Variable: pop-up-frames
pop-up-frames is a customizable variable defined in window.el.gz.
Value
nil
Documentation
Whether display-buffer should make a separate frame.
If nil, never make a separate frame.
If the value is graphic-only, make a separate frame
on graphic displays only.
Any other non-nil value means always make a separate frame.
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.
Probably introduced at or before Emacs version 19.23.
Source Code
;; Defined in /usr/src/emacs/lisp/window.el.gz
(defcustom pop-up-frames nil
"Whether `display-buffer' should make a separate frame.
If nil, never make a separate frame.
If the value is `graphic-only', make a separate frame
on graphic displays only.
Any other non-nil value means always make a separate frame.
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 '(choice
(const :tag "Never" nil)
(const :tag "On graphic displays only" graphic-only)
(const :tag "Always" t))
:group 'windows)