lisp/emacs-lisp/helper.el

   1 ;;; helper.el --- utility help package supporting help in electric modes
   2
   3 ;; Copyright (C) 1985, 2001-2014 Free Software Foundation, Inc.
   4
   5 ;; Author: K. Shane Hartman
   6 ;; Maintainer: FSF
   7 ;; Keywords: help
   8 ;; Package: emacs
   9
  10 ;; This file is part of GNU Emacs.
  11
  12 ;; GNU Emacs is free software: you can redistribute it and/or modify
  13 ;; it under the terms of the GNU General Public License as published by
  14 ;; the Free Software Foundation, either version 3 of the License, or
  15 ;; (at your option) any later version.
  16
  17 ;; GNU Emacs is distributed in the hope that it will be useful,
  18 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  19 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20 ;; GNU General Public License for more details.
  21
  22 ;; You should have received a copy of the GNU General Public License
  23 ;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
  24
  25 ;;; Commentary:
  26
  27 ;;; Code:
  28
  29 ;; hey, here's a helping hand.
  30
  31 ;; Bind this to a string for <blank> in "... Other keys <blank>".
  32 ;; Helper-help uses this to construct help string when scrolling.
  33 ;; Defaults to "return"
  34 (defvar Helper-return-blurb nil)
  35
  36 ;; Keymap implementation doesn't work too well for non-standard loops.
  37 ;; But define it anyway for those who can use it.  Non-standard loops
  38 ;; will probably have to use Helper-help.  You can't autoload the
  39 ;; keymap either.
  40
  41
  42 (defvar Helper-help-map nil)
  43 (if Helper-help-map
  44     nil
  45   (setq Helper-help-map (make-keymap))
  46   ;(fillarray Helper-help-map 'undefined)
  47   (define-key Helper-help-map "m" 'Helper-describe-mode)
  48   (define-key Helper-help-map "b" 'Helper-describe-bindings)
  49   (define-key Helper-help-map "c" 'Helper-describe-key-briefly)
  50   (define-key Helper-help-map "k" 'Helper-describe-key)
  51   ;(define-key Helper-help-map "f" 'Helper-describe-function)
  52   ;(define-key Helper-help-map "v" 'Helper-describe-variable)
  53   (define-key Helper-help-map "?" 'Helper-help-options)
  54   (define-key Helper-help-map (char-to-string help-char) 'Helper-help-options)
  55   (fset 'Helper-help-map Helper-help-map))
  56
  57 (defun Helper-help-scroller ()
  58   (let ((blurb (or (and (boundp 'Helper-return-blurb)
  59                         Helper-return-blurb)
  60                    "return")))
  61     (save-window-excursion
  62       (goto-char (window-start))
  63       (if (get-buffer-window "*Help*")
  64           (pop-to-buffer "*Help*")
  65         (switch-to-buffer "*Help*"))
  66       (goto-char (point-min))
  67       (let ((continue t) state)
  68         (while continue
  69           (setq state (+ (* 2 (if (pos-visible-in-window-p (point-max)) 1 0))
  70                          (if (pos-visible-in-window-p (point-min)) 1 0)))
  71           (message
  72             (nth state
  73                  '("Space forward, Delete back. Other keys %s"
  74                    "Space scrolls forward. Other keys %s"
  75                    "Delete scrolls back. Other keys %s"
  76                    "Type anything to %s"))
  77             blurb)
  78           (setq continue (read-event))
  79           (cond ((and (memq continue '(?\s ?\C-v)) (< state 2))
  80                  (scroll-up))
  81                 ((= continue ?\C-l)
  82                  (recenter))
  83                 ((and (= continue ?\177) (zerop (% state 2)))
  84                  (scroll-down))
  85                 (t (setq continue nil))))))))
  86
  87 (defun Helper-help-options ()
  88   "Describe help options."
  89   (interactive)
  90   (message "c (key briefly), m (mode), k (key), b (bindings)")
  91   ;(message "c (key briefly), m (mode), k (key), v (variable), f (function)")
  92   (sit-for 4))
  93
  94 (defun Helper-describe-key-briefly (key)
  95   "Briefly describe binding of KEY."
  96   (interactive "kDescribe key briefly: ")
  97   (describe-key-briefly key)
  98   (sit-for 4))
  99
 100 (defun Helper-describe-key (key)
 101   "Describe binding of KEY."
 102   (interactive "kDescribe key: ")
 103   (save-window-excursion (describe-key key))
 104   (Helper-help-scroller))
 105
 106 (defun Helper-describe-function ()
 107   "Describe a function.  Name read interactively."
 108   (interactive)
 109   (save-window-excursion (call-interactively 'describe-function))
 110   (Helper-help-scroller))
 111
 112 (defun Helper-describe-variable ()
 113   "Describe a variable.  Name read interactively."
 114   (interactive)
 115   (save-window-excursion (call-interactively 'describe-variable))
 116   (Helper-help-scroller))
 117
 118 (defun Helper-describe-mode ()
 119   "Describe the current mode."
 120   (interactive)
 121   (let ((name (format-mode-line mode-name))
 122         (documentation (documentation major-mode)))
 123     (with-current-buffer (get-buffer-create "*Help*")
 124       (setq buffer-read-only nil)
 125       (erase-buffer)
 126       (insert name " Mode\n" documentation)
 127       (help-mode)))
 128   (Helper-help-scroller))
 129
 130 ;;;###autoload
 131 (defun Helper-describe-bindings ()
 132   "Describe local key bindings of current mode."
 133   (interactive)
 134   (message "Making binding list...")
 135   (save-window-excursion (describe-bindings))
 136   (Helper-help-scroller))
 137
 138 ;;;###autoload
 139 (defun Helper-help ()
 140   "Provide help for current mode."
 141   (interactive)
 142   (let ((continue t) c)
 143     (while continue
 144       (message "Help (Type ? for further options)")
 145       (setq c (read-key-sequence nil))
 146       (setq c (lookup-key Helper-help-map c))
 147       (cond ((eq c 'Helper-help-options)
 148              (Helper-help-options))
 149             ((commandp c)
 150              (call-interactively c)
 151              (setq continue nil))
 152             (t
 153              (ding)
 154              (setq continue nil))))))
 155
 156 (provide 'helper)
 157
 158 ;;; helper.el ends here