Re: [BUG] Infinite loop in org-agenda-show-new-time

[Matt Lundin <mdl@imapmail.org>]

Nick Dokos <ndokos@gmail.com> writes:

> Matt Lundin <mdl@imapmail.org> writes:
>
> My one feeble attempt to reproduce this failed. Looking at the code

Here are the steps to reproduce the problem:

1. Create file test.org with the following content:

--8<---------------cut here---------------start------------->8---
* TODO A							       :home:
  SCHEDULED: <2013-08-05 Mon>
* TODO B							       :work:
  SCHEDULED: <2013-08-05 Mon>
* TODO C							       :play:
  SCHEDULED: <2013-08-05 Mon>
* TODO D							       :home:
  SCHEDULED: <2013-08-05 Mon>
* TODO E							       :work:
  SCHEDULED: <2013-08-05 Mon>
* TODO F							       :play:
  SCHEDULED: <2013-08-05 Mon>
* TODO G							       :home:
  SCHEDULED: <2013-08-05 Mon>
* TODO H							       :work:
  SCHEDULED: <2013-08-05 Mon>
* TODO I							       :play:
  SCHEDULED: <2013-08-05 Mon>
--8<---------------cut here---------------end--------------->8---

2. /usr/bin/emacs -Q 

3. find file test.org

4. M-x org-agenda -> hit "<" to restrict to buffer and then "a" for
diary

5. / home

6. Attempt to reschedule one of the visible items.

>       (while (not (bobp))
> 	(when (equal marker (org-get-at-bol 'org-marker))
> 	  (org-move-to-column (- (window-width) (length stamp)) t)
> 	  (org-agenda-fix-tags-filter-overlays-at (point))
>           ...
> 	  (beginning-of-line 1))
> 	(beginning-of-line 0)))))
>
> let's assume we are not at the beginning of the buffer, so we don't exit
> the loop that way.  If the when succeeds, we do a couple of things and
> then do (beginning-of-line 1). This just takes us to the beginning of
> the current line. But after the when is done, we do (beginning-of-line
> 0) which should take us to the previous line.  So we should be making
> steady progress towards the beginning of the buffer and the loop should
> terminate.
>
> Since you can reproduce it (and you've already done the hard work of
> figuring out where the inf loop is), maybe you can edebug the function
> and step through it a couple of times to see what's happening.

Thanks for the pointers. Running edebug with the file above reveals that
org-move-to-column is not working with the invisible sections of the
buffer.

With the sample file above, I filter the agenda to display only items
tagged :home:.

--8<---------------cut here---------------start------------->8---
Day-agenda (W32):
Monday      5 August 2013 W32
  test:       Scheduled:  TODO A                                          :home:
  test:       Scheduled:  TODO D                                          :home:
  test:       Scheduled:  TODO G                                          :home:
--8<---------------cut here---------------end--------------->8---

When stepping through org-agenda-do-date-later, edebug reveals that the
point goes to the end of the buffer, as expected and then works its way
backward. When it arrives at the beginning of the line with task "G", it
finds and match and executes the following functions:

--8<---------------cut here---------------start------------->8---
	  (org-move-to-column (- (window-width) (length stamp)) t)
	  (org-agenda-fix-tags-filter-overlays-at (point))
--8<---------------cut here---------------end--------------->8---

The problem is that org-move-to-column shifts the point several lines
forward. In fact, if I make all contents of the agenda buffer visible
after edebug executes org-move-to-column, I find that the point is now
all the way at the end of line "I," which, of course, will trigger an
endless loop. In other words, org-move-to-column moves the point to the
end of the entire invisible section.

--8<---------------cut here---------------start------------->8---
Day-agenda (W32):
Monday      5 August 2013 W32
  test:       Scheduled:  TODO A                                          :home:
  test:       Scheduled:  TODO B                                          :work:
  test:       Scheduled:  TODO C                                          :play:
  test:       Scheduled:  TODO D                                          :home:
  test:       Scheduled:  TODO E                                          :work:
  test:       Scheduled:  TODO F                                          :play:
  test:       Scheduled:  TODO G                                          :home:
  test:       Scheduled:  TODO H                                          :work:
  test:       Scheduled:  TODO I                                          :play:
--8<---------------cut here---------------end--------------->8---
                                                                                ^
                                                                                |
                                                                             here

This bug was introduced with the following commit:

--8<---------------cut here---------------start------------->8---
commit fafb5f3429c41cba1eddb9fc78d9f9e0980acbe2
Author: Bastien Guerry <bzg@altern.org>
Date:   Mon Feb 11 14:56:38 2013 +0100

    org-agenda.el: Fix bug when displaying a temporary overlay
    
    * org-agenda.el (org-agenda-schedule, org-agenda-deadline):
    Cosmetic changes.
    (org-agenda-show-new-time): Fix bug when displaying a
    temporary overlay with the scheduled/deadline information.
    
    Thanks to Thomas Morgan for reporting this bug and testing the patch.
--8<---------------cut here---------------end--------------->8---

This commit removed the local binding of buffer-invisibility-spec to
nil in org-agenda-show-new-time.

Here is the bug this change was meant to fix:

http://permalink.gmane.org/gmane.emacs.orgmode/52667

Might we revert this change? The original bug was cosmetic. This bug,
however, interferes in an essential way with the functioning of agenda
buffers.

Best,
Matt