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

[Dmitry Gutov]

Barry Margolin <barmar@alum.mit.edu> writes:

> In article <mailman.4537.1341978452.855.help-gnu-emacs@gnu.org>,
>> >> 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?

The global mode has a corresponding local minor mode which needs to be
initialized in each buffer it applies to. That's the initialization I
was referring to.

See `define-globalized-minor-mode'.

>> 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.

There is no such function.