Re: How do I initialize globalized minor mode only once?

[Barry Margolin]

In article <mailman.4537.1341978452.855.help-gnu-emacs@gnu.org>,
 Dmitry Gutov <dgutov@yandex.ru> wrote:

> Barry Margolin <barmar@alum.mit.edu> writes:
> 
> > In article <mailman.4534.1341975266.855.help-gnu-emacs@gnu.org>,
> >  Dmitry Gutov <dgutov@yandex.ru> wrote:
> >
> >> Hi all,
> >> 
> >> I have written a globalized minor mode which has a relatively costly
> >> initialization (external process call), which I need to do when the mode
> >> is enabled.
> >> 
> >> But the turn-on function is getting called twice for each new opened
> >> buffer, once in default major mode, and once in the final major mode.
> >> 
> >> What's the best way to turn on the minor mode only once?
> >> Currently I'm comparing major-mode value to the default value, but
> >> that's probably not the best solution, since the minor mode in question
> >> can apply to some fundamental-mode (or other default mode) buffers, too.
> >
> > Why not just set a variable saying whether you've done the 
> > initialization:
> >
> > (defvar *my-mode-initialized* nil)
> > ...
> >
> >   (if (not *my-mode-initialized*)
> >       (progn
> >         ... 
> >         (setq *my-mode-initialized* t)))
> 
> My first reaction was "because major mode change kills all local variables",
> but that's not exactly true - with enough sprinkling of 'permanent-local
> and 'permanent-local-hook properties, this might work.

If this is a global minor mode, why would you use a local variable?

> 
> But what if the user tries to turn off and on the minor mode, or the
> global mode, or both? I'd want the initialization performed in these
> cases. When or where would I set the variable to nil?

In the turn-off function.

-- 
Barry Margolin, barmar@alum.mit.edu
Arlington, MA
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