emacs/lisp/image-mode.el

;;; image-mode.el --- support for visiting image files
;;
;; Copyright (C) 2005-2011 Free Software Foundation, Inc.
;;
;; Author: Richard Stallman <rms@gnu.org>
;; Keywords: multimedia
;; Package: emacs

;; This file is part of GNU Emacs.

;; GNU Emacs is free software: you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.

;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.

;;; Commentary:

;; Defines a major mode for visiting image files
;; that allows conversion between viewing the text of the file
;; and viewing the file as an image.  Viewing the image
;; works by putting a `display' text-property on the
;; image data, with the image-data still present underneath; if the
;; resulting buffer file is saved to another name it will correctly save
;; the image data to the new file.

;;; Code:

(require 'image)
(eval-when-compile (require 'cl))

;;; Image mode window-info management.

(defvar image-mode-winprops-alist t)
(make-variable-buffer-local 'image-mode-winprops-alist)

(defvar image-mode-new-window-functions nil
  "Special hook run when image data is requested in a new window.
It is called with one argument, the initial WINPROPS.")

(defun image-mode-winprops (&optional window cleanup)
  "Return winprops of WINDOW.
A winprops object has the shape (WINDOW . ALIST)."
  (cond ((null window)
	 (setq window (selected-window)))
	((not (windowp window))
	 (error "Not a window: %s" window)))
  (when cleanup
    (setq image-mode-winprops-alist
  	  (delq nil (mapcar (lambda (winprop)
  			      (if (window-live-p (car-safe winprop))
  				  winprop))
  			    image-mode-winprops-alist))))
  (let ((winprops (assq window image-mode-winprops-alist)))
    ;; For new windows, set defaults from the latest.
    (unless winprops
      (setq winprops (cons window
                           (copy-alist (cdar image-mode-winprops-alist))))
      (run-hook-with-args 'image-mode-new-window-functions winprops))
    ;; Move window to front.
    (setq image-mode-winprops-alist
          (cons winprops (delq winprops image-mode-winprops-alist)))
    winprops))

(defun image-mode-window-get (prop &optional winprops)
  (unless (consp winprops) (setq winprops (image-mode-winprops winprops)))
  (cdr (assq prop (cdr winprops))))

(defsetf image-mode-window-get (prop &optional winprops) (val)
  `(image-mode-window-put ,prop ,val ,winprops))

(defun image-mode-window-put (prop val &optional winprops)
  (unless (consp winprops) (setq winprops (image-mode-winprops winprops)))
  (setcdr winprops (cons (cons prop val)
                         (delq (assq prop (cdr winprops)) (cdr winprops)))))

(defun image-set-window-vscroll (vscroll)
  (setf (image-mode-window-get 'vscroll) vscroll)
  (set-window-vscroll (selected-window) vscroll))

(defun image-set-window-hscroll (ncol)
  (setf (image-mode-window-get 'hscroll) ncol)
  (set-window-hscroll (selected-window) ncol))

(defun image-mode-reapply-winprops ()
  ;; When set-window-buffer, set hscroll and vscroll to what they were
  ;; last time the image was displayed in this window.
  (when (and (image-get-display-property)
	     (listp image-mode-winprops-alist))
    (let* ((winprops (image-mode-winprops nil t))
           (hscroll (image-mode-window-get 'hscroll winprops))
           (vscroll (image-mode-window-get 'vscroll winprops)))
      (if hscroll (set-window-hscroll (selected-window) hscroll))
      (if vscroll (set-window-vscroll (selected-window) vscroll)))))

(defun image-mode-setup-winprops ()
  ;; Record current scroll settings.
  (unless (listp image-mode-winprops-alist)
    (setq image-mode-winprops-alist nil))
  (add-hook 'window-configuration-change-hook
 	    'image-mode-reapply-winprops nil t))

;;; Image scrolling functions

(defun image-get-display-property ()
  (get-char-property (point-min) 'display
                     ;; There might be different images for different displays.
                     (if (eq (window-buffer) (current-buffer))
                         (selected-window))))

(declare-function image-size "image.c" (spec &optional pixels frame))

(defun image-display-size (spec &optional pixels frame)
  "Wrapper around `image-size', handling slice display properties.
Like `image-size', the return value is (WIDTH . HEIGHT).
WIDTH and HEIGHT are in canonical character units if PIXELS is
nil, and in pixel units if PIXELS is non-nil.

