From: Stefan Monnier <monnier@IRO.UMontreal.CA>
To: "Bill Brodie" <wbrodie@panix.com>
Cc: 12170@debbugs.gnu.org
Subject: bug#12170: save-excursion fails boundary case with recenter
Date: Fri, 10 Aug 2012 11:04:47 -0400 [thread overview]
Message-ID: <jwv4noag5if.fsf-monnier+emacs@gnu.org> (raw)
In-Reply-To: <003601cd76fd$b21cd590$165680b0$@com> (Bill Brodie's message of "Fri, 10 Aug 2012 09:40:24 -0400")
> (progn
> (defun f (n)
> (save-excursion (forward-line (- n)) (recenter 0)))
> (let ((buffer (switch-to-buffer "foo"))
> (height (1- (window-height (get-buffer-window "foo")))))
> (insert-char 10 (* height 2))
> (let ((pt (point)))
> (f height)
> (redisplay)
> (message "height %s old %s new %s" height pt (point)))))
As mentioned by Martin, this is a misunderstanding about what
save-excursion does and what `point' is.
Every buffer can have many different `point's (it basically has one per
window, accessible via `window-point' and changeable via
`set-window-point', plus one for itself, called `point').
`save-excursion' preserves only `point'.
`recenter' changes `window-point'.
But `point' and `window-point' are linked (point is set to window-point
and vice-versa in various occasions), so they're often confused.
It seems your real problem is not that `point' changes but that the
cursor ends up in a different position than the one you wanted (the
cursor position, is represented by `window-point' rather than by
`point'), right?
If so, you want to preserve window-point. And there's nothing quite
like save-excursion to preserve window-point. You can try
save-window-excursion, tho it will do a lot more than you asked for.
Or otherwise manually read window-point at the beginning and
set-window-point at the end.
Stefan
next prev parent reply other threads:[~2012-08-10 15:04 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-10 1:23 bug#12170: save-excursion fails boundary case with recenter Bill Brodie
2012-08-10 9:34 ` martin rudalics
2012-08-10 9:50 ` Bastien
2012-08-10 13:03 ` martin rudalics
2012-08-10 13:40 ` Bill Brodie
2012-08-10 14:47 ` martin rudalics
2012-08-10 16:18 ` Stefan Monnier
2012-08-10 16:47 ` martin rudalics
2012-08-10 17:07 ` Stefan Monnier
2012-08-10 19:01 ` Eli Zaretskii
2012-08-11 9:32 ` martin rudalics
2012-08-11 11:11 ` Eli Zaretskii
2012-08-11 14:22 ` martin rudalics
2012-08-11 15:10 ` Eli Zaretskii
2012-08-11 16:05 ` martin rudalics
2012-08-11 16:31 ` Eli Zaretskii
2012-08-11 16:49 ` Eli Zaretskii
2012-08-12 10:31 ` martin rudalics
2012-08-11 16:27 ` Bill Brodie
2012-08-10 15:04 ` Stefan Monnier [this message]
2012-08-10 15:46 ` Bill Brodie
2012-08-10 16:46 ` martin rudalics
2012-08-10 16:46 ` martin rudalics
2012-08-10 18:58 ` Eli Zaretskii
2012-08-11 9:31 ` martin rudalics
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