Variable: pop-up-windows
pop-up-windows is a customizable variable defined in window.el.gz.
Value
t
Documentation
Non-nil means display-buffer should make a new window.
This variable is provided mainly for backward compatibility and
should not be used in new code. To make display-buffer behave
as if this were t, customize display-buffer-base-action
instead. See Info node (elisp) Choosing Window Options in the
Emacs Lisp manual for an example.
Source Code
;; Defined in /usr/src/emacs/lisp/window.el.gz
(defcustom pop-up-windows t
"Non-nil means `display-buffer' should make a new window.
This variable is provided mainly for backward compatibility and
should not be used in new code. To make `display-buffer' behave
as if this were t, customize `display-buffer-base-action'
instead. See Info node `(elisp) Choosing Window Options' in the
Emacs Lisp manual for an example."
:type 'boolean
:group 'windows)