If SPEC is an image display property, this function is equivalent
to `image-size'.  If SPEC is a list of properties containing
`image' and `slice' properties, return the display size taking
the slice property into account.  If the list contains `image'
but not `slice', return the `image-size' of the specified image."
  (if (eq (car spec) 'image)
      (image-size spec pixels frame)
    (let ((image (assoc 'image spec))
	  (slice (assoc 'slice spec)))
      (cond ((and image slice)
	     (if pixels
		 (cons (nth 3 slice) (nth 4 slice))
	       (cons (/ (float (nth 3 slice)) (frame-char-width frame))
		     (/ (float (nth 4 slice)) (frame-char-height frame)))))
	    (image
	     (image-size image pixels frame))
	    (t
	     (error "Invalid image specification: %s" spec))))))

(defun image-forward-hscroll (&optional n)
  "Scroll image in current window to the left by N character widths.
Stop if the right edge of the image is reached."
  (interactive "p")
  (cond ((= n 0) nil)
	((< n 0)
	 (image-set-window-hscroll (max 0 (+ (window-hscroll) n))))
	(t
	 (let* ((image (image-get-display-property))
		(edges (window-inside-edges))
		(win-width (- (nth 2 edges) (nth 0 edges)))
		(img-width (ceiling (car (image-display-size image)))))
	   (image-set-window-hscroll (min (max 0 (- img-width win-width))
					  (+ n (window-hscroll))))))))

(defun image-backward-hscroll (&optional n)
  "Scroll image in current window to the right by N character widths.
Stop if the left edge of the image is reached."
  (interactive "p")
  (image-forward-hscroll (- n)))

(defun image-next-line (&optional n)
  "Scroll image in current window upward by N lines.
Stop if the bottom edge of the image is reached."
  (interactive "p")
  (cond ((= n 0) nil)
	((< n 0)
	 (image-set-window-vscroll (max 0 (+ (window-vscroll) n))))
	(t
	 (let* ((image (image-get-display-property))
		(edges (window-inside-edges))
		(win-height (- (nth 3 edges) (nth 1 edges)))
		(img-height (ceiling (cdr (image-display-size image)))))
	   (image-set-window-vscroll (min (max 0 (- img-height win-height))
					  (+ n (window-vscroll))))))))

(defun image-previous-line (&optional n)
  "Scroll image in current window downward by N lines.
Stop if the top edge of the image is reached."
  (interactive "p")
  (image-next-line (- n)))

(defun image-scroll-up (&optional n)
  "Scroll image in current window upward by N lines.
Stop if the bottom edge of the image is reached.
If ARG is omitted or nil, scroll upward by a near full screen.
A near full screen is `next-screen-context-lines' less than a full screen.
Negative ARG means scroll downward.
If ARG is the atom `-', scroll downward by nearly full screen.
When calling from a program, supply as argument a number, nil, or `-'."
  (interactive "P")
  (cond ((null n)
	 (let* ((edges (window-inside-edges))
		(win-height (- (nth 3 edges) (nth 1 edges))))
	   (image-next-line
	    (max 0 (- win-height next-screen-context-lines)))))
	((eq n '-)
	 (let* ((edges (window-inside-edges))
		(win-height (- (nth 3 edges) (nth 1 edges))))
	   (image-next-line
	    (min 0 (- next-screen-context-lines win-height)))))
	(t (image-next-line (prefix-numeric-value n)))))

(defun image-scroll-down (&optional n)
  "Scroll image in current window downward by N lines.
Stop if the top edge of the image is reached.
If ARG is omitted or nil, scroll downward by a near full screen.
A near full screen is `next-screen-context-lines' less than a full screen.
Negative ARG means scroll upward.
If ARG is the atom `-', scroll upward by nearly full screen.
When calling from a program, supply as argument a number, nil, or `-'."
  (interactive "P")
  (cond ((null n)
	 (let* ((edges (window-inside-edges))
		(win-height (- (nth 3 edges) (nth 1 edges))))
	   (image-next-line
	    (min 0 (- next-screen-context-lines win-height)))))
	((eq n '-)
	 (let* ((edges (window-inside-edges))
		(win-height (- (nth 3 edges) (nth 1 edges))))
	   (image-next-line
	    (max 0 (- win-height next-screen-context-lines)))))
	(t (image-next-line (- (prefix-numeric-value n))))))

