about summary refs log tree commit diff
path: root/configs/shared/emacs/.emacs.d/elpa/undo-tree-0.6.5/undo-tree.el
diff options
context:
space:
mode:
Diffstat (limited to 'configs/shared/emacs/.emacs.d/elpa/undo-tree-0.6.5/undo-tree.el')
-rw-r--r--configs/shared/emacs/.emacs.d/elpa/undo-tree-0.6.5/undo-tree.el4418
1 files changed, 0 insertions, 4418 deletions
diff --git a/configs/shared/emacs/.emacs.d/elpa/undo-tree-0.6.5/undo-tree.el b/configs/shared/emacs/.emacs.d/elpa/undo-tree-0.6.5/undo-tree.el
deleted file mode 100644
index 3e45b84e137c..000000000000
--- a/configs/shared/emacs/.emacs.d/elpa/undo-tree-0.6.5/undo-tree.el
+++ /dev/null
@@ -1,4418 +0,0 @@
-;;; undo-tree.el --- Treat undo history as a tree  -*- lexical-binding: t; -*-
-
-;; Copyright (C) 2009-2013  Free Software Foundation, Inc
-
-;; Author: Toby Cubitt <toby-undo-tree@dr-qubit.org>
-;; Version: 0.6.5
-;; Keywords: convenience, files, undo, redo, history, tree
-;; URL: http://www.dr-qubit.org/emacs.php
-;; Repository: http://www.dr-qubit.org/git/undo-tree.git
-
-;; This file is part of Emacs.
-;;
-;; This file is free software: you can redistribute it and/or modify it under
-;; the terms of the GNU General Public License as published by the Free
-;; Software Foundation, either version 3 of the License, or (at your option)
-;; any later version.
-;;
-;; This program is distributed in the hope that it will be useful, but WITHOUT
-;; ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
-;; FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
-;; more details.
-;;
-;; You should have received a copy of the GNU General Public License along
-;; with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
-
-
-;;; Commentary:
-;;
-;; Emacs has a powerful undo system. Unlike the standard undo/redo system in
-;; most software, it allows you to recover *any* past state of a buffer
-;; (whereas the standard undo/redo system can lose past states as soon as you
-;; redo). However, this power comes at a price: many people find Emacs' undo
-;; system confusing and difficult to use, spawning a number of packages that
-;; replace it with the less powerful but more intuitive undo/redo system.
-;;
-;; Both the loss of data with standard undo/redo, and the confusion of Emacs'
-;; undo, stem from trying to treat undo history as a linear sequence of
-;; changes. It's not. The `undo-tree-mode' provided by this package replaces
-;; Emacs' undo system with a system that treats undo history as what it is: a
-;; branching tree of changes. This simple idea allows the more intuitive
-;; behaviour of the standard undo/redo system to be combined with the power of
-;; never losing any history. An added side bonus is that undo history can in
-;; some cases be stored more efficiently, allowing more changes to accumulate
-;; before Emacs starts discarding history.
-;;
-;; The only downside to this more advanced yet simpler undo system is that it
-;; was inspired by Vim. But, after all, most successful religions steal the
-;; best ideas from their competitors!
-;;
-;;
-;; Installation
-;; ============
-;;
-;; This package has only been tested with Emacs versions 24 and CVS. It should
-;; work in Emacs versions 22 and 23 too, but will not work without
-;; modifications in earlier versions of Emacs.
-;;
-;; To install `undo-tree-mode', make sure this file is saved in a directory in
-;; your `load-path', and add the line:
-;;
-;;   (require 'undo-tree)
-;;
-;; to your .emacs file. Byte-compiling undo-tree.el is recommended (e.g. using
-;; "M-x byte-compile-file" from within emacs).
-;;
-;; If you want to replace the standard Emacs' undo system with the
-;; `undo-tree-mode' system in all buffers, you can enable it globally by
-;; adding:
-;;
-;;   (global-undo-tree-mode)
-;;
-;; to your .emacs file.
-;;
-;;
-;; Quick-Start
-;; ===========
-;;
-;; If you're the kind of person who likes to jump in the car and drive,
-;; without bothering to first figure out whether the button on the left dips
-;; the headlights or operates the ejector seat (after all, you'll soon figure
-;; it out when you push it), then here's the minimum you need to know:
-;;
-;; `undo-tree-mode' and `global-undo-tree-mode'
-;;   Enable undo-tree mode (either in the current buffer or globally).
-;;
-;; C-_  C-/  (`undo-tree-undo')
-;;   Undo changes.
-;;
-;; M-_  C-?  (`undo-tree-redo')
-;;   Redo changes.
-;;
-;; `undo-tree-switch-branch'
-;;   Switch undo-tree branch.
-;;   (What does this mean? Better press the button and see!)
-;;
-;; C-x u  (`undo-tree-visualize')
-;;   Visualize the undo tree.
-;;   (Better try pressing this button too!)
-;;
-;; C-x r u  (`undo-tree-save-state-to-register')
-;;   Save current buffer state to register.
-;;
-;; C-x r U  (`undo-tree-restore-state-from-register')
-;;   Restore buffer state from register.
-;;
-;;
-;;
-;; In the undo-tree visualizer:
-;;
-;; <up>  p  C-p  (`undo-tree-visualize-undo')
-;;   Undo changes.
-;;
-;; <down>  n  C-n  (`undo-tree-visualize-redo')
-;;   Redo changes.
-;;
-;; <left>  b  C-b  (`undo-tree-visualize-switch-branch-left')
-;;   Switch to previous undo-tree branch.
-;;
-;; <right>  f  C-f  (`undo-tree-visualize-switch-branch-right')
-;;   Switch to next undo-tree branch.
-;;
-;; C-<up>  M-{  (`undo-tree-visualize-undo-to-x')
-;;   Undo changes up to last branch point.
-;;
-;; C-<down>  M-}  (`undo-tree-visualize-redo-to-x')
-;;   Redo changes down to next branch point.
-;;
-;; <down>  n  C-n  (`undo-tree-visualize-redo')
-;;   Redo changes.
-;;
-;; <mouse-1>  (`undo-tree-visualizer-mouse-set')
-;;   Set state to node at mouse click.
-;;
-;; t  (`undo-tree-visualizer-toggle-timestamps')
-;;   Toggle display of time-stamps.
-;;
-;; d  (`undo-tree-visualizer-toggle-diff')
-;;   Toggle diff display.
-;;
-;; s  (`undo-tree-visualizer-selection-mode')
-;;   Toggle keyboard selection mode.
-;;
-;; q  (`undo-tree-visualizer-quit')
-;;   Quit undo-tree-visualizer.
-;;
-;; C-q  (`undo-tree-visualizer-abort')
-;;   Abort undo-tree-visualizer.
-;;
-;; ,  <
-;;   Scroll left.
-;;
-;; .  >
-;;   Scroll right.
-;;
-;; <pgup>  M-v
-;;   Scroll up.
-;;
-;; <pgdown>  C-v
-;;   Scroll down.
-;;
-;;
-;;
-;; In visualizer selection mode:
-;;
-;; <up>  p  C-p  (`undo-tree-visualizer-select-previous')
-;;   Select previous node.
-;;
-;; <down>  n  C-n  (`undo-tree-visualizer-select-next')
-;;   Select next node.
-;;
-;; <left>  b  C-b  (`undo-tree-visualizer-select-left')
-;;   Select left sibling node.
-;;
-;; <right>  f  C-f  (`undo-tree-visualizer-select-right')
-;;   Select right sibling node.
-;;
-;; <pgup>  M-v
-;;   Select node 10 above.
-;;
-;; <pgdown>  C-v
-;;   Select node 10 below.
-;;
-;; <enter>  (`undo-tree-visualizer-set')
-;;   Set state to selected node and exit selection mode.
-;;
-;; s  (`undo-tree-visualizer-mode')
-;;   Exit selection mode.
-;;
-;; t  (`undo-tree-visualizer-toggle-timestamps')
-;;   Toggle display of time-stamps.
-;;
-;; d  (`undo-tree-visualizer-toggle-diff')
-;;   Toggle diff display.
-;;
-;; q  (`undo-tree-visualizer-quit')
-;;   Quit undo-tree-visualizer.
-;;
-;; C-q  (`undo-tree-visualizer-abort')
-;;   Abort undo-tree-visualizer.
-;;
-;; ,  <
-;;   Scroll left.
-;;
-;; .  >
-;;   Scroll right.
-;;
-;;
-;;
-;; Persistent undo history:
-;;
-;; Note: Requires Emacs version 24.3 or higher.
-;;
-;; `undo-tree-auto-save-history' (variable)
-;;    automatically save and restore undo-tree history along with buffer
-;;    (disabled by default)
-;;
-;; `undo-tree-save-history' (command)
-;;    manually save undo history to file
-;;
-;; `undo-tree-load-history' (command)
-;;    manually load undo history from file
-;;
-;;
-;;
-;; Compressing undo history:
-;;
-;;   Undo history files cannot grow beyond the maximum undo tree size, which
-;;   is limited by `undo-limit', `undo-strong-limit' and
-;;   `undo-outer-limit'. Nevertheless, undo history files can grow quite
-;;   large. If you want to automatically compress undo history, add the
-;;   following advice to your .emacs file (replacing ".gz" with the filename
-;;   extension of your favourite compression algorithm):
-;;
-;;   (defadvice undo-tree-make-history-save-file-name
-;;     (after undo-tree activate)
-;;     (setq ad-return-value (concat ad-return-value ".gz")))
-;;
-;;
-;;
-;;
-;; Undo Systems
-;; ============
-;;
-;; To understand the different undo systems, it's easiest to consider an
-;; example. Imagine you make a few edits in a buffer. As you edit, you
-;; accumulate a history of changes, which we might visualize as a string of
-;; past buffer states, growing downwards:
-;;
-;;                                o  (initial buffer state)
-;;                                |
-;;                                |
-;;                                o  (first edit)
-;;                                |
-;;                                |
-;;                                o  (second edit)
-;;                                |
-;;                                |
-;;                                x  (current buffer state)
-;;
-;;
-;; Now imagine that you undo the last two changes. We can visualize this as
-;; rewinding the current state back two steps:
-;;
-;;                                o  (initial buffer state)
-;;                                |
-;;                                |
-;;                                x  (current buffer state)
-;;                                |
-;;                                |
-;;                                o
-;;                                |
-;;                                |
-;;                                o
-;;
-;;
-;; However, this isn't a good representation of what Emacs' undo system
-;; does. Instead, it treats the undos as *new* changes to the buffer, and adds
-;; them to the history:
-;;
-;;                                o  (initial buffer state)
-;;                                |
-;;                                |
-;;                                o  (first edit)
-;;                                |
-;;                                |
-;;                                o  (second edit)
-;;                                |
-;;                                |
-;;                                x  (buffer state before undo)
-;;                                |
-;;                                |
-;;                                o  (first undo)
-;;                                |
-;;                                |
-;;                                x  (second undo)
-;;
-;;
-;; Actually, since the buffer returns to a previous state after an undo,
-;; perhaps a better way to visualize it is to imagine the string of changes
-;; turning back on itself:
-;;
-;;        (initial buffer state)  o
-;;                                |
-;;                                |
-;;                  (first edit)  o  x  (second undo)
-;;                                |  |
-;;                                |  |
-;;                 (second edit)  o  o  (first undo)
-;;                                | /
-;;                                |/
-;;                                o  (buffer state before undo)
-;;
-;; Treating undos as new changes might seem a strange thing to do. But the
-;; advantage becomes clear as soon as we imagine what happens when you edit
-;; the buffer again. Since you've undone a couple of changes, new edits will
-;; branch off from the buffer state that you've rewound to. Conceptually, it
-;; looks like this:
-;;
-;;                                o  (initial buffer state)
-;;                                |
-;;                                |
-;;                                o
-;;                                |\
-;;                                | \
-;;                                o  x  (new edit)
-;;                                |
-;;                                |
-;;                                o
-;;
-;; The standard undo/redo system only lets you go backwards and forwards
-;; linearly. So as soon as you make that new edit, it discards the old
-;; branch. Emacs' undo just keeps adding changes to the end of the string. So
-;; the undo history in the two systems now looks like this:
-;;
-;;            Undo/Redo:                      Emacs' undo
-;;
-;;               o                                o
-;;               |                                |
-;;               |                                |
-;;               o                                o  o
-;;               .\                               |  |\
-;;               . \                              |  | \
-;;               .  x  (new edit)                 o  o  |
-;;   (discarded  .                                | /   |
-;;     branch)   .                                |/    |
-;;               .                                o     |
-;;                                                      |
-;;                                                      |
-;;                                                      x  (new edit)
-;;
-;; Now, what if you change your mind about those undos, and decide you did
-;; like those other changes you'd made after all? With the standard undo/redo
-;; system, you're lost. There's no way to recover them, because that branch
-;; was discarded when you made the new edit.
-;;
-;; However, in Emacs' undo system, those old buffer states are still there in
-;; the undo history. You just have to rewind back through the new edit, and
-;; back through the changes made by the undos, until you reach them. Of
-;; course, since Emacs treats undos (even undos of undos!) as new changes,
-;; you're really weaving backwards and forwards through the history, all the
-;; time adding new changes to the end of the string as you go:
-;;
-;;                       o
-;;                       |
-;;                       |
-;;                       o  o     o  (undo new edit)
-;;                       |  |\    |\
-;;                       |  | \   | \
-;;                       o  o  |  |  o  (undo the undo)
-;;                       | /   |  |  |
-;;                       |/    |  |  |
-;;      (trying to get   o     |  |  x  (undo the undo)
-;;       to this state)        | /
-;;                             |/
-;;                             o
-;;
-;; So far, this is still reasonably intuitive to use. It doesn't behave so
-;; differently to standard undo/redo, except that by going back far enough you
-;; can access changes that would be lost in standard undo/redo.
-;;
-;; However, imagine that after undoing as just described, you decide you
-;; actually want to rewind right back to the initial state. If you're lucky,
-;; and haven't invoked any command since the last undo, you can just keep on
-;; undoing until you get back to the start:
-;;
-;;      (trying to get   o              x  (got there!)
-;;       to this state)  |              |
-;;                       |              |
-;;                       o  o     o     o  (keep undoing)
-;;                       |  |\    |\    |
-;;                       |  | \   | \   |
-;;                       o  o  |  |  o  o  (keep undoing)
-;;                       | /   |  |  | /
-;;                       |/    |  |  |/
-;;      (already undid   o     |  |  o  (got this far)
-;;       to this state)        | /
-;;                             |/
-;;                             o
-;;
-;; But if you're unlucky, and you happen to have moved the point (say) after
-;; getting to the state labelled "got this far", then you've "broken the undo
-;; chain". Hold on to something solid, because things are about to get
-;; hairy. If you try to undo now, Emacs thinks you're trying to undo the
-;; undos! So to get back to the initial state you now have to rewind through
-;; *all* the changes, including the undos you just did:
-;;
-;;      (trying to get   o                          x  (finally got there!)
-;;       to this state)  |                          |
-;;                       |                          |
-;;                       o  o     o     o     o     o
-;;                       |  |\    |\    |\    |\    |
-;;                       |  | \   | \   | \   | \   |
-;;                       o  o  |  |  o  o  o  |  o  o
-;;                       | /   |  |  | /   |  |  | /
-;;                       |/    |  |  |/    |  |  |/
-;;      (already undid   o     |  |  o<.   |  |  o
-;;       to this state)        | /     :   | /
-;;                             |/      :   |/
-;;                             o       :   o
-;;                                     :
-;;                             (got this far, but
-;;                              broke the undo chain)
-;;
-;; Confused?
-;;
-;; In practice you can just hold down the undo key until you reach the buffer
-;; state that you want. But whatever you do, don't move around in the buffer
-;; to *check* that you've got back to where you want! Because you'll break the
-;; undo chain, and then you'll have to traverse the entire string of undos
-;; again, just to get back to the point at which you broke the
-;; chain. Undo-in-region and commands such as `undo-only' help to make using
-;; Emacs' undo a little easier, but nonetheless it remains confusing for many
-;; people.
-;;
-;;
-;; So what does `undo-tree-mode' do? Remember the diagram we drew to represent
-;; the history we've been discussing (make a few edits, undo a couple of them,
-;; and edit again)? The diagram that conceptually represented our undo
-;; history, before we started discussing specific undo systems? It looked like
-;; this:
-;;
-;;                                o  (initial buffer state)
-;;                                |
-;;                                |
-;;                                o
-;;                                |\
-;;                                | \
-;;                                o  x  (current state)
-;;                                |
-;;                                |
-;;                                o
-;;
-;; Well, that's *exactly* what the undo history looks like to
-;; `undo-tree-mode'.  It doesn't discard the old branch (as standard undo/redo
-;; does), nor does it treat undos as new changes to be added to the end of a
-;; linear string of buffer states (as Emacs' undo does). It just keeps track
-;; of the tree of branching changes that make up the entire undo history.
-;;
-;; If you undo from this point, you'll rewind back up the tree to the previous
-;; state:
-;;
-;;                                o
-;;                                |
-;;                                |
-;;                                x  (undo)
-;;                                |\
-;;                                | \
-;;                                o  o
-;;                                |
-;;                                |
-;;                                o
-;;
-;; If you were to undo again, you'd rewind back to the initial state. If on
-;; the other hand you redo the change, you'll end up back at the bottom of the
-;; most recent branch:
-;;
-;;                                o  (undo takes you here)
-;;                                |
-;;                                |
-;;                                o  (start here)
-;;                                |\
-;;                                | \
-;;                                o  x  (redo takes you here)
-;;                                |
-;;                                |
-;;                                o
-;;
-;; So far, this is just like the standard undo/redo system. But what if you
-;; want to return to a buffer state located on a previous branch of the
-;; history? Since `undo-tree-mode' keeps the entire history, you simply need
-;; to tell it to switch to a different branch, and then redo the changes you
-;; want:
-;;
-;;                                o
-;;                                |
-;;                                |
-;;                                o  (start here, but switch
-;;                                |\  to the other branch)
-;;                                | \
-;;                        (redo)  o  o
-;;                                |
-;;                                |
-;;                        (redo)  x
-;;
-;; Now you're on the other branch, if you undo and redo changes you'll stay on
-;; that branch, moving up and down through the buffer states located on that
-;; branch. Until you decide to switch branches again, of course.
-;;
-;; Real undo trees might have multiple branches and sub-branches:
-;;
-;;                                o
-;;                            ____|______
-;;                           /           \
-;;                          o             o
-;;                      ____|__         __|
-;;                     /    |  \       /   \
-;;                    o     o   o     o     x
-;;                    |               |
-;;                   / \             / \
-;;                  o   o           o   o
-;;
-;; Trying to imagine what Emacs' undo would do as you move about such a tree
-;; will likely frazzle your brain circuits! But in `undo-tree-mode', you're
-;; just moving around this undo history tree. Most of the time, you'll
-;; probably only need to stay on the most recent branch, in which case it
-;; behaves like standard undo/redo, and is just as simple to understand. But
-;; if you ever need to recover a buffer state on a different branch, the
-;; possibility of switching between branches and accessing the full undo
-;; history is still there.
