lisp/minibuf-eldef.el

   1 ;;; minibuf-eldef.el --- Only show defaults in prompts when applicable  -*- lexical-binding: t -*-
   2 ;;
   3 ;; Copyright (C) 2000-2016 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 <http://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 With a prefix argument ARG, enable Minibuffer Electric Default
 167 mode if ARG is positive, and disable it otherwise.  If called
 168 from Lisp, enable the mode if ARG is omitted or nil.
 169
 170 Minibuffer Electric Default mode is a global minor mode.  When
 171 enabled, minibuffer prompts that show a default value only show
 172 the default when it's applicable -- that is, when hitting RET
 173 would yield the default value.  If the user modifies the input
 174 such that hitting RET would enter a non-default value, the prompt
 175 is modified to remove the default indication."
 176   :global t
 177   :group 'minibuffer
 178   (if minibuffer-electric-default-mode
 179       ;; Enable the mode
 180       (add-hook 'minibuffer-setup-hook 'minibuf-eldef-setup-minibuffer)
 181     ;; Disable the mode
 182     (remove-hook 'minibuffer-setup-hook 'minibuf-eldef-setup-minibuffer)
 183     ;; Remove our entry from any post-command-hook variable's it's still in
 184     (dolist (minibuf minibuf-eldef-frobbed-minibufs)
 185       (with-current-buffer minibuf
 186         (remove-hook 'post-command-hook #'minibuf-eldef-update-minibuffer t)))
 187     (setq minibuf-eldef-frobbed-minibufs nil)))
 188
 189
 190 (provide 'minibuf-eldef)
 191
 192 ;;; minibuf-eldef.el ends here