Use of where-is-internal

Use of where-is-internal

[Paul W. Rankin]

I'm considering of using where-is-internal in a program outside of the
help library. I've used the following in my init for a while to cycle
windows and so far the world has persisted unscathed:

   (defun other-window-and-beyond (count &optional all-frames)
     "Select another window in cyclic ordering of windows.
   Successive pressing `o' calls `other-window'."
     (interactive "p")
     (let ((key-vector (where-is-internal this-command
                                          overriding-local-map t)))
       (set-transient-map
        (let ((map (make-sparse-keymap)))
          (define-key map (vector (aref key-vector (1- (length key-vector))))
            'other-window)
          map)
        t)
       (other-window count all-frames)))

This function allows me to type C-x o o o o to cycle through all windows
with the idea being to allow the command to work with any key binding
rather than hardcoding anything.

I maintain a minor mode called olivetti that also uses a transient key
map to allow changing a buffer-local variable with C-c { { { ... The key
binding is currently hardcoded within the transient key map but I'd like
to allow user customisation.

So, should I throw caution to the wind and reimplement the transient key
map in olivetti using where-is-internal despite it being clearly marked
as internal, or is there a better way?

Thanks,

--
Paul W. Rankin
https://www.paulwrankin.com

Re: Use of where-is-internal

[Adam Porter]

Paul W. Rankin <hello@paulwrankin.com> writes:

> I'm considering of using where-is-internal in a program outside of the
> help library. I've used the following in my init for a while to cycle
> windows and so far the world has persisted unscathed:
>
>    (defun other-window-and-beyond (count &optional all-frames)
>      "Select another window in cyclic ordering of windows.
>    Successive pressing `o' calls `other-window'."
>      (interactive "p")
>      (let ((key-vector (where-is-internal this-command
>                                           overriding-local-map t)))
>        (set-transient-map
>         (let ((map (make-sparse-keymap)))
>           (define-key map (vector (aref key-vector (1- (length key-vector))))
>             'other-window)
>           map)
>         t)
>        (other-window count all-frames)))
>
> This function allows me to type C-x o o o o to cycle through all windows
> with the idea being to allow the command to work with any key binding
> rather than hardcoding anything.
>
> I maintain a minor mode called olivetti that also uses a transient key
> map to allow changing a buffer-local variable with C-c { { { ... The key
> binding is currently hardcoded within the transient key map but I'd like
> to allow user customisation.
>
> So, should I throw caution to the wind and reimplement the transient key
> map in olivetti using where-is-internal despite it being clearly marked
> as internal, or is there a better way?

This isn't what you asked, but here's a simple way to define commands
that repeat in the way you described:

https://github.com/alphapapa/defrepeater.el

In fact, other-window is what's used in the readme's example:

    (global-set-key (kbd "C-x o") (defrepeater #'other-window))

It's also useful with winner-undo.

Re: Use of where-is-internal

[Stefan Monnier]

> I'm considering of using where-is-internal in a program outside of the
> help library. I've used the following in my init for a while to cycle
> windows and so far the world has persisted unscathed:
>
>    (defun other-window-and-beyond (count &optional all-frames)
>      "Select another window in cyclic ordering of windows.
>    Successive pressing `o' calls `other-window'."
>      (interactive "p")
>      (let ((key-vector (where-is-internal this-command
>                                           overriding-local-map t)))
>        (set-transient-map
>         (let ((map (make-sparse-keymap)))
>           (define-key map (vector (aref key-vector (1- (length key-vector))))
>             'other-window)
>           map)
>         t)
>        (other-window count all-frames)))

I have a feeling of "déjà vu"!

The answer involved `this-single-command-keys`.


        Stefan

Re: Use of where-is-internal

[Noam Postavsky]

On Sat, 1 Feb 2020 at 09:25, Stefan Monnier <monnier@iro.umontreal.ca> wrote:
>
> > I'm considering of using where-is-internal in a program outside of the
> > help library. I've used the following in my init for a while to cycle
> > windows and so far the world has persisted unscathed:
> >
> >    (defun other-window-and-beyond (count &optional all-frames)
> >      "Select another window in cyclic ordering of windows.
> >    Successive pressing `o' calls `other-window'."
> >      (interactive "p")
> >      (let ((key-vector (where-is-internal this-command
> >                                           overriding-local-map t)))
> >        (set-transient-map
> >         (let ((map (make-sparse-keymap)))
> >           (define-key map (vector (aref key-vector (1- (length key-vector))))
> >             'other-window)
> >           map)
> >         t)
> >        (other-window count all-frames)))
>
> I have a feeling of "déjà vu"!

Yeah, https://lists.gnu.org/archive/html/help-gnu-emacs/2020-01/msg00176.html