(defun image-bol (arg)
  "Scroll horizontally to the left edge of the image in the current window.
With argument ARG not nil or 1, move forward ARG - 1 lines first,
stopping if the top or bottom edge of the image is reached."
  (interactive "p")
  (and arg
       (/= (setq arg (prefix-numeric-value arg)) 1)
       (image-next-line (- arg 1)))
  (image-set-window-hscroll 0))

(defun image-eol (arg)
  "Scroll horizontally to the right edge of the image in the current window.
With argument ARG not nil or 1, move forward ARG - 1 lines first,
stopping if the top or bottom edge of the image is reached."
  (interactive "p")
  (and arg
       (/= (setq arg (prefix-numeric-value arg)) 1)
       (image-next-line (- arg 1)))
  (let* ((image (image-get-display-property))
	 (edges (window-inside-edges))
	 (win-width (- (nth 2 edges) (nth 0 edges)))
	 (img-width (ceiling (car (image-display-size image)))))
    (image-set-window-hscroll (max 0 (- img-width win-width)))))

(defun image-bob ()
  "Scroll to the top-left corner of the image in the current window."
  (interactive)
  (image-set-window-hscroll 0)
  (image-set-window-vscroll 0))

(defun image-eob ()
  "Scroll to the bottom-right corner of the image in the current window."
  (interactive)
  (let* ((image (image-get-display-property))
	 (edges (window-inside-edges))
	 (win-width (- (nth 2 edges) (nth 0 edges)))
	 (img-width (ceiling (car (image-display-size image))))
	 (win-height (- (nth 3 edges) (nth 1 edges)))
	 (img-height (ceiling (cdr (image-display-size image)))))
    (image-set-window-hscroll (max 0 (- img-width win-width)))
    (image-set-window-vscroll (max 0 (- img-height win-height)))))

;; Adjust frame and image size.

(defun image-mode-fit-frame ()
  "Fit the frame to the current image.
This function assumes the current frame has only one window."
  ;; FIXME: This does not take into account decorations like mode-line,
  ;; minibuffer, header-line, ...
  (interactive)
  (let* ((saved (frame-parameter nil 'image-mode-saved-size))
         (display (image-get-display-property))
         (size (image-display-size display)))
    (if (and saved
             (eq (caar saved) (frame-width))
             (eq (cdar saved) (frame-height)))
        (progn ;; Toggle back to previous non-fitted size.
          (set-frame-parameter nil 'image-mode-saved-size nil)
          (setq size (cdr saved)))
      ;; Round up size, and save current size so we can toggle back to it.
      (setcar size (ceiling (car size)))
      (setcdr size (ceiling (cdr size)))
      (set-frame-parameter nil 'image-mode-saved-size
                           (cons size (cons (frame-width) (frame-height)))))
    (set-frame-width  (selected-frame) (car size))
    (set-frame-height (selected-frame) (cdr size))))

;;; Image Mode setup

(defvar image-type nil
  "Current image type.
This variable is used to display the current image type in the mode line.")
(make-variable-buffer-local 'image-type)

(defvar image-mode-previous-major-mode nil
  "Internal variable to keep the previous non-image major mode.")

