lisp/minibuf-eldef.el

   1 ;;; minibuf-eldef.el --- Only show defaults in prompts when applicable  -*- lexical-binding: t -*-
   2 ;;
   3 ;; Copyright (C) 2000-2018 Free Software Foundation, Inc.
   4 ;;
   5 ;; Author: Miles Bader <miles@gnu.org>
   6 ;; Keywords: convenience
   7
   8 ;; This file is part of GNU Emacs.
   9
  10 ;; GNU Emacs is free software: you can redistribute it and/or modify
  11 ;; it under the terms of the GNU General Public License as published by
  12 ;; the Free Software Foundation, either version 3 of the License, or
  13 ;; (at your option) any later version.
  14
  15 ;; GNU Emacs is distributed in the hope that it will be useful,
  16 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  17 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18 ;; GNU General Public License for more details.
  19
  20 ;; You should have received a copy of the GNU General Public License
  21 ;; along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.
  22
  23 ;;; Commentary:
  24 ;;
  25 ;; Defines the mode `minibuffer-electric-default-mode'.
  26 ;;
  27 ;; When active, minibuffer prompts that show a default value only show
  28 ;; the default when it's applicable -- that is, when hitting RET would
  29 ;; yield the default value.  If the user modifies the input such that
  30 ;; hitting RET would enter a non-default value, the prompt is modified
  31 ;; to remove the default indication (which is restored if the input is
  32 ;; ever restore to the match the initial input).
  33
  34 ;;; Code:
  35
  36 (defvar minibuffer-eldef-shorten-default)
  37
  38 (defun minibuffer-default--in-prompt-regexps ()
  39   `(("\\( (default\\(?: is\\)? \\(.*\\))\\):? \\'"
  40      1 ,(if minibuffer-eldef-shorten-default " [\\2]"))
  41     ("([^(]+?\\(, default\\(?: is\\)? \\(.*\\)\\)):? \\'" 1)
  42     ("\\( \\[.*\\]\\):? *\\'" 1)))
  43
  44 (defcustom minibuffer-eldef-shorten-default nil
  45   "If non-nil, shorten \"(default ...)\" to \"[...]\" in minibuffer prompts."
  46   :set (lambda (symbol value)
  47          (set-default symbol value)
  48          (setq-default minibuffer-default-in-prompt-regexps
  49                        (minibuffer-default--in-prompt-regexps)))
  50   :type 'boolean
  51   :group 'minibuffer
  52   :version "24.3")
  53
  54 (defvar minibuffer-default-in-prompt-regexps
  55   (minibuffer-default--in-prompt-regexps)
  56   "A list of regexps matching the parts of minibuffer prompts showing defaults.
  57 When `minibuffer-electric-default-mode' is active, these regexps are
  58 used to identify the portions of prompts to elide.
  59
  60 Each entry is of the form (REGEXP MATCH-NUM &optional REWRITE),
  61 where REGEXP should match the default part of the prompt,
  62 MATCH-NUM is the subgroup that matched the actual default indicator,
  63 and REWRITE, if present, is a string to pass to `replace-match' that
  64 should be displayed in its place.")
  65
  66 \f
  67 ;;; Internal variables
  68
  69 ;; A list of minibuffers to which we've added a post-command-hook.
  70 (defvar minibuf-eldef-frobbed-minibufs nil)
  71
  72 ;;; The following are all local variables in the minibuffer
  73
  74 ;; Input pre-inserted into the minibuffer before the user can edit it.
  75 (defvar minibuf-eldef-initial-input)
  76 (make-variable-buffer-local 'minibuf-eldef-initial-input)
  77 ;; and the length of the buffer with it inserted.
  78 (defvar minibuf-eldef-initial-buffer-length)
  79 (make-variable-buffer-local 'minibuf-eldef-initial-buffer-length)
  80
  81 ;; True if the current minibuffer prompt contains the default spec.
  82 (defvar minibuf-eldef-showing-default-in-prompt)
  83 (make-variable-buffer-local 'minibuf-eldef-showing-default-in-prompt)
  84
  85 ;; An overlay covering the default portion of the prompt
  86 (defvar minibuf-eldef-overlay)
  87 (make-variable-buffer-local 'minibuf-eldef-overlay)
  88
  89 \f
  90 ;;; Hook functions
  91
  92 ;; This function goes on minibuffer-setup-hook
  93 (defun minibuf-eldef-setup-minibuffer ()
  94   "Set up a minibuffer for `minibuffer-electric-default-mode'.
  95 The prompt and initial input should already have been inserted."
  96   (let ((regexps minibuffer-default-in-prompt-regexps)
  97         (match nil)
  98         (inhibit-point-motion-hooks t))
  99     (save-excursion
 100       (save-restriction
 101         ;; Narrow to only the prompt.