-;;
-;;
-;;
-;; The Undo-Tree Visualizer
-;; ========================
-;;
-;; Actually, it gets better. You don't have to imagine all these tree
-;; diagrams, because `undo-tree-mode' includes an undo-tree visualizer which
-;; draws them for you! In fact, it draws even better diagrams: it highlights
-;; the node representing the current buffer state, it highlights the current
-;; branch, and you can toggle the display of time-stamps (by hitting "t") and
-;; a diff of the undo changes (by hitting "d"). (There's one other tiny
-;; difference: the visualizer puts the most recent branch on the left rather
-;; than the right.)
-;;
-;; Bring up the undo tree visualizer whenever you want by hitting "C-x u".
-;;
-;; In the visualizer, the usual keys for moving up and down a buffer instead
-;; move up and down the undo history tree (e.g. the up and down arrow keys, or
-;; "C-n" and "C-p"). The state of the "parent" buffer (the buffer whose undo
-;; history you are visualizing) is updated as you move around the undo tree in
-;; the visualizer. If you reach a branch point in the visualizer, the usual
-;; keys for moving forward and backward in a buffer instead switch branch
-;; (e.g. the left and right arrow keys, or "C-f" and "C-b").
-;;
-;; Clicking with the mouse on any node in the visualizer will take you
-;; directly to that node, resetting the state of the parent buffer to the
-;; state represented by that node.
-;;
-;; You can also select nodes directly using the keyboard, by hitting "s" to
-;; toggle selection mode. The usual motion keys now allow you to move around
-;; the tree without changing the parent buffer. Hitting <enter> will reset the
-;; state of the parent buffer to the state represented by the currently
-;; selected node.
-;;
-;; It can be useful to see how long ago the parent buffer was in the state
-;; represented by a particular node in the visualizer. Hitting "t" in the
-;; visualizer toggles the display of time-stamps for all the nodes. (Note
-;; that, because of the way `undo-tree-mode' works, these time-stamps may be
-;; somewhat later than the true times, especially if it's been a long time
-;; since you last undid any changes.)
-;;
-;; To get some idea of what changes are represented by a given node in the
-;; tree, it can be useful to see a diff of the changes. Hit "d" in the
-;; visualizer to toggle a diff display. This normally displays a diff between
-;; the current state and the previous one, i.e. it shows you the changes that
-;; will be applied if you undo (move up the tree). However, the diff display
-;; really comes into its own in the visualizer's selection mode (see above),
-;; where it instead shows a diff between the current state and the currently
-;; selected state, i.e. it shows you the changes that will be applied if you
-;; reset to the selected state.
-;;
-;; (Note that the diff is generated by the Emacs `diff' command, and is
-;; displayed using `diff-mode'. See the corresponding customization groups if
-;; you want to customize the diff display.)
-;;
-;; Finally, hitting "q" will quit the visualizer, leaving the parent buffer in
-;; whatever state you ended at. Hitting "C-q" will abort the visualizer,
-;; returning the parent buffer to whatever state it was originally in when the
-;; visualizer was .
-;;
-;;
-;;
-;; Undo-in-Region
-;; ==============
-;;
-;; Emacs allows a very useful and powerful method of undoing only selected
-;; changes: when a region is active, only changes that affect the text within
-;; that region will be undone. With the standard Emacs undo system, changes
-;; produced by undoing-in-region naturally get added onto the end of the
-;; linear undo history:
-;;
-;;                       o
-;;                       |
-;;                       |  x  (second undo-in-region)
-;;                       o  |
-;;                       |  |
-;;                       |  o  (first undo-in-region)
-;;                       o  |
-;;                       | /
-;;                       |/
-;;                       o
-;;
-;; You can of course redo these undos-in-region as usual, by undoing the
-;; undos:
-;;
-;;                       o
-;;                       |
-;;                       |  o_
-;;                       o  | \
-;;                       |  |  |
-;;                       |  o  o  (undo the undo-in-region)
-;;                       o  |  |
-;;                       | /   |
-;;                       |/    |
-;;                       o     x  (undo the undo-in-region)
-;;
-;;
-;; In `undo-tree-mode', undo-in-region works similarly: when there's an active
-;; region, undoing only undoes changes that affect that region. However, the
-;; way these undos-in-region are recorded in the undo history is quite
-;; different. In `undo-tree-mode', undo-in-region creates a new branch in the
-;; undo history. The new branch consists of an undo step that undoes some of
-;; the changes that affect the current region, and another step that undoes
-;; the remaining changes needed to rejoin the previous undo history.
-;;
-;;      Previous undo history                Undo-in-region
-;;
-;;               o                                o
-;;               |                                |
-;;               |                                |
-;;               o                                o
-;;               |                                |\
-;;               |                                | \
-;;               o                                o  x  (undo-in-region)
-;;               |                                |  |
-;;               |                                |  |
-;;               x                                o  o
-;;
-;; As long as you don't change the active region after undoing-in-region,
-;; continuing to undo-in-region extends the new branch, pulling more changes
-;; that affect the current region into an undo step immediately above your
-;; current location in the undo tree, and pushing the point at which the new
-;; branch is attached further up the tree:
-;;
-;;      First undo-in-region                 Second undo-in-region
-;;
-;;               o                                o
-;;               |                                |\
-;;               |                                | \
-;;               o                                o  x  (undo-in-region)
-;;               |\                               |  |
-;;               | \                              |  |
-;;               o  x                             o  o
-;;               |  |                             |  |
-;;               |  |                             |  |
-;;               o  o                             o  o
-;;
-;; Redoing takes you back down the undo tree, as usual (as long as you haven't
-;; changed the active region after undoing-in-region, it doesn't matter if it
-;; is still active):
-;;
-;;                       o
-;;			 |\
-;;			 | \
-;;			 o  o
-;;			 |  |
-;;			 |  |
-;;			 o  o  (redo)
-;;			 |  |
-;;			 |  |
-;;			 o  x  (redo)
-;;
-;;
-;; What about redo-in-region? Obviously, this only makes sense if you have
-;; already undone some changes, so that there are some changes to redo!
-;; Redoing-in-region splits off a new branch of the undo history below your
-;; current location in the undo tree. This time, the new branch consists of a
-;; redo step that redoes some of the redo changes that affect the current
-;; region, followed by all the remaining redo changes.
-;;
-;;      Previous undo history                Redo-in-region
-;;
-;;               o                                o
-;;               |                                |
-;;               |                                |
-;;               x                                o
-;;               |                                |\
-;;               |                                | \
-;;               o                                o  x  (redo-in-region)
-;;               |                                |  |
-;;               |                                |  |
-;;               o                                o  o
-;;
-;; As long as you don't change the active region after redoing-in-region,
-;; continuing to redo-in-region extends the new branch, pulling more redo
-;; changes into a redo step immediately below your current location in the
-;; undo tree.
-;;
-;;      First redo-in-region                 Second redo-in-region
-;;
-;;          o                                     o
-;;          |                                     |
-;;          |                                     |
-;;          o                                     o
-;;          |\                                    |\
-;;          | \                                   | \
-;;          o  x  (redo-in-region)                o  o
-;;          |  |                                  |  |
-;;          |  |                                  |  |
-;;          o  o                                  o  x  (redo-in-region)
-;;                                                   |
-;;                                                   |
-;;                                                   o
-;;
-;; Note that undo-in-region and redo-in-region only ever add new changes to
-;; the undo tree, they *never* modify existing undo history. So you can always
-;; return to previous buffer states by switching to a previous branch of the
-;; tree.
-
-
-
-;;; Code:
-
-(eval-when-compile (require 'cl))
-(require 'diff)
-
-
-
-;;; =====================================================================
-;;;              Compatibility hacks for older Emacsen
-
-;; `characterp' isn't defined in Emacs versions < 23
-(unless (fboundp 'characterp)
-  (defalias 'characterp 'char-valid-p))
-
-;; `region-active-p' isn't defined in Emacs versions < 23
-(unless (fboundp 'region-active-p)
-  (defun region-active-p () (and transient-mark-mode mark-active)))
-
-
-;; `registerv' defstruct isn't defined in Emacs versions < 24
-(unless (fboundp 'registerv-make)
-  (defmacro registerv-make (data &rest _dummy) data))
-
-(unless (fboundp 'registerv-data)
-  (defmacro registerv-data (data) data))
-
-
-;; `diff-no-select' and `diff-file-local-copy' aren't defined in Emacs
-;; versions < 24 (copied and adapted from Emacs 24)
-(unless (fboundp 'diff-no-select)
-  (defun diff-no-select (old new &optional switches no-async buf)
-    ;; Noninteractive helper for creating and reverting diff buffers
-    (unless (bufferp new) (setq new (expand-file-name new)))
-    (unless (bufferp old) (setq old (expand-file-name old)))
-    (or switches (setq switches diff-switches)) ; If not specified, use default.
-    (unless (listp switches) (setq switches (list switches)))
-    (or buf (setq buf (get-buffer-create "*Diff*")))
-    (let* ((old-alt (diff-file-local-copy old))
-	   (new-alt (diff-file-local-copy new))
-	   (command
-	    (mapconcat 'identity
-		       `(,diff-command
-			 ;; Use explicitly specified switches
-			 ,@switches
-			 ,@(mapcar #'shell-quote-argument
-				   (nconc
-				    (when (or old-alt new-alt)
-				      (list "-L" (if (stringp old)
-						     old (prin1-to-string old))
-					    "-L" (if (stringp new)
-						     new (prin1-to-string new))))
-				    (list (or old-alt old)
-					  (or new-alt new)))))
-		       " "))
-	   (thisdir default-directory))
-      (with-current-buffer buf
-	(setq buffer-read-only t)
-	(buffer-disable-undo (current-buffer))
-	(let ((inhibit-read-only t))
-	  (erase-buffer))
-	(buffer-enable-undo (current-buffer))
-	(diff-mode)
-	(set (make-local-variable 'revert-buffer-function)
-	     (lambda (_ignore-auto _noconfirm)
-	       (diff-no-select old new switches no-async (current-buffer))))
-	(setq default-directory thisdir)
-	(let ((inhibit-read-only t))
-	  (insert command "\n"))
-	(if (and (not no-async) (fboundp 'start-process))
-	    (let ((proc (start-process "Diff" buf shell-file-name
-				       shell-command-switch command)))
-	      (set-process-filter proc 'diff-process-filter)
-	      (set-process-sentinel
-	       proc (lambda (proc _msg)
-		      (with-current-buffer (process-buffer proc)
-			(diff-sentinel (process-exit-status proc))
-			(if old-alt (delete-file old-alt))
-			(if new-alt (delete-file new-alt))))))
-	  ;; Async processes aren't available.
-	  (let ((inhibit-read-only t))
-	    (diff-sentinel
-	     (call-process shell-file-name nil buf nil
-			   shell-command-switch command))
-	    (if old-alt (delete-file old-alt))
-	    (if new-alt (delete-file new-alt)))))
-      buf)))
-
-(unless (fboundp 'diff-file-local-copy)
-  (defun diff-file-local-copy (file-or-buf)
-    (if (bufferp file-or-buf)
-	(with-current-buffer file-or-buf
-	  (let ((tempfile (make-temp-file "buffer-content-")))
-	    (write-region nil nil tempfile nil 'nomessage)
-	    tempfile))
-      (file-local-copy file-or-buf))))
-
-
-;; `user-error' isn't defined in Emacs < 24.3
-(unless (fboundp 'user-error)
-  (defalias 'user-error 'error)
-  ;; prevent debugger being called on user errors
-  (add-to-list 'debug-ignored-errors "^No further undo information")
-  (add-to-list 'debug-ignored-errors "^No further redo information")
-  (add-to-list 'debug-ignored-errors "^No further redo information for region"))
-
-
-
-
-
-;;; =====================================================================
-;;;              Global variables and customization options
-
-(defvar buffer-undo-tree nil
-  "Tree of undo entries in current buffer.")
-(put 'buffer-undo-tree 'permanent-local t)
-(make-variable-buffer-local 'buffer-undo-tree)
-
-
-(defgroup undo-tree nil
-  "Tree undo/redo."
-  :group 'undo)
-
-(defcustom undo-tree-mode-lighter " Undo-Tree"
-  "Lighter displayed in mode line
-when `undo-tree-mode' is enabled."
-  :group 'undo-tree
-  :type 'string)
-
-
-(defcustom undo-tree-incompatible-major-modes '(term-mode)
-  "List of major-modes in which `undo-tree-mode' should not be enabled.
-\(See `turn-on-undo-tree-mode'.\)"
-  :group 'undo-tree
-  :type '(repeat symbol))
-
-
-(defcustom undo-tree-enable-undo-in-region t
-  "When non-nil, enable undo-in-region.
-
-When undo-in-region is enabled, undoing or redoing when the
-region is active (in `transient-mark-mode') or with a prefix
-argument (not in `transient-mark-mode') only undoes changes
-within the current region."
-  :group 'undo-tree
-  :type 'boolean)
-
-
-(defcustom undo-tree-auto-save-history nil
-  "When non-nil, `undo-tree-mode' will save undo history to file
-when a buffer is saved to file.
-
-It will automatically load undo history when a buffer is loaded
-from file, if an undo save file exists.
-
-By default, undo-tree history is saved to a file called
-\".<buffer-file-name>.~undo-tree~\" in the same directory as the
-file itself. To save under a different directory, customize
-`undo-tree-history-directory-alist' (see the documentation for
-that variable for details).
-
-WARNING! `undo-tree-auto-save-history' will not work properly in
-Emacs versions prior to 24.3, so it cannot be enabled via
-the customization interface in versions earlier than that one. To
-ignore this warning and enable it regardless, set
-`undo-tree-auto-save-history' to a non-nil value outside of
-customize."
-  :group 'undo-tree
-  :type (if (version-list-< (version-to-list emacs-version) '(24 3))
-	    '(choice (const :tag "<disabled>" nil))
-	  'boolean))
-
-
-(defcustom undo-tree-history-directory-alist nil
-  "Alist of filename patterns and undo history directory names.
-Each element looks like (REGEXP . DIRECTORY).  Undo history for
-files with names matching REGEXP will be saved in DIRECTORY.
-DIRECTORY may be relative or absolute.  If it is absolute, so
-that all matching files are backed up into the same directory,
-the file names in this directory will be the full name of the
-file backed up with all directory separators changed to `!' to
-prevent clashes.  This will not work correctly if your filesystem
-truncates the resulting name.
-
-For the common case of all backups going into one directory, the
-alist should contain a single element pairing \".\" with the
-appropriate directory name.
-
-If this variable is nil, or it fails to match a filename, the
-backup is made in the original file's directory.
-
-On MS-DOS filesystems without long names this variable is always
-ignored."
-  :group 'undo-tree
-  :type '(repeat (cons (regexp :tag "Regexp matching filename")
-		       (directory :tag "Undo history directory name"))))
-
-
-
-(defcustom undo-tree-visualizer-relative-timestamps t
-  "When non-nil, display times relative to current time
-when displaying time stamps in visualizer.
-
-Otherwise, display absolute times."
-  :group 'undo-tree
-  :type 'boolean)
-
-
-(defcustom undo-tree-visualizer-timestamps nil
-  "When non-nil, display time-stamps by default
-in undo-tree visualizer.
-
-\\<undo-tree-visualizer-mode-map>You can always toggle time-stamps on and off \
-using \\[undo-tree-visualizer-toggle-timestamps], regardless of the
-setting of this variable."
-  :group 'undo-tree
-  :type 'boolean)
-
-
-(defcustom undo-tree-visualizer-diff nil
-  "When non-nil, display diff by default in undo-tree visualizer.
-
-\\<undo-tree-visualizer-mode-map>You can always toggle the diff display \
-using \\[undo-tree-visualizer-toggle-diff], regardless of the
-setting of this variable."
-  :group 'undo-tree
-  :type 'boolean)
-
-
-(defcustom undo-tree-visualizer-lazy-drawing 100
-  "When non-nil, use lazy undo-tree drawing in visualizer.
-
-Setting this to a number causes the visualizer to switch to lazy
-drawing when the number of nodes in the tree is larger than this
-value.
-
-Lazy drawing means that only the visible portion of the tree will
-be drawn initially, and the tree will be extended later as
-needed. For the most part, the only visible effect of this is to
-significantly speed up displaying the visualizer for very large
-trees.
-
-There is one potential negative effect of lazy drawing. Other
-branches of the tree will only be drawn once the node from which
-they branch off becomes visible. So it can happen that certain
-portions of the tree that would be shown with lazy drawing
-disabled, will not be drawn immediately when it is
-enabled. However, this effect is quite rare in practice."
-  :group 'undo-tree
-  :type '(choice (const :tag "never" nil)
-		 (const :tag "always" t)
-		 (integer :tag "> size")))
-
-
-(defface undo-tree-visualizer-default-face
-  '((((class color)) :foreground "gray"))
-  "Face used to draw undo-tree in visualizer."
-  :group 'undo-tree)
-
-(defface undo-tree-visualizer-current-face
-  '((((class color)) :foreground "red"))
-  "Face used to highlight current undo-tree node in visualizer."
-  :group 'undo-tree)
-
-(defface undo-tree-visualizer-active-branch-face
-  '((((class color) (background dark))
-     (:foreground "white" :weight bold))
-    (((class color) (background light))
-     (:foreground "black" :weight bold)))
-  "Face used to highlight active undo-tree branch in visualizer."
-  :group 'undo-tree)
-
-(defface undo-tree-visualizer-register-face
-  '((((class color)) :foreground "yellow"))
-  "Face used to highlight undo-tree nodes saved to a register
-in visualizer."
-  :group 'undo-tree)
-
-(defface undo-tree-visualizer-unmodified-face
-  '((((class color)) :foreground "cyan"))
-  "Face used to highlight nodes corresponding to unmodified buffers
-in visualizer."
-  :group 'undo-tree)
-
-
-(defvar undo-tree-visualizer-parent-buffer nil
-  "Parent buffer in visualizer.")
