lisp/image-file.el

   1 ;;; image-file.el --- support for visiting image files
   2 ;;
   3 ;; Copyright (C) 2000-2011 Free Software Foundation, Inc.
   4 ;;
   5 ;; Author: Miles Bader <miles@gnu.org>
   6 ;; Keywords: multimedia
   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 a file-name-handler hook that transforms visited (or
  26 ;; inserted) image files so that they are displayed by Emacs as
  27 ;; images.  This is done by putting a `display' text-property on the
  28 ;; image data, with the image-data still present underneath; if the
  29 ;; resulting buffer file is saved to another name it will correctly save
  30 ;; the image data to the new file.
  31
  32 ;;; Code:
  33
  34 (require 'image)
  35
  36
  37 ;;;###autoload
  38 (defcustom image-file-name-extensions
  39   (purecopy '("png" "jpeg" "jpg" "gif" "tiff" "tif" "xbm" "xpm" "pbm" "pgm" "ppm" "pnm" "svg"))
  40   "A list of image-file filename extensions.
  41 Filenames having one of these extensions are considered image files,
  42 in addition to those matching `image-file-name-regexps'.
  43
  44 See `auto-image-file-mode'; if `auto-image-file-mode' is enabled,
  45 setting this variable directly does not take effect unless
  46 `auto-image-file-mode' is re-enabled; this happens automatically when
  47 the variable is set using \\[customize]."
  48   :type '(repeat string)
  49   :set (lambda (sym val)
  50          (set-default sym val)
  51          (when auto-image-file-mode
  52            ;; Re-initialize the image-file handler
  53            (auto-image-file-mode t)))
  54   :initialize 'custom-initialize-default
  55   :group 'image)
  56
  57 ;;;###autoload
  58 (defcustom image-file-name-regexps nil
  59   "List of regexps matching image-file filenames.
  60 Filenames matching one of these regexps are considered image files,
  61 in addition to those with an extension in `image-file-name-extensions'.
  62
  63 See function `auto-image-file-mode'; if `auto-image-file-mode' is
  64 enabled, setting this variable directly does not take effect unless
  65 `auto-image-file-mode' is re-enabled; this happens automatically when
  66 the variable is set using \\[customize]."
  67   :type '(repeat regexp)
  68   :set (lambda (sym val)
  69          (set-default sym val)
  70          (when auto-image-file-mode
  71            ;; Re-initialize the image-file handler
  72            (auto-image-file-mode t)))
  73   :initialize 'custom-initialize-default
  74   :group 'image)
  75
  76
  77 ;;;###autoload
  78 (defun image-file-name-regexp ()
  79   "Return a regular expression matching image-file filenames."
  80   (let ((exts-regexp
  81          (and image-file-name-extensions
  82               (concat "\\."
  83                       (regexp-opt (nconc (mapcar #'upcase
  84                                                  image-file-name-extensions)
  85                                          image-file-name-extensions)
  86                                   t)
  87                       "\\'"))))
  88     (if image-file-name-regexps
  89         (mapconcat 'identity
  90                    (if exts-regexp
  91                        (cons exts-regexp image-file-name-regexps)
  92                      image-file-name-regexps)
  93                    "\\|")
  94       exts-regexp)))
  95
  96
  97 ;;;###autoload
  98 (defun insert-image-file (file &optional visit beg end replace)
  99   "Insert the image file FILE into the current buffer.
 100 Optional arguments VISIT, BEG, END, and REPLACE are interpreted as for
 101 the command `insert-file-contents'."
