bug#48917: 28.0.50; allow user to choose what function is used when windmove create a window

[pillule <pillule@riseup.net>]

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Juri Linkov <juri@linkov.net> writes:

>>>>    :version "27.1")
>>>
>>> The :version tag should be updated, because the defcustom was changed.
>>
>> -  :version "27.1")
>> +  :version "28.0.50")

Done.

> Thanks for sending two patches in bug#48916 and bug#48917.
> If you have not signed papers yet, I guess
> these patches are small enough to push.
>
> But in both patches please change the :version tag to "28.1".

I get the papers now \o/

I was a little bit worried that this user-option is quite obscure to understand,
so among other little docstring fixes, I documented an usage with
'display-buffer-alist' in the commentary section of the package.

Please let me know if it is not desirable, in which case I will remove it.

Also I added the parent function ARG to be passed, it is an universal-argument.


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From f276e2b7fe96512b1ed88be8f8da66faab7a24e4 Mon Sep 17 00:00:00 2001
From: Trust me I am a doctor <pillule@riseup.net>
Date: Tue, 8 Jun 2021 11:44:54 +0200
Subject: [PATCH] User option to choose a function triggered by windmove-create

* lisp/windmove.el (windmove-create-window): Add a defcustom choice.
(windmove-do-window-select): Trigger custom functions, update the
docstring.

Commentary: document the usage of this user option with a basic
'display-buffer-alist', a dispatcher function for
'windmove-create-window' and an alist to hold the dispatch.
---
 lisp/windmove.el | 92 ++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 85 insertions(+), 7 deletions(-)

diff --git a/lisp/windmove.el b/lisp/windmove.el
index f558903681..e49b6ad654 100644
--- a/lisp/windmove.el
+++ b/lisp/windmove.el
@@ -110,6 +110,72 @@
 ;;    (setq windmove-wrap-around t)
 ;;
 
+;; Configuring windmove to display side windows :
+;;
+;; Assuming you have customized your 'display-buffer-alist' to
+;; uses side-windows, see (info "(elisp) Choosing Window")
+;;
+;; Or refer to this basic example :
+;;
+;; (customize-set-variable 'display-buffer-alist
+;; 			'(("\\*Ibuffer\\*"
+;; 			   (display-buffer-in-side-window)
+;; 			   (side . left) (window-width . 42))
+;; 			  ("\\*Info.*"
+;; 			   (display-buffer-in-side-window)
+;; 			   (side . right) (window-width . 80))
+;; 			  ("\\*e?shell.*"
+;; 			   (display-buffer-in-side-window)
+;; 			   (side . top))
+;; 			  ("\\*Messages.*"
+;; 			   (display-buffer-in-side-window)
+;; 			   (side . bottom))))
+;;
+;; You can create a function that will dispatch the calls by direction :
+;;
+;; (defun windmove-create-side-window (dir arg window)
+;;   "Intermedary function choosing what to call on direction DIR.
+;; If the selected-window is a side-window, delete it, otherwise,
+;; select the relevant window from `windmove-dispatch-sides-functions'.
+;; Only pass ARG and WINDOW to the childs functions."
+;;   ;; normalise the direction
+;;   (let ((dir (pcase dir (`up 'top) (`down 'bottom) (_ dir))))
+;;     (funcall (if (eq dir (window-parameter window 'window-side))
+;;                  (lambda (_dir _arg window)
+;;                    (prog1 (get-mru-window) (delete-window window)))
+;;                (alist-get dir windmove-dispatch-sides-functions))
+;;              dir arg window)))
+;;
+;; Then assign it to 'windmove-create-window'
+;;
+;; (customize-set-variable 'windmove-create-window
+;;                         #'windmove-create-side-window)
+;;
+;; You can then specify an alist to actually hold the functions
+;; to be called with their directions :
+;;
+;; (defvar windmove-dispatch-sides-functions
+;;   '((left . (lambda (_dir _arg _window)
+;;               (ibuffer 'other-window)
+;;               (get-buffer-window "*Ibuffer*")))
+;;     (right . (lambda (_dir _arg _window)
+;;                (let ((buffer (get-buffer "*info*")))
+;;                  (if buffer
+;;                      (display-buffer buffer)
+;;                    (info))
+;;                  (get-buffer-window "*info*"))))
+;;     (top . (lambda (_dir _arg _window)
+;;              (shell)
+;;              (get-buffer-window "*shell*")))
+;;     (bottom . (lambda (_arg _dir _window)
+;;                 (view-echo-area-messages)
+;;                 'no-select)))
+;;   "Alist to dispatch by direction the calls of `windmove-create-side-window'")
+;;
+;; And also activate this recommended setting :
+;;
+;; (customize-set-variable 'windmove-allow-all-windows t)
+
 ;; Acknowledgments:
 ;;
 ;; Special thanks to Julian Assange (proff@iq.org), whose
@@ -142,13 +208,21 @@ windmove-wrap-around
   :group 'windmove)
 
 (defcustom windmove-create-window nil
-  "Whether movement off the edge of the frame creates a new window.
+  "Whether movement off the edge of the frame create a new window.
 If this variable is set to t, moving left from the leftmost window in
 a frame will create a new window on the left, and similarly for the other
-directions."
-  :type 'boolean
-  :group 'windmove
-  :version "27.1")
+directions.
+This variable may also be a function to be called in this circumstance
+by `windmove-do-window-select'.  The function should accept then as
+argument the DIRECTION targeted, an interactive ARG and a WINDOW
+corresponding to the currently selected window.  It should also returns
+or a valid window that `windmove-do-window-select' will select,
+or the symbol 'no-select to ignore that final selection.
+The comments of windmove.el show an example of this utilisation."
+  :type '(choice (const :tag "Don't create new windows" nil)
+          (const :tag "Create new windows" t)
+          (function :tag "Provide a function"))
+  :version "28.1")
 
 ;; If your Emacs sometimes places an empty column between two adjacent
 ;; windows, you may wish to set this delta to 2.
@@ -350,19 +424,23 @@ windmove-do-window-select
   "Move to the window at direction DIR as seen from WINDOW.
 DIR, ARG, and WINDOW are handled as by `windmove-find-other-window'.
 If no window is at direction DIR, an error is signaled.
-If `windmove-create-window' is non-nil, try to create a new window
+If `windmove-create-window' is a function, call that function with
+DIR, ARG and WINDOW, if it is non-nil, try to create a new window
 in direction DIR instead."
   (let ((other-window (windmove-find-other-window dir arg window)))
     (when (and windmove-create-window
                (or (null other-window)
                    (and (window-minibuffer-p other-window)
                         (not (minibuffer-window-active-p other-window)))))
-      (setq other-window (split-window window nil dir)))
+      (setq other-window (if (functionp windmove-create-window)
+                             (funcall windmove-create-window dir arg window)
+                           (split-window window nil dir))))
     (cond ((null other-window)
            (user-error "No window %s from selected window" dir))
           ((and (window-minibuffer-p other-window)
                 (not (minibuffer-window-active-p other-window)))
            (user-error "Minibuffer is inactive"))
+          ((eq other-window 'no-select))
           (t
            (select-window other-window)))))
 
-- 
2.20.1


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