From: Kaushal Modi <kaushal.modi@gmail.com>
To: Alan Mackenzie <acm@muc.de>
Cc: 23460@debbugs.gnu.org
Subject: bug#23460: 25.1.50; Strange behavior in local variables like start-comment
Date: Thu, 05 May 2016 22:35:23 +0000 [thread overview]
Message-ID: <CAFyQvY1h=5atq23SPTu1SJxydhuWyz+BJLWoszJZm4pN9Yf0HQ@mail.gmail.com> (raw)
In-Reply-To: <20160505222211.GE1950@acm.fritz.box>
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>
> I haven't actually looked at that yet. But where, with respect to
> setting the major mode, does the outshine function look at
> comment-start?
>
Yes
> Were you doing anything involving changing the major mode at the time?
> (See below.)
>
Apologies for that misleading first version of the MWE; the issue I am
seeing has nothing to do with changing major mode (I think).
Thanks for taking the trouble to create this minimal test code. It
> makes it so much easier to understand when people do this. :-)
>
No worries. But unintentional I caused more trouble for you by posting an
incorrect version of MWE (the 1st version). The second version I posted few
minutes back is thoroughly tested in both emacs-25 and master and has no
outshine.el dependency i.e. you can focus only on that 2nd version of MWE.
OK. Have a look at the *Messages* buffer. You will see the messages
> come in pairs: (I actually did this in a C Mode buffer.)
>
> `comment-start' = `/* '
> `comment-start' is undefined, it's value is: `nil'
>
> But in the echo area, you will only see the second one.
>
> > I have tested this only for comment-start. But I suspect this might
> affect
> > buffer local vars in general?
>
> I think so, too. When you visit a buffer, Emacs calls `normal-mode' to
> determine and set the major mode. The first thing `normal-mode' does is
> to call `fundamental-mode'. This invokes `change-major-mode-hook',
> which outputs the first "comment-start" message. Then
> `fundamental-mode' kills all local variables, including `comment-start'.
>
> `normal-mode' then determines the correct major mode, and calls it.
> This invokes `change-major-mode-hook' again, which outputs the second
> "comment-start" message with the `nil'. The major mode is then fully
> set up, including giving a value to `comment-start'.
>
> So, this code seems to be working the way it's intended to.
Thank you for that detailed explanation. I was not aware of the major mode
changes that were happening behind the scenes.
> What is
> outshine doing that triggers a problem in this area?
The outshine-mode-function function is actually added to
outline-minor-mode-hook. I have updated MWE version 2 with that in mind.
Is it doing things
> with the `change-major-mode-hook' that involve using `comment-start'?
> Maybe this is the problem.
>
No, it does not use change-major-mode-hook. But it does depend on the
buffer local value of comment-start.
In summary, the 2nd version of my MWE should help you consistently show the
behavior difference between emacs-25 and master.
--
--
Kaushal Modi
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next prev parent reply other threads:[~2016-05-05 22:35 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-05 20:35 bug#23460: 25.1.50; Strange behavior in local variables like start-comment Kaushal Modi
2016-05-05 21:40 ` Kaushal Modi
2016-05-05 22:20 ` Kaushal Modi
2016-05-06 9:37 ` Alan Mackenzie
2016-05-06 14:31 ` Kaushal Modi
2016-05-05 22:22 ` Alan Mackenzie
2016-05-05 22:35 ` Kaushal Modi [this message]
2016-05-05 22:29 ` Michael Heerdegen
2016-05-06 19:25 ` Alan Mackenzie
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