-(put 'undo-tree-visualizer-parent-buffer 'permanent-local t)
-(make-variable-buffer-local 'undo-tree-visualizer-parent-buffer)
-
-;; stores modification time of parent buffer's file, if any
-(defvar undo-tree-visualizer-parent-mtime nil)
-(put 'undo-tree-visualizer-parent-mtime 'permanent-local t)
-(make-variable-buffer-local 'undo-tree-visualizer-parent-mtime)
-
-;; stores current horizontal spacing needed for drawing undo-tree
-(defvar undo-tree-visualizer-spacing nil)
-(put 'undo-tree-visualizer-spacing 'permanent-local t)
-(make-variable-buffer-local 'undo-tree-visualizer-spacing)
-
-;; calculate horizontal spacing required for drawing tree with current
-;; settings
-(defsubst undo-tree-visualizer-calculate-spacing ()
-  (if undo-tree-visualizer-timestamps
-      (if undo-tree-visualizer-relative-timestamps 9 13)
-    3))
-
-;; holds node that was current when visualizer was invoked
-(defvar undo-tree-visualizer-initial-node nil)
-(put 'undo-tree-visualizer-initial-node 'permanent-local t)
-(make-variable-buffer-local 'undo-tree-visualizer-initial-node)
-
-;; holds currently selected node in visualizer selection mode
-(defvar undo-tree-visualizer-selected-node nil)
-(put 'undo-tree-visualizer-selected-node 'permanent-local t)
-(make-variable-buffer-local 'undo-tree-visualizer-selected)
-
-;; used to store nodes at edge of currently drawn portion of tree
-(defvar undo-tree-visualizer-needs-extending-down nil)
-(put 'undo-tree-visualizer-needs-extending-down 'permanent-local t)
-(make-variable-buffer-local 'undo-tree-visualizer-needs-extending-down)
-(defvar undo-tree-visualizer-needs-extending-up nil)
-(put 'undo-tree-visualizer-needs-extending-up 'permanent-local t)
-(make-variable-buffer-local 'undo-tree-visualizer-needs-extending-up)
-
-;; dynamically bound to t when undoing from visualizer, to inhibit
-;; `undo-tree-kill-visualizer' hook function in parent buffer
-(defvar undo-tree-inhibit-kill-visualizer nil)
-
-;; can be let-bound to a face name, used in drawing functions
-(defvar undo-tree-insert-face nil)
-
-;; visualizer buffer names
-(defconst undo-tree-visualizer-buffer-name " *undo-tree*")
-(defconst undo-tree-diff-buffer-name "*undo-tree Diff*")
-
-;; install history-auto-save hooks
-(add-hook 'write-file-functions 'undo-tree-save-history-hook)
-(add-hook 'find-file-hook 'undo-tree-load-history-hook)
-
-
-
-
-;;; =================================================================
-;;;                          Default keymaps
-
-(defvar undo-tree-map nil
-  "Keymap used in undo-tree-mode.")
-
-(unless undo-tree-map
-  (let ((map (make-sparse-keymap)))
-    ;; remap `undo' and `undo-only' to `undo-tree-undo'
-    (define-key map [remap undo] 'undo-tree-undo)
-    (define-key map [remap undo-only] 'undo-tree-undo)
-    ;; bind standard undo bindings (since these match redo counterparts)
-    (define-key map (kbd "C-/") 'undo-tree-undo)
-    (define-key map "\C-_" 'undo-tree-undo)
-    ;; redo doesn't exist normally, so define our own keybindings
-    (define-key map (kbd "C-?") 'undo-tree-redo)
-    (define-key map (kbd "M-_") 'undo-tree-redo)
-    ;; just in case something has defined `redo'...
-    (define-key map [remap redo] 'undo-tree-redo)
-    ;; we use "C-x u" for the undo-tree visualizer
-    (define-key map (kbd "\C-x u") 'undo-tree-visualize)
-    ;; bind register commands
-    (define-key map (kbd "C-x r u") 'undo-tree-save-state-to-register)
-    (define-key map (kbd "C-x r U") 'undo-tree-restore-state-from-register)
-    ;; set keymap
-    (setq undo-tree-map map)))
-
-
-(defvar undo-tree-visualizer-mode-map nil
-  "Keymap used in undo-tree visualizer.")
-
-(unless undo-tree-visualizer-mode-map
-  (let ((map (make-sparse-keymap)))
-    ;; vertical motion keys undo/redo
-    (define-key map [remap previous-line] 'undo-tree-visualize-undo)
-    (define-key map [remap next-line] 'undo-tree-visualize-redo)
-    (define-key map [up] 'undo-tree-visualize-undo)
-    (define-key map "p" 'undo-tree-visualize-undo)
-    (define-key map "\C-p" 'undo-tree-visualize-undo)
-    (define-key map [down] 'undo-tree-visualize-redo)
-    (define-key map "n" 'undo-tree-visualize-redo)
-    (define-key map "\C-n" 'undo-tree-visualize-redo)
-    ;; horizontal motion keys switch branch
-    (define-key map [remap forward-char]
-      'undo-tree-visualize-switch-branch-right)
-    (define-key map [remap backward-char]
-      'undo-tree-visualize-switch-branch-left)
-    (define-key map [right] 'undo-tree-visualize-switch-branch-right)
-    (define-key map "f" 'undo-tree-visualize-switch-branch-right)
-    (define-key map "\C-f" 'undo-tree-visualize-switch-branch-right)
-    (define-key map [left] 'undo-tree-visualize-switch-branch-left)
-    (define-key map "b" 'undo-tree-visualize-switch-branch-left)
-    (define-key map "\C-b" 'undo-tree-visualize-switch-branch-left)
-    ;; paragraph motion keys undo/redo to significant points in tree
-    (define-key map [remap backward-paragraph] 'undo-tree-visualize-undo-to-x)
-    (define-key map [remap forward-paragraph] 'undo-tree-visualize-redo-to-x)
-    (define-key map "\M-{" 'undo-tree-visualize-undo-to-x)
-    (define-key map "\M-}" 'undo-tree-visualize-redo-to-x)
-    (define-key map [C-up] 'undo-tree-visualize-undo-to-x)
-    (define-key map [C-down] 'undo-tree-visualize-redo-to-x)
-    ;; mouse sets buffer state to node at click
-    (define-key map [mouse-1] 'undo-tree-visualizer-mouse-set)
-    ;; toggle timestamps
-    (define-key map "t" 'undo-tree-visualizer-toggle-timestamps)
-    ;; toggle diff
-    (define-key map "d" 'undo-tree-visualizer-toggle-diff)
-    ;; toggle selection mode
-    (define-key map "s" 'undo-tree-visualizer-selection-mode)
-    ;; horizontal scrolling may be needed if the tree is very wide
-    (define-key map "," 'undo-tree-visualizer-scroll-left)
-    (define-key map "." 'undo-tree-visualizer-scroll-right)
-    (define-key map "<" 'undo-tree-visualizer-scroll-left)
-    (define-key map ">" 'undo-tree-visualizer-scroll-right)
-    ;; vertical scrolling may be needed if the tree is very tall
-    (define-key map [next] 'undo-tree-visualizer-scroll-up)
-    (define-key map [prior] 'undo-tree-visualizer-scroll-down)
-    ;; quit/abort visualizer
-    (define-key map "q" 'undo-tree-visualizer-quit)
-    (define-key map "\C-q" 'undo-tree-visualizer-abort)
-    ;; set keymap
-    (setq undo-tree-visualizer-mode-map map)))
-
-
-(defvar undo-tree-visualizer-selection-mode-map nil
-  "Keymap used in undo-tree visualizer selection mode.")
-
-(unless undo-tree-visualizer-selection-mode-map
-  (let ((map (make-sparse-keymap)))
-    ;; vertical motion keys move up and down tree
-    (define-key map [remap previous-line]
-      'undo-tree-visualizer-select-previous)
-    (define-key map [remap next-line]
-      'undo-tree-visualizer-select-next)
-    (define-key map [up] 'undo-tree-visualizer-select-previous)
-    (define-key map "p" 'undo-tree-visualizer-select-previous)
-    (define-key map "\C-p" 'undo-tree-visualizer-select-previous)
-    (define-key map [down] 'undo-tree-visualizer-select-next)
-    (define-key map "n" 'undo-tree-visualizer-select-next)
-    (define-key map "\C-n" 'undo-tree-visualizer-select-next)
-    ;; vertical scroll keys move up and down quickly
-    (define-key map [next]
-      (lambda () (interactive) (undo-tree-visualizer-select-next 10)))
-    (define-key map [prior]
-      (lambda () (interactive) (undo-tree-visualizer-select-previous 10)))
-    ;; horizontal motion keys move to left and right siblings
-    (define-key map [remap forward-char] 'undo-tree-visualizer-select-right)
-    (define-key map [remap backward-char] 'undo-tree-visualizer-select-left)
-    (define-key map [right] 'undo-tree-visualizer-select-right)
-    (define-key map "f" 'undo-tree-visualizer-select-right)
-    (define-key map "\C-f" 'undo-tree-visualizer-select-right)
-    (define-key map [left] 'undo-tree-visualizer-select-left)
-    (define-key map "b" 'undo-tree-visualizer-select-left)
-    (define-key map "\C-b" 'undo-tree-visualizer-select-left)
-    ;; horizontal scroll keys move left or right quickly
-    (define-key map ","
-      (lambda () (interactive) (undo-tree-visualizer-select-left 10)))
-    (define-key map "."
-      (lambda () (interactive) (undo-tree-visualizer-select-right 10)))
-    (define-key map "<"
-      (lambda () (interactive) (undo-tree-visualizer-select-left 10)))
-    (define-key map ">"
-      (lambda () (interactive) (undo-tree-visualizer-select-right 10)))
-    ;; <enter> sets buffer state to node at point
-    (define-key map "\r" 'undo-tree-visualizer-set)
-    ;; mouse selects node at click
-    (define-key map [mouse-1] 'undo-tree-visualizer-mouse-select)
-    ;; toggle diff
-    (define-key map "d" 'undo-tree-visualizer-selection-toggle-diff)
-    ;; set keymap
-    (setq undo-tree-visualizer-selection-mode-map map)))
-
-
-(defvar undo-tree-old-undo-menu-item nil)
-
-(defun undo-tree-update-menu-bar ()
-  "Update `undo-tree-mode' Edit menu items."
-  (if undo-tree-mode
-      (progn
-	;; save old undo menu item, and install undo/redo menu items
-	(setq undo-tree-old-undo-menu-item
-	      (cdr (assq 'undo (lookup-key global-map [menu-bar edit]))))
-	(define-key (lookup-key global-map [menu-bar edit])
-	  [undo] '(menu-item "Undo" undo-tree-undo
-			     :enable (and undo-tree-mode
-					  (not buffer-read-only)
-					  (not (eq t buffer-undo-list))
-					  (undo-tree-node-previous
-					   (undo-tree-current buffer-undo-tree)))
-			     :help "Undo last operation"))
-	(define-key-after (lookup-key global-map [menu-bar edit])
-	  [redo] '(menu-item "Redo" undo-tree-redo
-			     :enable (and undo-tree-mode
-					  (not buffer-read-only)
-					  (not (eq t buffer-undo-list))
-					  (undo-tree-node-next
-					   (undo-tree-current buffer-undo-tree)))
-			     :help "Redo last operation")
-	  'undo))
-    ;; uninstall undo/redo menu items
-    (define-key (lookup-key global-map [menu-bar edit])
-      [undo] undo-tree-old-undo-menu-item)
-    (define-key (lookup-key global-map [menu-bar edit])
-      [redo] nil)))
-
-(add-hook 'menu-bar-update-hook 'undo-tree-update-menu-bar)
-
-
-
-
-
-;;; =====================================================================
-;;;                     Undo-tree data structure
-
-(defstruct
-  (undo-tree
-   :named
-   (:constructor nil)
-   (:constructor make-undo-tree
-                 (&aux
-                  (root (undo-tree-make-node nil nil))
-                  (current root)
-                  (size 0)
-		  (count 0)
-		  (object-pool (make-hash-table :test 'eq :weakness 'value))))
-   ;;(:copier nil)
-   )
-  root current size count object-pool)
-
-
-
-(defstruct
-  (undo-tree-node
-   (:type vector)   ; create unnamed struct
-   (:constructor nil)
-   (:constructor undo-tree-make-node
-                 (previous undo
-		  &optional redo
-                  &aux
-                  (timestamp (current-time))
-                  (branch 0)))
-   (:constructor undo-tree-make-node-backwards
-                 (next-node undo
-		  &optional redo
-                  &aux
-                  (next (list next-node))
-                  (timestamp (current-time))
-                  (branch 0)))
-   (:copier nil))
-  previous next undo redo timestamp branch meta-data)
-
-
-(defmacro undo-tree-node-p (n)
-  (let ((len (length (undo-tree-make-node nil nil))))
-    `(and (vectorp ,n) (= (length ,n) ,len))))
-
-
-
-(defstruct
-  (undo-tree-region-data
-   (:type vector)   ; create unnamed struct
-   (:constructor nil)
-   (:constructor undo-tree-make-region-data
-		 (&optional undo-beginning undo-end
-			     redo-beginning redo-end))
-   (:constructor undo-tree-make-undo-region-data
-		 (undo-beginning undo-end))
-   (:constructor undo-tree-make-redo-region-data
-		 (redo-beginning redo-end))
-   (:copier nil))
-  undo-beginning undo-end redo-beginning redo-end)
-
-
-(defmacro undo-tree-region-data-p (r)
-  (let ((len (length (undo-tree-make-region-data))))
-    `(and (vectorp ,r) (= (length ,r) ,len))))
-
-(defmacro undo-tree-node-clear-region-data (node)
-  `(setf (undo-tree-node-meta-data ,node)
-	 (delq nil
-	       (delq :region
-		     (plist-put (undo-tree-node-meta-data ,node)
-				:region nil)))))
-
-
-(defmacro undo-tree-node-undo-beginning (node)
-  `(let ((r (plist-get (undo-tree-node-meta-data ,node) :region)))
-     (when (undo-tree-region-data-p r)
-       (undo-tree-region-data-undo-beginning r))))
-
-(defmacro undo-tree-node-undo-end (node)
-  `(let ((r (plist-get (undo-tree-node-meta-data ,node) :region)))
-     (when (undo-tree-region-data-p r)
-       (undo-tree-region-data-undo-end r))))
-
-(defmacro undo-tree-node-redo-beginning (node)
-  `(let ((r (plist-get (undo-tree-node-meta-data ,node) :region)))
-     (when (undo-tree-region-data-p r)
-       (undo-tree-region-data-redo-beginning r))))
-
-(defmacro undo-tree-node-redo-end (node)
-  `(let ((r (plist-get (undo-tree-node-meta-data ,node) :region)))
-     (when (undo-tree-region-data-p r)
-       (undo-tree-region-data-redo-end r))))
-
-
-(defsetf undo-tree-node-undo-beginning (node) (val)
-  `(let ((r (plist-get (undo-tree-node-meta-data ,node) :region)))
-     (unless (undo-tree-region-data-p r)
-       (setf (undo-tree-node-meta-data ,node)
-	     (plist-put (undo-tree-node-meta-data ,node) :region
-			(setq r (undo-tree-make-region-data)))))
-     (setf (undo-tree-region-data-undo-beginning r) ,val)))
-
-(defsetf undo-tree-node-undo-end (node) (val)
-  `(let ((r (plist-get (undo-tree-node-meta-data ,node) :region)))
-     (unless (undo-tree-region-data-p r)
-       (setf (undo-tree-node-meta-data ,node)
-	     (plist-put (undo-tree-node-meta-data ,node) :region
-			(setq r (undo-tree-make-region-data)))))
-     (setf (undo-tree-region-data-undo-end r) ,val)))
-
-(defsetf undo-tree-node-redo-beginning (node) (val)
-  `(let ((r (plist-get (undo-tree-node-meta-data ,node) :region)))
-     (unless (undo-tree-region-data-p r)
-       (setf (undo-tree-node-meta-data ,node)
-	     (plist-put (undo-tree-node-meta-data ,node) :region
-			(setq r (undo-tree-make-region-data)))))
-     (setf (undo-tree-region-data-redo-beginning r) ,val)))
-
-(defsetf undo-tree-node-redo-end (node) (val)
-  `(let ((r (plist-get (undo-tree-node-meta-data ,node) :region)))
-     (unless (undo-tree-region-data-p r)
-       (setf (undo-tree-node-meta-data ,node)
-	     (plist-put (undo-tree-node-meta-data ,node) :region
-			(setq r (undo-tree-make-region-data)))))
-     (setf (undo-tree-region-data-redo-end r) ,val)))
-
-
-
-(defstruct
-  (undo-tree-visualizer-data
-   (:type vector)   ; create unnamed struct
-   (:constructor nil)
-   (:constructor undo-tree-make-visualizer-data
-		 (&optional lwidth cwidth rwidth marker))
-   (:copier nil))
-  lwidth cwidth rwidth marker)
-
-
-(defmacro undo-tree-visualizer-data-p (v)
-  (let ((len (length (undo-tree-make-visualizer-data))))
-    `(and (vectorp ,v) (= (length ,v) ,len))))
-
-(defun undo-tree-node-clear-visualizer-data (node)
-  (let ((plist (undo-tree-node-meta-data node)))
-    (if (eq (car plist) :visualizer)
-	(setf (undo-tree-node-meta-data node) (nthcdr 2 plist))
-      (while (and plist (not (eq (cadr plist) :visualizer)))
-	(setq plist (cdr plist)))
-      (if plist (setcdr plist (nthcdr 3 plist))))))
-
-(defmacro undo-tree-node-lwidth (node)
-  `(let ((v (plist-get (undo-tree-node-meta-data ,node) :visualizer)))
-     (when (undo-tree-visualizer-data-p v)
-       (undo-tree-visualizer-data-lwidth v))))
-
-(defmacro undo-tree-node-cwidth (node)
-  `(let ((v (plist-get (undo-tree-node-meta-data ,node) :visualizer)))
-     (when (undo-tree-visualizer-data-p v)
-       (undo-tree-visualizer-data-cwidth v))))
-
-(defmacro undo-tree-node-rwidth (node)
-  `(let ((v (plist-get (undo-tree-node-meta-data ,node) :visualizer)))
-     (when (undo-tree-visualizer-data-p v)
-       (undo-tree-visualizer-data-rwidth v))))
-
-(defmacro undo-tree-node-marker (node)
-  `(let ((v (plist-get (undo-tree-node-meta-data ,node) :visualizer)))
-     (when (undo-tree-visualizer-data-p v)
-       (undo-tree-visualizer-data-marker v))))
-
-
-(defsetf undo-tree-node-lwidth (node) (val)
-  `(let ((v (plist-get (undo-tree-node-meta-data ,node) :visualizer)))
-     (unless (undo-tree-visualizer-data-p v)
-       (setf (undo-tree-node-meta-data ,node)
-	     (plist-put (undo-tree-node-meta-data ,node) :visualizer
-			(setq v (undo-tree-make-visualizer-data)))))
-     (setf (undo-tree-visualizer-data-lwidth v) ,val)))
-
-(defsetf undo-tree-node-cwidth (node) (val)
-  `(let ((v (plist-get (undo-tree-node-meta-data ,node) :visualizer)))
-     (unless (undo-tree-visualizer-data-p v)
-       (setf (undo-tree-node-meta-data ,node)
-	     (plist-put (undo-tree-node-meta-data ,node) :visualizer
-			(setq v (undo-tree-make-visualizer-data)))))
-     (setf (undo-tree-visualizer-data-cwidth v) ,val)))
-
-(defsetf undo-tree-node-rwidth (node) (val)
-  `(let ((v (plist-get (undo-tree-node-meta-data ,node) :visualizer)))
-     (unless (undo-tree-visualizer-data-p v)
-       (setf (undo-tree-node-meta-data ,node)
-	     (plist-put (undo-tree-node-meta-data ,node) :visualizer
-			(setq v (undo-tree-make-visualizer-data)))))
-     (setf (undo-tree-visualizer-data-rwidth v) ,val)))
-
-(defsetf undo-tree-node-marker (node) (val)
-  `(let ((v (plist-get (undo-tree-node-meta-data ,node) :visualizer)))
-     (unless (undo-tree-visualizer-data-p v)
-       (setf (undo-tree-node-meta-data ,node)
-	     (plist-put (undo-tree-node-meta-data ,node) :visualizer
-			(setq v (undo-tree-make-visualizer-data)))))
-     (setf (undo-tree-visualizer-data-marker v) ,val)))
-
-
-
-(defstruct
-  (undo-tree-register-data
-   (:type vector)
-   (:constructor nil)
-   (:constructor undo-tree-make-register-data (buffer node)))
-  buffer node)
-
-(defun undo-tree-register-data-p (data)
-  (and (vectorp data)
-       (= (length data) 2)
-       (undo-tree-node-p (undo-tree-register-data-node data))))
-
-(defun undo-tree-register-data-print-func (data)
-  (princ (format "an undo-tree state for buffer %s"
-		 (undo-tree-register-data-buffer data))))
-
-(defmacro undo-tree-node-register (node)
-  `(plist-get (undo-tree-node-meta-data ,node) :register))
-
-(defsetf undo-tree-node-register (node) (val)
-  `(setf (undo-tree-node-meta-data ,node)
-	 (plist-put (undo-tree-node-meta-data ,node) :register ,val)))
-
-
-
-
-;;; =====================================================================
-;;;              Basic undo-tree data structure functions
-
-(defun undo-tree-grow (undo)
-  "Add an UNDO node to current branch of `buffer-undo-tree'."
