Make the user customizable display-buffer variable empty by default.

* lisp/window.el (display-buffer-base-action): Rename from
display-buffer-default-action.  Make default value empty.
(display-buffer-overriding-action): Convert to defvar.
(display-buffer-fallback-action): New var.

2 files changed, 39 insertions, 26 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 91ffbcff96b..57c623df56a 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,5 +1,12 @@
 2011-09-15  Chong Yidong  <cyd@stupidchicken.com>
 
+	* window.el (display-buffer-base-action): Rename from
+	display-buffer-default-action.  Make default value empty.
+	(display-buffer-overriding-action): Convert to defvar.
+	(display-buffer-fallback-action): New var.
+
+2011-09-15  Chong Yidong  <cyd@stupidchicken.com>
+
 	* emacs-lisp/package.el (package-alist): Fix risky-local-variable
 	declaration.
 	(package--add-to-archive-contents): If there is a duplicate entry
diff --git a/lisp/window.el b/lisp/window.el
index 24d95f367e4..c0e8781aab0 100644
--- a/lisp/window.el
+++ b/lisp/window.el
@@ -4465,6 +4465,14 @@ BUFFER-OR-NAME and return that buffer."
 		:value-type (sexp :tag "Value")))
   "Custom type for `display-buffer' actions.")
 
+(defvar display-buffer-overriding-action '(nil . nil)
+  "Overriding action to perform to display a buffer.
+It should be a cons cell (FUNCTION . ALIST), where FUNCTION is a
+function or a list of functions.  Each function should accept 2
+arguments: a buffer to display and an alist similar to ALIST.
+See `display-buffer' for details.")
+(put 'display-buffer-overriding-action 'risky-local-variable t)
+
 (defcustom display-buffer-alist nil
   "Alist of conditional actions for `display-buffer'.
 This is a list of elements (CONDITION . ACTION), where:
@@ -4485,15 +4493,8 @@ This is a list of elements (CONDITION . ACTION), where:
   :version "24.1"
   :group 'windows)
 
-(defcustom display-buffer-default-action
-  '((display-buffer--maybe-same-window
-     display-buffer-reuse-window
-     display-buffer--special
-     display-buffer--maybe-pop-up-frame-or-window
-     display-buffer-use-some-window
-     ;; If all else fails, pop up a new frame.
-     display-buffer-pop-up-frame))
-  "List of default actions for `display-buffer'.
+(defcustom display-buffer-base-action '(nil . nil)
+  "User-specified default action for `display-buffer'.
 It should be a cons cell (FUNCTION . ALIST), where FUNCTION is a
 function or a list of functions.  Each function should accept 2
 arguments: a buffer to display and an alist similar to ALIST.
@@ -4503,16 +4504,19 @@ See `display-buffer' for details."
   :version "24.1"
   :group 'windows)
 
-(defcustom display-buffer-overriding-action '(nil . nil)
-  "Overriding action to perform to display a buffer.
-It should be a cons cell (FUNCTION . ALIST), where FUNCTION is a
-function or a list of functions.  Each function should accept 2
-arguments: a buffer to display and an alist similar to ALIST.
-See `display-buffer' for details."
-  :type display-buffer--action-custom-type
-  :risky t
-  :version "24.1"
-  :group 'windows)
+(defconst display-buffer-fallback-action
+  '((display-buffer--maybe-same-window
+     display-buffer-reuse-window
+     display-buffer--special
+     display-buffer--maybe-pop-up-frame-or-window
+     display-buffer-use-some-window
+     ;; If all else fails, pop up a new frame.
+     display-buffer-pop-up-frame))
+  "Default fallback action for `display-buffer'.
+This is the action used by `display-buffer' if no other actions
+specified, e.g. by the user options `display-buffer-alist' or
+`display-buffer-base-action'.  See `display-buffer'.")
+(put 'display-buffer-fallback-action 'risky-local-variable t)
 
 (defun display-buffer-assq-regexp (buffer-name alist)
   "Retrieve ALIST entry corresponding to BUFFER-NAME."
@@ -4553,12 +4557,13 @@ function is called with 2 arguments: the buffer to display and an
 alist.  It should either display the buffer and return the
 window, or return nil if unable to display the buffer.
 
-`display-buffer' builds a function list and an alist from
-`display-buffer-overriding-action', `display-buffer-alist',
-ACTION, and `display-buffer-default-action' (in that order).
-Then it calls each function in the combined function list in
-turn, passing the buffer as the first argument and the combined
-alist as the second argument, until a function returns non-nil.
+The `display-buffer' function builds a function list and an alist
+from `display-buffer-overriding-action', `display-buffer-alist',
+the ACTION argument, `display-buffer-base-action', and
+`display-buffer-fallback-action' (in that order).  Then it calls
+each function in the combined function list in turn, passing the
+buffer as the first argument and the combined alist as the second
+argument, until one of the functions returns non-nil.
 
 Available action functions include:
  `display-buffer-same-window'
@@ -4608,7 +4613,8 @@ search for a window that is already displaying the buffer.  See
 	     ;; Construct action function list and action alist.
 	     (actions (list display-buffer-overriding-action
 			    user-action action extra-action
-			    display-buffer-default-action))
+			    display-buffer-base-action
+			    display-buffer-fallback-action))
 	     (functions (apply 'append
 			       (mapcar (lambda (x)
 					 (setq x (car x))