroller ()
  59   (let ((blurb (or (and (boundp 'Helper-return-blurb)
  60                         Helper-return-blurb)
  61                    "return")))
  62     (save-window-excursion
  63       (goto-char (window-start (selected-window)))
  64       (if (get-buffer-window "*Help*")
  65           (pop-to-buffer "*Help*")
  66         (switch-to-buffer "*Help*"))
  67       (goto-char (point-min))
  68       (let ((continue t) state)
  69         (while continue
  70           (setq state (+ (* 2 (if (pos-visible-in-window-p (point-max)) 1 0))
  71                          (if (pos-visible-in-window-p (point-min)) 1 0)))
  72           (message
  73             (nth state
  74                  '("Space forward, Delete back. Other keys %s"
  75                    "Space scrolls forward. Other keys %s"
  76                    "Delete scrolls back. Other keys %s"
  77                    "Type anything to %s"))
  78             blurb)
  79           (setq continue (read-char))
  80           (cond ((and (memq continue '(?\ ?\C-v)) (< state 2))
  81                  (scroll-up))
  82                 ((= continue ?\C-l)
  83                  (recenter))
  84                 ((and (= continue ?\177) (zerop (% state 2)))
  85                  (scroll-down))
  86                 (t (setq continue nil))))))))
  87
  88 (defun Helper-help-options ()
  89   "Describe help options."
  90   (interactive)
  91   (message "c (key briefly), m (mode), k (key), b (bindings)")
  92   ;(message "c (key briefly), m (mode), k (key), v (variable), f (function)")
  93   (sit-for 4))
  94
  95 (defun Helper-describe-key-briefly (key)
  96   "Briefly describe binding of KEY."
  97   (interactive "kDescribe key briefly: ")
  98   (describe-key-briefly key)
  99   (sit-for 4))
 100
 101 (defun Helper-describe-key (key)
 102   "Describe binding of KEY."
 103   (interactive "kDescribe key: ")
 104   (save-window-excursion (describe-key key))
 105   (Helper-help-scroller))
 106
 107 (defun Helper-describe-function ()
 108   "Describe a function.  Name read interactively."
 109   (interactive)
 110   (save-window-excursion (call-interactively 'describe-function))
 111   (Helper-help-scroller))
 112
 113 (defun Helper-describe-variable ()
 114   "Describe a variable.  Name read interactively."
 115   (interactive)
 116   (save-window-excursion (call-interactively 'describe-variable))
 117   (Helper-help-scroller))
 118
 119 (defun Helper-describe-mode ()
 120   "Describe the current mode."
 121   (interactive)
 122   (let ((name mode-name)
 123         (documentation (documentation major-mode)))
 124     (save-excursion
 125       (set-buffer (get-buffer-create "*Help*"))
 126       (setq buffer-read-only nil)
 127       (erase-buffer)
 128       (insert name " Mode\n" documentation)
 129       (help-mode)))
 130   (Helper-help-scroller))
 131
 132 ;;;###autoload
 133 (defun Helper-describe-bindings ()
 134   "Describe local key bindings of current mode."
 135   (interactive)
 136   (message "Making binding list...")
 137   (save-window-excursion (describe-bindings))
 138   (Helper-help-scroller))
 139
 140 ;;;###autoload
 141 (defun Helper-help ()
 142   "Provide help for current mode."
 143   (interactive)
 144   (let ((continue t) c)
 145     (while continue
 146       (message "Help (Type ? for further options)")
 147       (setq c (read-key-sequence nil))
 148       (setq c (lookup-key Helper-help-map c))
 149       (cond ((eq c 'Helper-help-options)
 150              (Helper-help-options))
 151             ((commandp c)
 152              (call-interactively c)
 153              (setq continue nil))
 154             (t
 155              (ding)
 156              (setq continue nil))))))
 157
 158 (provide 'helper)
 159
 160 ;;; helper.el ends here