Re: [GNU ELPA] I'd like to add switchy.el: a last-recently-used window switcher

[Tassilo Horn]

Tassilo Horn <tsdh@gnu.org> writes:

Hi Philip,

I've added the package to ELPA as switchy-window as suggested by Eli.

>>> ;; Package-Requires: ((emacs "25.1") (compat "29.1.3.4"))
>> 
>> If you are to use compat 29.1.0.0 or newer then you also have to
>> require it!

Ah, thanks.  I'm new to the compat game but it's a relief not to worry
about compatibility. :-)

>>> ;; SPDX-License-Identifier: GPL-3.0-or-later
>>> ;;
>>> ;; This file is NOT part of GNU Emacs.
>> 
>> If added to GNU ELPA, this should be change to "... is part of GNU
>> Emacs", right?

Yes, I've changed that now.

>>>   ;; Remove dead windows.
>>>   (setq switchy--tick-alist (seq-filter
>>>                              (lambda (e)
>>>                                (window-live-p (car e)))
>>>                              switchy--tick-alist))
>>>   ;; Add windows never selected.
>>>   (dolist (win (window-list (selected-frame)))
>>>     (unless (assq win switchy--tick-alist)
>>>       (setf (alist-get win switchy--tick-alist) 0)))
>> 
>> The setf is strictly speaking unnecessary here and causes an
>> accidental O(n^2) slowdown, since you traverse the list once to check
>> if it has an entry and then traverse it again to check if you can set
>> 0 to an existing entry.  You could also just push a cons-cell to the
>> beginning.  Then again, this is all bounded by the maximal number of
>> windows that someone has open so it doesn't matter in practice.

Yup, I've kept that as-is because the theoretical slowdown is not
practical and it's easier to debug when the alist ist free of
duplicates.

>>>   (let ((win-entries (seq-filter
>>>                       (lambda (e)
>>>                         (let ((win (car e)))
>>>                           (and (eq (window-frame win) (selected-frame))
>>>                                (or (minibuffer-window-active-p win)
>>>                                    (not (eq win (minibuffer-window
>>>                                                  (selected-frame)))))
>>>                                (not (memq win switchy--visited-windows)))))
>>>                       switchy--tick-alist)))
>>>     (if win-entries
>>>         (when-let ((win (car (seq-reduce (lambda (x e)
>>>                                            (if (and x (funcall (if arg #'<
>>> #'>)
>>>                                                                (cdr x) (cdr
>>> e)))
>>>                                                x
>>>                                              e))
>>>                                          win-entries nil))))
>>> 
>>>           (progn
>> 
>> Why the progn if you are using when-let?

A left-over of an earlier version.

>>>       ;; Start a new cycle if we're not at the start already, i.e., we
>>> visited
>>>       ;; just one (the current) window.
>>>       (when (> (length switchy--visited-windows) 1)
>> 
>> Or (length> switchy--visited-windows 1)?

Oh, I didn't know that.

>>> (defvar switchy-minor-mode-map (make-sparse-keymap)
>>>   "The mode map of `switchy-minor-mode'.
>>> No keys are bound by default.  Bind the main command
>>> `switchy-window' to a key of your liking, e.g.,
>>> 
>>>   ;; That\\='s what I use.
>>>   (keymap-set switchy-minor-mode-map \"C-<\" #\\='switchy-window)
>> 
>> If you are already making use of keymap-set, you might as well define
>> the map itself using defvar-keymap (Compat provides it).

Yes, thanks!

>>> (define-minor-mode switchy-minor-mode
>>>   "Activates recording of window selection ticks.
>>> Those are the timestamps for figuring out the last-recently-used
>>> order of windows.
>>> 
>>> The minor-mode provides the keymap `switchy-minor-mode-map',
>>> which see."
>>>   :global t
>>>   :keymap switchy-minor-mode-map
>> 
>> Isn't this the default anyway?

Yes, it is.  Removed.

>>> (provide 'switchy)
>>> 
>>> (provide 'switchy)
>> 
>> Accidentally duplicated?

Just to be on the safe side it is really provided! ;-)

Thanks,
Tassilo