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

[Philip Kaludercic]

Tassilo Horn <tsdh@gnu.org> writes:

> Thanks Philip,
>
> I'll address your comments before adding the package.

Great, looking forward to seeing the package on ELPA :)

> Bye,
> Tassilo
>
> 09.04.2023 10:56:28 Philip Kaludercic <philipk@posteo.net>:
>
>> Tassilo Horn <tsdh@gnu.org> writes:
>> 
>>> Hi all,
>>> 
>>> I've written a small utility called switchy.el which I'd like to add to
>>> GNU ELPA.  I can do that on my own but wanted to give you a chance for
>>> commenting first.  I'm attaching the file below.
>>> 
>>> In essence, the single command provided is `switchy-window' which is
>>> similar to `other-window' except that it switches to other windows in
>>> last-recently-used order instead of top-to-bottom-left-to-right order.
>>> With quick consecutive invocations you can reach any window but if you
>>> have a small delay between invocations (controlled by the single
>>> defcustom `switchy-delay'), you toggle between the two last recently
>>> used windows.
>>> 
>>> Bye,
>>> Tassilo
>>> 
>>> ;;; switchy.el --- A last-recently-used window switcher  -*- 
>>> lexical-binding: t; -*-
>>> ;;
>>> ;; Copyright (C) 2023 Tassilo Horn
>>> ;;
>>> ;; Author: Tassilo Horn <tsdh@gnu.org>
>>> ;; Version: 1.0
>>> ;; Keywords: windows
>>> ;; Homepage: https://sr.ht/~tsdh/switchy/
>>> ;; Repository: https://git.sr.ht/~tsdh/switchy
>>> ;; 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!
>> 
>>> ;; 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?
>> 
>>> ;;
>>> ;; This program is free software; you can redistribute it and/or
>>> ;; modify it under the terms of the GNU General Public License
>>> ;; as published by the Free Software Foundation; either version 3
>>> ;; of the License, or (at your option) any later version.
>>> ;;
>>> ;; This program is distributed in the hope that it will be useful,
>>> ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
>>> ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>>> ;; GNU General Public License for more details.
>>> ;;
>>> ;; You should have received a copy of the GNU General Public License
>>> ;; along with this program.  If not, see <http://www.gnu.org/licenses/>.
>>> ;;
>>> ;;; Commentary:
>>> ;;
>>> ;; Switchy is a last-recently-used window switcher.  It suits my personal 
>>> Emacs
>>> ;; layout and workflow where I usually have at most two editing windows but 
>>> up
>>> ;; to three side-windows which I have to select only seldomly.
>>> ;;
>>> ;; The idea of switchy is simple: when you invoke `switchy-window' in quick
>>> ;; succession, it will switch to one window after the other in
>>> ;; last-recently-used order.  Once you stop switching for long enough time
>>> ;; (`switchy-delay', 1.5 seconds by default), the selected window gets 
>>> locked
>>> ;; in, i.e., its LRU timestamp is updated and this switching sequence is 
>>> ended.
>>> ;; Thusly, you can toggle between two windows simply by invoking
>>> ;; `switchy-window', waiting at least `switchy-delay', and then invoking
>>> ;; `switchy-window' again to switch back to the original window.
>>> ;;
>>> ;; Activate `switchy-minor-mode' which tracks window changes and bind
>>> ;; `switchy-window' to a key of your liking in `switchy-minor-mode-map' (or
>>> ;; globally, see the variable's docstring for examples).
>>> ;;
>>> ;; Hint: Since the order of window switching is not as obvious as it is with
>>> ;; `other-window', adding a bit visual feedback to window selection changes 
>>> can
>>> ;; be helpful.  That can be done easily with the stock Emacs pulse.el, e.g.:
>>> ;;
>>> ;;  (add-hook 'window-selection-change-functions
>>> ;;            (lambda (frame)
>>> ;;              (when (eq frame (selected-frame))
>>> ;;                (pulse-momentary-highlight-one-line))))
>>> 
>>> 
>>> ;;; Code:
>>> 
>>> (defgroup switchy nil
>>>   "Switchy is a last-recently-used window-switcher."
