>From c1c9f28a03d46595a53561036cf0fb57e340d8e1 Mon Sep 17 00:00:00 2001
From: Hugo Heagren <hugo@heagren.com>
Date: Tue, 26 Jul 2022 22:37:21 +0100
Subject: [PATCH 2/6] split-root-window-below: New function

* lisp/window.el (split-root-window-below): New function to split
whole frame.
* doc/lispref/windows.texi (Splitting Windows): Add documentation for
`split-root-window-below'.
---
 doc/lispref/windows.texi | 7 +++++++
 lisp/window.el           | 8 ++++++++
 2 files changed, 15 insertions(+)

diff --git a/doc/lispref/windows.texi b/doc/lispref/windows.texi
index 255e33ad0d..51e54ebcd4 100644
--- a/doc/lispref/windows.texi
+++ b/doc/lispref/windows.texi
@@ -1485,6 +1485,13 @@ Splitting Windows
 negative, the lower window gets @minus{}@var{size} lines.
 @end deffn
 
+@deffn Command split-root-window-below &optional size
+This function splits the whole frame in two.  The current window
+configuration is retained on the top, and a new window is created
+below, taking up the whole width of the frame.  @var{size} is treated
+as by @code{split-window-below}.
+@end deffn
+
 @defopt split-window-keep-point
 If the value of this variable is non-@code{nil} (the default),
 @code{split-window-below} behaves as described above.
diff --git a/lisp/window.el b/lisp/window.el
index 69089e63f5..556fcddf47 100644
--- a/lisp/window.el
+++ b/lisp/window.el
@@ -5726,6 +5726,14 @@ split-window-below
 
 (defalias 'split-window-vertically 'split-window-below)
 
+(defun split-root-window-below (&optional size)
+  "Split root window of current frame in two.
+The current window configuration is retained in the top window,
+the lower window takes up the whole width of the frame.  SIZE is
+handled as in `split-window-below'."
+  (interactive "P")
+  (split-window-below size (frame-root-window)))
+
 (defun split-window-right (&optional size)
   "Split the selected window into two side-by-side windows.
 The selected window is on the left.  The newly split-off window
-- 
2.20.1