Hi Henry,

Thank you for using org-tree-slide and reporting the issue.
Please use the following patch to avoid the error.

PATCH:
Replace the original code with
----
(defun ots-display-tree-with-narrow ()
  "Show a tree with narrowing and also set a header at the head of slide."
  (goto-char (point-at-bol))
  (when (ots-last-heading-position)
    (hide-subtree) ; support CONTENT (subtrees are shown)
    (org-show-entry)
    (show-children)
    (org-cycle-hide-drawers 'all)
    (org-narrow-to-subtree))
  (setq display-tree-slide-string
(if (equal org-tree-slide-modeline-display 'outside)
    (ots-count-slide (point))
  ""))
  (when org-tree-slide-slide-in-effect
    (ots-slide-in org-tree-slide-slide-in-brank-lines))
  (when org-tree-slide-header
    (ots-show-slide-header)))
----

This patch is a tentative code for checking behavior in your environments,
but I think you will be able to open org files without heading.
I'll update it again within a few days.


Best,
Takaaki



2013/7/15 Nick Dokos <ndokos@gmail.com>

> henry atts <snd@online.de> writes:
>
> > Carsten Dominik <carsten.dominik@gmail.com> writes:
> >
> >> On 15.7.2013, at 10:33, henry atts <snd@online.de> wrote:
> >>
> >>> I use org-tree-slide-mode by default with
> >>>
> >>>  (add-hook 'org-mode-hook 'org-tree-slide-mode)
> >>>
> >>> This works kind of acceptable minus some minor annoyances. But one
> thing
> >>> makes it nearly unusuable. tree-slide rigidly expects at least one
> >>> header. So if I open an org file without heading, or if I create a new
> >>> one, I get an error message:
> >>>
> >>> File mode specification error: (error "before first heading")
> >>>
> >>> If I include a setup file with `#+SETUPFILE:', which of course has no
> >>> headings in it,  org-tree-slide stops working at all.
> >>
> >>
> >> Hi Henry,
> >>
> >> you could wrap turning on of the mode into a function
> >> that checks if there is a node, and if not, just add one.
> >>
> >> - Carsten
> >
> > Okay, but on the one hand this doesn't solve the problem with
> > `SETUPFILE'. On the other hand what if I want an org file without any
> > heading on purpose? Or otherwise asked is a file a `real' org file only
> > if it has headings in it?
> >
>
> No, I don't think so, but there are bugs (there was a bug in the latex
> exporter once that required a heading at the beginning). I presume
> Carsten's suggestion was as a workaround to a bug (although I might
> have misinterpreted his comment).
>
> > You might say if you want some features of orgmode _and_ an org file
> > without heading you can always use, say, text-mode and load orgstruct as
> > a minor mode. Which does not solve the problem as well because with the
> > org-tree-mode hook for orgmode it shows some strange behaviour equally.
> >
> > I like org-tree-mode but I think it does not play well with orgmode in
> > some cases. And as far as I see it even is not in contrib.
> >
>
> Yes, I went looking for it there and did not find it :-) So maybe you
> can ping the author about the bug - s/he might even fix it, particularly
> now that the package is being used by at least one other person! Or
> contribute the fix yourself - if you like the package, then others might
> too, so it might even end up in contrib at some point.
>
> --
> Nick
>
>
>