bug in forward-visible-line: Patch

[Luc Teirlinck <teirllm@dms.auburn.edu>]

Start out with the following buffer:

line 1;line 2
line 3;line 4
line 5

Where, after each ";" there is an invisible newline.  With point at
the beginning of the buffer, do M-: (forward-visible-line arg) for
various args. 1 carries us to the beginning of line 3 and 2 to the
beginning of line 5 (as I expected).  Now put point at the end of line
4.  There 0 carries us to the beginning of line 4, -1 to the beginning
of line 3, -2 to the beginning of line 2 and -3 carries us also to the
beginning of line 2.

Makes no sense.  The following patch seems to fix the problem:

Change log:

2003-05-21  Luc Teirlinck  <teirllm@mail.auburn.edu>

        * simple.el (forward-visible-line): Fix negative arguments.

Patch:

===File ~/simplediff========================================
cd /usr/local/share/emacs/21.3.50/lisp/
diff -c /usr/local/share/emacs/21.3.50/lisp/simple.old.el /usr/local/share/emacs/21.3.50/lisp/simple.el
*** /usr/local/share/emacs/21.3.50/lisp/simple.old.el	Wed May 21 18:33:45 2003
--- /usr/local/share/emacs/21.3.50/lisp/simple.el	Wed May 21 23:13:01 2003
***************
*** 2265,2272 ****
  	      (unless (bolp)
  		(goto-char opoint))))
  	(let ((first t))
! 	  (while (or first (< arg 0))
! 	    (if (zerop arg)
  		(beginning-of-line)
  	      (or (zerop (forward-line -1))
  		  (signal 'beginning-of-buffer nil)))
--- 2265,2272 ----
  	      (unless (bolp)
  		(goto-char opoint))))
  	(let ((first t))
! 	  (while (or first (<= arg 0))
! 	    (if first
  		(beginning-of-line)
  	      (or (zerop (forward-line -1))
  		  (signal 'beginning-of-buffer nil)))
***************
*** 2275,2287 ****
  	    (unless (bobp)
  	      (let ((prop
  		     (get-char-property (1- (point)) 'invisible)))
! 		(if (if (eq buffer-invisibility-spec t)
! 			prop
! 		      (or (memq prop buffer-invisibility-spec)
! 			  (assq prop buffer-invisibility-spec)))
! 		    (setq arg (1+ arg)))))
! 	    (setq first nil)
! 	    (setq arg (1+ arg)))
  	  ;; If invisible text follows, and it is a number of complete lines,
  	  ;; skip it.
  	  (let ((opoint (point)))
--- 2275,2286 ----
  	    (unless (bobp)
  	      (let ((prop
  		     (get-char-property (1- (point)) 'invisible)))
! 		(unless (if (eq buffer-invisibility-spec t)
! 			    prop
! 			  (or (memq prop buffer-invisibility-spec)
! 			      (assq prop buffer-invisibility-spec)))
! 		  (setq arg (1+ arg)))))
! 	    (setq first nil))
  	  ;; If invisible text follows, and it is a number of complete lines,
  	  ;; skip it.
  	  (let ((opoint (point)))

Diff finished at Wed May 21 23:13:27
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