From: Alan Mackenzie <acm@muc.de>
To: Stefan Monnier <monnier@iro.umontreal.ca>
Cc: emacs-devel@gnu.org
Subject: Re: (insert ?\n) spuriously calls before-change-functions twice. Help!
Date: Wed, 6 Jan 2010 13:05:21 +0000 [thread overview]
Message-ID: <20100106130521.GA2447@muc.de> (raw)
In-Reply-To: <jwv1vi4l4ef.fsf-monnier+emacs@gnu.org>
Hi, Stefan,
On Tue, Jan 05, 2010 at 02:52:37PM -0500, Stefan Monnier wrote:
> > I think I've tracked down what's happening. After inserting the ?\n (any
> > other character is just the same), Emacs clears any text properties from
> > the new character by calling set_properties. This, in its turn, invokes
> > before-change-functions. A more detailed call stack is:
> Sounds like a bug indeed.
> > There doesn't seem to be any system in where the two change hooks are
> > invoked. For example, insert directly calls signal_after_change, yet not
> > signal_before_change; surely invocations of these should be paired.
> Agreed. Patch very welcome,
I'll look at this. It looks impractical to change the source to do this.
signal_after_change seems usually to be paired with modify_region or
prepare_to_modify_buffer. But I'll certainly fix the current bug, and
check (as far as I can) for other circumstances it might happen.
> > For CC Mode, I will put in a test for two consecutive invocations of
> > before-change-functions without an after-change-functions between
> > them. In such a case, I then ignore the second invocation. I think.
> Even if we fix the bug, there can be any number of reasons why the two
> hooks may occasionally not be paired, .....
Really? I would have thought they should be rigorously paired, without
any "recursive" invocations in-between (barring elisp code doing this
deliberately).
> .... so your hooks should be robust against such situations. IOW it's
> best to try and avoid relying in the after-hook on info passed from the
> before hook.
Haven't we discussed this before at some time? ;-)
> Stefan
--
Alan Mackenzie (Nuremberg, Germany).
next prev parent reply other threads:[~2010-01-06 13:05 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-01-05 11:09 (insert ?\n) spuriously calls before-change-functions twice. Help! Alan Mackenzie
2010-01-05 15:22 ` Stefan Monnier
2010-01-05 17:31 ` Alan Mackenzie
2010-01-05 19:52 ` Stefan Monnier
2010-01-06 13:05 ` Alan Mackenzie [this message]
2010-01-06 14:33 ` Stefan Monnier
2010-01-19 13:23 ` Alan Mackenzie
2010-01-19 15:11 ` Chong Yidong
2010-01-19 17:11 ` Alan Mackenzie
2010-01-19 18:02 ` Chong Yidong
2010-01-19 22:30 ` Alan Mackenzie
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