Re: BUG+patch: line-move-1 ignores buffer-invisibility-spec

[Max Mikhanosha]

Oops please disregard this bug report.

Apparently I had some really old piece of code (library called APEL)
loaded, which had a definition of (invisible-p) function in it, which ignored
the buffer-invisibility-spec.

At Wed, 31 Aug 2011 00:20:07 -0400,
Max Mikhanosha wrote:
> 
> I had started using egg (the fancy vc-git replacement) and had noticed
> that sometimes point jumps all over the place weirdly inside Egg
> buffers. For example pressing down arrow on the very first change in
> 500 line diff, would jump to the end of the buffer.
> 
> After debugging it, it seems that Egg is using unique 'invisible text
> property for every diff hunk text in the buffer, and sets
> `buffer-invisibility-spec' to nil initially. It has the command to
> show/hide diff hunks, which it accomplishes by adding/removing that
> hunk's unique 'invisible property value to `buffer-invisibility-spec'
> variable.
> 
> So far so good, but I was wondering why `next-line' function sometimes
> skips the text that is not hidden. After debugging it, much to my
> surprise, it appears that line-move-1 function in simple.el,
> completely ignores `buffer-invisibility-spec' and skips any text with
> non-NIL 'invisible property.
> 
> I had found the correct code to skip invisible text that takes
> `buffer-invisibility-spec' into account in the forward-visual-line
> function.
> 
> After changing the line-move-1 invisibility code to be the same, it had
> fixed my problem with point jumping erratically in Egg buffers.
> 
> This is for Emacs 23, but Emacs 24 simple.el appears to have the same
> problem.
> 
> Patch pasted below
> 
> === modified file 'lisp/simple.el'
> *** lisp/simple.el    2011-02-17 07:43:53 +0000
> --- lisp/simple.el    2011-08-31 03:51:26 +0000
> ***************
> *** 4254,4261 ****
>             (while (and (> arg 0) (not done))
>               ;; If the following character is currently invisible,
>               ;; skip all characters with that same `invisible' property 
> value.
> !             (while (and (not (eobp)) (invisible-p (point)))
> !               (goto-char (next-char-property-change (point))))
>               ;; Move a line.
>               ;; We don't use `end-of-line', since we want to escape
>               ;; from field boundaries occurring exactly at point.
> --- 4254,4272 ----
>             (while (and (> arg 0) (not done))
>               ;; If the following character is currently invisible,
>               ;; skip all characters with that same `invisible' property 
> value.
> !                 (while (and (not (eobp))
> !                             (let ((prop
> !                                    (get-char-property (point) 'invisible)))
> !                               (if (eq buffer-invisibility-spec t)
> !                                   prop
> !                                 (or (memq prop buffer-invisibility-spec)
> !                                     (assq prop buffer-invisibility-spec)))))
> !                   (goto-char
> !                    (if (get-text-property (point) 'invisible)
> !                        (or (next-single-property-change (point) 'invisible)
> !                            (point-max))
> !                      (next-overlay-change (point)))))
> ! 
>               ;; Move a line.
>               ;; We don't use `end-of-line', since we want to escape
>               ;; from field boundaries occurring exactly at point.
> ***************
> *** 4309,4320 ****
>                   (setq done t))))
>               (unless done
>                 (setq arg (1+ arg))
> !               (while (and ;; Don't move over previous invis lines
> !                       ;; if our target is the middle of this line.
> !                       (or (zerop (or goal-column temporary-goal-column))
> !                           (< arg 0))
> !                       (not (bobp)) (invisible-p (1- (point))))
> !                 (goto-char (previous-char-property-change (point))))))))
>         ;; This is the value the function returns.
>         (= arg 0))
>   
> --- 4320,4337 ----
>                   (setq done t))))
>               (unless done
>                 (setq arg (1+ arg))
> !                   (while (and (not (bobp))
> !                               (let ((prop
> !                                      (get-char-property (1- (point)) 
> 'invisible)))
> !                                 (if (eq buffer-invisibility-spec t)
> !                                     prop
> !                                   (or (memq prop buffer-invisibility-spec)
> !                                       (assq prop 
> buffer-invisibility-spec)))))
> !                     (goto-char
> !                      (if (get-text-property (1- (point)) 'invisible)
> !                          (or (previous-single-property-change (point) 
> 'invisible)
> !                              (point-min))
> !                        (previous-overlay-change (point)))))))))
>         ;; This is the value the function returns.
>         (= arg 0))
>   
> ***************
> *** 4352,4360 ****
>            (save-excursion
>              ;; Like end-of-line but ignores fields.
>              (skip-chars-forward "^\n")
> !            (while (and (not (eobp)) (invisible-p (point)))
> !              (goto-char (next-char-property-change (point)))
> !              (skip-chars-forward "^\n"))
>              (point))))
>   
>       ;; Move to the desired column.
> --- 4369,4387 ----
>            (save-excursion
>              ;; Like end-of-line but ignores fields.
>              (skip-chars-forward "^\n")
> !                (while (and (not (eobp))
> !                            (let ((prop
> !                                   (get-char-property (point) 'invisible)))
> !                              (if (eq buffer-invisibility-spec t)
> !                                  prop
> !                                (or (memq prop buffer-invisibility-spec)
> !                                    (assq prop buffer-invisibility-spec)))))
> !                  (goto-char
> !                   (if (get-text-property (point) 'invisible)
> !                       (or (next-single-property-change (point) 'invisible)
> !                           (point-max))
> !                     (next-overlay-change (point))))
> !                  (skip-chars-forward "^\n"))
>              (point))))
>   
>       ;; Move to the desired column.
> 
> 
>