 102   (let ((rval
 103          (image-file-call-underlying #'insert-file-contents-literally
 104                                      'insert-file-contents
 105                                      file visit beg end replace)))
 106     ;; Turn the image data into a real image, but only if the whole file
 107     ;; was inserted
 108     (when (and (or (null beg) (zerop beg)) (null end))
 109       (let* ((ibeg (point))
 110              (iend (+ (point) (cadr rval)))
 111              (visitingp (and visit (= ibeg (point-min)) (= iend (point-max))))
 112              (data
 113               (string-make-unibyte
 114                (buffer-substring-no-properties ibeg iend)))
 115              (image
 116               (create-image data nil t))
 117              (props
 118               `(display ,image
 119                         yank-handler
 120                         (image-file-yank-handler nil t)
 121                         intangible ,image
 122                         rear-nonsticky (display intangible)
 123                         ;; This a cheap attempt to make the whole buffer
 124                         ;; read-only when we're visiting the file (as
 125                         ;; opposed to just inserting it).
 126                         ,@(and visitingp
 127                                '(read-only t front-sticky (read-only))))))
 128         (add-text-properties ibeg iend props)
 129         (when visitingp
 130           ;; Inhibit the cursor when the buffer contains only an image,
 131           ;; because cursors look very strange on top of images.
 132           (setq cursor-type nil)
 133           ;; This just makes the arrow displayed in the right fringe
 134           ;; area look correct when the image is wider than the window.
 135           (setq truncate-lines t))))
 136     rval))
 137
 138 ;; We use a yank-handler to make yanked images unique, so that
 139 ;; yanking two copies of the same image next to each other are
 140 ;; recognized as two different images.
 141 (defun image-file-yank-handler (string)
 142   "Yank handler for inserting an image into a buffer."
 143   (let ((len (length string))
 144         (image (get-text-property 0 'display string)))
 145     (remove-text-properties 0 len yank-excluded-properties string)
 146     (if (consp image)
 147         (add-text-properties 0
 148                              (or (next-single-property-change 0 'image-counter string)
 149                                  (length string))
 150                              `(display
 151                                ,(cons (car image) (cdr image))
 152                                yank-handler
 153                                ,(cons 'image-file-yank-handler '(nil t)))
 154                              string))
 155     (insert string)))
 156
 157 (put 'image-file-handler 'safe-magic t)
 158 (defun image-file-handler (operation &rest args)
 159   "Filename handler for inserting image files.
 160 OPERATION is the operation to perform, on ARGS.
 161 See `file-name-handler-alist' for details."
 162   (if (and (eq operation 'insert-file-contents)
 163            auto-image-file-mode)
 164       (apply #'insert-image-file args)
 165     ;; We don't handle OPERATION, use another handler or the default
 166     (apply #'image-file-call-underlying operation operation args)))
 167
 168 (defun image-file-call-underlying (function operation &rest args)
 169   "Call FUNCTION with `image-file-handler' and OPERATION inhibited.
 170 Optional argument ARGS are the arguments to call FUNCTION with."
 171   (let ((inhibit-file-name-handlers
 172          (cons 'image-file-handler
 173                (and (eq inhibit-file-name-operation operation)
 174                     inhibit-file-name-handlers)))
 175         (inhibit-file-name-operation operation))
 176     (apply function args)))
 177
 178
 179 ;;;###autoload
 180 (define-minor-mode auto-image-file-mode
 181   "Toggle visiting of image files as images.
 182 With prefix argument ARG, turn on if positive, otherwise off.
 183 Returns non-nil if the new state is enabled.
 184
 185 Image files are those whose name has an extension in
 186 `image-file-name-extensions', or matches a regexp in
 187 `image-file-name-regexps'."
 188   :global t
 189   :group 'image
 190   ;; Remove existing handler
 191   (let ((existing-entry
 192          (rassq 'image-file-handler file-name-handler-alist)))
 193     (when existing-entry
 194       (setq file-name-handler-alist
 195             (delq existing-entry file-name-handler-alist))))
 196   ;; Add new handler, if enabled
 197   (when auto-image-file-mode
 198     (push (cons (image-file-name-regexp) 'image-file-handler)
 199           file-name-handler-alist)))
 200
 201
 202 (provide 'image-file)
 203
 204 ;;; image-file.el ends here