Subject: 27.0.50; Directional window swap states

From: Juri Linkov <[email-masked]>
Date: Mon, 25 Feb 2019 22:51:06 +0200

Tags: patch
Severity: wishlist

Now we have a useful command ‘window-swap-states’ whose only drawback is that
it operates on a random window, i.e. a next window in some mystic cyclic ordering
whose logic I've never been able to understand.

To simplify its logic, windmove could be extended to support directional swapping
where the user can point at the window whose state should be swapped
with the selected window.

As a funny effect, when windows are arranged as 4x4 square tiles, e.g.

(window-state-put
 '(()
   hc
   (vc
    (leaf (buffer "1"))
    (leaf (buffer "5"))
    (leaf (buffer "9"))
    (leaf (buffer "13")))
   (vc
    (leaf (buffer "2"))
    (leaf (buffer "6"))
    (leaf (buffer "10"))
    (leaf (buffer "14")))
   (vc
    (leaf (buffer "3"))
    (leaf (buffer "7"))
    (leaf (buffer "11"))
    (leaf (buffer "15")))
   (vc
    (leaf (buffer "4"))
    (leaf (buffer "8"))
    (leaf (buffer "12"))
    (leaf (buffer " "))))
 (frame-root-window))

sliding them has the same feeling like solving the 15 puzzle :)

diff --git a/lisp/windmove.el b/lisp/windmove.el
index 65270d9bbe..e2422a7df4 100644
--- a/lisp/windmove.el
+++ b/lisp/windmove.el
@@ -750,6 +752,60 @@ windmove-delete-default-keybindings
   (global-set-key (vector prefix (append modifiers '(up)))    'windmove-delete-up)
   (global-set-key (vector prefix (append modifiers '(down)))  'windmove-delete-down))
 
+
+;;; Directional window swap states
+
+(defun windmove-swap-states-in-direction (dir)
+  "Swap the states of the selected window and the window at direction DIR.
+When `windmove-wrap-around' is non-nil, takes the window
+from the opposite side of the frame."
+  (let ((other-window (window-in-direction dir nil nil nil
+                                           windmove-wrap-around t)))
+    (cond ((null other-window)
+           (user-error "No window %s from selected window" dir))
+          (t
+           (window-swap-states nil other-window)))))
+
+;;;###autoload
+(defun windmove-swap-states-left ()
+  "Swap the states with the window on the left from the current one."
+  (interactive)
+  (windmove-swap-states-in-direction 'left))
+
+;;;###autoload
+(defun windmove-swap-states-up ()
+  "Swap the states with the window above from the current one."
+  (interactive)
+  (windmove-swap-states-in-direction 'up))
+
+;;;###autoload
+(defun windmove-swap-states-down ()
+  "Swap the states with the window below from the current one."
+  (interactive)
+  (windmove-swap-states-in-direction 'down))
+
+;;;###autoload
+(defun windmove-swap-states-right ()
+  "Swap the states with the window on the right from the current one."
+  (interactive)
+  (windmove-swap-states-in-direction 'right))
+
+;;;###autoload
+(defun windmove-swap-states-default-keybindings (&optional modifiers)
+  "Set up keybindings for directional window swap states.
+Keys are bound to commands that swap the states of the selected window
+with the window in the specified direction.  Keybindings are of the form
+MODIFIERS-{left,right,up,down}, where MODIFIERS is either a list of modifiers
+or a single modifier.  Default value of MODIFIERS is `shift-super'."
+  (interactive)
+  (unless modifiers (setq modifiers '(shift super)))
+  (unless (listp modifiers) (setq modifiers (list modifiers)))
+  (global-set-key (vector (append modifiers '(left)))  'windmove-swap-states-left)
+  (global-set-key (vector (append modifiers '(right))) 'windmove-swap-states-right)
+  (global-set-key (vector (append modifiers '(up)))    'windmove-swap-states-up)
+  (global-set-key (vector (append modifiers '(down)))  'windmove-swap-states-down))
+
+
 (provide 'windmove)
 
 ;;; windmove.el ends here