-  (let* ((current (undo-tree-current buffer-undo-tree))
-         (new (undo-tree-make-node current undo)))
-    (push new (undo-tree-node-next current))
-    (setf (undo-tree-current buffer-undo-tree) new)))
-
-
-(defun undo-tree-grow-backwards (node undo &optional redo)
-  "Add new node *above* undo-tree NODE, and return new node.
-Note that this will overwrite NODE's \"previous\" link, so should
-only be used on a detached NODE, never on nodes that are already
-part of `buffer-undo-tree'."
-  (let ((new (undo-tree-make-node-backwards node undo redo)))
-    (setf (undo-tree-node-previous node) new)
-    new))
-
-
-(defun undo-tree-splice-node (node splice)
-  "Splice NODE into undo tree, below node SPLICE.
-Note that this will overwrite NODE's \"next\" and \"previous\"
-links, so should only be used on a detached NODE, never on nodes
-that are already part of `buffer-undo-tree'."
-  (setf (undo-tree-node-next node) (undo-tree-node-next splice)
-	(undo-tree-node-branch node) (undo-tree-node-branch splice)
-	(undo-tree-node-previous node) splice
-	(undo-tree-node-next splice) (list node)
-	(undo-tree-node-branch splice) 0)
-  (dolist (n (undo-tree-node-next node))
-    (setf (undo-tree-node-previous n) node)))
-
-
-(defun undo-tree-snip-node (node)
-  "Snip NODE out of undo tree."
-  (let* ((parent (undo-tree-node-previous node))
-	 position p)
-    ;; if NODE is only child, replace parent's next links with NODE's
-    (if (= (length (undo-tree-node-next parent)) 0)
-	(setf (undo-tree-node-next parent) (undo-tree-node-next node)
-	      (undo-tree-node-branch parent) (undo-tree-node-branch node))
-      ;; otherwise...
-      (setq position (undo-tree-position node (undo-tree-node-next parent)))
-      (cond
-       ;; if active branch used do go via NODE, set parent's branch to active
-       ;; branch of NODE
-       ((= (undo-tree-node-branch parent) position)
-	(setf (undo-tree-node-branch parent)
-	      (+ position (undo-tree-node-branch node))))
-       ;; if active branch didn't go via NODE, update parent's branch to point
-       ;; to same node as before
-       ((> (undo-tree-node-branch parent) position)
-	(incf (undo-tree-node-branch parent)
-	      (1- (length (undo-tree-node-next node))))))
-      ;; replace NODE in parent's next list with NODE's entire next list
-      (if (= position 0)
-	  (setf (undo-tree-node-next parent)
-		(nconc (undo-tree-node-next node)
-		       (cdr (undo-tree-node-next parent))))
-	(setq p (nthcdr (1- position) (undo-tree-node-next parent)))
-	(setcdr p (nconc (undo-tree-node-next node) (cddr p)))))
-    ;; update previous links of NODE's children
-    (dolist (n (undo-tree-node-next node))
-      (setf (undo-tree-node-previous n) parent))))
-
-
-(defun undo-tree-mapc (--undo-tree-mapc-function-- node)
-  ;; Apply FUNCTION to NODE and to each node below it.
-  (let ((stack (list node))
-	n)
-    (while stack
-      (setq n (pop stack))
-      (funcall --undo-tree-mapc-function-- n)
-      (setq stack (append (undo-tree-node-next n) stack)))))
-
-
-(defmacro undo-tree-num-branches ()
-  "Return number of branches at current undo tree node."
-  '(length (undo-tree-node-next (undo-tree-current buffer-undo-tree))))
-
-
-(defun undo-tree-position (node list)
-  "Find the first occurrence of NODE in LIST.
-Return the index of the matching item, or nil of not found.
-Comparison is done with `eq'."
-  (let ((i 0))
-    (catch 'found
-      (while (progn
-               (when (eq node (car list)) (throw 'found i))
-               (incf i)
-               (setq list (cdr list))))
-      nil)))
-
-
-(defvar *undo-tree-id-counter* 0)
-(make-variable-buffer-local '*undo-tree-id-counter*)
-
-(defmacro undo-tree-generate-id ()
-  ;; Generate a new, unique id (uninterned symbol).
-  ;; The name is made by appending a number to "undo-tree-id".
-  ;; (Copied from CL package `gensym'.)
-  `(let ((num (prog1 *undo-tree-id-counter* (incf *undo-tree-id-counter*))))
-     (make-symbol (format "undo-tree-id%d" num))))
-
-
-(defun undo-tree-decircle (undo-tree)
-  ;; Nullify PREVIOUS links of UNDO-TREE nodes, to make UNDO-TREE data
-  ;; structure non-circular.
-  (undo-tree-mapc
-   (lambda (node)
-     (dolist (n (undo-tree-node-next node))
-       (setf (undo-tree-node-previous n) nil)))
-   (undo-tree-root undo-tree)))
-
-
-(defun undo-tree-recircle (undo-tree)
-  ;; Recreate PREVIOUS links of UNDO-TREE nodes, to restore circular UNDO-TREE
-  ;; data structure.
-  (undo-tree-mapc
-   (lambda (node)
-     (dolist (n (undo-tree-node-next node))
-       (setf (undo-tree-node-previous n) node)))
-   (undo-tree-root undo-tree)))
-
-
-
-
-;;; =====================================================================
-;;;             Undo list and undo changeset utility functions
-
-(defmacro undo-list-marker-elt-p (elt)
-  `(markerp (car-safe ,elt)))
-
-(defmacro undo-list-GCd-marker-elt-p (elt)
-  ;; Return t if ELT is a marker element whose marker has been moved to the
-  ;; object-pool, so may potentially have been garbage-collected.
-  ;; Note: Valid marker undo elements should be uniquely identified as cons
-  ;; cells with a symbol in the car (replacing the marker), and a number in
-  ;; the cdr. However, to guard against future changes to undo element
-  ;; formats, we perform an additional redundant check on the symbol name.
-  `(and (car-safe ,elt)
-	(symbolp (car ,elt))
-	(let ((str (symbol-name (car ,elt))))
-	  (and (> (length str) 12)
-	       (string= (substring str 0 12) "undo-tree-id")))
-	(numberp (cdr-safe ,elt))))
-
-
-(defun undo-tree-move-GC-elts-to-pool (elt)
-  ;; Move elements that can be garbage-collected into `buffer-undo-tree'
-  ;; object pool, substituting a unique id that can be used to retrieve them
-  ;; later. (Only markers require this treatment currently.)
-  (when (undo-list-marker-elt-p elt)
-    (let ((id (undo-tree-generate-id)))
-      (puthash id (car elt) (undo-tree-object-pool buffer-undo-tree))
-      (setcar elt id))))
-
-
-(defun undo-tree-restore-GC-elts-from-pool (elt)
-  ;; Replace object id's in ELT with corresponding objects from
-  ;; `buffer-undo-tree' object pool and return modified ELT, or return nil if
-  ;; any object in ELT has been garbage-collected.
-  (if (undo-list-GCd-marker-elt-p elt)
-      (when (setcar elt (gethash (car elt)
-				 (undo-tree-object-pool buffer-undo-tree)))
-	elt)
-    elt))
-
-
-(defun undo-list-clean-GCd-elts (undo-list)
-  ;; Remove object id's from UNDO-LIST that refer to elements that have been
-  ;; garbage-collected. UNDO-LIST is modified by side-effect.
-  (while (undo-list-GCd-marker-elt-p (car undo-list))
-    (unless (gethash (caar undo-list)
-		     (undo-tree-object-pool buffer-undo-tree))
-      (setq undo-list (cdr undo-list))))
-  (let ((p undo-list))
-    (while (cdr p)
-      (when (and (undo-list-GCd-marker-elt-p (cadr p))
-		 (null (gethash (car (cadr p))
-				(undo-tree-object-pool buffer-undo-tree))))
-	(setcdr p (cddr p)))
-      (setq p (cdr p))))
-  undo-list)
-
-
-(defun undo-list-pop-changeset (&optional discard-pos)
-  ;; Pop changeset from `buffer-undo-list'. If DISCARD-POS is non-nil, discard
-  ;; any position entries from changeset.
-
-  ;; discard undo boundaries and (if DISCARD-POS is non-nil) position entries
-  ;; at head of undo list
-  (while (or (null (car buffer-undo-list))
-	     (and discard-pos (integerp (car buffer-undo-list))))
-    (setq buffer-undo-list (cdr buffer-undo-list)))
-  ;; pop elements up to next undo boundary, discarding position entries if
-  ;; DISCARD-POS is non-nil
-  (if (eq (car buffer-undo-list) 'undo-tree-canary)
-      (push nil buffer-undo-list)
-    (let* ((changeset (list (pop buffer-undo-list)))
-           (p changeset))
-      (while (progn
-	       (undo-tree-move-GC-elts-to-pool (car p))
-	       (while (and discard-pos (integerp (car buffer-undo-list)))
-		 (setq buffer-undo-list (cdr buffer-undo-list)))
-	       (and (car buffer-undo-list)
-		    (not (eq (car buffer-undo-list) 'undo-tree-canary))))
-        (setcdr p (list (pop buffer-undo-list)))
-	(setq p (cdr p)))
-      changeset)))
-
-
-(defun undo-tree-copy-list (undo-list)
-  ;; Return a deep copy of first changeset in `undo-list'. Object id's are
-  ;; replaced by corresponding objects from `buffer-undo-tree' object-pool.
-  (when undo-list
-    (let (copy p)
-      ;; if first element contains an object id, replace it with object from
-      ;; pool, discarding element entirely if it's been GC'd
-      (while (null copy)
-	(setq copy
-	      (undo-tree-restore-GC-elts-from-pool (pop undo-list))))
-      (setq copy (list copy)
-	    p copy)
-      ;; copy remaining elements, replacing object id's with objects from
-      ;; pool, or discarding them entirely if they've been GC'd
-      (while undo-list
-	(when (setcdr p (undo-tree-restore-GC-elts-from-pool
-			 (undo-copy-list-1 (pop undo-list))))
-	  (setcdr p (list (cdr p)))
-	  (setq p (cdr p))))
-      copy)))
-
-
-
-(defun undo-list-transfer-to-tree ()
-  ;; Transfer entries accumulated in `buffer-undo-list' to `buffer-undo-tree'.
-
-  ;; `undo-list-transfer-to-tree' should never be called when undo is disabled
-  ;; (i.e. `buffer-undo-tree' is t)
-  (assert (not (eq buffer-undo-tree t)))
-
-  ;; if `buffer-undo-tree' is empty, create initial undo-tree
-  (when (null buffer-undo-tree) (setq buffer-undo-tree (make-undo-tree)))
-  ;; make sure there's a canary at end of `buffer-undo-list'
-  (when (null buffer-undo-list)
-    (setq buffer-undo-list '(nil undo-tree-canary)))
-
-  (unless (or (eq (cadr buffer-undo-list) 'undo-tree-canary)
-	      (eq (car buffer-undo-list) 'undo-tree-canary))
-    ;; create new node from first changeset in `buffer-undo-list', save old
-    ;; `buffer-undo-tree' current node, and make new node the current node
-    (let* ((node (undo-tree-make-node nil (undo-list-pop-changeset)))
-	   (splice (undo-tree-current buffer-undo-tree))
-	   (size (undo-list-byte-size (undo-tree-node-undo node)))
-	   (count 1))
-      (setf (undo-tree-current buffer-undo-tree) node)
-      ;; grow tree fragment backwards using `buffer-undo-list' changesets
-      (while (and buffer-undo-list
-		  (not (eq (cadr buffer-undo-list) 'undo-tree-canary)))
-	(setq node
-	      (undo-tree-grow-backwards node (undo-list-pop-changeset)))
-	(incf size (undo-list-byte-size (undo-tree-node-undo node)))
-	(incf count))
-      ;; if no undo history has been discarded from `buffer-undo-list' since
-      ;; last transfer, splice new tree fragment onto end of old
-      ;; `buffer-undo-tree' current node
-      (if (or (eq (cadr buffer-undo-list) 'undo-tree-canary)
-	      (eq (car buffer-undo-list) 'undo-tree-canary))
-	  (progn
-	    (setf (undo-tree-node-previous node) splice)
-	    (push node (undo-tree-node-next splice))
-	    (setf (undo-tree-node-branch splice) 0)
-	    (incf (undo-tree-size buffer-undo-tree) size)
-	    (incf (undo-tree-count buffer-undo-tree) count))
-	;; if undo history has been discarded, replace entire
-	;; `buffer-undo-tree' with new tree fragment
-	(setq node (undo-tree-grow-backwards node nil))
-	(setf (undo-tree-root buffer-undo-tree) node)
-	(setq buffer-undo-list '(nil undo-tree-canary))
-	(setf (undo-tree-size buffer-undo-tree) size)
-	(setf (undo-tree-count buffer-undo-tree) count)
-	(setq buffer-undo-list '(nil undo-tree-canary))))
-    ;; discard undo history if necessary
-    (undo-tree-discard-history)))
-
-
-(defun undo-list-byte-size (undo-list)
-  ;; Return size (in bytes) of UNDO-LIST
-  (let ((size 0) (p undo-list))
-    (while p
-      (incf size 8)  ; cons cells use up 8 bytes
-      (when (and (consp (car p)) (stringp (caar p)))
-        (incf size (string-bytes (caar p))))
-      (setq p (cdr p)))
-    size))
-
-
-
-(defun undo-list-rebuild-from-tree ()
-  "Rebuild `buffer-undo-list' from information in `buffer-undo-tree'."
-  (unless (eq buffer-undo-list t)
-    (undo-list-transfer-to-tree)
-    (setq buffer-undo-list nil)
-    (when buffer-undo-tree
-      (let ((stack (list (list (undo-tree-root buffer-undo-tree)))))
-	(push (sort (mapcar 'identity (undo-tree-node-next (caar stack)))
-		    (lambda (a b)
-		      (time-less-p (undo-tree-node-timestamp a)
-				   (undo-tree-node-timestamp b))))
-	      stack)
-	;; Traverse tree in depth-and-oldest-first order, but add undo records
-	;; on the way down, and redo records on the way up.
-	(while (or (car stack)
-		   (not (eq (car (nth 1 stack))
-			    (undo-tree-current buffer-undo-tree))))
-	  (if (car stack)
-	      (progn
-		(setq buffer-undo-list
-		      (append (undo-tree-node-undo (caar stack))
-			      buffer-undo-list))
-		(undo-boundary)
-		(push (sort (mapcar 'identity
-				    (undo-tree-node-next (caar stack)))
-			    (lambda (a b)
-			      (time-less-p (undo-tree-node-timestamp a)
-					   (undo-tree-node-timestamp b))))
-		      stack))
-	    (pop stack)
-	    (setq buffer-undo-list
-		  (append (undo-tree-node-redo (caar stack))
-			  buffer-undo-list))
-	    (undo-boundary)
-	    (pop (car stack))))))))
-
-
-
-
-;;; =====================================================================
-;;;                History discarding utility functions
-
-(defun undo-tree-oldest-leaf (node)
-  ;; Return oldest leaf node below NODE.
-  (while (undo-tree-node-next node)
-    (setq node
-          (car (sort (mapcar 'identity (undo-tree-node-next node))
-                     (lambda (a b)
-                       (time-less-p (undo-tree-node-timestamp a)
-                                    (undo-tree-node-timestamp b)))))))
-  node)
-
-
-(defun undo-tree-discard-node (node)
-  ;; Discard NODE from `buffer-undo-tree', and return next in line for
-  ;; discarding.
-
-  ;; don't discard current node
-  (unless (eq node (undo-tree-current buffer-undo-tree))
-
-    ;; discarding root node...
