Re: [BUG] widget-field-overlay becomes wrong

[Lars Hansen]

Richard Stallman wrote:

> What will happen if the user deletes all the text in the editable field,
> then inserts new text?  Will that newly inserted text be treated
> as part of a neighboring widget?  It seems likely.
>  
You are right, zero-sized overlays cannot be ignored as I did. Such 
overlays should only go in overlays-after. This is done in the patch 
attached.

> I don't think it is worth spending a lot of time to fix this,
> because I think it is fundamentally impossible, and there are
> more important things to do.
I don't see why it should be fundamentally impossible to fix this bug. 
AFAICS a widget cannot have zero size, and if it has a zero-sized 
overlay at one end, it is at the start.

I want to fix this bug because it annoys me in some tests I am doing.
I suggest we install my patch. It can always be removed if it has 
undesirable consequences.

> For instance, would you be interested
> in working on making saving of text properties in files more
> convenient?  That is more important.
I would be happy to work much more on Emacs. However, that requires 
someone to finance it :-). Right now I don't have the time :-(.

*** wid-edit.el.~1.128.~        Tue Jun  8 21:50:16 2004
--- wid-edit.el Sun Jul  4 10:34:13 2004
***************
*** 414,426 ****
      (widget-put widget :doc-overlay overlay)))
  
  (defmacro widget-specify-insert (&rest form)
!   "Execute FORM without inheriting any text properties."
    `(save-restriction
      (let ((inhibit-read-only t)
!         (inhibit-modification-hooks t))
        (narrow-to-region (point) (point))
        (prog1 (progn ,@form)
!       (goto-char (point-max))))))
  
  (defface widget-inactive-face '((((class grayscale color)
                                  (background dark))
--- 414,444 ----
      (widget-put widget :doc-overlay overlay)))
  
  (defmacro widget-specify-insert (&rest form)
!   "Execute FORM without inheriting any text properties.
! Furthermore, ensure overlays ending at point or starting at point
! does not include text inserted."
    `(save-restriction
      (let ((inhibit-read-only t)
!         (inhibit-modification-hooks t)
!           overlays-before
!           overlays-after)
!       (mapc (lambda (overlay)
!               (when (and (= (point) (overlay-end overlay))
!                          (not (= (point) (overlay-start overlay))))
!                 (setq overlays-before (cons overlay overlays-before)))
!               (when (= (point) (overlay-start overlay))
!                 (setq overlays-after (cons overlay overlays-after))))
!             (overlays-in (if (= (point) (point-min)) (point) (1- (point)))
!                          (if (= (point) (point-max)) (point) (1+ (point)))))
        (narrow-to-region (point) (point))
        (prog1 (progn ,@form)
!         (mapc (lambda (overlay)
!                 (move-overlay overlay (overlay-start overlay) (point-min)))
!               overlays-before)
!         (mapc (lambda (overlay)
!                 (move-overlay overlay (point-max) (overlay-end overlay)))
!               overlays-after)
!         (goto-char (point-max))))))
  
  (defface widget-inactive-face '((((class grayscale color)
                                  (background dark))
***************
*** 1530,1538 ****
                     (if (>= old-pos (1- to))
                         (- old-pos to 1)
                       (- old-pos from)))))
-     ;;??? Bug: this ought to insert the new value before deleting the old one,
-     ;; so that markers on either side of the value automatically
-     ;; stay on the same side.  -- rms.
      (save-excursion
        (goto-char (widget-get widget :from))
        (widget-apply widget :delete)
--- 1548,1553 ----