(defvar image-mode-map
  (let ((map (make-sparse-keymap)))
    (set-keymap-parent map special-mode-map)
    (define-key map "\C-c\C-c" 'image-toggle-display)
    (define-key map (kbd "SPC")       'image-scroll-up)
    (define-key map (kbd "DEL")       'image-scroll-down)
    (define-key map [remap forward-char] 'image-forward-hscroll)
    (define-key map [remap backward-char] 'image-backward-hscroll)
    (define-key map [remap right-char] 'image-forward-hscroll)
    (define-key map [remap left-char] 'image-backward-hscroll)
    (define-key map [remap previous-line] 'image-previous-line)
    (define-key map [remap next-line] 'image-next-line)
    (define-key map [remap scroll-up] 'image-scroll-up)
    (define-key map [remap scroll-down] 'image-scroll-down)
    (define-key map [remap scroll-up-command] 'image-scroll-up)
    (define-key map [remap scroll-down-command] 'image-scroll-down)
    (define-key map [remap move-beginning-of-line] 'image-bol)
    (define-key map [remap move-end-of-line] 'image-eol)
    (define-key map [remap beginning-of-buffer] 'image-bob)
    (define-key map [remap end-of-buffer] 'image-eob)
    map)
  "Major mode keymap for viewing images in Image mode.")

(defvar image-minor-mode-map
  (let ((map (make-sparse-keymap)))
    (define-key map "\C-c\C-c" 'image-toggle-display)
    map)
  "Minor mode keymap for viewing images as text in Image mode.")

(defvar bookmark-make-record-function)

(put 'image-mode 'mode-class 'special)

;;;###autoload
(defun image-mode ()
  "Major mode for image files.
You can use \\<image-mode-map>\\[image-toggle-display]
to toggle between display as an image and display as text."
  (interactive)
  (condition-case err
      (progn
	(unless (display-images-p)
	  (error "Display does not support images"))

	(kill-all-local-variables)
	(setq major-mode 'image-mode)

	(if (not (image-get-display-property))
	    (progn
	      (image-toggle-display-image)
	      ;; If attempt to display the image fails.
	      (if (not (image-get-display-property))
		  (error "Invalid image")))
	  ;; Set next vars when image is already displayed but local
	  ;; variables were cleared by kill-all-local-variables
	  (setq cursor-type nil truncate-lines t
		image-type (plist-get (cdr (image-get-display-property)) :type)))

	(setq mode-name (if image-type (format "Image[%s]" image-type) "Image"))
	(use-local-map image-mode-map)

	;; Use our own bookmarking function for images.
	(set (make-local-variable 'bookmark-make-record-function)
	     'image-bookmark-make-record)

	;; Keep track of [vh]scroll when switching buffers
	(image-mode-setup-winprops)

	(add-hook 'change-major-mode-hook 'image-toggle-display-text nil t)
	(add-hook 'after-revert-hook 'image-after-revert-hook nil t)
	(run-mode-hooks 'image-mode-hook)
	(message "%s" (concat
		       (substitute-command-keys
			"Type \\[image-toggle-display] to view the image as ")
		       (if (image-get-display-property)
			   "text" "an image") ".")))
    (error
     (image-mode-as-text)
     (funcall
      (if (called-interactively-p 'any) 'error 'message)
      "Cannot display image: %s" (cdr err)))))
;;;###autoload
(define-minor-mode image-minor-mode
  "Toggle Image minor mode.
With arg, turn Image minor mode on if arg is positive, off otherwise.
It provides the key \\<image-mode-map>\\[image-toggle-display] \
to switch back to `image-mode'
to display an image file as the actual image."
  nil (:eval (if image-type (format " Image[%s]" image-type) " Image"))
  image-minor-mode-map
  :group 'image
  :version "22.1"
  (if image-minor-mode
      (add-hook 'change-major-mode-hook (lambda () (image-minor-mode -1)) nil t)))

;;;###autoload
(defun image-mode-as-text ()
  "Set a non-image mode as major mode in combination with image minor mode.
A non-image major mode found from `auto-mode-alist' or Fundamental mode
displays an image file as text.  `image-minor-mode' provides the key
\\<image-mode-map>\\[image-toggle-display] to switch back to `image-mode'
to display an image file as the actual image.

You can use `image-mode-as-text' in `auto-mode-alist' when you want
to display an image file as text initially.

