Adding window layout toggle (vertical <-> horizontal)

[nixmaniack]

Generally I find toggling window layout when window I open unintentionally opens in other layout. This PR adds a toggle to easily switch between the layouts using SPC w +. Used + as it's free binding and denotes both layouts in one symbol.

[robbyoconnor]

I love this :D

[bmag]

Nice idea, but the current implementation doesn't save any window parameters or the window's dedication status. For example, if the non-selected window is dedicated to its buffer, after toggling the layout it becomes non-dedicated. Also, all window parameters that it had are lost.

How about this implementation, which uses window-state-get and window-state-put? (I'm not sure how to make a PR for an existing PR, so posting it here)

(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)))))

[nixmaniack]

@bmag Oh never thought about dedicated windows! That's one awesome feature. I'm pushing to this PR just add to avoid duplication (with all due credits to you! Thanks).

[bmag]

@nixmaniack I'd like to (finally) merge this one in the next few days. Can you fix the conflicts please?

[nixmaniack]

@bmag Applied the patch on current develop. Should be good to go.

[bmag]

Thank you 👍 Cherry-picked into develop, you can safely delete your branch. I added an error in case the number of windows isn't exactly 2 in 0d4a8a4