lisp/minibuf-eldef.el

   1 ;;; minibuf-eldef.el --- Only show defaults in prompts when applicable
   2 ;;
   3 ;; Copyright (C) 2000-2011 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-default-in-prompt-regexps
  37   '(("\\( (default\\>.*)\\):? \\'" . 1) ("\\( \\[.*\\]\\):? *\\'" . 1))
  38   "*A list of regexps matching the parts of minibuffer prompts showing defaults.
  39 When `minibuffer-electric-default-mode' is active, these regexps are
  40 used to identify the portions of prompts to elide.
  41
  42 Each entry is either a string, which should be a regexp matching the
  43 default portion of the prompt, or a cons cell, who's car is a regexp
  44 matching the default part of the prompt, and who's cdr indicates the
  45 regexp subexpression that matched.")
  46
  47 \f
  48 ;;; Internal variables
  49
  50 ;; A list of minibuffers to which we've added a post-command-hook.
  51 (defvar minibuf-eldef-frobbed-minibufs nil)
  52
  53 ;;; The following are all local variables in the minibuffer
  54
  55 ;; Input pre-inserted into the minibuffer before the user can edit it.
  56 (defvar minibuf-eldef-initial-input)
  57 (make-variable-buffer-local 'minibuf-eldef-initial-input)
  58 ;; and the length of the buffer with it inserted.
  59 (defvar minibuf-eldef-initial-buffer-length)
  60 (make-variable-buffer-local 'minibuf-eldef-initial-buffer-length)
  61
  62 ;; True if the current minibuffer prompt contains the default spec.
  63 (defvar minibuf-eldef-showing-default-in-prompt)
  64 (make-variable-buffer-local 'minibuf-eldef-showing-default-in-prompt)
  65
  66 ;; An overlay covering the default portion of the prompt
  67 (defvar minibuf-eldef-overlay)
  68 (make-variable-buffer-local 'minibuf-eldef-overlay)
  69
  70 \f
  71 ;;; Hook functions
  72
  73 ;; This function goes on minibuffer-setup-hook
  74 (defun minibuf-eldef-setup-minibuffer ()
  75   "Set up a minibuffer for `minibuffer-electric-default-mode'.
  76 The prompt and initial input should already have been inserted."
  77   (let ((regexps minibuffer-default-in-prompt-regexps)
  78         (match nil)
  79         (inhibit-point-motion-hooks t))
  80     (save-excursion
  81       (save-restriction
  82         ;; Narrow to only the prompt
  83         (goto-char (point-min))
  84         (narrow-to-region (point) (minibuffer-prompt-end))
  85         ;; See the prompt contains a default input indicator
  86         (while regexps
  87           (setq match (pop regexps))
  88           (if (re-search-forward (if (stringp match) match (car match)) nil t)
  89               (setq regexps nil)
  90             (setq match nil)))))
  91     (if (not match)
  92         ;; Nope, so just make sure our post-command-hook isn't left around.
  93         (remove-hook 'post-command-hook #'minibuf-eldef-update-minibuffer t)
  94       ;; Yup; set things up so we can frob the prompt as the state of
  95       ;; the input string changes.
  96       (setq match (if (consp match) (cdr match) 0))
  97       (setq minibuf-eldef-overlay
  98             (make-overlay (match-beginning match) (match-end match)))
  99       (setq minibuf-eldef-showing-default-in-prompt t)
 100       (setq minibuf-eldef-initial-input
 101             (minibuffer-contents-no-properties))
 102       (setq minibuf-eldef-initial-buffer-length (point-max))
 103       (add-to-list 'minibuf-eldef-frobbed-minibufs (current-buffer))
 104       (add-hook 'post-command-hook #'minibuf-eldef-update-minibuffer nil t))))
 105
 106 ;; post-command-hook to swap prompts when necessary
 107 (defun minibuf-eldef-update-minibuffer ()
 108   "Update a minibuffer's prompt to include a default only when applicable.
 109 This is intended to be used as a minibuffer post-command-hook for
 110 `minibuffer-electric-default-mode'; the minibuffer should have already
 111 been set up by `minibuf-eldef-setup-minibuffer'."
 112   (unless (eq minibuf-eldef-showing-default-in-prompt
 113               (and (= (point-max) minibuf-eldef-initial-buffer-length)
 114                    (string-equal (minibuffer-contents-no-properties)
 115                                  minibuf-eldef-initial-input)))
 116     ;; swap state
 117     (setq minibuf-eldef-showing-default-in-prompt
 118           (not minibuf-eldef-showing-default-in-prompt))
 119     (cond (minibuf-eldef-showing-default-in-prompt
 120            (overlay-put minibuf-eldef-overlay 'invisible nil)
 121            (overlay-put minibuf-eldef-overlay 'intangible nil))
 122           (t
 123            (overlay-put minibuf-eldef-overlay 'invisible t)
 124            (overlay-put minibuf-eldef-overlay 'intangible t)))))
 125
 126 \f
 127 ;;; Note this definition must be at the end of the file, because
 128 ;;; `define-minor-mode' actually calls the mode-function if the
 129 ;;; associated variable is non-nil, which requires that all needed
 130 ;;; functions be already defined.  [This is arguably a bug in d-m-m]
 131 ;;;###autoload
 132 (define-minor-mode minibuffer-electric-default-mode
 133   "Toggle Minibuffer Electric Default mode.
 134 When active, minibuffer prompts that show a default value only show the
 135 default when it's applicable -- that is, when hitting RET would yield
 136 the default value.  If the user modifies the input such that hitting RET
 137 would enter a non-default value, the prompt is modified to remove the
 138 default indication.
 139
 140 With prefix argument ARG, turn on if positive, otherwise off.
 141 Returns non-nil if the new state is enabled."
 142   :global t
 143   :group 'minibuffer
 144   (if minibuffer-electric-default-mode
 145       ;; Enable the mode
 146       (add-hook 'minibuffer-setup-hook 'minibuf-eldef-setup-minibuffer)
 147     ;; Disable the mode
 148     (remove-hook 'minibuffer-setup-hook 'minibuf-eldef-setup-minibuffer)
 149     ;; Remove our entry from any post-command-hook variable's it's still in
 150     (dolist (minibuf minibuf-eldef-frobbed-minibufs)
 151       (with-current-buffer minibuf
 152         (remove-hook 'post-command-hook #'minibuf-eldef-update-minibuffer t)))
 153     (setq minibuf-eldef-frobbed-minibufs nil)))
 154
 155
 156 (provide 'minibuf-eldef)
 157
 158 ;;; minibuf-eldef.el ends here