-    (if (eq node (undo-tree-root buffer-undo-tree))
-        (cond
-         ;; should always discard branches before root
-         ((> (length (undo-tree-node-next node)) 1)
-          (error "Trying to discard undo-tree root which still\
- has multiple branches"))
-         ;; don't discard root if current node is only child
-         ((eq (car (undo-tree-node-next node))
-              (undo-tree-current buffer-undo-tree))
-	  nil)
-	 ;; discard root
-         (t
-	  ;; clear any register referring to root
-	  (let ((r (undo-tree-node-register node)))
-	    (when (and r (eq (get-register r) node))
-	      (set-register r nil)))
-          ;; make child of root into new root
-          (setq node (setf (undo-tree-root buffer-undo-tree)
-                           (car (undo-tree-node-next node))))
-	  ;; update undo-tree size
-	  (decf (undo-tree-size buffer-undo-tree)
-		(+ (undo-list-byte-size (undo-tree-node-undo node))
-		   (undo-list-byte-size (undo-tree-node-redo node))))
-	  (decf (undo-tree-count buffer-undo-tree))
-	  ;; discard new root's undo data and PREVIOUS link
-	  (setf (undo-tree-node-undo node) nil
-		(undo-tree-node-redo node) nil
-		(undo-tree-node-previous node) nil)
-          ;; if new root has branches, or new root is current node, next node
-          ;; to discard is oldest leaf, otherwise it's new root
-          (if (or (> (length (undo-tree-node-next node)) 1)
-                  (eq (car (undo-tree-node-next node))
-                      (undo-tree-current buffer-undo-tree)))
-              (undo-tree-oldest-leaf node)
-            node)))
-
-      ;; discarding leaf node...
-      (let* ((parent (undo-tree-node-previous node))
-             (current (nth (undo-tree-node-branch parent)
-                           (undo-tree-node-next parent))))
-	;; clear any register referring to the discarded node
-	(let ((r (undo-tree-node-register node)))
-	  (when (and r (eq (get-register r) node))
-	    (set-register r nil)))
-	;; update undo-tree size
-	(decf (undo-tree-size buffer-undo-tree)
-	      (+ (undo-list-byte-size (undo-tree-node-undo node))
-		 (undo-list-byte-size (undo-tree-node-redo node))))
-	(decf (undo-tree-count buffer-undo-tree))
-	;; discard leaf
-        (setf (undo-tree-node-next parent)
-                (delq node (undo-tree-node-next parent))
-              (undo-tree-node-branch parent)
-                (undo-tree-position current (undo-tree-node-next parent)))
-        ;; if parent has branches, or parent is current node, next node to
-        ;; discard is oldest leaf, otherwise it's the parent itself
-        (if (or (eq parent (undo-tree-current buffer-undo-tree))
-                (and (undo-tree-node-next parent)
-                     (or (not (eq parent (undo-tree-root buffer-undo-tree)))
-                         (> (length (undo-tree-node-next parent)) 1))))
-            (undo-tree-oldest-leaf parent)
-          parent)))))
-
-
-
-(defun undo-tree-discard-history ()
-  "Discard undo history until we're within memory usage limits
-set by `undo-limit', `undo-strong-limit' and `undo-outer-limit'."
-
-  (when (> (undo-tree-size buffer-undo-tree) undo-limit)
-    ;; if there are no branches off root, first node to discard is root;
-    ;; otherwise it's leaf node at botom of oldest branch
-    (let ((node (if (> (length (undo-tree-node-next
-                                (undo-tree-root buffer-undo-tree))) 1)
-                    (undo-tree-oldest-leaf (undo-tree-root buffer-undo-tree))
-                  (undo-tree-root buffer-undo-tree))))
-
-      ;; discard nodes until memory use is within `undo-strong-limit'
-      (while (and node
-                  (> (undo-tree-size buffer-undo-tree) undo-strong-limit))
-        (setq node (undo-tree-discard-node node)))
-
-      ;; discard nodes until next node to discard would bring memory use
-      ;; within `undo-limit'
-      (while (and node
-		  ;; check first if last discard has brought us within
-		  ;; `undo-limit', in case we can avoid more expensive
-		  ;; `undo-strong-limit' calculation
-		  ;; Note: this assumes undo-strong-limit > undo-limit;
-		  ;;       if not, effectively undo-strong-limit = undo-limit
-		  (> (undo-tree-size buffer-undo-tree) undo-limit)
-                  (> (- (undo-tree-size buffer-undo-tree)
-			;; if next node to discard is root, the memory we
-			;; free-up comes from discarding changesets from its
-			;; only child...
-			(if (eq node (undo-tree-root buffer-undo-tree))
-			    (+ (undo-list-byte-size
-				(undo-tree-node-undo
-				 (car (undo-tree-node-next node))))
-			       (undo-list-byte-size
-				(undo-tree-node-redo
-				 (car (undo-tree-node-next node)))))
-			  ;; ...otherwise, it comes from discarding changesets
-			  ;; from along with the node itself
-			  (+ (undo-list-byte-size (undo-tree-node-undo node))
-			     (undo-list-byte-size (undo-tree-node-redo node)))
-			  ))
-                     undo-limit))
-        (setq node (undo-tree-discard-node node)))
-
-      ;; if we're still over the `undo-outer-limit', discard entire history
-      (when (> (undo-tree-size buffer-undo-tree) undo-outer-limit)
-        ;; query first if `undo-ask-before-discard' is set
-        (if undo-ask-before-discard
-            (when (yes-or-no-p
-                   (format
-                    "Buffer `%s' undo info is %d bytes long;  discard it? "
-                    (buffer-name) (undo-tree-size buffer-undo-tree)))
-              (setq buffer-undo-tree nil))
-          ;; otherwise, discard and display warning
-          (display-warning
-           '(undo discard-info)
-           (concat
-            (format "Buffer `%s' undo info was %d bytes long.\n"
-                    (buffer-name) (undo-tree-size buffer-undo-tree))
-            "The undo info was discarded because it exceeded\
- `undo-outer-limit'.
-
-This is normal if you executed a command that made a huge change
-to the buffer. In that case, to prevent similar problems in the
-future, set `undo-outer-limit' to a value that is large enough to
-cover the maximum size of normal changes you expect a single
-command to make, but not so large that it might exceed the
-maximum memory allotted to Emacs.
-
-If you did not execute any such command, the situation is
-probably due to a bug and you should report it.
-
-You can disable the popping up of this buffer by adding the entry
-\(undo discard-info) to the user option `warning-suppress-types',
-which is defined in the `warnings' library.\n")
-           :warning)
-          (setq buffer-undo-tree nil)))
-      )))
-
-
-
-
-;;; =====================================================================
-;;;                   Visualizer utility functions
-
-(defun undo-tree-compute-widths (node)
-  "Recursively compute widths for nodes below NODE."
-  (let ((stack (list node))
-        res)
-    (while stack
-      ;; try to compute widths for node at top of stack
-      (if (undo-tree-node-p
-           (setq res (undo-tree-node-compute-widths (car stack))))
-          ;; if computation fails, it returns a node whose widths still need
-          ;; computing, which we push onto the stack
-          (push res stack)
-        ;; otherwise, store widths and remove it from stack
-        (setf (undo-tree-node-lwidth (car stack)) (aref res 0)
-              (undo-tree-node-cwidth (car stack)) (aref res 1)
-              (undo-tree-node-rwidth (car stack)) (aref res 2))
-        (pop stack)))))
-
-
-(defun undo-tree-node-compute-widths (node)
-  ;; Compute NODE's left-, centre-, and right-subtree widths. Returns widths
-  ;; (in a vector) if successful. Otherwise, returns a node whose widths need
-  ;; calculating before NODE's can be calculated.
-  (let ((num-children (length (undo-tree-node-next node)))
-        (lwidth 0) (cwidth 0) (rwidth 0) p)
-    (catch 'need-widths
-      (cond
-       ;; leaf nodes have 0 width
-       ((= 0 num-children)
-        (setf cwidth 1
-              (undo-tree-node-lwidth node) 0
-              (undo-tree-node-cwidth node) 1
-              (undo-tree-node-rwidth node) 0))
-
-       ;; odd number of children
-       ((= (mod num-children 2) 1)
-        (setq p (undo-tree-node-next node))
-        ;; compute left-width
-        (dotimes (i (/ num-children 2))
-          (if (undo-tree-node-lwidth (car p))
-              (incf lwidth (+ (undo-tree-node-lwidth (car p))
-                              (undo-tree-node-cwidth (car p))
-                              (undo-tree-node-rwidth (car p))))
-            ;; if child's widths haven't been computed, return that child
-            (throw 'need-widths (car p)))
-          (setq p (cdr p)))
-        (if (undo-tree-node-lwidth (car p))
-            (incf lwidth (undo-tree-node-lwidth (car p)))
-          (throw 'need-widths (car p)))
-        ;; centre-width is inherited from middle child
-        (setf cwidth (undo-tree-node-cwidth (car p)))
-        ;; compute right-width
-        (incf rwidth (undo-tree-node-rwidth (car p)))
-        (setq p (cdr p))
-        (dotimes (i (/ num-children 2))
-          (if (undo-tree-node-lwidth (car p))
-              (incf rwidth (+ (undo-tree-node-lwidth (car p))
-                              (undo-tree-node-cwidth (car p))
-                              (undo-tree-node-rwidth (car p))))
-            (throw 'need-widths (car p)))
-          (setq p (cdr p))))
-
-       ;; even number of children
-       (t
-        (setq p (undo-tree-node-next node))
-        ;; compute left-width
-        (dotimes (i (/ num-children 2))
-          (if (undo-tree-node-lwidth (car p))
-              (incf lwidth (+ (undo-tree-node-lwidth (car p))
-                              (undo-tree-node-cwidth (car p))
-                              (undo-tree-node-rwidth (car p))))
-            (throw 'need-widths (car p)))
-          (setq p (cdr p)))
-        ;; centre-width is 0 when number of children is even
-        (setq cwidth 0)
-        ;; compute right-width
-        (dotimes (i (/ num-children 2))
-          (if (undo-tree-node-lwidth (car p))
-              (incf rwidth (+ (undo-tree-node-lwidth (car p))
-                              (undo-tree-node-cwidth (car p))
-                              (undo-tree-node-rwidth (car p))))
-            (throw 'need-widths (car p)))
-          (setq p (cdr p)))))
-
-      ;; return left-, centre- and right-widths
-      (vector lwidth cwidth rwidth))))
-
-
-(defun undo-tree-clear-visualizer-data (tree)
-  ;; Clear visualizer data below NODE.
-  (undo-tree-mapc
-   (lambda (n) (undo-tree-node-clear-visualizer-data n))
-   (undo-tree-root tree)))
-
-
-(defun undo-tree-node-unmodified-p (node &optional mtime)
-  ;; Return non-nil if NODE corresponds to a buffer state that once upon a
-  ;; time was unmodified. If a file modification time MTIME is specified,
-  ;; return non-nil if the corresponding buffer state really is unmodified.
-  (let (changeset ntime)
-    (setq changeset
-	  (or (undo-tree-node-redo node)
-	      (and (setq changeset (car (undo-tree-node-next node)))
-		   (undo-tree-node-undo changeset)))
-	  ntime
-	  (catch 'found
-	    (dolist (elt changeset)
-	      (when (and (consp elt) (eq (car elt) t) (consp (cdr elt))
-			 (throw 'found (cdr elt)))))))
-    (and ntime
-	 (or (null mtime)
-	     ;; high-precision timestamps
-	     (if (listp (cdr ntime))
-		 (equal ntime mtime)
-	       ;; old-style timestamps
-	       (and (= (car ntime) (car mtime))
-		    (= (cdr ntime) (cadr mtime))))))))
-
-
-
-
-;;; =====================================================================
-;;;                  Undo-in-region utility functions
-
-;; `undo-elt-in-region' uses this as a dynamically-scoped variable
-(defvar undo-adjusted-markers nil)
-
-
-(defun undo-tree-pull-undo-in-region-branch (start end)
-  ;; Pull out entries from undo changesets to create a new undo-in-region
-  ;; branch, which undoes changeset entries lying between START and END first,
-  ;; followed by remaining entries from the changesets, before rejoining the
-  ;; existing undo tree history. Repeated calls will, if appropriate, extend
-  ;; the current undo-in-region branch rather than creating a new one.
-
-  ;; if we're just reverting the last redo-in-region, we don't need to
-  ;; manipulate the undo tree at all
-  (if (undo-tree-reverting-redo-in-region-p start end)
-      t  ; return t to indicate success
-
-    ;; We build the `region-changeset' and `delta-list' lists forwards, using
-    ;; pointers `r' and `d' to the penultimate element of the list. So that we
-    ;; don't have to treat the first element differently, we prepend a dummy
-    ;; leading nil to the lists, and have the pointers point to that
-    ;; initially.
-    ;; Note: using '(nil) instead of (list nil) in the `let*' results in
-    ;;       bizarre errors when the code is byte-compiled, where parts of the
-    ;;       lists appear to survive across different calls to this function.
-    ;;       An obscure byte-compiler bug, perhaps?
-    (let* ((region-changeset (list nil))
-	   (r region-changeset)
-	   (delta-list (list nil))
-	   (d delta-list)
-	   (node (undo-tree-current buffer-undo-tree))
-	   (repeated-undo-in-region
-	    (undo-tree-repeated-undo-in-region-p start end))
-	   undo-adjusted-markers  ; `undo-elt-in-region' expects this
-	   fragment splice original-fragment original-splice original-current
-	   got-visible-elt undo-list elt)
-
-      ;; --- initialisation ---
-      (cond
-       ;; if this is a repeated undo in the same region, start pulling changes
-       ;; from NODE at which undo-in-region branch iss attached, and detatch
-       ;; the branch, using it as initial FRAGMENT of branch being constructed
-       (repeated-undo-in-region
-	(setq original-current node
-	      fragment (car (undo-tree-node-next node))
-	      splice node)
-	;; undo up to node at which undo-in-region branch is attached
-	;; (recognizable as first node with more than one branch)
-	(let ((mark-active nil))
-	  (while (= (length (undo-tree-node-next node)) 1)
-	    (undo-tree-undo-1)
-	    (setq fragment node
-		  node (undo-tree-current buffer-undo-tree))))
-	(when (eq splice node) (setq splice nil))
-	;; detatch undo-in-region branch
-	(setf (undo-tree-node-next node)
-	      (delq fragment (undo-tree-node-next node))
-	      (undo-tree-node-previous fragment) nil
-	      original-fragment fragment
-	      original-splice node))
-
-       ;; if this is a new undo-in-region, initial FRAGMENT is a copy of all
-       ;; nodes below the current one in the active branch
-       ((undo-tree-node-next node)
-	(setq fragment (undo-tree-make-node nil nil)
-	      splice fragment)
-	(while (setq node (nth (undo-tree-node-branch node)
-			       (undo-tree-node-next node)))
-	  (push (undo-tree-make-node
-		 splice
-		 (undo-copy-list (undo-tree-node-undo node))
-		 (undo-copy-list (undo-tree-node-redo node)))
-		(undo-tree-node-next splice))
-	  (setq splice (car (undo-tree-node-next splice))))
-	(setq fragment (car (undo-tree-node-next fragment))
-	      splice nil
-	      node (undo-tree-current buffer-undo-tree))))
-
-
-      ;; --- pull undo-in-region elements into branch ---
-      ;; work backwards up tree, pulling out undo elements within region until
-      ;; we've got one that undoes a visible change (insertion or deletion)
-      (catch 'abort
-	(while (and (not got-visible-elt) node (undo-tree-node-undo node))
-	  ;; we cons a dummy nil element on the front of the changeset so that
-	  ;; we can conveniently remove the first (real) element from the
-	  ;; changeset if we need to; the leading nil is removed once we're
-	  ;; done with this changeset
-	  (setq undo-list (cons nil (undo-copy-list (undo-tree-node-undo node)))
-		elt (cadr undo-list))
-	  (if fragment
-	      (progn
-		(setq fragment (undo-tree-grow-backwards fragment undo-list))
-		(unless splice (setq splice fragment)))
-	    (setq fragment (undo-tree-make-node nil undo-list))
-	    (setq splice fragment))
-
-	  (while elt
-	    (cond
-	     ;; keep elements within region
-	     ((undo-elt-in-region elt start end)
-	      ;; set flag if kept element is visible (insertion or deletion)
-	      (when (and (consp elt)
-			 (or (stringp (car elt)) (integerp (car elt))))
-		(setq got-visible-elt t))
-	      ;; adjust buffer positions in elements previously undone before
-	      ;; kept element, as kept element will now be undone first
-	      (undo-tree-adjust-elements-to-elt splice elt)
-	      ;; move kept element to undo-in-region changeset, adjusting its
-	      ;; buffer position as it will now be undone first
-	      (setcdr r (list (undo-tree-apply-deltas elt (cdr delta-list))))
-	      (setq r (cdr r))
-	      (setcdr undo-list (cddr undo-list)))
-
-	     ;; discard "was unmodified" elements
-	     ;; FIXME: deal properly with these
-	     ((and (consp elt) (eq (car elt) t))
-	      (setcdr undo-list (cddr undo-list)))
-
-	     ;; if element crosses region, we can't pull any more elements
-	     ((undo-elt-crosses-region elt start end)
-	      ;; if we've found a visible element, it must be earlier in
-	      ;; current node's changeset; stop pulling elements (null
-	      ;; `undo-list' and non-nil `got-visible-elt' cause loop to exit)
-	      (if got-visible-elt
-		  (setq undo-list nil)
-		;; if we haven't found a visible element yet, pulling
-		;; undo-in-region branch has failed
-		(setq region-changeset nil)
-		(throw 'abort t)))
-
-	     ;; if rejecting element, add its delta (if any) to the list
-	     (t
-	      (let ((delta (undo-delta elt)))
-		(when (/= 0 (cdr delta))
-		  (setcdr d (list delta))
-		  (setq d (cdr d))))
-	      (setq undo-list (cdr undo-list))))
-
-	    ;; process next element of current changeset
-	    (setq elt (cadr undo-list)))
-
-	  ;; if there are remaining elements in changeset, remove dummy nil
-	  ;; from front
-	  (if (cadr (undo-tree-node-undo fragment))
-	      (pop (undo-tree-node-undo fragment))
-	    ;; otherwise, if we've kept all elements in changeset, discard
-	    ;; empty changeset
-	    (when (eq splice fragment) (setq splice nil))
-	    (setq fragment (car (undo-tree-node-next fragment))))
-	  ;; process changeset from next node up the tree
-	  (setq node (undo-tree-node-previous node))))
-
-      ;; pop dummy nil from front of `region-changeset'
-      (setq region-changeset (cdr region-changeset))
-
-
-      ;; --- integrate branch into tree ---
-      ;; if no undo-in-region elements were found, restore undo tree
-      (if (null region-changeset)
-	  (when original-current
-	    (push original-fragment (undo-tree-node-next original-splice))
-	    (setf (undo-tree-node-branch original-splice) 0
-		  (undo-tree-node-previous original-fragment) original-splice)
-	    (let ((mark-active nil))
-	      (while (not (eq (undo-tree-current buffer-undo-tree)
-			      original-current))
-		(undo-tree-redo-1)))
-	    nil)  ; return nil to indicate failure
-
-	;; otherwise...
