minor bug in next-error-follow-minor-mode?

minor bug in next-error-follow-minor-mode?

[Bruce Stephens]

I was confused by the behaviour of next-error-follow-minor-mode in the
current emacs CVS.  I vaguely remembered that it was on by default,
and indeed found that C-c C-f switched it off (and another C-c C-f
switched it on).  However, now I look at the code, I think it's just a
minor bug, where ":init-value" ought to be ":lighter", in simple.el.
(" Fol" is presumably a valid non-nil value, but it looks suspiciously
like something meant for the modeline.)

(define-minor-mode next-error-follow-minor-mode
  "Minor mode for compilation, occur and diff modes.
When turned on, cursor motion in the compilation, grep, occur or diff
buffer causes automatic display of the corresponding source code
location."
  :group 'next-error :init-value " Fol"
  (if (not next-error-follow-minor-mode)
      (remove-hook 'post-command-hook 'next-error-follow-mode-post-command-hook t)
    (add-hook 'post-command-hook 'next-error-follow-mode-post-command-hook nil t)
    (make-local-variable 'next-error-follow-last-line)))

Re: minor bug in next-error-follow-minor-mode?

[Dan Nicolaescu]

Bruce Stephens <bruce@cenderis.demon.co.uk> writes:

  > I was confused by the behaviour of next-error-follow-minor-mode in the
  > current emacs CVS.  I vaguely remembered that it was on by default,

I don't think it was supposed to be on by default.

  > and indeed found that C-c C-f switched it off (and another C-c C-f
  > switched it on).  However, now I look at the code, I think it's just a
  > minor bug, where ":init-value" ought to be ":lighter", in simple.el.
  > (" Fol" is presumably a valid non-nil value, but it looks suspiciously
  > like something meant for the modeline.)

You are right, I fixed this.

diff-mode-hook (was Re: minor bug in next-error-follow-minor-mode?)

[Bruce Stephens]

Dan Nicolaescu <dann@ics.uci.edu> writes:

> Bruce Stephens <bruce@cenderis.demon.co.uk> writes:

[...]

>   > and indeed found that C-c C-f switched it off (and another C-c C-f
>   > switched it on).  However, now I look at the code, I think it's just a
>   > minor bug, where ":init-value" ought to be ":lighter", in simple.el.
>   > (" Fol" is presumably a valid non-nil value, but it looks suspiciously
>   > like something meant for the modeline.)
>
> You are right, I fixed this.

Yes, I just noticed.  Thanks for that.

While investigating that, I tried switching on
next-error-follow-minor-mode explicitly:

(add-hook 'diff-mode-hook (function () (next-error-follow-minor-mode t)))

But that failed, and then I tried a function that did (setq foo 42),
and that didn't seem to set foo.  

I suspect diff-mode doesn't call diff-mode-hook.  The documentation
for diff-mode doesn't say it does, but diff-mode-hook does suggest it
gets called.  So something seems wrong.

Re: diff-mode-hook (was Re: minor bug in next-error-follow-minor-mode?)

[Dan Nicolaescu]

Bruce Stephens <bruce@cenderis.demon.co.uk> writes:

  > Dan Nicolaescu <dann@ics.uci.edu> writes:
  > 
  > > Bruce Stephens <bruce@cenderis.demon.co.uk> writes:
  > 
  > [...]
  > 
  > >   > and indeed found that C-c C-f switched it off (and another C-c C-f
  > >   > switched it on).  However, now I look at the code, I think it's just a
  > >   > minor bug, where ":init-value" ought to be ":lighter", in simple.el.
  > >   > (" Fol" is presumably a valid non-nil value, but it looks suspiciously
  > >   > like something meant for the modeline.)
  > >
  > > You are right, I fixed this.
  > 
  > Yes, I just noticed.  Thanks for that.
  > 
  > While investigating that, I tried switching on
  > next-error-follow-minor-mode explicitly:
  > 
  > (add-hook 'diff-mode-hook (function () (next-error-follow-minor-mode t)))


(add-hook 'diff-mode-hook (lambda () (next-error-follow-minor-mode t)))
should work.

Re: diff-mode-hook

[Bruce Stephens]

Dan Nicolaescu <dann@ics.uci.edu> writes:

> Bruce Stephens <bruce@cenderis.demon.co.uk> writes:

[...]

>   > (add-hook 'diff-mode-hook (function () (next-error-follow-minor-mode t)))
>
>
> (add-hook 'diff-mode-hook (lambda () (next-error-follow-minor-mode t)))
> should work.

So it does.  I was just confused.  (The documentation's clear about
what "function" does.)

Re: minor bug in next-error-follow-minor-mode?

[Richard M. Stallman]

Thanks.

Re: diff-mode-hook (was Re: minor bug in next-error-follow-minor-mode?)

[Richard M. Stallman]

    But that failed, and then I tried a function that did (setq foo 42),
    and that didn't seem to set foo.  

    I suspect diff-mode doesn't call diff-mode-hook.

The disassembled code says that it does.  It uses run-mode-hooks.
Under some circumstances the running of those hooks can be delayed
till when a calling function exits, but that is supposed to occur
only if it is called from anothetr major mode.