Re: save-excursion doesn't always work

[David Kastrup <David.Kastrup@t-online.de>]

ittay@qlusters.com (Ittay Freiman) writes:

> i found this behavior while using auctex. to recreate, create a new
> buffer for a tex document, with auctex as the mode
> (LaTeX-mode). type in the first line 'this is a test'.
> 
> go down one line. '(point)' should return 16. now evaluate
> '(save-excursion (LaTeX-fill-region-as-paragraph 1 16 t))'. nothing
> actually changes in the buffer,

Wrong.  A lot changes in the buffer.  Place some text property on the
space in question: it will be gone afterwards.  AUCTeX in the process
of filling deletes sequences of spaces completely, then reinserts a
single one.  Whether you were before or in or after such a deleted
space before the operation. you'll end up on the same side of the
reinserted space afterwards.

> but the cursor jumps to point 15. you can repeat this with the same
> results.
> 
> can someone please tell me what is going on? also, if i write a
> function that uses LaTeX-fill-region-as-paragraph, how can i return
> the cursor to its original place (i'm currently using markers,
> however, putting the cursor inside the filled region creates weird
> behaviors)

You can't, for the above reason.  AUCTeX's filling modes would have to
be rewritten so that instead of deleting all spaces and reinserting
one space, AUCTeX would delete all spaces except one.

I think Emacs' default filling by now does something like that.  If
you volunteer in trying to port the relevant portions, I will check
them into the AUCTeX code base: the current behavior is a nuisance
for other reasons as well.

-- 
David Kastrup, Kriemhildstr. 15, 44793 Bochum