-	;; need to undo up to node where new branch will be attached, to
-	;; ensure redo entries are populated, and then redo back to where we
-	;; started
-	(let ((mark-active nil)
-	      (current (undo-tree-current buffer-undo-tree)))
-	  (while (not (eq (undo-tree-current buffer-undo-tree) node))
-	    (undo-tree-undo-1))
-	  (while (not (eq (undo-tree-current buffer-undo-tree) current))
-	    (undo-tree-redo-1)))
-
-	(cond
-	 ;; if there's no remaining fragment, just create undo-in-region node
-	 ;; and attach it to parent of last node from which elements were
-	 ;; pulled
-	 ((null fragment)
-	  (setq fragment (undo-tree-make-node node region-changeset))
-	  (push fragment (undo-tree-node-next node))
-	  (setf (undo-tree-node-branch node) 0)
-	  ;; set current node to undo-in-region node
-	  (setf (undo-tree-current buffer-undo-tree) fragment))
-
-	 ;; if no splice point has been set, add undo-in-region node to top of
-	 ;; fragment and attach it to parent of last node from which elements
-	 ;; were pulled
-	 ((null splice)
-	  (setq fragment (undo-tree-grow-backwards fragment region-changeset))
-	  (push fragment (undo-tree-node-next node))
-	  (setf (undo-tree-node-branch node) 0
-		(undo-tree-node-previous fragment) node)
-	  ;; set current node to undo-in-region node
-	  (setf (undo-tree-current buffer-undo-tree) fragment))
-
-	 ;; if fragment contains nodes, attach fragment to parent of last node
-	 ;; from which elements were pulled, and splice in undo-in-region node
-	 (t
-	  (setf (undo-tree-node-previous fragment) node)
-	  (push fragment (undo-tree-node-next node))
-	  (setf (undo-tree-node-branch node) 0)
-	  ;; if this is a repeated undo-in-region, then we've left the current
-	  ;; node at the original splice-point; we need to set the current
-	  ;; node to the equivalent node on the undo-in-region branch and redo
-	  ;; back to where we started
-	  (when repeated-undo-in-region
-	    (setf (undo-tree-current buffer-undo-tree)
-		  (undo-tree-node-previous original-fragment))
-	    (let ((mark-active nil))
-	      (while (not (eq (undo-tree-current buffer-undo-tree) splice))
-		(undo-tree-redo-1 nil 'preserve-undo))))
-	  ;; splice new undo-in-region node into fragment
-	  (setq node (undo-tree-make-node nil region-changeset))
-	  (undo-tree-splice-node node splice)
-	  ;; set current node to undo-in-region node
-	  (setf (undo-tree-current buffer-undo-tree) node)))
-
-	;; update undo-tree size
-	(setq node (undo-tree-node-previous fragment))
-	(while (progn
-		 (and (setq node (car (undo-tree-node-next node)))
-		      (not (eq node original-fragment))
-		      (incf (undo-tree-count buffer-undo-tree))
-		      (incf (undo-tree-size buffer-undo-tree)
-			    (+ (undo-list-byte-size (undo-tree-node-undo node))
-			       (undo-list-byte-size (undo-tree-node-redo node)))))))
-	t)  ; indicate undo-in-region branch was successfully pulled
-      )))
-
-
-
-(defun undo-tree-pull-redo-in-region-branch (start end)
-  ;; Pull out entries from redo changesets to create a new redo-in-region
-  ;; branch, which redoes changeset entries lying between START and END first,
-  ;; followed by remaining entries from the changesets. Repeated calls will,
-  ;; if appropriate, extend the current redo-in-region branch rather than
-  ;; creating a new one.
-
-  ;; if we're just reverting the last undo-in-region, we don't need to
-  ;; manipulate the undo tree at all
-  (if (undo-tree-reverting-undo-in-region-p start end)
-      t  ; return t to indicate success
-
-    ;; We build the `region-changeset' and `delta-list' lists forwards, using
-    ;; pointers `r' and `d' to the penultimate element of the list. So that we
-    ;; don't have to treat the first element differently, we prepend a dummy
-    ;; leading nil to the lists, and have the pointers point to that
-    ;; initially.
-    ;; Note: using '(nil) instead of (list nil) in the `let*' causes bizarre
-    ;;       errors when the code is byte-compiled, where parts of the lists
-    ;;       appear to survive across different calls to this function.  An
-    ;;       obscure byte-compiler bug, perhaps?
-    (let* ((region-changeset (list nil))
-	   (r region-changeset)
-	   (delta-list (list nil))
-	   (d delta-list)
-	   (node (undo-tree-current buffer-undo-tree))
-	   (repeated-redo-in-region
-	    (undo-tree-repeated-redo-in-region-p start end))
-	   undo-adjusted-markers  ; `undo-elt-in-region' expects this
-	   fragment splice got-visible-elt redo-list elt)
-
-      ;; --- inisitalisation ---
-      (cond
-       ;; if this is a repeated redo-in-region, detach fragment below current
-       ;; node
-       (repeated-redo-in-region
-	(when (setq fragment (car (undo-tree-node-next node)))
-	  (setf (undo-tree-node-previous fragment) nil
-		(undo-tree-node-next node)
-		(delq fragment (undo-tree-node-next node)))))
-       ;; if this is a new redo-in-region, initial fragment is a copy of all
-       ;; nodes below the current one in the active branch
-       ((undo-tree-node-next node)
-	(setq fragment (undo-tree-make-node nil nil)
-	      splice fragment)
-	(while (setq node (nth (undo-tree-node-branch node)
-			       (undo-tree-node-next node)))
-	  (push (undo-tree-make-node
-		 splice nil
-		 (undo-copy-list (undo-tree-node-redo node)))
-		(undo-tree-node-next splice))
-	  (setq splice (car (undo-tree-node-next splice))))
-	(setq fragment (car (undo-tree-node-next fragment)))))
-
-
-      ;; --- pull redo-in-region elements into branch ---
-      ;; work down fragment, pulling out redo elements within region until
-      ;; we've got one that redoes a visible change (insertion or deletion)
-      (setq node fragment)
-      (catch 'abort
-	(while (and (not got-visible-elt) node (undo-tree-node-redo node))
-	  ;; we cons a dummy nil element on the front of the changeset so that
-	  ;; we can conveniently remove the first (real) element from the
-	  ;; changeset if we need to; the leading nil is removed once we're
-	  ;; done with this changeset
-	  (setq redo-list (push nil (undo-tree-node-redo node))
-		elt (cadr redo-list))
-	  (while elt
-	    (cond
-	     ;; keep elements within region
-	     ((undo-elt-in-region elt start end)
-	      ;; set flag if kept element is visible (insertion or deletion)
-	      (when (and (consp elt)
-			 (or (stringp (car elt)) (integerp (car elt))))
-		(setq got-visible-elt t))
-	      ;; adjust buffer positions in elements previously redone before
-	      ;; kept element, as kept element will now be redone first
-	      (undo-tree-adjust-elements-to-elt fragment elt t)
-	      ;; move kept element to redo-in-region changeset, adjusting its
-	      ;; buffer position as it will now be redone first
-	      (setcdr r (list (undo-tree-apply-deltas elt (cdr delta-list) -1)))
-	      (setq r (cdr r))
-	      (setcdr redo-list (cddr redo-list)))
-
-	     ;; discard "was unmodified" elements
-	     ;; FIXME: deal properly with these
-	     ((and (consp elt) (eq (car elt) t))
-	      (setcdr redo-list (cddr redo-list)))
-
-	     ;; if element crosses region, we can't pull any more elements
-	     ((undo-elt-crosses-region elt start end)
-	      ;; if we've found a visible element, it must be earlier in
-	      ;; current node's changeset; stop pulling elements (null
-	      ;; `redo-list' and non-nil `got-visible-elt' cause loop to exit)
-	      (if got-visible-elt
-		  (setq redo-list nil)
-		;; if we haven't found a visible element yet, pulling
-		;; redo-in-region branch has failed
-		(setq region-changeset nil)
-		(throw 'abort t)))
-
-	     ;; if rejecting element, add its delta (if any) to the list
-	     (t
-	      (let ((delta (undo-delta elt)))
-		(when (/= 0 (cdr delta))
-		  (setcdr d (list delta))
-		  (setq d (cdr d))))
-	      (setq redo-list (cdr redo-list))))
-
-	    ;; process next element of current changeset
-	    (setq elt (cadr redo-list)))
-
-	  ;; if there are remaining elements in changeset, remove dummy nil
-	  ;; from front
-	  (if (cadr (undo-tree-node-redo node))
-	      (pop (undo-tree-node-undo node))
-	    ;; otherwise, if we've kept all elements in changeset, discard
-	    ;; empty changeset
-	    (if (eq fragment node)
-		(setq fragment (car (undo-tree-node-next fragment)))
-	      (undo-tree-snip-node node)))
-	  ;; process changeset from next node in fragment
-	  (setq node (car (undo-tree-node-next node)))))
-
-      ;; pop dummy nil from front of `region-changeset'
-      (setq region-changeset (cdr region-changeset))
-
-
-      ;; --- integrate branch into tree ---
-      (setq node (undo-tree-current buffer-undo-tree))
-      ;; if no redo-in-region elements were found, restore undo tree
-      (if (null (car region-changeset))
-	  (when (and repeated-redo-in-region fragment)
-	    (push fragment (undo-tree-node-next node))
-	    (setf (undo-tree-node-branch node) 0
-		  (undo-tree-node-previous fragment) node)
-	    nil)  ; return nil to indicate failure
-
-	;; otherwise, add redo-in-region node to top of fragment, and attach
-	;; it below current node
-	(setq fragment
-	      (if fragment
-		  (undo-tree-grow-backwards fragment nil region-changeset)
-		(undo-tree-make-node nil nil region-changeset)))
-	(push fragment (undo-tree-node-next node))
-	(setf (undo-tree-node-branch node) 0
-	      (undo-tree-node-previous fragment) node)
-	;; update undo-tree size
-	(unless repeated-redo-in-region
-	  (setq node fragment)
-	  (while (and (setq node (car (undo-tree-node-next node)))
-		      (incf (undo-tree-count buffer-undo-tree))
-		      (incf (undo-tree-size buffer-undo-tree)
-			    (undo-list-byte-size
-			     (undo-tree-node-redo node))))))
-	(incf (undo-tree-size buffer-undo-tree)
-	      (undo-list-byte-size (undo-tree-node-redo fragment)))
-	t)  ; indicate redo-in-region branch was successfully pulled
-      )))
-
-
-
-(defun undo-tree-adjust-elements-to-elt (node undo-elt &optional below)
-  "Adjust buffer positions of undo elements, starting at NODE's
-and going up the tree (or down the active branch if BELOW is
-non-nil) and through the nodes' undo elements until we reach
-UNDO-ELT.  UNDO-ELT must appear somewhere in the undo changeset
-of either NODE itself or some node above it in the tree."
-  (let ((delta (list (undo-delta undo-elt)))
-	(undo-list (undo-tree-node-undo node)))
-    ;; adjust elements until we reach UNDO-ELT
-    (while (and (car undo-list)
-		(not (eq (car undo-list) undo-elt)))
-      (setcar undo-list
-	      (undo-tree-apply-deltas (car undo-list) delta -1))
-      ;; move to next undo element in list, or to next node if we've run out
-      ;; of elements
-      (unless (car (setq undo-list (cdr undo-list)))
-	(if below
-	    (setq node (nth (undo-tree-node-branch node)
-			    (undo-tree-node-next node)))
-	  (setq node (undo-tree-node-previous node)))
-	(setq undo-list (undo-tree-node-undo node))))))
-
-
-
-(defun undo-tree-apply-deltas (undo-elt deltas &optional sgn)
-  ;; Apply DELTAS in order to UNDO-ELT, multiplying deltas by SGN
-  ;; (only useful value for SGN is -1).
-  (let (position offset)
-    (dolist (delta deltas)
-      (setq position (car delta)
-	    offset (* (cdr delta) (or sgn 1)))
-      (cond
-       ;; POSITION
-       ((integerp undo-elt)
-	(when (>= undo-elt position)
-	  (setq undo-elt (- undo-elt offset))))
-       ;; nil (or any other atom)
-       ((atom undo-elt))
-       ;; (TEXT . POSITION)
-       ((stringp (car undo-elt))
-	(let ((text-pos (abs (cdr undo-elt)))
-	      (point-at-end (< (cdr undo-elt) 0)))
-	  (if (>= text-pos position)
-	      (setcdr undo-elt (* (if point-at-end -1 1)
-				  (- text-pos offset))))))
-       ;; (BEGIN . END)
-       ((integerp (car undo-elt))
-	(when (>= (car undo-elt) position)
-	  (setcar undo-elt (- (car undo-elt) offset))
-	  (setcdr undo-elt (- (cdr undo-elt) offset))))
-       ;; (nil PROPERTY VALUE BEG . END)
-       ((null (car undo-elt))
-	(let ((tail (nthcdr 3 undo-elt)))
-	  (when (>= (car tail) position)
-	    (setcar tail (- (car tail) offset))
-	    (setcdr tail (- (cdr tail) offset)))))
-       ))
-    undo-elt))
-
-
-
-(defun undo-tree-repeated-undo-in-region-p (start end)
-  ;; Return non-nil if undo-in-region between START and END is a repeated
-  ;; undo-in-region
-  (let ((node (undo-tree-current buffer-undo-tree)))
-    (and (setq node
-	       (nth (undo-tree-node-branch node) (undo-tree-node-next node)))
-	 (eq (undo-tree-node-undo-beginning node) start)
-	 (eq (undo-tree-node-undo-end node) end))))
-
-
-(defun undo-tree-repeated-redo-in-region-p (start end)
-  ;; Return non-nil if undo-in-region between START and END is a repeated
-  ;; undo-in-region
-  (let ((node (undo-tree-current buffer-undo-tree)))
-    (and (eq (undo-tree-node-redo-beginning node) start)
-	 (eq (undo-tree-node-redo-end node) end))))
-
-
-;; Return non-nil if undo-in-region between START and END is simply
-;; reverting the last redo-in-region
-(defalias 'undo-tree-reverting-undo-in-region-p
-  'undo-tree-repeated-undo-in-region-p)
-
-
-;; Return non-nil if redo-in-region between START and END is simply
-;; reverting the last undo-in-region
-(defalias 'undo-tree-reverting-redo-in-region-p
-  'undo-tree-repeated-redo-in-region-p)
-
-
-
-
-;;; =====================================================================
-;;;                        Undo-tree commands
-
-;;;###autoload
-(define-minor-mode undo-tree-mode
-  "Toggle undo-tree mode.
-With no argument, this command toggles the mode.
-A positive prefix argument turns the mode on.
-A negative prefix argument turns it off.
-
-Undo-tree-mode replaces Emacs' standard undo feature with a more
-powerful yet easier to use version, that treats the undo history
-as what it is: a tree.
-
-The following keys are available in `undo-tree-mode':
-
-  \\{undo-tree-map}
-
-Within the undo-tree visualizer, the following keys are available:
-
-  \\{undo-tree-visualizer-mode-map}"
-
-  nil                       ; init value
-  undo-tree-mode-lighter    ; lighter
-  undo-tree-map             ; keymap
-
-  ;; if disabling `undo-tree-mode', rebuild `buffer-undo-list' from tree so
-  ;; Emacs undo can work
-  (when (not undo-tree-mode)
-    (undo-list-rebuild-from-tree)
-    (setq buffer-undo-tree nil)))
-
-
-(defun turn-on-undo-tree-mode (&optional print-message)
-  "Enable `undo-tree-mode' in the current buffer, when appropriate.
-Some major modes implement their own undo system, which should
-not normally be overridden by `undo-tree-mode'. This command does
-not enable `undo-tree-mode' in such buffers. If you want to force
-`undo-tree-mode' to be enabled regardless, use (undo-tree-mode 1)
-instead.
-
-The heuristic used to detect major modes in which
-`undo-tree-mode' should not be used is to check whether either
-the `undo' command has been remapped, or the default undo
-keybindings (C-/ and C-_) have been overridden somewhere other
-than in the global map. In addition, `undo-tree-mode' will not be
-enabled if the buffer's `major-mode' appears in
-`undo-tree-incompatible-major-modes'."
-  (interactive "p")
-  (if (or (key-binding [remap undo])
-	  (undo-tree-overridden-undo-bindings-p)
-	  (memq major-mode undo-tree-incompatible-major-modes))
-      (when print-message
-	(message "Buffer does not support undo-tree-mode;\
- undo-tree-mode NOT enabled"))
-    (undo-tree-mode 1)))
-
-
-(defun undo-tree-overridden-undo-bindings-p ()
-  "Returns t if default undo bindings are overridden, nil otherwise.
-Checks if either of the default undo key bindings (\"C-/\" or
-\"C-_\") are overridden in the current buffer by any keymap other
-than the global one. (So global redefinitions of the default undo
-key bindings do not count.)"
-  (let ((binding1 (lookup-key (current-global-map) [?\C-/]))
-	(binding2 (lookup-key (current-global-map) [?\C-_])))
-    (global-set-key [?\C-/] 'undo)
-    (global-set-key [?\C-_] 'undo)
-    (unwind-protect
-	(or (and (key-binding [?\C-/])
-		 (not (eq (key-binding [?\C-/]) 'undo)))
-	    (and (key-binding [?\C-_])
-		 (not (eq (key-binding [?\C-_]) 'undo))))
-      (global-set-key [?\C-/] binding1)
-      (global-set-key [?\C-_] binding2))))
-
-
-;;;###autoload
-(define-globalized-minor-mode global-undo-tree-mode
-  undo-tree-mode turn-on-undo-tree-mode)
-
-
-
-(defun undo-tree-undo (&optional arg)
-  "Undo changes.
-Repeat this command to undo more changes.
-A numeric ARG serves as a repeat count.
-
-In Transient Mark mode when the mark is active, only undo changes
-within the current region. Similarly, when not in Transient Mark
-mode, just \\[universal-argument] as an argument limits undo to
-changes within the current region."
-  (interactive "*P")
-  ;; throw error if undo is disabled in buffer
-  (when (eq buffer-undo-list t)
-    (user-error "No undo information in this buffer"))
-  (undo-tree-undo-1 arg)
-  ;; inform user if at branch point
-  (when (> (undo-tree-num-branches) 1) (message "Undo branch point!")))
-
-
-(defun undo-tree-undo-1 (&optional arg preserve-redo preserve-timestamps)
-  ;; Internal undo function. An active mark in `transient-mark-mode', or
-  ;; non-nil ARG otherwise, enables undo-in-region. Non-nil PRESERVE-REDO
-  ;; causes the existing redo record to be preserved, rather than replacing it
-  ;; with the new one generated by undoing. Non-nil PRESERVE-TIMESTAMPS
-  ;; disables updating of timestamps in visited undo-tree nodes. (This latter
-  ;; should *only* be used when temporarily visiting another undo state and
-  ;; immediately returning to the original state afterwards. Otherwise, it
-  ;; could cause history-discarding errors.)
