Re: Cursor Moving on Image Broken?

[MJ Chan]

This is a follow-up to a bug report (included below) that I sent
yesterday regarding cursor moving on image. Kim, thank you for
pointing me to report-emacs-bug.

I did some further testing and found that the problem will take place
when the window width is less than the image. Below is a simplified
lisp code that I use to display an image file in multi-rows and
columns. I then call "(display-image "c:/tmp/pretest/pic.jpg")" to
display an image file. When the window is wider than the image itself,
cursor moving has no problem (see the first attachment). However, if I
resize the window to make it smaller than the image (red arrows will
be shown in the right fringe area, see the second attachment), then I
cannot go up (going down is fine). That is, the cursor will not move
if I do "previous-line" (^N). 

There is also a similar problem when I move to the right side of the
image while it's being displayed in multi-columns. When trying to move
to the left, I won't be able to see the left side of the image. 

Also, the 3rd attachment shows a corrupted display of the left fringe
when I tried to move up and down while the cursor is at the end of the
line. 

Please let me know if you need additional information. 

------------------- sample lisp code -----------------------------------------
(defun display-image (image-file &optional scale)
  "Display the file as an image in the current buffer."
  (interactive)
  (let ((image-type nil))
    (unless (or image-type
                (setq image-type (image-type-from-file-header image-file)))
      (let ((extension (file-name-extension image-file)))
        (unless extension
          (error "Cannot determine image type"))
        (setq image-type (intern extension))))
    (if (and (fboundp 'image-type-available-p) image-type
             (image-type-available-p image-type))
        (let (start (selective-display nil)
                    image work-buffer o width height (rows 1) (cols 1) 
(x-margin 0)
                    (scale 1)
                    (image-buffer (get-buffer-create  (concat "*Image: " 
                                                              
(file-name-nondirectory image-file))))
                    (buffer-read-only nil))
          (set-buffer image-buffer)
          (erase-buffer)
          (setq truncate-lines t)
          (setq cursor-type 1)
          (setq start (point))
          (make-variable-buffer-local 'images-current-image-filename)
          (setq image (list 'image ':type image-type ':file image-file))
          (setq width (car (image-size image t))
                height (cdr (image-size image t)))
          (if (> height (* 2 (frame-char-height)))
              (setq rows (/ height (* 2 (frame-char-height)))))
          (if (> width (frame-pixel-width))
              (setq cols (/ (+ width (/ (frame-pixel-width) 2)) (/ 
(frame-pixel-width) 2))))
          (if images-extra-centered-image
              (setq image (list 'image ':type image-type ':file image-file 
':pointer 'hand ':margin (cons x-margin 10))))
          (insert-sliced-image image "z" nil rows cols)
          (clear-image-cache t)
          (setq o (make-overlay start (point) nil t nil))
          (overlay-put o 'evaporate t)
          (goto-char start)
          (switch-to-buffer image-buffer)
          t)
      nil)))

(display-image "c:/tmp/pretest/pic.jpg")



>>>>> On Thursday, April 14 2005, Kim F Storm said:

    > MJ Chan <address@hidden> writes:
    >> First of all, I apologize if this is not the right mailing list to post
    >> a possible problem with latest CVS Emacs. (I am not on the list). 

    > You should use M-x report-emacs-bug to report bugs with CVS Emacs.

    >> However, today I checked out latest Emacs from CVS and I found that I
    >> have a problem with ^P (previous line) when the cursor is on the
    >> image. I can do ^N (next-line) without a problem, but ^P will not move
    >> to the previous line. That is, I can only go down and cannot go up. 
    >> 
    >> Another problem is that when I scroll a wide image to the right (with
    >> my multi-column image display), I no longer can scroll back  to
    >> beginning of the line (an image strip actually) with ^P. 

    > Can you post a specific test case (lisp code + image + step-by-step
    > instructions) that shows the bogus behaviour, or at least some more
    > specific instructions like "size of slices" etc...

    >> 
    >> I looked through the mailing archive, and saw a similar post that
    >> talks about partial image scrolling in January, but I am not sure if
    >> it is related. I also learned that the new move-line lisp function is
    >> also trying to help solve the scrolling of tall image. Would that have
    >> something to do with the problem I reported?

    > It could very well be a problem...  Line scrolling now tries
    > to scroll correctly in tall images -- but it may have broken
    > something else.


    > -- 
    > Kim F. Storm <address@hidden> http://www.cua.dk

------------------------------------------------------------------------
In GNU Emacs 22.0.50.1 (i386-mingw-nt5.1.2600)
 of 2005-04-12 on MCHANXP648L
Distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc (3.2) --cflags -I../../GnuWin32/include'

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: ENU
  locale-coding-system: chinese-big5
  default-enable-multibyte-characters: t

Major mode: Fundamental

Minor modes in effect:
  file-name-shadow-mode: t
  auto-image-file-mode: t
  tooltip-mode: t
  encoded-kbd-mode: t
  mouse-wheel-mode: t
  menu-bar-mode: t
  global-font-lock-mode: t
  unify-8859-on-encoding-mode: t
  utf-translate-cjk-mode: t
  line-number-mode: t
  next-error-follow-minor-mode:  Fol

Recent input:
C-n C-n C-n C-n C-n C-n C-p C-p C-p C-p C-p C-p C-p 
C-p C-p C-p C-p C-p C-p C-p C-p C-n C-n C-n C-n C-n 
C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n C-n 
C-n C-n C-n C-n C-n C-n C-p C-p C-p C-p C-p C-p C-p 
C-p C-p C-p C-p C-p C-p C-p C-p C-p C-p C-p C-p C-p 
C-p C-p C-p C-p C-p C-n C-n C-n M-x e m a c s - b u 
<tab> <backspace> <backspace> r e <tab> <backspace> 
<backspace> C-g M-x r e p o r t <tab> <return>

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