Function: split-window-below

split-window-below is an interactive and byte-compiled function defined in window.el.gz.

Signature

(split-window-below &optional SIZE)

Documentation

Split the selected window into two windows, one above the other.

The selected window is above. The newly split-off window is below and displays the same buffer. Return the new window.

If optional argument SIZE is omitted or nil, both windows get the same height, or close to it. If SIZE is positive, the upper
(selected) window gets SIZE lines. If SIZE is negative, the
lower (new) window gets -SIZE lines.

If the variable split-window-keep-point is non-nil, both windows get the same value of point as the selected window. Otherwise, the window starts are chosen so as to minimize the amount of redisplay; this is convenient on slow terminals.

Probably introduced at or before Emacs version 24.1.

Key Bindings

Aliases

split-window-vertically

Source Code

;; Defined in /usr/src/emacs/lisp/window.el.gz
(defun split-window-below (&optional size)
  "Split the selected window into two windows, one above the other.
The selected window is above.  The newly split-off window is
below and displays the same buffer.  Return the new window.

If optional argument SIZE is omitted or nil, both windows get the
same height, or close to it.  If SIZE is positive, the upper
\(selected) window gets SIZE lines.  If SIZE is negative, the
lower (new) window gets -SIZE lines.

If the variable `split-window-keep-point' is non-nil, both
windows get the same value of point as the selected window.
Otherwise, the window starts are chosen so as to minimize the
amount of redisplay; this is convenient on slow terminals."
  (interactive "P")
  (let ((old-window (selected-window))
	(old-point (window-point))
	(size (and size (prefix-numeric-value size)))
        moved-by-window-height moved new-window bottom)
    (when (and size (< size 0) (< (- size) window-min-height))
      ;; `split-window' would not signal an error here.
      (error "Size of new window too small"))
    (setq new-window (split-window nil size))
    (unless split-window-keep-point
      (with-current-buffer (window-buffer)
	;; Use `save-excursion' around vertical movements below
	;; (Bug#10971).  Note: When the selected window's buffer has a
	;; header line, up to two lines of the buffer may not show up
	;; in the resulting configuration.
	(save-excursion
	  (goto-char (window-start))
	  (setq moved (vertical-motion (window-height)))
	  (set-window-start new-window (point))
	  (when (> (point) (window-point new-window))
	    (set-window-point new-window (point)))
	  (when (= moved (window-height))
	    (setq moved-by-window-height t)
	    (vertical-motion -1))
	  (setq bottom (point)))
	(and moved-by-window-height
	     (<= bottom (point))
	     (set-window-point old-window (1- bottom)))
	(and moved-by-window-height
	     (<= (window-start new-window) old-point)
	     (set-window-point new-window old-point)
	     (select-window new-window))))
    ;; Always copy quit-restore parameter in interactive use.
    (let ((quit-restore (window-parameter old-window 'quit-restore)))
      (when quit-restore
	(set-window-parameter new-window 'quit-restore quit-restore)))
    new-window))