Add variable scroll-error-top-bottom.

http://lists.gnu.org/archive/html/emacs-devel/2010-04/msg00403.html

* simple.el (scroll-error-top-bottom): New defcustom.
(scroll-up-command, scroll-down-command): Use it.  Doc fix.

* emulation/pc-select.el (pc-select-override-scroll-error):
Obsolete in favor of `scroll-error-top-bottom'.

4 files changed, 38 insertions, 8 deletions

diff --git a/etc/NEWS b/etc/NEWS
index b559b9c93a6..6bb48fe59b0 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -69,8 +69,9 @@ Use `set-scroll-bar-mode' to change this.
 with Xft.
 
 ** New scrolling commands `scroll-up-command' and `scroll-down-command'
-(bound to [next] and [prior]) does not signal errors at top/bottom
-of buffer at first key-press (instead moves to top/bottom of buffer).
+(bound to C-v/[next] and M-v/[prior]) does not signal errors at top/bottom
+of buffer at first key-press (instead moves to top/bottom of buffer)
+when a new variable `scroll-error-top-bottom' is non-nil.
 
 ** New scrolling commands `scroll-up-line' and `scroll-down-line'
 scroll a line instead of full screen.
diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 01bfbf55434..89d56ffd323 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,5 +1,13 @@
 2010-04-14  Juri Linkov  <juri@jurta.org>
 
+        * simple.el (scroll-error-top-bottom): New defcustom.
+        (scroll-up-command, scroll-down-command): Use it.  Doc fix.
+
+        * emulation/pc-select.el (pc-select-override-scroll-error):
+        Obsolete in favor of `scroll-error-top-bottom'.
+
+2010-04-14  Juri Linkov  <juri@jurta.org>
+
         * tutorial.el (tutorial--default-keys): Rebind `C-v' to
         `scroll-up-command' and `M-v' to `scroll-down-command'.
 
diff --git a/lisp/emulation/pc-select.el b/lisp/emulation/pc-select.el
index 175999b6e37..529ba290cb8 100644
--- a/lisp/emulation/pc-select.el
+++ b/lisp/emulation/pc-select.el
@@ -93,6 +93,9 @@ text with these commands.  If you set this variable to non-nil, these
 errors are suppressed."
   :type 'boolean
   :group 'pc-select)
+(define-obsolete-variable-alias 'pc-select-override-scroll-error
+                                'scroll-error-top-bottom
+                                "24.1")
 
 (defcustom pc-select-selection-keys-only nil
   "*Non-nil means only bind the basic selection keys when started.
diff --git a/lisp/simple.el b/lisp/simple.el
index 60fe6c875d2..34e31b10276 100644
--- a/lisp/simple.el
+++ b/lisp/simple.el
@@ -4744,20 +4744,34 @@ This also turns on `word-wrap' in the buffer."
 ;;; of buffer at first key-press (instead moves to top/bottom
 ;;; of buffer).
 
+(defcustom scroll-error-top-bottom nil
+  "Move point to top/bottom of buffer before signalling a scrolling error.
+A value of nil means just signal an error if no more scrolling possible.
+A value of t means point moves to the beginning or the end of the buffer
+\(depending on scrolling direction) when no more scrolling possible.
+When point is already on that position, then signal an error."
+  :type 'boolean
+  :group 'scrolling
+  :version "24.1")
+
 (defun scroll-up-command (&optional arg)
   "Scroll text of selected window upward ARG lines; or near full screen if no ARG.
-If `scroll-up' cannot scroll window further, move cursor to the bottom line.
+If `scroll-error-top-bottom' is non-nil and `scroll-up' cannot
+scroll window further, move cursor to the bottom line.
 When point is already on that position, then signal an error.
 A near full screen is `next-screen-context-lines' less than a full screen.
 Negative ARG means scroll downward.
 If ARG is the atom `-', scroll downward by nearly full screen."
   (interactive "^P")
   (cond
-   ((eq arg '-) (scroll-down-command nil))
+   ((null scroll-error-top-bottom)
+    (scroll-up arg))
+   ((eq arg '-)
+    (scroll-down-command nil))
    ((< (prefix-numeric-value arg) 0)
     (scroll-down-command (- (prefix-numeric-value arg))))
    ((eobp)
-    (scroll-up arg))  ; signal error
+    (scroll-up arg))                    ; signal error
    (t
     (condition-case nil
         (scroll-up arg)
@@ -4775,18 +4789,22 @@ If ARG is the atom `-', scroll downward by nearly full screen."
 
 (defun scroll-down-command (&optional arg)
   "Scroll text of selected window down ARG lines; or near full screen if no ARG.
-If `scroll-down' cannot scroll window further, move cursor to the top line.
+If `scroll-error-top-bottom' is non-nil and `scroll-down' cannot
+scroll window further, move cursor to the top line.
 When point is already on that position, then signal an error.
 A near full screen is `next-screen-context-lines' less than a full screen.
 Negative ARG means scroll upward.
 If ARG is the atom `-', scroll upward by nearly full screen."
   (interactive "^P")
   (cond
-   ((eq arg '-) (scroll-up-command nil))
+   ((null scroll-error-top-bottom)
+    (scroll-down arg))
+   ((eq arg '-)
+    (scroll-up-command nil))
    ((< (prefix-numeric-value arg) 0)
     (scroll-up-command (- (prefix-numeric-value arg))))
    ((bobp)
-    (scroll-down arg))  ; signal error
+    (scroll-down arg))                  ; signal error
    (t
     (condition-case nil
         (scroll-down arg)