Variable: ediff-split-window-function
ediff-split-window-function is a customizable variable defined in
ediff-wind.el.gz.
Value
split-window-vertically
Documentation
The function used to split the main window between buffer-A and buffer-B.
You can set it to a horizontal split instead of the default vertical split
by setting this variable to split-window-horizontally.
You can also have your own function to do fancy splits.
This variable has no effect when buffer-A/B are shown in different frames.
In this case, Ediff will use those frames to display these buffers.
Source Code
;; Defined in /usr/src/emacs/lisp/vc/ediff-wind.el.gz
(defcustom ediff-split-window-function #'split-window-vertically
"The function used to split the main window between buffer-A and buffer-B.
You can set it to a horizontal split instead of the default vertical split
by setting this variable to `split-window-horizontally'.
You can also have your own function to do fancy splits.
This variable has no effect when buffer-A/B are shown in different frames.
In this case, Ediff will use those frames to display these buffers."
:type '(choice
(const :tag "Split vertically" split-window-vertically)
(const :tag "Split horizontally" split-window-horizontally)
function))