I want to write a shackle rule to split the current window (top/bottom) instead of splitting the root window to display the new buffer.

Here is what I'm getting:

|       |current |
|       |        |
|      new       |

here is the associated code

;; shackle
(setq shackle-rules '(("*Flycheck errors*" :regexp t :align 'below :size 10)
                      ("*compilation*"     :regexp t :align 'below :size 0.4)))

this is what I want:

|       |current |
|       |        |
|       +--------+
|       |  new   |
  • 2
    :align is the wrong action for that then, you'll have to write a custom one.
    – wasamasa
    Aug 9, 2017 at 19:22

2 Answers 2


Going off of wasamasa's suggestion, I wrote a simple shackle rule that happened to do what I wanted (extremely simple dynamic tiling). Hopefully with the example (and/or looking at shackle source) you'll be able to get what you wanted.

  (defun jay/shackle--smart-split-dir ()
    (if (>= (window-pixel-height)

  (defun jay/shackle-dynamic-tyling (buffer alist plist)
        ((frame (shackle--splittable-frame))
         (window (if (eq (jay/shackle--smart-split-dir) 'below)
          (window--display-buffer buffer window 'window alist display-buffer-mark-dedicated)
        (when window
          (setq shackle-last-window window
                shackle-last-buffer buffer))
        (unless (cdr (assq 'inhibit-switch-frame alist))
          (window--maybe-raise-frame frame)))))

  (setq shackle-rules
           :regexp t
           :select t
           :custom jay/shackle-dynamic-tyling)))

The rules I tend to use for shackle follow the general form:

:regexp t :popup t :select t :align bottom

And the :select value may be nil depending on whether you want point to move to the new window. So, a couple notes on your code:

  1. I think your :align value is not correct.
  2. If you supply t for :regexp, remember that asterisks in the string are interpreted as special modifying characters, so your buffer names are not matching quite what you might expect. I would remove the :regexp unless you explicitly need it to match multiple buffer names.
  3. I have never tried specifying explicit sizes myself, so cannot advise you on how that works.

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