+;; $Id: smooth-scrolling.el,v 1.8 2007/09/11 23:38:09 adam Exp $
+;; Adam Spiers <email@example.com>
+;; Make emacs scroll smoothly, keeping the point away from the top and
+;; bottom of the current buffer's window in order to keep lines of
+;; context around the point visible as much as possible, whilst
+;; avoiding sudden scroll jumps which are visually confusing.
+;; This is a nice alternative to all the native scroll-* custom
+;; variables, which unfortunately cannot provide this functionality
+;; perfectly. `scroll-margin' comes closest, but has some bugs
+;; (e.g. with handling of mouse clicks). See
+;; for the gory details.
+;; Put somewhere on your `load-path' and include
+;; (require 'smooth-scrolling)
+;; in your .emacs initialization file.
+;; This only affects the behaviour of the `next-line' and
+;; `previous-line' functions, usually bound to the cursor keys and
+;; C-n/C-p. Other methods of moving the point will behave as normal
+;; according to the standard custom variables.
+;; Prefix arguments to `next-line' and `previous-line' are honoured.
+;; The minimum number of lines are scrolled in order to keep the
+;; point outside the margin.
+;; There is one case where moving the point in this fashion may cause
+;; a jump: if the point is placed inside one of the margins by another
+;; method (e.g. left mouse click, or M-x goto-line) and then moved in
+;; the normal way, the advice code will scroll the minimum number of
+;; lines in order to keep the point outside the margin. This jump may
+;; cause some slight confusion at first, but hopefully it is justified
+;; by the benefit of automatically ensuring `smooth-scroll-margin'
+;; lines of context are visible around the point as often as possible.
+;; - Maybe add option to avoid scroll jumps when point is within
+;; Thanks to Mark Hulme-Jones and consolers on #emacs for helping
+;; debug issues with line-wrapping.
+;; Released under the GNU General Public License v2 or later, with
+;; all rights assigned to the Free Software Foundation.
+;;;_ + disable `scroll-margin'
+(defcustom smooth-scroll-margin 10
+ "Number of lines of visible margin at the top and bottom of a window.
+If the point is within these margins, then scrolling will occur
+smoothly for `previous-line' at the top of the window, and for
+`next-line' at the bottom.
+This is very similar in its goal to `scroll-margin'. However, it
+is implemented by activating `smooth-scroll-down' and
+`smooth-scroll-up' advise via `defadvice' for `previous-line' and
+`next-line' respectively. As a result it avoids problems
+afflicting `scroll-margin', such as a sudden jump and unexpected
+highlighting of a region when the mouse is clicked in the margin.
+Scrolling only occurs when the point is closer to the window
+boundary it is heading for (top or bottom) than the middle of the
+window. This is to intelligently handle the case where the
+margins cover the whole buffer (e.g. `smooth-scroll-margin' set
+to 5 and `window-height' returning 10 or less).
+See also `smooth-scroll-strict-margins'."
+(defcustom smooth-scroll-strict-margins t
+ "If true, the advice code supporting `smooth-scroll-margin'
+will use `count-screen-lines' to determine the number of
+*visible* lines between the point and the window top/bottom,
+rather than `count-lines' which obtains the number of actual
+newlines. This is because there might be extra newlines hidden
+by a mode such as folding-mode, outline-mode, org-mode etc., or
+fewer due to very long lines being displayed wrapped when
+`truncate-lines' is nil.
+However, using `count-screen-lines' can supposedly cause
+performance issues in buffers with extremely long lines. Setting
+`cache-long-line-scans' may be able to address this;
+alternatively you can set this variable to nil so that the advice