Re: proper use of add-function

[Michael Heerdegen <michael_heerdegen@web.de>]

Eric Abrahamsen <eric@ericabrahamsen.net> writes:

> And another very basic question:
>
> I can't get `add-function' to do its thing. I want to add a :filter-args
> function to #'canonically-space-region, and because this is a minor
> mode, I want it set locally.

I guess there is a problem with what you want to achieve: we have no
buffer local function bindings of symbols.

> (add-function
>    :filter-args
>    (local 'canonically-space-region)
>    #'my-canonical-space-region)
>
> (defun my-canonical-space-region (bounds)
>   ;; etc
>   (list (car bounds) (nth 1 bounds)))

Technically ok, but this tries to bind the (value cell of the) symbol
canonically-space-region.

What I typically do in this (quite common) scenario is to install the
advice (globally) and check for the mode in the `current-buffer' in the
advice.  I guess there is no alternative unless you find a different way
to reach what you want (like advising `canonical-space-region-function',
which doesn't exist).


Michael.