lisp/emacs-lisp/helper.el

   1 ;;; helper.el --- utility help package supporting help in electric modes
   2
   3 ;; Author: K. Shane Hartman
   4 ;; Maintainer: FSF
   5 ;; Last-Modified: 16 Mar 1991
   6
   7 ;; Copyright (C) 1985 Free Software Foundation, Inc.
   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
  23 ;; the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
  24
  25 ;;; Code:
  26
  27 ; hey, here's a helping hand.
  28
  29 ;; Bind this to a string for <blank> in "... Other keys <blank>".
  30 ;; Helper-help uses this to construct help string when scrolling.
  31 ;; Defaults to "return"
  32 (defvar Helper-return-blurb nil)
  33
  34 ;; Keymap implementation doesn't work too well for non-standard loops.
  35 ;; But define it anyway for those who can use it.  Non-standard loops
  36 ;; will probably have to use Helper-help.  You can't autoload the
  37 ;; keymap either.
  38
  39
  40 (defvar Helper-help-map nil)
  41 (if Helper-help-map
  42     nil
  43   (setq Helper-help-map (make-keymap))
  44   ;(fillarray Helper-help-map 'undefined)
  45   (define-key Helper-help-map "m" 'Helper-describe-mode)
  46   (define-key Helper-help-map "b" 'Helper-describe-bindings)
  47   (define-key Helper-help-map "c" 'Helper-describe-key-briefly)
  48   (define-key Helper-help-map "k" 'Helper-describe-key)
  49   ;(define-key Helper-help-map "f" 'Helper-describe-function)
  50   ;(define-key Helper-help-map "v" 'Helper-describe-variable)
  51   (define-key Helper-help-map "?" 'Helper-help-options)
  52   (define-key Helper-help-map (char-to-string help-char) 'Helper-help-options)
  53   (fset 'Helper-help-map Helper-help-map))
  54
  55 (defun Helper-help-scroller ()
  56   (let ((blurb (or (and (boundp 'Helper-return-blurb)
  57                         Helper-return-blurb)
  58                    "return")))
  59     (save-window-excursion
  60       (goto-char (window-start (selected-window)))
  61       (if (get-buffer-window "*Help*")
  62           (pop-to-buffer "*Help*")
  63         (switch-to-buffer "*Help*"))
  64       (goto-char (point-min))
  65       (let ((continue t) state)
  66         (while continue
  67           (setq state (+ (* 2 (if (pos-visible-in-window-p (point-max)) 1 0))
  68                          (if (pos-visible-in-window-p (point-min)) 1 0)))
  69           (message
  70             (nth state
  71                  '("Space forward, Delete back. Other keys %s"
  72                    "Space scrolls forward. Other keys %s"
  73                    "Delete scrolls back. Other keys %s"
  74                    "Type anything to %s"))
  75             blurb)
  76           (setq continue (read-char))
  77           (cond ((and (memq continue '(?\ ?\C-v)) (< state 2))
  78                  (scroll-up))
  79                 ((= continue ?\C-l)
  80                  (recenter))
  81                 ((and (= continue ?\177) (zerop (% state 2)))
  82                  (scroll-down))
  83                 (t (setq continue nil))))))))
  84
  85 (defun Helper-help-options ()
  86   "Describe help options."
  87   (interactive)
  88   (message "c (key briefly), m (mode), k (key), b (bindings)")
  89   ;(message "c (key briefly), m (mode), k (key), v (variable), f (function)")
  90   (sit-for 4))
  91
  92 (defun Helper-describe-key-briefly (key)
  93   "Briefly describe binding of KEY."
  94   (interactive "kDescribe key briefly: ")
  95   (describe-key-briefly key)
  96   (sit-for 4))
  97
  98 (defun Helper-describe-key (key)
  99   "Describe binding of KEY."
 100   (interactive "kDescribe key: ")
 101   (save-window-excursion (describe-key key))
 102   (Helper-help-scroller))
 103
 104 (defun Helper-describe-function ()
 105   "Describe a function.  Name read interactively."
 106   (interactive)
 107   (save-window-excursion (call-interactively 'describe-function))
 108   (Helper-help-scroller))
 109
 110 (defun Helper-describe-variable ()
 111   "Describe a variable.  Name read interactively."
 112   (interactive)
 113   (save-window-excursion (call-interactively 'describe-variable))
 114   (Helper-help-scroller))
 115
 116 (defun Helper-describe-mode ()
 117   "Describe the current mode."
 118   (interactive)
 119   (let ((name mode-name)
 120         (documentation (documentation major-mode)))
 121     (save-excursion
 122       (set-buffer (get-buffer-create "*Help*"))
 123       (erase-buffer)
 124       (insert name " Mode\n" documentation)))
 125   (Helper-help-scroller))
 126
 127 ;;;###autoload
 128 (defun Helper-describe-bindings ()
 129   "Describe local key bindings of current mode."
 130   (interactive)
 131   (message "Making binding list...")
 132   (save-window-excursion (describe-bindings))
 133   (Helper-help-scroller))
 134
 135 ;;;###autoload
 136 (defun Helper-help ()
 137   "Provide help for current mode."
 138   (interactive)
 139   (let ((continue t) c)
 140     (while continue
 141       (message "Help (Type ? for further options)")
 142       (setq c (char-to-string (downcase (read-char))))
 143       (setq c (lookup-key Helper-help-map c))
 144       (cond ((eq c 'Helper-help-options)
 145              (Helper-help-options))
 146             ((commandp c)
 147              (call-interactively c)
 148              (setq continue nil))
 149             (t
 150              (ding)
 151              (setq continue nil))))))
 152
 153 (provide 'helper)
 154
 155 ;;; helper.el ends here