Re: Image mode

[Chong Yidong <cyd@stupidchicken.com>]

I would like to present a concrete proposal based on the discussion
over the last couple of days.

Firstly, turn image autodetection off for xpm and xbm.  The reason for
this is that these are text-based image formats that will be handled
differently from binary images (see below).  An additional reason is
that C header files easily match the header-regexp for xbm, so the
main distinguishing feature of an xbm image is its filename, which
makes autodetection pointless.

Secondly, make autodetected images call image-mode instead of
image-mode-maybe, since only binary image formats are autodetected.

Thirdly, make the function image-type-auto-detected-p scan
auto-mode-alist for a non-image-mode match, and returns nil if one is
found.

Forthly, associate xpm and xbm files with image-mode-maybe in
auto-mode-alist; this will be the only use of image-mode-maybe.
image-mode-maybe scans auto-mode-alist for a non-image major mode,
turns on that mode, and turns on image-minor-mode.

The result is that binary image files are displayed in image-mode iff
their file contents are autodetected and their filenames do not
indicate a non-image mode.  This addresses the issue raised by several
people that a file named foo.c should never be opened as an image.
Binary image files are never displayed in image-minor-mode.
Text-based image files (xpm and xbm) are only detected by their
filename, and are opened in (in this case) C mode plus
image-minor-mode.

Finally, the `disabled' tag for image-toggle-display is removed, and
image-mode goes back to showing the image by default.

Any comments?

*** emacs/lisp/files.el.~1.882.~	2007-02-05 12:05:37.000000000 -0500
--- emacs/lisp/files.el	2007-02-06 20:27:53.000000000 -0500
***************
*** 2127,2133 ****
  associated with that interpreter in `interpreter-mode-alist'.")
  
  (defvar magic-mode-alist
!   `((image-type-auto-detected-p . image-mode-maybe)
      ;; The < comes before the groups (but the first) to reduce backtracking.
      ;; TODO: UTF-16 <?xml may be preceded by a BOM 0xff 0xfe or 0xfe 0xff.
      ;; We use [ \t\n] instead of `\\s ' to make regex overflow less likely.
--- 2127,2133 ----
  associated with that interpreter in `interpreter-mode-alist'.")
  
  (defvar magic-mode-alist
!   `((image-type-auto-detected-p . image-mode)
      ;; The < comes before the groups (but the first) to reduce backtracking.
      ;; TODO: UTF-16 <?xml may be preceded by a BOM 0xff 0xfe or 0xfe 0xff.
      ;; We use [ \t\n] instead of `\\s ' to make regex overflow less likely.
*** emacs/lisp/image.el.~1.69.~	2007-01-28 10:49:26.000000000 -0500
--- emacs/lisp/image.el	2007-02-07 14:05:28.000000000 -0500
***************
*** 67,77 ****
  
  (defvar image-type-auto-detectable
    '((pbm . t)
!     (xbm . t)
      (bmp . maybe)
      (gif . maybe)
      (png . maybe)
!     (xpm . maybe)
      (jpeg . maybe)
      (tiff . maybe)
      (postscript . nil))
--- 67,77 ----
  
  (defvar image-type-auto-detectable
    '((pbm . t)
!     (xbm . nil)
      (bmp . maybe)
      (gif . maybe)
      (png . maybe)
!     (xpm . nil)
      (jpeg . maybe)
      (tiff . maybe)
      (postscript . nil))
***************
*** 340,354 ****
  ;;;###autoload
  (defun image-type-auto-detected-p ()
    "Return t iff the current buffer contains an auto-detectable image.
! Whether image types are auto-detectable or not depends on the setting
! of the variable `image-type-auto-detectable'.
  
! This function is intended to be used from `magic-mode-alist' (which see)."
    (let* ((type (image-type-from-buffer))
  	 (auto (and type (cdr (assq type image-type-auto-detectable)))))
      (and auto
! 	 (or (eq auto t)
! 	     (image-type-available-p type)))))
  
  
  ;;;###autoload
--- 340,370 ----
  ;;;###autoload
  (defun image-type-auto-detected-p ()
    "Return t iff the current buffer contains an auto-detectable image.
! This function is intended to be used from `magic-mode-alist' (which see).
  
! First, compare the first few bytes of the buffer with
! `image-type-header-regexps'.  If an appropriate image type is
! found, consult the variable `image-type-auto-detectable' to see
! if it can be autodetected.  Finally, if `buffer-file-name' is
! non-nil, check if it matches another major mode in
! `auto-mode-alist' apart from `image-mode'; if there is another
! match, the autodetection is considered to have failed.  If all
! the preceding steps succeeded, return t."
    (let* ((type (image-type-from-buffer))
  	 (auto (and type (cdr (assq type image-type-auto-detectable)))))
      (and auto
! 	 (or (eq auto t) (image-type-available-p type))
! 	 (or (null buffer-file-name)
! 	     (not (assoc-default
! 		   buffer-file-name
! 		   (delq nil (mapcar 
! 			      (lambda (elt)
! 				(unless (memq (or (car-safe (cdr elt))
! 						  (cdr elt))
! 					      '(image-mode image-mode-maybe))
! 				  elt))
! 			      auto-mode-alist))
! 		   'string-match))))))
  
  
  ;;;###autoload
*** emacs/lisp/image-mode.el.~1.20.~	2007-02-02 20:00:19.000000000 -0500
--- emacs/lisp/image-mode.el	2007-02-07 13:53:58.000000000 -0500
***************
*** 60,65 ****
--- 60,71 ----
    (setq major-mode 'image-mode)
    (use-local-map image-mode-map)
    (add-hook 'change-major-mode-hook 'image-toggle-display-text nil t)
+   (if (and (display-images-p)
+ 	   (not (get-text-property (point-min) 'display)))
+       (image-toggle-display)
+     ;; 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))
    (run-mode-hooks 'image-mode-hook)
    (if (display-images-p)
        (message "%s" (concat
***************
*** 174,189 ****
        (if (called-interactively-p)
  	  (message "Repeat this command to go back to displaying the file as text")))))
  
- ;; Don't override the setting from .emacs.
- ;;;###autoload (put 'image-toggle-display 'disabled t)
- 
- (if (get 'image-toggle-display 'disabled)
-     (put 'image-toggle-display 'disabled "\
- 
- Warning: Displaying images in Emacs could be a security risk.
- Please ensure that you are using up-to-date image libraries
- and that the images being displayed come from a trusted source."))
- 
  (provide 'image-mode)
  
  ;; arch-tag: b5b2b7e6-26a7-4b79-96e3-1546b5c4c6cb
--- 180,185 ----