Re: line-move-finish (simple.el) hangs on invisible&intangible text.

[Eli Zaretskii <eliz@fencepost.gnu.org>]

> Date: Fri, 19 Apr 2002 12:32:15 +0200
> From: Juanma Barranquero <lektu@terra.es>
> 
> line-move-finish calls line-move-to-column to set the cursor to the
> desired column, and that function does:
> 
>   (if (zerop col)
>       (beginning-of-line)
>     (move-to-column col))
> 
> That's why it works from column 0 and not others. In my system, puting
> the cursor at the beginning of a line that only contains i&i characters
> and evaling
> 
>  (beginning-of-line)
> 
> does not move the cursor, while evaling
> 
>  (move-to-column 0)
> 
> moves it. Doesn't that happen on your system?

Yes, it does.

The following tentative change (not installed) detects a possible
infloop and breaks out of it with the last good position it found,
hopefully without breaking anything else.  I will install this if
people who understand more than I do the intricacies of the invisible
and intangible properties take a good look at the patch and approve
it.

Index: lisp/simple.el
===================================================================
RCS file: /cvsroot/emacs/emacs/lisp/simple.el,v
retrieving revision 1.537
diff -c -r1.537 simple.el
*** lisp/simple.el	19 Apr 2002 00:05:22 -0000	1.537
--- lisp/simple.el	20 Apr 2002 11:32:46 -0000
***************
*** 2633,2676 ****
    nil)
  
  (defun line-move-finish (column opoint)
!   (let ((repeat t))
      (while repeat
        ;; Set REPEAT to t to repeat the whole thing.
        (setq repeat nil)
  
        ;; Move to the desired column.
        (line-move-to-column column)
! 
!       (let ((new (point))
! 	    (line-beg (save-excursion (beginning-of-line) (point)))
! 	    (line-end (save-excursion (end-of-line) (point))))
! 
! 	;; Process intangibility within a line.
! 	;; Move to the chosen destination position from above,
! 	;; with intangibility processing enabled.
! 
! 	(goto-char (point-min))
! 	(let ((inhibit-point-motion-hooks nil))
! 	  (goto-char new)
! 
! 	  ;; If intangibility moves us to a different (later) place
! 	  ;; in the same line, use that as the destination.
! 	  (if (<= (point) line-end)
! 	      (setq new (point))))
! 
! 	;; Now move to the updated destination, processing fields
! 	;; as well as intangibility.
! 	(goto-char opoint)
! 	(let ((inhibit-point-motion-hooks nil))
! 	  (goto-char
! 	   (constrain-to-field new opoint nil t
! 			       'inhibit-line-move-field-capture)))
! 
! 	;; If intangibility processing moved us to a different line,
! 	;; retry everything within that new line.
! 	(when (or (< (point) line-beg) (> (point) line-end))
! 	  ;; Repeat the intangibility and field processing.
! 	  (setq repeat t))))))
  
  (defun line-move-to-column (col)
    "Try to find column COL, considering invisibility.
--- 2633,2681 ----
    nil)
  
  (defun line-move-finish (column opoint)
!   (let ((repeat t)
! 	(prev-new -1)
! 	last-good-point)
      (while repeat
        ;; Set REPEAT to t to repeat the whole thing.
        (setq repeat nil)
  
        ;; Move to the desired column.
+       (setq last-good-point (point))
        (line-move-to-column column)
!       (if (= (point) prev-new)
! 	  (goto-char last-good-point)
! 	(let ((new (point))
! 	      (line-beg (save-excursion (beginning-of-line) (point)))
! 	      (line-end (save-excursion (end-of-line) (point))))
! 
! 	  (setq prev-new new)
! 	  ;; Process intangibility within a line.
! 	  ;; Move to the chosen destination position from above,
! 	  ;; with intangibility processing enabled.
! 
! 	  (goto-char (point-min))
! 	  (let ((inhibit-point-motion-hooks nil))
! 	    (goto-char new)
! 
! 	    ;; If intangibility moves us to a different (later) place
! 	    ;; in the same line, use that as the destination.
! 	    (if (<= (point) line-end)
! 		(setq new (point))))
! 
! 	  ;; Now move to the updated destination, processing fields
! 	  ;; as well as intangibility.
! 	  (goto-char opoint)
! 	  (let ((inhibit-point-motion-hooks nil))
! 	    (goto-char
! 	     (constrain-to-field new opoint nil t
! 				 'inhibit-line-move-field-capture)))
! 
! 	  ;; If intangibility processing moved us to a different line,
! 	  ;; retry everything within that new line.
! 	  (when (or (< (point) line-beg) (> (point) line-end))
! 	    ;; Repeat the intangibility and field processing.
! 	    (setq repeat t)))))))
  
  (defun line-move-to-column (col)
    "Try to find column COL, considering invisibility.