-  (let ((undo-in-progress t)
-	(undo-in-region (and undo-tree-enable-undo-in-region
-			     (or (region-active-p)
-				 (and arg (not (numberp arg))))))
-	pos current)
-    ;; transfer entries accumulated in `buffer-undo-list' to
-    ;; `buffer-undo-tree'
-    (undo-list-transfer-to-tree)
-
-    (dotimes (i (or (and (numberp arg) (prefix-numeric-value arg)) 1))
-      ;; check if at top of undo tree
-      (unless (undo-tree-node-previous (undo-tree-current buffer-undo-tree))
-	(user-error "No further undo information"))
-
-      ;; if region is active, or a non-numeric prefix argument was supplied,
-      ;; try to pull out a new branch of changes affecting the region
-      (when (and undo-in-region
-		 (not (undo-tree-pull-undo-in-region-branch
-		       (region-beginning) (region-end))))
-	(user-error "No further undo information for region"))
-
-      ;; remove any GC'd elements from node's undo list
-      (setq current (undo-tree-current buffer-undo-tree))
-      (decf (undo-tree-size buffer-undo-tree)
-	    (undo-list-byte-size (undo-tree-node-undo current)))
-      (setf (undo-tree-node-undo current)
-	    (undo-list-clean-GCd-elts (undo-tree-node-undo current)))
-      (incf (undo-tree-size buffer-undo-tree)
-	    (undo-list-byte-size (undo-tree-node-undo current)))
-      ;; undo one record from undo tree
-      (when undo-in-region
-	(setq pos (set-marker (make-marker) (point)))
-	(set-marker-insertion-type pos t))
-      (primitive-undo 1 (undo-tree-copy-list (undo-tree-node-undo current)))
-      (undo-boundary)
-
-      ;; if preserving old redo record, discard new redo entries that
-      ;; `primitive-undo' has added to `buffer-undo-list', and remove any GC'd
-      ;; elements from node's redo list
-      (if preserve-redo
-	  (progn
-	    (undo-list-pop-changeset)
-	    (decf (undo-tree-size buffer-undo-tree)
-		  (undo-list-byte-size (undo-tree-node-redo current)))
-	    (setf (undo-tree-node-redo current)
-		  (undo-list-clean-GCd-elts (undo-tree-node-redo current)))
-	    (incf (undo-tree-size buffer-undo-tree)
-		  (undo-list-byte-size (undo-tree-node-redo current))))
-	;; otherwise, record redo entries that `primitive-undo' has added to
-	;; `buffer-undo-list' in current node's redo record, replacing
-	;; existing entry if one already exists
-	(decf (undo-tree-size buffer-undo-tree)
-	      (undo-list-byte-size (undo-tree-node-redo current)))
-	(setf (undo-tree-node-redo current)
-	      (undo-list-pop-changeset 'discard-pos))
-	(incf (undo-tree-size buffer-undo-tree)
-	      (undo-list-byte-size (undo-tree-node-redo current))))
-
-      ;; rewind current node and update timestamp
-      (setf (undo-tree-current buffer-undo-tree)
-	    (undo-tree-node-previous (undo-tree-current buffer-undo-tree)))
-      (unless preserve-timestamps
-	(setf (undo-tree-node-timestamp (undo-tree-current buffer-undo-tree))
-	      (current-time)))
-
-      ;; if undoing-in-region, record current node, region and direction so we
-      ;; can tell if undo-in-region is repeated, and re-activate mark if in
-      ;; `transient-mark-mode'; if not, erase any leftover data
-      (if (not undo-in-region)
-	  (undo-tree-node-clear-region-data current)
-	(goto-char pos)
-	;; note: we deliberately want to store the region information in the
-	;; node *below* the now current one
-	(setf (undo-tree-node-undo-beginning current) (region-beginning)
-	      (undo-tree-node-undo-end current) (region-end))
-	(set-marker pos nil)))
-
-    ;; undo deactivates mark unless undoing-in-region
-    (setq deactivate-mark (not undo-in-region))))
-
-
-
-(defun undo-tree-redo (&optional arg)
-  "Redo changes. A numeric ARG serves as a repeat count.
-
-In Transient Mark mode when the mark is active, only redo changes
-within the current region. Similarly, when not in Transient Mark
-mode, just \\[universal-argument] as an argument limits redo to
-changes within the current region."
-  (interactive "*P")
-  ;; throw error if undo is disabled in buffer
-  (when (eq buffer-undo-list t)
-    (user-error "No undo information in this buffer"))
-  (undo-tree-redo-1 arg)
-  ;; inform user if at branch point
-  (when (> (undo-tree-num-branches) 1) (message "Undo branch point!")))
-
-
-(defun undo-tree-redo-1 (&optional arg preserve-undo preserve-timestamps)
-  ;; Internal redo function. An active mark in `transient-mark-mode', or
-  ;; non-nil ARG otherwise, enables undo-in-region. Non-nil PRESERVE-UNDO
-  ;; causes the existing redo record to be preserved, rather than replacing it
-  ;; with the new one generated by undoing. Non-nil PRESERVE-TIMESTAMPS
-  ;; disables updating of timestamps in visited undo-tree nodes. (This latter
-  ;; should *only* be used when temporarily visiting another undo state and
-  ;; immediately returning to the original state afterwards. Otherwise, it
-  ;; could cause history-discarding errors.)
-  (let ((undo-in-progress t)
-	(redo-in-region (and undo-tree-enable-undo-in-region
-			     (or (region-active-p)
-				 (and arg (not (numberp arg))))))
-	pos current)
-    ;; transfer entries accumulated in `buffer-undo-list' to
-    ;; `buffer-undo-tree'
-    (undo-list-transfer-to-tree)
-
-    (dotimes (i (or (and (numberp arg) (prefix-numeric-value arg)) 1))
-      ;; check if at bottom of undo tree
-      (when (null (undo-tree-node-next (undo-tree-current buffer-undo-tree)))
-	(user-error "No further redo information"))
-
-      ;; if region is active, or a non-numeric prefix argument was supplied,
-      ;; try to pull out a new branch of changes affecting the region
-      (when (and redo-in-region
-		 (not (undo-tree-pull-redo-in-region-branch
-		       (region-beginning) (region-end))))
-	(user-error "No further redo information for region"))
-
-      ;; get next node (but DON'T advance current node in tree yet, in case
-      ;; redoing fails)
-      (setq current (undo-tree-current buffer-undo-tree)
-	    current (nth (undo-tree-node-branch current)
-			 (undo-tree-node-next current)))
-      ;; remove any GC'd elements from node's redo list
-      (decf (undo-tree-size buffer-undo-tree)
-	    (undo-list-byte-size (undo-tree-node-redo current)))
-      (setf (undo-tree-node-redo current)
-	    (undo-list-clean-GCd-elts (undo-tree-node-redo current)))
-      (incf (undo-tree-size buffer-undo-tree)
-	    (undo-list-byte-size (undo-tree-node-redo current)))
-      ;; redo one record from undo tree
-      (when redo-in-region
-	(setq pos (set-marker (make-marker) (point)))
-	(set-marker-insertion-type pos t))
-      (primitive-undo 1 (undo-tree-copy-list (undo-tree-node-redo current)))
-      (undo-boundary)
-      ;; advance current node in tree
-      (setf (undo-tree-current buffer-undo-tree) current)
-
-      ;; if preserving old undo record, discard new undo entries that
-      ;; `primitive-undo' has added to `buffer-undo-list', and remove any GC'd
-      ;; elements from node's redo list
-      (if preserve-undo
-	  (progn
-	    (undo-list-pop-changeset)
-	    (decf (undo-tree-size buffer-undo-tree)
-		  (undo-list-byte-size (undo-tree-node-undo current)))
-	    (setf (undo-tree-node-undo current)
-		  (undo-list-clean-GCd-elts (undo-tree-node-undo current)))
-	    (incf (undo-tree-size buffer-undo-tree)
-		  (undo-list-byte-size (undo-tree-node-undo current))))
-	;; otherwise, record undo entries that `primitive-undo' has added to
-	;; `buffer-undo-list' in current node's undo record, replacing
-	;; existing entry if one already exists
-	(decf (undo-tree-size buffer-undo-tree)
-	      (undo-list-byte-size (undo-tree-node-undo current)))
-	(setf (undo-tree-node-undo current)
-	      (undo-list-pop-changeset 'discard-pos))
-	(incf (undo-tree-size buffer-undo-tree)
-	      (undo-list-byte-size (undo-tree-node-undo current))))
-
-      ;; update timestamp
-      (unless preserve-timestamps
-	(setf (undo-tree-node-timestamp current) (current-time)))
-
-      ;; if redoing-in-region, record current node, region and direction so we
-      ;; can tell if redo-in-region is repeated, and re-activate mark if in
-      ;; `transient-mark-mode'
-      (if (not redo-in-region)
-	  (undo-tree-node-clear-region-data current)
-	(goto-char pos)
-	(setf (undo-tree-node-redo-beginning current) (region-beginning)
-	      (undo-tree-node-redo-end current) (region-end))
-	(set-marker pos nil)))
-
-    ;; redo deactivates the mark unless redoing-in-region
-    (setq deactivate-mark (not redo-in-region))))
-
-
-
-(defun undo-tree-switch-branch (branch)
-  "Switch to a different BRANCH of the undo tree.
-This will affect which branch to descend when *redoing* changes
-using `undo-tree-redo'."
-  (interactive (list (or (and prefix-arg (prefix-numeric-value prefix-arg))
-                         (and (not (eq buffer-undo-list t))
-			      (or (undo-list-transfer-to-tree) t)
-			      (let ((b (undo-tree-node-branch
-					(undo-tree-current
-					 buffer-undo-tree))))
-				(cond
-				 ;; switch to other branch if only 2
-				 ((= (undo-tree-num-branches) 2) (- 1 b))
-				 ;; prompt if more than 2
-				 ((> (undo-tree-num-branches) 2)
-				  (read-number
-				   (format "Branch (0-%d, on %d): "
-					   (1- (undo-tree-num-branches)) b)))
-				 ))))))
-  ;; throw error if undo is disabled in buffer
-  (when (eq buffer-undo-list t)
-    (user-error "No undo information in this buffer"))
-  ;; sanity check branch number
-  (when (<= (undo-tree-num-branches) 1)
-    (user-error "Not at undo branch point"))
-  (when (or (< branch 0) (> branch (1- (undo-tree-num-branches))))
-    (user-error "Invalid branch number"))
-  ;; transfer entries accumulated in `buffer-undo-list' to `buffer-undo-tree'
-  (undo-list-transfer-to-tree)
-  ;; switch branch
-  (setf (undo-tree-node-branch (undo-tree-current buffer-undo-tree))
-	branch)
-  (message "Switched to branch %d" branch))
-
-
-(defun undo-tree-set (node &optional preserve-timestamps)
-  ;; Set buffer to state corresponding to NODE. Returns intersection point
-  ;; between path back from current node and path back from selected NODE.
-  ;; Non-nil PRESERVE-TIMESTAMPS disables updating of timestamps in visited
-  ;; undo-tree nodes. (This should *only* be used when temporarily visiting
-  ;; another undo state and immediately returning to the original state
-  ;; afterwards. Otherwise, it could cause history-discarding errors.)
-  (let ((path (make-hash-table :test 'eq))
-        (n node))
-    (puthash (undo-tree-root buffer-undo-tree) t path)
-    ;; build list of nodes leading back from selected node to root, updating
-    ;; branches as we go to point down to selected node
-    (while (progn
-             (puthash n t path)
-             (when (undo-tree-node-previous n)
-               (setf (undo-tree-node-branch (undo-tree-node-previous n))
-                     (undo-tree-position
-                      n (undo-tree-node-next (undo-tree-node-previous n))))
-               (setq n (undo-tree-node-previous n)))))
-    ;; work backwards from current node until we intersect path back from
-    ;; selected node
-    (setq n (undo-tree-current buffer-undo-tree))
-    (while (not (gethash n path))
-      (setq n (undo-tree-node-previous n)))
-    ;; ascend tree until intersection node
-    (while (not (eq (undo-tree-current buffer-undo-tree) n))
-      (undo-tree-undo-1 nil nil preserve-timestamps))
-    ;; descend tree until selected node
-    (while (not (eq (undo-tree-current buffer-undo-tree) node))
-      (undo-tree-redo-1 nil nil preserve-timestamps))
-    n))  ; return intersection node
-
-
-
-(defun undo-tree-save-state-to-register (register)
-  "Store current undo-tree state to REGISTER.
-The saved state can be restored using
-`undo-tree-restore-state-from-register'.
-Argument is a character, naming the register."
-  (interactive "cUndo-tree state to register: ")
-  ;; throw error if undo is disabled in buffer
-  (when (eq buffer-undo-list t)
-    (user-error "No undo information in this buffer"))
-  ;; transfer entries accumulated in `buffer-undo-list' to `buffer-undo-tree'
-  (undo-list-transfer-to-tree)
-  ;; save current node to REGISTER
-  (set-register
-   register (registerv-make
-	     (undo-tree-make-register-data
-	      (current-buffer) (undo-tree-current buffer-undo-tree))
-	     :print-func 'undo-tree-register-data-print-func))
-  ;; record REGISTER in current node, for visualizer
-  (setf (undo-tree-node-register (undo-tree-current buffer-undo-tree))
-	register))
-
-
-
-(defun undo-tree-restore-state-from-register (register)
-  "Restore undo-tree state from REGISTER.
-The state must be saved using `undo-tree-save-state-to-register'.
-Argument is a character, naming the register."
-  (interactive "*cRestore undo-tree state from register: ")
-  ;; throw error if undo is disabled in buffer, or if register doesn't contain
-  ;; an undo-tree node
-  (let ((data (registerv-data (get-register register))))
-    (cond
-     ((eq buffer-undo-list t)
-      (user-error "No undo information in this buffer"))
-     ((not (undo-tree-register-data-p data))
-      (user-error "Register doesn't contain undo-tree state"))
-     ((not (eq (current-buffer) (undo-tree-register-data-buffer data)))
-      (user-error "Register contains undo-tree state for a different buffer")))
-    ;; transfer entries accumulated in `buffer-undo-list' to `buffer-undo-tree'
-    (undo-list-transfer-to-tree)
-    ;; restore buffer state corresponding to saved node
-    (undo-tree-set (undo-tree-register-data-node data))))
-
-
-
-
-;;; =====================================================================
-;;;                    Persistent storage commands
-
-(defun undo-tree-make-history-save-file-name (file)
-  "Create the undo history file name for FILE.
-Normally this is the file's name with \".\" prepended and
-\".~undo-tree~\" appended.
-
-A match for FILE is sought in `undo-tree-history-directory-alist'
-\(see the documentation of that variable for details\). If the
-directory for the backup doesn't exist, it is created."
-  (let* ((backup-directory-alist undo-tree-history-directory-alist)
-	 (name (make-backup-file-name-1 file)))
-    (concat (file-name-directory name) "." (file-name-nondirectory name)
-	    ".~undo-tree~")))
-
-
-(defun undo-tree-save-history (&optional filename overwrite)
-  "Store undo-tree history to file.
-
-If optional argument FILENAME is omitted, default save file is
-\".<buffer-file-name>.~undo-tree\" if buffer is visiting a file.
-Otherwise, prompt for one.
-
-If OVERWRITE is non-nil, any existing file will be overwritten
-without asking for confirmation."
-  (interactive)
-  (when (eq buffer-undo-list t)
-    (user-error "No undo information in this buffer"))
-  (undo-list-transfer-to-tree)
-  (when (and buffer-undo-tree (not (eq buffer-undo-tree t)))
-    (condition-case nil
-	(undo-tree-kill-visualizer)
-      (error (undo-tree-clear-visualizer-data buffer-undo-tree)))
-    (let ((buff (current-buffer))
-	  tree)
-      ;; get filename
-      (unless filename
-	(setq filename
-	      (if buffer-file-name
-		  (undo-tree-make-history-save-file-name buffer-file-name)
-		(expand-file-name (read-file-name "File to save in: ") nil))))
-      (when (or (not (file-exists-p filename))
-		overwrite
-		(yes-or-no-p (format "Overwrite \"%s\"? " filename)))
-	(unwind-protect
-	    (progn
-	      ;; transform undo-tree into non-circular structure, and make
-	      ;; temporary copy
-	      (undo-tree-decircle buffer-undo-tree)
-	      (setq tree (copy-undo-tree buffer-undo-tree))
-	      ;; discard undo-tree object pool before saving
-	      (setf (undo-tree-object-pool tree) nil)
-	      ;; print undo-tree to file
-	      ;; NOTE: We use `with-temp-buffer' instead of `with-temp-file'
-	      ;;       to allow `auto-compression-mode' to take effect, in
-	      ;;       case user has overridden or advised the default
-	      ;;       `undo-tree-make-history-save-file-name' to add a
-	      ;;       compressed file extension.
-	      (with-auto-compression-mode
-		(with-temp-buffer
-		  (prin1 (sha1 buff) (current-buffer))
-		  (terpri (current-buffer))
-		  (let ((print-circle t)) (prin1 tree (current-buffer)))
-		  (write-region nil nil filename))))
-	  ;; restore circular undo-tree data structure
-	  (undo-tree-recircle buffer-undo-tree))
-	))))
-
-
-
-(defun undo-tree-load-history (&optional filename noerror)
-  "Load undo-tree history from file.
-
-If optional argument FILENAME is null, default load file is
-\".<buffer-file-name>.~undo-tree\" if buffer is visiting a file.
-Otherwise, prompt for one.
-
-If optional argument NOERROR is non-nil, return nil instead of
-signaling an error if file is not found."