See commands `image-mode' and `image-minor-mode' for more information
on these modes."
  (interactive)
  ;; image-mode-as-text = normal-mode + image-minor-mode
  (let ((previous-image-type image-type)) ; preserve `image-type'
    (if image-mode-previous-major-mode
	;; Restore previous major mode that was already found by this
	;; function and cached in `image-mode-previous-major-mode'
	(funcall image-mode-previous-major-mode)
      (let ((auto-mode-alist
	     (delq nil (mapcar
			(lambda (elt)
			  (unless (memq (or (car-safe (cdr elt)) (cdr elt))
					'(image-mode image-mode-maybe image-mode-as-text))
			    elt))
			auto-mode-alist)))
	    (magic-fallback-mode-alist
	     (delq nil (mapcar
			(lambda (elt)
			  (unless (memq (or (car-safe (cdr elt)) (cdr elt))
					'(image-mode image-mode-maybe image-mode-as-text))
			    elt))
			magic-fallback-mode-alist))))
	(normal-mode)
	(set (make-local-variable 'image-mode-previous-major-mode) major-mode)))
    ;; Restore `image-type' after `kill-all-local-variables' in `normal-mode'.
    (setq image-type previous-image-type)
    ;; Enable image minor mode with `C-c C-c'.
    (image-minor-mode 1)
    ;; Show the image file as text.
    (image-toggle-display-text)
    (message "%s" (concat
		   (substitute-command-keys
		    "Type \\[image-toggle-display] to view the image as ")
		   (if (image-get-display-property)
		       "text" "an image") "."))))

(define-obsolete-function-alias 'image-mode-maybe 'image-mode "23.2")

(defun image-toggle-display-text ()
  "Show the image file as text.
Remove text properties that display the image."
  (let ((inhibit-read-only t)
	(buffer-undo-list t)
	(modified (buffer-modified-p)))
    (remove-list-of-text-properties (point-min) (point-max)
				    '(display intangible read-nonsticky
					      read-only front-sticky))
    (set-buffer-modified-p modified)
    (if (called-interactively-p 'any)
	(message "Repeat this command to go back to displaying the image"))))

(defvar archive-superior-buffer)
(defvar tar-superior-buffer)
(declare-function image-flush "image.c" (spec &optional frame))

(defun image-toggle-display-image ()
  "Show the image of the image file.
Turn the image data into a real image, but only if the whole file
was inserted."
  (let* ((filename (buffer-file-name))
	 (data-p (not (and filename
			   (file-readable-p filename)
			   (not (file-remote-p filename))
			   (not (buffer-modified-p))
			   (not (and (boundp 'archive-superior-buffer)
				     archive-superior-buffer))
			   (not (and (boundp 'tar-superior-buffer)
				     tar-superior-buffer)))))
	 (file-or-data (if data-p
			   (string-make-unibyte
			    (buffer-substring-no-properties (point-min) (point-max)))
			 filename))
	 (type (image-type file-or-data nil data-p))
         (image0 (create-animated-image file-or-data type data-p))
	 (image (append image0
                        (image-transform-properties image0)
                        ))
	 (props
	  `(display ,image
		    intangible ,image
		    rear-nonsticky (display intangible)
		    read-only t front-sticky (read-only)))
	 (inhibit-read-only t)
	 (buffer-undo-list t)
	 (modified (buffer-modified-p)))
    (image-flush image)
    (let ((buffer-file-truename nil)) ; avoid changing dir mtime by lock_file
      (add-text-properties (point-min) (point-max) props)
      (restore-buffer-modified-p modified))
    ;; Inhibit the cursor when the buffer contains only an image,
    ;; because cursors look very strange on top of images.
    (setq cursor-type nil)
    ;; This just makes the arrow displayed in the right fringe
    ;; area look correct when the image is wider than the window.
    (setq truncate-lines t)
    ;; Disable adding a newline at the end of the image file when it
    ;; is written with, e.g., C-x C-w.
    (if (coding-system-equal (coding-system-base buffer-file-coding-system)
			     'no-conversion)
	(set (make-local-variable 'find-file-literally) t))
    ;; Allow navigation of large images
    (set (make-local-variable 'auto-hscroll-mode) nil)
    (setq image-type type)
    (if (eq major-mode 'image-mode)
	(setq mode-name (format "Image[%s]" type)))
    (if (called-interactively-p 'any)
	(message "Repeat this command to go back to displaying the file as text"))))

