+;;; Scrolling commands.
+
+;;; Scrolling commands which does not signal errors at top/bottom
+;;; 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-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
+ ((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
+ (t
+ (condition-case nil
+ (scroll-up arg)
+ (end-of-buffer
+ (if arg
+ ;; When scrolling by ARG lines can't be done,
+ ;; move by ARG lines instead.
+ (forward-line arg)
+ ;; When ARG is nil for full-screen scrolling,
+ ;; move to the bottom of the buffer.
+ (goto-char (point-max))))))))
+
+(put 'scroll-up-command 'isearch-scroll t)
+(add-to-list 'scroll-preserve-screen-position-commands 'scroll-up-command)
+
+(defun scroll-down-command (&optional arg)
+ "Scroll text of selected window down ARG lines; or near full screen if no ARG.
+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
+ ((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
+ (t
+ (condition-case nil
+ (scroll-down arg)
+ (beginning-of-buffer
+ (if arg
+ ;; When scrolling by ARG lines can't be done,
+ ;; move by ARG lines instead.
+ (forward-line (- arg))
+ ;; When ARG is nil for full-screen scrolling,
+ ;; move to the top of the buffer.
+ (goto-char (point-min))))))))
+
+(put 'scroll-down-command 'isearch-scroll t)
+(add-to-list 'scroll-preserve-screen-position-commands 'scroll-down-command)
+
+;;; Scrolling commands which scroll a line instead of full screen.
+
+(defun scroll-up-line (&optional arg)
+ "Scroll text of selected window upward ARG lines; or one line if no ARG.
+If ARG is omitted or nil, scroll upward by one line.
+This is different from `scroll-up-command' that scrolls a full screen."
+ (interactive "p")
+ (scroll-up (or arg 1)))
+
+(put 'scroll-up-line 'isearch-scroll t)
+(add-to-list 'scroll-preserve-screen-position-commands 'scroll-up-line)
+
+(defun scroll-down-line (&optional arg)
+ "Scroll text of selected window down ARG lines; or one line if no ARG.
+If ARG is omitted or nil, scroll down by one line.
+This is different from `scroll-down-command' that scrolls a full screen."
+ (interactive "p")
+ (scroll-down (or arg 1)))
+
+(put 'scroll-down-line 'isearch-scroll t)
+(add-to-list 'scroll-preserve-screen-position-commands 'scroll-down-line)
+
+\f