feat(windows): use new windmove-swap-* functions on Emacs 27 and later

Fallback onto buffer-move package for Emacs versions prior to 27.

modules/windows/siren-windmove.el

@@ -6,6 +6,9 @@
 
 ;;; Code:
 
+(when (version< emacs-version "27.0")
+  (require 'siren-buffer-move))
+
 (use-package windmove
   :straight (:type built-in)
 
@@ -14,6 +17,10 @@
   ("M-k" . siren-windmove-down)
   ("M-j" . siren-windmove-left)
   ("M-l" . siren-windmove-right)
+  ("M-K" . siren-windmove-swap-down)
+  ("M-I" . siren-windmove-swap-up)
+  ("M-J" . siren-windmove-swap-left)
+  ("M-L" . siren-windmove-swap-right)
 
   :custom
   (siren-windmove-tmux-fallback (if (getenv "TMUX") t nil))
@@ -41,7 +48,21 @@
     (interactive)
     (if (and (not (ignore-errors (windmove-right)))
              siren-windmove-tmux-fallback)
-        (shell-command "tmux select-pane -R"))))
+        (shell-command "tmux select-pane -R")))
 
+  (defun siren-windmove-swap-defun (direction)
+    "Define window swap function for DIRECTION.
+On Emacs 27.0 or later use windmove, on earlier use buffer-move package."
+    `(defun ,(intern (format "siren-windmove-swap-%s" direction)) ()
+       (interactive)
+       (,(intern (format (if (version< emacs-version "27.0")
+                             "buf-move-%s"
+                           "windmove-swap-states-%s")
+                         direction)))))
+
+  (defmacro siren-windmove-swap-defuns (directions)
+    `(progn ,@(mapcar 'siren-windmove-swap-defun directions)))
+
+  (siren-windmove-swap-defuns (up down left right)))
 (provide 'siren-windmove)
 ;;; siren-windmove.el ends here