 102         (goto-char (point-min))
 103         (narrow-to-region (point) (minibuffer-prompt-end))
 104         ;; See if the prompt contains a default input indicator.
 105         (while regexps
 106           (setq match (pop regexps))
 107           (cond
 108            ((not (re-search-forward (if (stringp match) match (car match))
 109                                     nil t))
 110             ;; No match yet, try the next rule.
 111             (setq match nil))
 112            ((and (consp (cdr-safe match)) (nth 2 match))
 113             ;; Matched a replacement rule.
 114             (let* ((inhibit-read-only t)
 115                    (buffer-undo-list t)
 116                    (submatch (nth 1 match))
 117                    (replacement (nth 2 match))
 118                    (props (text-properties-at (match-beginning submatch))))
 119               (replace-match replacement nil nil nil submatch)
 120               (set-text-properties (match-beginning submatch)
 121                                    (match-end submatch)
 122                                    props)
 123               ;; Replacement done, now keep trying with subsequent rules.
 124               (setq match nil)
 125               (goto-char (point-min))))
 126            ;; Matched a non-replacement (i.e. electric hide) rule, no need to
 127            ;; keep trying.
 128            (t (setq regexps nil))))))
 129     (if (not match)
 130         ;; No match for electric hiding, so just make sure our
 131         ;; post-command-hook isn't left around.
 132         (remove-hook 'post-command-hook #'minibuf-eldef-update-minibuffer t)
 133       ;; Yup; set things up so we can frob the prompt as the state of
 134       ;; the input string changes.
 135       (setq match (if (consp match) (cdr match) 0))
 136       (setq match (if (consp match) (car match) match))
 137       (setq minibuf-eldef-overlay
 138             (make-overlay (match-beginning match) (match-end match)))
 139       (setq minibuf-eldef-showing-default-in-prompt t)
 140       (setq minibuf-eldef-initial-input
 141             (minibuffer-contents-no-properties))
 142       (setq minibuf-eldef-initial-buffer-length (point-max))
 143       (add-to-list 'minibuf-eldef-frobbed-minibufs (current-buffer))
 144       (add-hook 'post-command-hook #'minibuf-eldef-update-minibuffer nil t))))
 145
 146 ;; post-command-hook to swap prompts when necessary
 147 (defun minibuf-eldef-update-minibuffer ()
 148   "Update a minibuffer's prompt to include a default only when applicable.
 149 This is intended to be used as a minibuffer post-command-hook for
 150 `minibuffer-electric-default-mode'; the minibuffer should have already
 151 been set up by `minibuf-eldef-setup-minibuffer'."
 152   (unless (eq minibuf-eldef-showing-default-in-prompt
 153               (and (= (point-max) minibuf-eldef-initial-buffer-length)
 154                    (string-equal (minibuffer-contents-no-properties)
 155                                  minibuf-eldef-initial-input)))
 156     ;; Swap state.
 157     (setq minibuf-eldef-showing-default-in-prompt
 158           (not minibuf-eldef-showing-default-in-prompt))
 159     (overlay-put minibuf-eldef-overlay 'invisible
 160                  (not minibuf-eldef-showing-default-in-prompt))))
 161
 162 \f
 163 ;;;###autoload
 164 (define-minor-mode minibuffer-electric-default-mode
 165   "Toggle Minibuffer Electric Default mode.
 166
 167 Minibuffer Electric Default mode is a global minor mode.  When
 168 enabled, minibuffer prompts that show a default value only show
 169 the default when it's applicable -- that is, when hitting RET
 170 would yield the default value.  If the user modifies the input
 171 such that hitting RET would enter a non-default value, the prompt
 172 is modified to remove the default indication."
 173   :global t
 174   :group 'minibuffer
 175   (if minibuffer-electric-default-mode
 176       ;; Enable the mode
 177       (add-hook 'minibuffer-setup-hook 'minibuf-eldef-setup-minibuffer)
 178     ;; Disable the mode
 179     (remove-hook 'minibuffer-setup-hook 'minibuf-eldef-setup-minibuffer)
 180     ;; Remove our entry from any post-command-hook variable's it's still in
 181     (dolist (minibuf minibuf-eldef-frobbed-minibufs)
 182       (with-current-buffer minibuf
 183         (remove-hook 'post-command-hook #'minibuf-eldef-update-minibuffer t)))
 184     (setq minibuf-eldef-frobbed-minibufs nil)))
 185
 186
 187 (provide 'minibuf-eldef)
 188
 189 ;;; minibuf-eldef.el ends here