Bug: Undo does not work in org-agenda-todo when logging a note

Bug: Undo does not work in org-agenda-todo when logging a note

[Max Mikhanosha]

If I press 't' in the agenda buffer and the state change is logged
with a note, undo in the agenda buffer only undoes a note line in the
org buffer, leaving the item state changed, and now being out of sync
with agenda.

If there is no note, then undo works fine. 

Regards,
  Max

Re: Bug: Undo does not work in org-agenda-todo when logging a note

[Carsten Dominik]

On Jul 18, 2008, at 7:19 AM, Max Mikhanosha wrote:

> If I press 't' in the agenda buffer and the state change is logged
> with a note, undo in the agenda buffer only undoes a note line in the
> org buffer, leaving the item state changed, and now being out of sync
> with agenda.
>
> If there is no note, then undo works fine.


Hmmm.  yes.  This is hard to fix, but I will take a look.

- Carsten

Re: Bug: Undo does not work in org-agenda-todo when logging a note

[Max Mikhanosha]

At Sat, 19 Jul 2008 08:27:21 -0700,
Carsten Dominik wrote:
> 
> 
> On Jul 18, 2008, at 7:19 AM, Max Mikhanosha wrote:
> 
> > If I press 't' in the agenda buffer and the state change is logged
> > with a note, undo in the agenda buffer only undoes a note line in the
> > org buffer, leaving the item state changed, and now being out of sync
> > with agenda.
> >
> > If there is no note, then undo works fine.
> 
> 
> Hmmm.  yes.  This is hard to fix, but I will take a look.
> 

I've tried to fix it myself, and yes its non-trivial because one has
to adjust the undo boundary somehow after addinga a note.. After a few
hours of hacking I gave up on that, and instead came up with the
following:

You seem to be playing with (undo-boundary) which records nil in the
buffer-undo-list, which makes (undo-more) stop.

It seems that one can use arbitrary markers in the undo list, not just
nil. The (primitive-undo) function ignores anything in the undo list 
that is not a consp. 

Therefore the following code that implements named/storable undo-boundaries
seems to work, you can test it in scratch buffer

(defun make-undo-checkpoint ()
  (let ((checkpoint (gensym)))
    (push checkpoint buffer-undo-list)
    checkpoint))

(defun do-undo-until-checkpoint (checkpoint)
  (let ((ptr buffer-undo-list) prev found rest-of-undo)
    (while (and ptr (not found))
      (if (not (eq (car ptr) checkpoint))
          (setq prev ptr ptr (cdr ptr))
        (setq found t)))
    (when found
      ;; rest of undo list after our tag
      (setq rest-of-undo (cdr ptr))
      ;; split the undo list by putting NIL at the place of 
      ;; our tag
      (if (not prev)
          (setq buffer-undo-list nil)) ;; our tag was the 1st element
      (setcdr prev nil)                ;; previous elemen is now last
      (undo-start)
      (while (listp pending-undo-list)
        (undo-more 1)))))

(defvar checkpoints nil)
(make-variable-buffer-local 'checkpoints)

(defun record-undo-checkpoint (&optional arg)
  (interactive)
  (push (make-undo-checkpoint) checkpoints))


(defun undo-until-checkpoint (&optional arg)
  (interactive)
  (do-undo-until-checkpoint (pop checkpoints)))
  

Now if you do M-x record-undo-checkpoint in the buffer it pushes into
a stack of undo checkpoints. The M-x undo-until-checkpoint does undo
until that checkpoint. The checkpoint itself is a unique gensym.

Would it be possible to use this in the org-agenda undo functionality?

You can simply create an undo checkpoint before doing any agenda
command, and then call (undo-until-checkpoint) and it will undo all
the changes in between regardless of undo boundaries?

Regards,
  Max