(defun image-toggle-display ()
  "Start or stop displaying an image file as the actual image.
This command toggles between `image-mode-as-text' showing the text of
the image file and `image-mode' showing the image as an image."
  (interactive)
  (if (image-get-display-property)
      (image-mode-as-text)
    (image-mode)))

(defun image-after-revert-hook ()
  (when (image-get-display-property)
    (image-toggle-display-text)
    ;; Update image display.
    (redraw-frame (selected-frame))
    (image-toggle-display-image)))


;;; Support for bookmark.el
(declare-function bookmark-make-record-default
                  "bookmark" (&optional no-file no-context posn))
(declare-function bookmark-prop-get "bookmark" (bookmark prop))
(declare-function bookmark-default-handler "bookmark" (bmk))

(defun image-bookmark-make-record ()
  `(,@(bookmark-make-record-default nil 'no-context 0)
      (image-type . ,image-type)
      (handler    . image-bookmark-jump)))

;;;###autoload
(defun image-bookmark-jump (bmk)
  ;; This implements the `handler' function interface for record type
  ;; returned by `bookmark-make-record-function', which see.
  (prog1 (bookmark-default-handler bmk)
    (when (not (string= image-type (bookmark-prop-get bmk 'image-type)))
      (image-toggle-display))))


(defvar image-transform-minor-mode-map
  (let ((map (make-sparse-keymap)))
;    (define-key map  [(control ?+)] 'image-scale-in)
;    (define-key map  [(control ?-)] 'image-scale-out)
;    (define-key map  [(control ?=)] 'image-scale-none)
;;    (define-key map "c f h" 'image-scale-fit-height)
;;    (define-key map "c ]" 'image-rotate-right)
    map)
  "Minor mode keymap for transforming the view of images Image mode.")

(define-minor-mode image-transform-mode
  "minor mode for scaleing and rotation"
  nil "image-transform"
  image-transform-minor-mode-map)

(defvar image-transform-resize   nil
  "The image resize operation. See the command
  `image-transform-set-scale' for more information." )

(defvar image-transform-rotation 0.0)


(defun image-transform-properties (display)
  "Calculate the display properties for transformations; scaling
and rotation. "
  (let*
      ((size (image-size display t))
       (height
        (cond
         ((and (numberp image-transform-resize) (eq 100 image-transform-resize))
          nil)
         ((numberp image-transform-resize)
          (* image-transform-resize (cdr size)))
         ((eq image-transform-resize 'fit-height)
          (- (nth 3 (window-inside-pixel-edges)) (nth 1 (window-inside-pixel-edges))))
         (t nil)))
       (width (if (eq image-transform-resize 'fit-width)
                  (- (nth 2 (window-inside-pixel-edges)) (nth 0 (window-inside-pixel-edges))))))

    `(,@(if height (list :height height))
      ,@(if width (list :width width))
      ,@(if (not (equal 0.0 image-transform-rotation))
            (list :rotation image-transform-rotation))
      ;;TODO fit-to-* should consider the rotation angle
      )))

(defun image-transform-set-scale (scale)
  "SCALE sets the scaling for images. "
  (interactive "nscale:")
  (image-transform-set-resize (float scale)))

(defun image-transform-fit-to-height ()
  "Fit image height to window height. "
  (interactive)
  (image-transform-set-resize 'fit-height))

(defun image-transform-fit-to-width ()
  "Fit image width to window width. "
  (interactive)
  (image-transform-set-resize 'fit-width))

(defun image-transform-set-resize (resize)
  "Set the resize mode for images. The RESIZE value can be the
symbol fit-height which fits the image to the window height. The
symbol fit-width fits the image to the window width.  A number
indicates a scaling factor. nil indicates scale to 100%. "
  (setq image-transform-resize resize)
  (if (eq 'image-mode major-mode) (image-toggle-display-image)))

(defun image-transform-set-rotation (rotation)
  "Set the image ROTATION angle. "
  (interactive "nrotation:")
  ;;TODO 0 90 180 270 degrees are the only reasonable angles here
  ;;otherwise combining with rescaling will get very awkward
  (setq image-transform-rotation (float rotation))
  (if (eq major-mode 'image-mode) (image-toggle-display-image)))

(provide 'image-mode)

;;; image-mode.el ends here