lisp/image-file.el

   1 ;;; image-file.el --- support for visiting image files
   2 ;;
   3 ;; Copyright (C) 2000-2017 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 (Auto Image File mode).
 182 With a prefix argument ARG, enable Auto Image File mode if ARG is
 183 positive, and disable it otherwise.  If called from Lisp, enable
 184 the mode if ARG is omitted or nil.
 185
 186 An image file is one whose name has an extension in
 187 `image-file-name-extensions', or matches a regexp in
 188 `image-file-name-regexps'."
 189   :global t
 190   :group 'image
 191   ;; Remove existing handler
 192   (let ((existing-entry
 193          (rassq 'image-file-handler file-name-handler-alist)))
 194     (when existing-entry
 195       (setq file-name-handler-alist
 196             (delq existing-entry file-name-handler-alist))))
 197   ;; Add new handler, if enabled
 198   (when auto-image-file-mode
 199     (push (cons (image-file-name-regexp) 'image-file-handler)
 200           file-name-handler-alist)))
 201
 202
 203 (provide 'image-file)
 204
 205 ;;; image-file.el ends here