>>>   :group 'windows)
>>> 
>>> (defvar switchy--tick-counter 0
>>>   "Values of this counter represent the last-recently-used order of windows.
>>> Only for internal use.")
>>> 
>>> (defvar switchy--tick-alist nil
>>>   "An alist with entries (WINDOW . TICK).
>>> A higher TICK value means a window has more recently been visited.
>>> Only for internal use.")
>>> 
>>> (defcustom switchy-delay 1.5
>>>   "Number of seconds before the current window gets locked in.
>>> If more time elapses between consecutive invocations of
>>> `switchy-window', the current window's tick (timestamp) is
>>> updated in `switchy--tick-alist' and the current switching cycle
>>> ends."
>>>   :type 'number)
>>> 
>>> (defvar switchy--timer nil
>>>   "The timer locking in the current window after `switchy-delay' seconds.
>>> Only for internal use.")
>>> 
>>> (defvar switchy--visited-windows nil
>>>   "The windows having already been visited in the current switching cycle.")
>>> 
>>> (defun switchy--on-window-selection-change (&optional frame)
>>>   "Record the next `switchy--tick-counter' value for the selected window of 
>>> FRAME.
>>> Meant to be used in `window-selection-change-functions' which is
>>> arranged by `switchy-minor-mode'."
>>>   (when (eq frame (selected-frame))
>>>     (when switchy--timer
>>>       (cancel-timer switchy--timer))
>>>     (setq switchy--timer (run-at-time
>>>                           switchy-delay nil
>>>                           (lambda ()
>>>                             (setf (alist-get (selected-window)
>>>                                              switchy--tick-alist)
>>>                                   (cl-incf switchy--tick-counter))
>>>                             (setq switchy--visited-windows nil))))))
>>> 
>>> (defun switchy-window (&optional arg)
>>>   "Switch to other windows in last-recently-used order.
>>> If prefix ARG is given, use least-recently-used order.
>>> 
>>> If the time between consecutive invocations is smaller than
>>> `switchy-delay' seconds, selects one after the other window in
>>> LRU order and cycles when all windows have been visited.  If
>>> `switchy-delay' has passed, the current switching cycle ends and
>>> the now selected window gets its tick updated (a kind of
>>> timestamp)."
>>>   (interactive)
>>> 
>>>   (unless switchy-minor-mode
>>>     (user-error "switchy-window requires `switchy-minor-mode' being 
>>> active"))
>>> 
>>>   ;; 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.
>> 
>>>   ;; Ensure the current window is marked as visited.
>>>   (setq switchy--visited-windows (cons (selected-window)
>>>                                        switchy--visited-windows))
>>> 
>>>   (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?
>> 
>>>             (setq switchy--visited-windows (cons win 
>>> switchy--visited-windows))
>>>             (select-window win)))
>>>       ;; 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)?
>> 
>>>         (setq switchy--visited-windows nil)
>>>         (switchy-window)))))
>>> 
>>> (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).
>> 
>>>   ;; Or as a substitute for `other-window'.
>>>   (add-hook \\='switchy-minor-mode-hook
>>>             (lambda ()
>>>               (if switchy-minor-mode
>>>                   (keymap-global-set \"<remap> <other-window>\"
>>>                                      #\\='switchy-window)
>>>                 (keymap-global-unset \"<remap> <other-window>\"))))")
>>> 
>>> (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?
>> 
>>>   (if switchy-minor-mode
>>>       (add-hook 'window-selection-change-functions
>>>                 #'switchy--on-window-selection-change)
>>>     (remove-hook 'window-selection-change-functions
>>>                  #'switchy--on-window-selection-change)))
>>> 
>>> (provide 'switchy)
>>> 
>>> (provide 'switchy)
>> 
>> Accidentally duplicated?
>> 
>>> ;;; switchy.el ends here
>>> 
>> 

-- 
Philip Kaludercic