Adding window layout toggle (vertical <-> horizontal)

All credits to @bmag for this function with window state preservation

layers/+distribution/spacemacs-base/funcs.el

@@ -221,6 +221,24 @@ the current state and point position."
                (when (string-match regexp buf-name)
                  (return t))))))
 
+;; from @bmag
+(defun spacemacs/window-layout-toggle ()
+  "Toggle between horizontal and vertical layout of two windows."
+  (interactive)
+  (when (= (count-windows) 2)
+    (let* ((window-tree (car (window-tree)))
+           (current-split-vertical-p (car window-tree))
+           (first-window (nth 2 window-tree))
+           (second-window (nth 3 window-tree))
+           (second-window-state (window-state-get second-window))
+           (splitter (if current-split-vertical-p
+                         #'split-window-horizontally
+                       #'split-window-vertically)))
+      (delete-other-windows first-window)
+      ;; `window-state-put' also re-selects the window if needed, so we don't
+      ;; need to call `select-window'
+      (window-state-put second-window-state (funcall splitter)))))
+
 ;; from magnars modified by ffevotte for dedicated windows support
 (defun spacemacs/rotate-windows (count)
   "Rotate your windows.

layers/+distribution/spacemacs-base/keybindings.el

@@ -336,7 +336,8 @@ Ensure that helm is required before calling FUNC."
   "wV"  'split-window-right-and-focus
   "ww"  'other-window
   "w/"  'split-window-right
-  "w="  'balance-windows)
+  "w="  'balance-windows
+  "w+"  'spacemacs/window-layout-toggle)
 ;; text -----------------------------------------------------------------------
 (defalias 'count-region 'count-words-region)