;;; rmc.el --- read from a multiple choice question -*- lexical-binding: t -*-
;; Copyright (C) 2016-2017 Free Software Foundation, Inc.
;; Maintainer: emacs-devel@gnu.org
;; 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:
(require 'seq)
;;;###autoload
(defun read-multiple-choice (prompt choices)
"Ask user a multiple choice question.
PROMPT should be a string that will be displayed as the prompt.
CHOICES is an alist where the first element in each entry is a
character to be entered, the second element is a short name for
the entry to be displayed while prompting (if there's room, it
might be shortened), and the third, optional entry is a longer
explanation that will be displayed in a help buffer if the user
requests more help.
This function translates user input into responses by consulting
the bindings in `query-replace-map'; see the documentation of
that variable for more information. In this case, the useful
bindings are `recenter', `scroll-up', and `scroll-down'. If the
user enters `recenter', `scroll-up', or `scroll-down' responses,
perform the requested window recentering or scrolling and ask
again.
When `use-dialog-box' is t (the default), this function can pop
up a dialog window to collect the user input. That functionality
requires `display-popup-menus-p' to return t. Otherwise, a text
dialog will be used.
The return value is the matching entry from the CHOICES list.
Usage example:
\(read-multiple-choice \"Continue connecting?\"
\\='((?a \"always\")
(?s \"session only\")
(?n \"no\")))"
(let* ((altered-names nil)
(full-prompt
(format
"%s (%s): "
prompt
(mapconcat
(lambda (elem)
(let* ((name (cadr elem))
(pos (seq-position name (car elem)))
(altered-name
(cond
;; Not in the name string.
((not pos)
(format "[%c] %s" (car elem) name))
;; The prompt character is in the name, so highlight
;; it on graphical terminals...
((display-supports-face-attributes-p
'(:underline t) (window-frame))
(setq name (copy-sequence name))
(put-text-property pos (1+ pos)
'face 'read-multiple-choice-face
name)
name)
;; And put it in [bracket] on non-graphical terminals.
(t
(concat
(substring name 0 pos)
"["
(upcase (substring name pos (1+ pos)))
"]"
(substring name (1+ pos)))))))
(push (cons (car elem) altered-name)
altered-names)
altered-name))
(append choices '((?? "?")))
", ")))
tchar buf wrong-char answer)
(save-window-excursion
(save-excursion
(while (not tchar)
(message "%s%s"
(if wrong-char
"Invalid choice. "
"")
full-prompt)
(setq tchar
(if (and (display-popup-menus-p)
last-input-event ; not during startup
(listp last-nonmenu-event)
use-dialog-box)
(x-popup-dialog
t
(cons prompt
(mapcar
(lambda (elem)
(cons (capitalize (cadr elem))
(car elem)))
choices)))
(condition-case nil
(let ((cursor-in-echo-area t))
(read-char))
(error nil))))
(setq answer (lookup-key query-replace-map (vector tchar) t))
(setq tchar
(cond
((eq answer 'recenter)
(recenter) t)
((eq answer 'scroll-up)
(ignore-errors (scroll-up-command)) t)
((eq answer 'scroll-down)
(ignore-errors (scroll-down-command)) t)
((eq answer 'scroll-other-window)
(ignore-errors (scroll-other-window)) t)
((eq answer 'scroll-other-window-down)
(ignore-errors (scroll-other-window-down)) t)
(t tchar)))
(when (eq tchar t)
(setq wrong-char nil
tchar nil))
;; The user has entered an invalid choice, so display the
;; help messages.
(when (and (not (eq tchar nil))
(not (assq tchar choices)))
(setq wrong-char (not (memq tchar '(?? ?\C-h)))
tchar nil)
(when wrong-char
(ding))
(with-help-window (setq buf (get-buffer-create
"*Multiple Choice Help*"))
(with-current-buffer buf
(erase-buffer)
(pop-to-buffer buf)
(insert prompt "\n\n")
(let* ((columns (/ (window-width) 25))
(fill-column 21)
(times 0)
(start (point)))
(dolist (elem choices)
(goto-char start)
(unless (zerop times)
(if (zerop (mod times columns))
;; Go to the next "line".
(goto-char (setq start (point-max)))
;; Add padding.
(while (not (eobp))
(end-of-line)
(insert (make-string (max (- (* (mod times columns)
(+ fill-column 4))
(current-column))
0)
?\s))
(forward-line 1))))
(setq times (1+ times))
(let ((text
(with-temp-buffer
(insert (format
"%c: %s\n"
(car elem)
(cdr (assq (car elem) altered-names))))
(fill-region (point-min) (point-max))
(when (nth 2 elem)
(let ((start (point)))
(insert (nth 2 elem))
(unless (bolp)
(insert "\n"))
(fill-region start (point-max))))
(buffer-string))))
(goto-char start)
(dolist (line (split-string text "\n"))
(end-of-line)
(if (bolp)
(insert line "\n")
(insert line))
(forward-line 1)))))))))))
(when (buffer-live-p buf)
(kill-buffer buf))
(assq tchar choices)))
(provide 'rmc)
;;; rmc.el ends here