Emacs 21 bug scrolling image horizontally to right in other window

Emacs 21 bug scrolling image horizontally to right in other window

[Greg Hill]

When scrolling a window to the right in an "other-window", if the 
window being scrolled contains an image, under certain circumstances 
the rightmost character-width's worth of the image gets duplicated.

To see this happen, use the showImage routine below (referencing some 
image file you have) to display an image.  Use the scroll-image-left 
routine to scroll it to the left.  Then, with some window selected 
other than the one displaying the showImage buffer, use the 
scroll-image-right routine to scroll the image to the right, and 
notice what happens to its right-hand edge.

Then choose the window displaying the image as the selected window, 
and use the same scrolling routines.  Notice that the problem goes 
away.

Next, uncomment out the first (insert "\n") in showImage, and repeat 
the original experiment.  Notice that the problem goes away.

Finally, leave the initial (insert "\n") not commented out, change 
the 1 in the call to goto-char to a 2, and notice that the problem 
comes back.

(defun showImage ()
   (interactive)
   (save-selected-window
     (switch-to-buffer-other-window "showImage")
     (erase-buffer)
;;; (insert "\n")
     (insert-image (create-image "rms.jpeg") (point))
     (insert "\n")
     (goto-char 1) ))

(defun scroll-image-left ()
   (interactive)
   (save-selected-window
     (select-window (get-buffer-window "showImage"))
     (scroll-left 1)))

(defun scroll-image-right ()
   (interactive)
   (save-selected-window
     (select-window (get-buffer-window "showImage"))
     (scroll-right 1)))

(global-set-key [M-left] 'scroll-image-left)

(global-set-key [M-right] 'scroll-image-right)

--Greg