Re: Adding functionality to a minor mode

[Eric Abrahamsen <eric@ericabrahamsen.net>]

goncholden <goncholden@protonmail.com> writes:

> ------ Original Message -------
>
> On Saturday, February 5th, 2022 at 6:50 PM, goncholden <goncholden@protonmail.com> wrote:
>
>> ------- Original Message -------
>>
>> On Saturday, February 5th, 2022 at 10:00 AM, goncholden via Users
>> list for the GNU Emacs text editor help-gnu-emacs@gnu.org wrote:
>>
>> > I have made a minor-mode with some defvar and defun. Have added some functionality
>> >
>> > for comments, and put everything in the following function definition.
>> >
>> > (defun rich-annotation-tools ()
>> >
>> > "Aggregates annotation tools for comments."
>> >
>> > (rich-annotation-font-weight)
>> >
>> > (rich-annotation-low-contrast)
>> >
>> > (rich-annotation-keytrigger))
>> >
>> > I would expect to add "(rich-annotation-tools)" in
>> > define-minor-mode. Would I introduce it
>> >
>> > within the "(when rich-minor-mode" part?
>> >
>> > ;;;###autoload
>> >
>> > (define-minor-mode rich-minor-mode
>> >
>> > "This is the description."
>> > :lighter "rich" ; indicator in mode-line
>> > (font-lock-remove-keywords nil rich-font-lock)
>> >
>> > (when rich-minor-mode
>> >   (font-lock-add-keywords nil rich-font-lock 'append)
>> >   (set (make-local-variable 'jit-lock-contextually) t) )
>> >   (rich-annotation-tools)
>> >
>> > (with-no-warnings (font-lock-fontify-buffer)) )) )
>
> Could I get some clarification for using "(when rich-minor-mode" and when not to?

What's happening here is that, when you define a minor mode, it also
defines a variable of the same name, which can be tested as a boolean to
see if the minor mode is currently enabled or not.

The only thing you need to know is that, when the minor mode is turned
on or off, the variable is set *before* the body is run. So if you test
the boolean variable in the body code of the minor mode, it will be t if
you've just turned the mode on, and nil if you've just turned it off.

For some reason, when I first started playing with minor modes, this
struck me as backwards. I can no longer say why, exactly, but I remember
it did.