Re: [Emacs-diffs] master b75fb81 1/4: Extend button.el to take callback data

[Lars Ingebrigtsen]

"Basil L. Contovounesios" <address@hidden> writes:

> I don't understand what you mean by "recreate the data" or "looking at
> the extent of the buttons".
>
> If an action function depends on some data associated with its button,
> then it is up to the creator or modifier of the button to tag it with
> that data.  The action function then need only do a property lookup via
> button-get. 

Here's a typical usage:

      (make-text-button start (point)
                        'face 'rcirc-url
                        'follow-link t
                        'rcirc-url url
                        'action (lambda (button)
                                  (browse-url (button-get button 'rcirc-url))))

with the "button knows the data" change, it's:

      (make-text-button start (point)
                        'face 'rcirc-url
                        'follow-link t
                        'burron-data url
                        'action #'browse-url)

That looks like an interface improvement to me.

> Alternatively, action functions can also be closures.

They can be, in lexical packages.

> I don't mind the name 'button-data', and I wasn't worried about naming
> collisions.
>
> What I'm worried about is the existence of buttons in the wild, whose
> existing action functions will break if said buttons happen to be given
> a button-data property.  This seems unnecessarily brittle and
> backward-incompatible, in exchange for what seems like an insufficiently
> useful convenience.  Unless I'm missing something, that is.

But you said you're not worried about naming collisions?   How would
these buttons then "happen to be given" that property?

-- 
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   bloggy blog: http://lars.ingebrigtsen.no