-  (interactive)
-  ;; get filename
-  (unless filename
-    (setq filename
-	  (if buffer-file-name
-	      (undo-tree-make-history-save-file-name buffer-file-name)
-	    (expand-file-name (read-file-name "File to load from: ") nil))))
-
-  ;; attempt to read undo-tree from FILENAME
-  (catch 'load-error
-    (unless (file-exists-p filename)
-      (if noerror
-	  (throw 'load-error nil)
-	(error "File \"%s\" does not exist; could not load undo-tree history"
-	       filename)))
-    (let (buff hash tree)
-      (setq buff (current-buffer))
-      (with-auto-compression-mode
-	(with-temp-buffer
-	  (insert-file-contents filename)
-	  (goto-char (point-min))
-	  (condition-case nil
-	      (setq hash (read (current-buffer)))
-	    (error
-	     (kill-buffer nil)
-	     (funcall (if noerror 'message 'user-error)
-		      "Error reading undo-tree history from \"%s\"" filename)
-	     (throw 'load-error nil)))
-	  (unless (string= (sha1 buff) hash)
-	    (kill-buffer nil)
-	    (funcall (if noerror 'message 'user-error)
-		     "Buffer has been modified; could not load undo-tree history")
-	    (throw 'load-error nil))
-	  (condition-case nil
-	      (setq tree (read (current-buffer)))
-	    (error
-	     (kill-buffer nil)
-	     (funcall (if noerror 'message 'error)
-		      "Error reading undo-tree history from \"%s\"" filename)
-	     (throw 'load-error nil)))
-	  (kill-buffer nil)))
-      ;; initialise empty undo-tree object pool
-      (setf (undo-tree-object-pool tree)
-	    (make-hash-table :test 'eq :weakness 'value))
-      ;; restore circular undo-tree data structure
-      (undo-tree-recircle tree)
-      (setq buffer-undo-tree tree))))
-
-
-
-;; Versions of save/load functions for use in hooks
-(defun undo-tree-save-history-hook ()
-  (when (and undo-tree-mode undo-tree-auto-save-history
-	     (not (eq buffer-undo-list t)))
-    (undo-tree-save-history nil t) nil))
-
-(defun undo-tree-load-history-hook ()
-  (when (and undo-tree-mode undo-tree-auto-save-history
-	     (not (eq buffer-undo-list t))
-	     (not revert-buffer-in-progress-p))
-    (undo-tree-load-history nil t)))
-
-
-
-
-;;; =====================================================================
-;;;                    Visualizer drawing functions
-
-(defun undo-tree-visualize ()
-  "Visualize the current buffer's undo tree."
-  (interactive "*")
-  (deactivate-mark)
-  ;; throw error if undo is disabled in buffer
-  (when (eq buffer-undo-list t)
-    (user-error "No undo information in this buffer"))
-  ;; transfer entries accumulated in `buffer-undo-list' to `buffer-undo-tree'
-  (undo-list-transfer-to-tree)
-  ;; add hook to kill visualizer buffer if original buffer is changed
-  (add-hook 'before-change-functions 'undo-tree-kill-visualizer nil t)
-  ;; prepare *undo-tree* buffer, then draw tree in it
-  (let ((undo-tree buffer-undo-tree)
-        (buff (current-buffer))
-	(display-buffer-mark-dedicated 'soft))
-    (switch-to-buffer-other-window
-     (get-buffer-create undo-tree-visualizer-buffer-name))
-    (setq undo-tree-visualizer-parent-buffer buff)
-    (setq undo-tree-visualizer-parent-mtime
-	  (and (buffer-file-name buff)
-	       (nth 5 (file-attributes (buffer-file-name buff)))))
-    (setq undo-tree-visualizer-initial-node (undo-tree-current undo-tree))
-    (setq undo-tree-visualizer-spacing
-	  (undo-tree-visualizer-calculate-spacing))
-    (make-local-variable 'undo-tree-visualizer-timestamps)
-    (make-local-variable 'undo-tree-visualizer-diff)
-    (setq buffer-undo-tree undo-tree)
-    (undo-tree-visualizer-mode)
-    ;; FIXME; don't know why `undo-tree-visualizer-mode' clears this
-    (setq buffer-undo-tree undo-tree)
-    (set (make-local-variable 'undo-tree-visualizer-lazy-drawing)
-	 (or (eq undo-tree-visualizer-lazy-drawing t)
-	     (and (numberp undo-tree-visualizer-lazy-drawing)
-		  (>= (undo-tree-count undo-tree)
-		      undo-tree-visualizer-lazy-drawing))))
-    (when undo-tree-visualizer-diff (undo-tree-visualizer-show-diff))
-    (let ((inhibit-read-only t)) (undo-tree-draw-tree undo-tree))))
-
-
-(defun undo-tree-kill-visualizer (&rest _dummy)
-  ;; Kill visualizer. Added to `before-change-functions' hook of original
-  ;; buffer when visualizer is invoked.
-  (unless (or undo-tree-inhibit-kill-visualizer
-	      (null (get-buffer undo-tree-visualizer-buffer-name)))
-    (with-current-buffer undo-tree-visualizer-buffer-name
-      (undo-tree-visualizer-quit))))
-
-
-
-(defun undo-tree-draw-tree (undo-tree)
-  ;; Draw undo-tree in current buffer starting from NODE (or root if nil).
-  (let ((node (if undo-tree-visualizer-lazy-drawing
-		  (undo-tree-current undo-tree)
-		(undo-tree-root undo-tree))))
-    (erase-buffer)
-    (setq undo-tree-visualizer-needs-extending-down nil
-	  undo-tree-visualizer-needs-extending-up nil)
-    (undo-tree-clear-visualizer-data undo-tree)
-    (undo-tree-compute-widths node)
-    ;; lazy drawing starts vertically centred and displaced horizontally to
-    ;; the left (window-width/4), since trees will typically grow right
-    (if undo-tree-visualizer-lazy-drawing
-	(progn
-	  (undo-tree-move-down (/ (window-height) 2))
-	  (undo-tree-move-forward (max 2 (/ (window-width) 4)))) ; left margin
-      ;; non-lazy drawing starts in centre at top of buffer
-      (undo-tree-move-down 1)  ; top margin
-      (undo-tree-move-forward
-       (max (/ (window-width) 2)
-	    (+ (undo-tree-node-char-lwidth node)
-	       ;; add space for left part of left-most time-stamp
-	       (if undo-tree-visualizer-timestamps
-		   (/ (- undo-tree-visualizer-spacing 4) 2)
-		 0)
-	       2))))  ; left margin
-    ;; link starting node to its representation in visualizer
-    (setf (undo-tree-node-marker node) (make-marker))
-    (set-marker-insertion-type (undo-tree-node-marker node) nil)
-    (move-marker (undo-tree-node-marker node) (point))
-    ;; draw undo-tree
-    (let ((undo-tree-insert-face 'undo-tree-visualizer-default-face)
-	  node-list)
-      (if (not undo-tree-visualizer-lazy-drawing)
-	  (undo-tree-extend-down node t)
-	(undo-tree-extend-down node)
-	(undo-tree-extend-up node)
-	(setq node-list undo-tree-visualizer-needs-extending-down
-	      undo-tree-visualizer-needs-extending-down nil)
-	(while node-list (undo-tree-extend-down (pop node-list)))))
-    ;; highlight active branch
-    (let ((undo-tree-insert-face 'undo-tree-visualizer-active-branch-face))
-      (undo-tree-highlight-active-branch
-       (or undo-tree-visualizer-needs-extending-up
-	   (undo-tree-root undo-tree))))
-    ;; highlight current node
-    (undo-tree-draw-node (undo-tree-current undo-tree) 'current)))
-
-
-(defun undo-tree-extend-down (node &optional bottom)
-  ;; Extend tree downwards starting from NODE and point. If BOTTOM is t,
-  ;; extend all the way down to the leaves. If BOTTOM is a node, extend down
-  ;; as far as that node. If BOTTOM is an integer, extend down as far as that
-  ;; line. Otherwise, only extend visible portion of tree. NODE is assumed to
-  ;; already have a node marker. Returns non-nil if anything was actually
-  ;; extended.
-  (let ((extended nil)
-	(cur-stack (list node))
-	next-stack)
-    ;; don't bother extending if BOTTOM specifies an already-drawn node
-    (unless (and (undo-tree-node-p bottom) (undo-tree-node-marker bottom))
-      ;; draw nodes layer by layer
-      (while (or cur-stack
-		 (prog1 (setq cur-stack next-stack)
-		   (setq next-stack nil)))
-	(setq node (pop cur-stack))
-	;; if node is within range being drawn...
-	(if (or (eq bottom t)
-		(and (undo-tree-node-p bottom)
-		     (not (eq (undo-tree-node-previous node) bottom)))
-		(and (integerp bottom)
-		     (>= bottom (line-number-at-pos
-				 (undo-tree-node-marker node))))
-		(and (null bottom)
-		     (pos-visible-in-window-p (undo-tree-node-marker node)
-					      nil t)))
-	    ;; ...draw one layer of node's subtree (if not already drawn)
-	    (progn
-	      (unless (and (undo-tree-node-next node)
-			   (undo-tree-node-marker
-			    (nth (undo-tree-node-branch node)
-				 (undo-tree-node-next node))))
-		(goto-char (undo-tree-node-marker node))
-		(undo-tree-draw-subtree node)
-		(setq extended t))
-	      (setq next-stack
-		    (append (undo-tree-node-next node) next-stack)))
-	  ;; ...otherwise, postpone drawing until later
-	  (push node undo-tree-visualizer-needs-extending-down))))
-    extended))
-
-
-(defun undo-tree-extend-up (node &optional top)
-  ;; Extend tree upwards starting from NODE. If TOP is t, extend all the way
-  ;; to root. If TOP is a node, extend up as far as that node. If TOP is an
-  ;; integer, extend up as far as that line. Otherwise, only extend visible
-  ;; portion of tree. NODE is assumed to already have a node marker. Returns
-  ;; non-nil if anything was actually extended.
-  (let ((extended nil) parent)
-    ;; don't bother extending if TOP specifies an already-drawn node
-    (unless (and (undo-tree-node-p top) (undo-tree-node-marker top))
-      (while node
-	(setq parent (undo-tree-node-previous node))
-	;; if we haven't reached root...
-	(if parent
-	    ;; ...and node is within range being drawn...
-	    (if (or (eq top t)
-		    (and (undo-tree-node-p top) (not (eq node top)))
-		    (and (integerp top)
-			 (< top (line-number-at-pos
-				 (undo-tree-node-marker node))))
-		    (and (null top)
-			 ;; NOTE: we check point in case window-start is outdated
-			 (< (min (line-number-at-pos (point))
-				 (line-number-at-pos (window-start)))
-			    (line-number-at-pos
-			     (undo-tree-node-marker node)))))
-		;; ...and it hasn't already been drawn
-		(when (not (undo-tree-node-marker parent))
-		  ;; link parent node to its representation in visualizer
-		  (undo-tree-compute-widths parent)
-		  (undo-tree-move-to-parent node)
-		  (setf (undo-tree-node-marker parent) (make-marker))
-		  (set-marker-insertion-type
-		   (undo-tree-node-marker parent) nil)
-		  (move-marker (undo-tree-node-marker parent) (point))
-		  ;; draw subtree beneath parent
-		  (setq undo-tree-visualizer-needs-extending-down
-			(nconc (delq node (undo-tree-draw-subtree parent))
-			       undo-tree-visualizer-needs-extending-down))
-		  (setq extended t))
-	      ;; ...otherwise, postpone drawing for later and exit
-	      (setq undo-tree-visualizer-needs-extending-up (when parent node)
-		    parent nil))
-
-	  ;; if we've reached root, stop extending and add top margin
-	  (setq undo-tree-visualizer-needs-extending-up nil)
-	  (goto-char (undo-tree-node-marker node))
-	  (undo-tree-move-up 1)  ; top margin
-	  (delete-region (point-min) (line-beginning-position)))
-	;; next iteration
-	(setq node parent)))
-    extended))
-
-
-(defun undo-tree-expand-down (from &optional to)
-  ;; Expand tree downwards. FROM is the node to start expanding from. Stop
-  ;; expanding at TO if specified. Otherwise, just expand visible portion of
-  ;; tree and highlight active branch from FROM.
-  (when undo-tree-visualizer-needs-extending-down
-    (let ((inhibit-read-only t)
-	  node-list extended)
-      ;; extend down as far as TO node
-      (when to
-	(setq extended (undo-tree-extend-down from to))
-	(goto-char (undo-tree-node-marker to))
-	(redisplay t))  ; force redisplay to scroll buffer if necessary
-      ;; extend visible portion of tree downwards
-      (setq node-list undo-tree-visualizer-needs-extending-down
-	    undo-tree-visualizer-needs-extending-down nil)
-      (when node-list
-	(dolist (n node-list)
-	  (when (undo-tree-extend-down n) (setq extended t)))
-	;; highlight active branch in newly-extended-down portion, if any
-	(when extended
-	  (let ((undo-tree-insert-face
-		 'undo-tree-visualizer-active-branch-face))
-	    (undo-tree-highlight-active-branch from)))))))
-
-
-(defun undo-tree-expand-up (from &optional to)
-  ;; Expand tree upwards. FROM is the node to start expanding from, TO is the
-  ;; node to stop expanding at. If TO node isn't specified, just expand visible
-  ;; portion of tree and highlight active branch down to FROM.
-  (when undo-tree-visualizer-needs-extending-up
-    (let ((inhibit-read-only t)
-	  extended node-list)
-      ;; extend up as far as TO node
-      (when to
-	(setq extended (undo-tree-extend-up from to))
-	(goto-char (undo-tree-node-marker to))
-	;; simulate auto-scrolling if close to top of buffer
-	(when (<= (line-number-at-pos (point)) scroll-margin)
-	  (undo-tree-move-up (if (= scroll-conservatively 0)
-				 (/ (window-height) 2) 3))
-	  (when (undo-tree-extend-up to) (setq extended t))
-	  (goto-char (undo-tree-node-marker to))
-	  (unless (= scroll-conservatively 0) (recenter scroll-margin))))
-      ;; extend visible portion of tree upwards
-      (and undo-tree-visualizer-needs-extending-up
-	   (undo-tree-extend-up undo-tree-visualizer-needs-extending-up)
-	   (setq extended t))
-      ;; extend visible portion of tree downwards
-      (setq node-list undo-tree-visualizer-needs-extending-down
-	    undo-tree-visualizer-needs-extending-down nil)
-      (dolist (n node-list) (undo-tree-extend-down n))
-      ;; highlight active branch in newly-extended-up portion, if any
-      (when extended
-	(let ((undo-tree-insert-face
-	       'undo-tree-visualizer-active-branch-face))
-	  (undo-tree-highlight-active-branch
-	   (or undo-tree-visualizer-needs-extending-up
-	       (undo-tree-root buffer-undo-tree))
-	   from))))))
-
-
-
-(defun undo-tree-highlight-active-branch (node &optional end)
-  ;; Draw highlighted active branch below NODE in current buffer. Stop
-  ;; highlighting at END node if specified.
-  (let ((stack (list node)))
-    ;; draw active branch
-    (while stack
-      (setq node (pop stack))
-      (unless (or (eq node end)
-		  (memq node undo-tree-visualizer-needs-extending-down))
-	(goto-char (undo-tree-node-marker node))
-	(setq node (undo-tree-draw-subtree node 'active)
-	      stack (nconc stack node))))))
-
-
-(defun undo-tree-draw-node (node &optional current)
-  ;; Draw symbol representing NODE in visualizer. If CURRENT is non-nil, node
-  ;; is current node.
-  (goto-char (undo-tree-node-marker node))
-  (when undo-tree-visualizer-timestamps
-    (undo-tree-move-backward (/ undo-tree-visualizer-spacing 2)))
-
-  (let* ((undo-tree-insert-face (and undo-tree-insert-face
-				     (or (and (consp undo-tree-insert-face)
-					      undo-tree-insert-face)
-					 (list undo-tree-insert-face))))
-	 (register (undo-tree-node-register node))
-	 (unmodified (if undo-tree-visualizer-parent-mtime
-			 (undo-tree-node-unmodified-p
-			  node undo-tree-visualizer-parent-mtime)
-		       (undo-tree-node-unmodified-p node)))
-	node-string)
-    ;; check node's register (if any) still stores appropriate undo-tree state
-    (unless (and register
-		 (undo-tree-register-data-p
-		  (registerv-data (get-register register)))
-		 (eq node (undo-tree-register-data-node
-			   (registerv-data (get-register register)))))
-      (setq register nil))
-    ;; represent node by different symbols, depending on whether it's the
-    ;; current node, is saved in a register, or corresponds to an unmodified
-    ;; buffer
-    (setq node-string
-	    (cond
-	     (undo-tree-visualizer-timestamps
-	        (undo-tree-timestamp-to-string
-	         (undo-tree-node-timestamp node)
-		 undo-tree-visualizer-relative-timestamps
-		 current register))
-	     (register (char-to-string register))
-	     (unmodified "s")
-	     (current "x")
-	     (t "o"))
-	  undo-tree-insert-face
-	    (nconc
-	     (cond
-	      (current    '(undo-tree-visualizer-current-face))
-	      (unmodified '(undo-tree-visualizer-unmodified-face))
-	      (register   '(undo-tree-visualizer-register-face)))
-	     undo-tree-insert-face))
-    ;; draw node and link it to its representation in visualizer
-    (undo-tree-insert node-string)
-    (undo-tree-move-backward (if undo-tree-visualizer-timestamps
-				 (1+ (/ undo-tree-visualizer-spacing 2))
-			       1))
-    (move-marker (undo-tree-node-marker node) (point))
-    (put-text-property (point) (1+ (point)) 'undo-tree-node node)))
-
-
-(defun undo-tree-draw-subtree (node &optional active-branch)
-  ;; Draw subtree rooted at NODE. The subtree will start from point.
-  ;; If ACTIVE-BRANCH is non-nil, just draw active branch below NODE. Returns
-  ;; list of nodes below NODE.
-  (let ((num-children (length (undo-tree-node-next node)))
-        node-list pos trunk-pos n)
-    ;; draw node itself
-    (undo-tree-draw-node node)
-
-    (cond
-     ;; if we're at a leaf node, we're done
-     ((= num-children 0))
-
-     ;; if node has only one child, draw it (not strictly necessary to deal
-     ;; with this case separately, but as it's by far the most common case
-     ;; this makes the code clearer and more efficient)
-     ((= num-children 1)
-      (undo-tree-move-down 1)
-      (undo-tree-insert ?|)
-      (undo-tree-move-backward 1)
-      (undo-tree-move-down 1)
-      (undo-tree-insert ?|)
-      (undo-tree-move-backward 1)
-      (undo-tree-move-down 1)
-      (setq n (car (undo-tree-node-next node)))
-      ;; link next node to its representation in visualizer
-      (unless (markerp (undo-tree-node-marker n))
-        (setf (undo-tree-node-marker n) (make-marker))
-        (set-marker-insertion-type (undo-tree-node-marker n) nil))
-      (move-marker (undo-tree-node-marker n) (point))
-      ;; add next node to list of nodes to draw next
-      (push n node-list))
-
-     ;; if node has multiple children, draw branches
-     (t
-      (undo-tree-move-down 1)
-      (undo-tree-insert ?|)
-      (undo-tree-move-backward 1)
-      (move-marker (setq trunk-pos (make-marker)) (point))
-      ;; left subtrees
-      (undo-tree-move-backward
-       (- (undo-tree-node-char-lwidth node)
-          (undo-tree-node-char-lwidth
-           (car (undo-tree-node-next node)))))
-      (move-marker (setq pos (make-marker)) (point))
-      (setq n (cons nil (undo-tree-node-next node)))
-      (dotimes (i (/ num-children 2))
-        (setq n (cdr n))
-        (when (or (null active-branch)
-                  (eq (car n)
-                      (nth (undo-tree-node-branch node)
-                           (undo-tree-node-next node))))
-          (undo-tree-move-forward 2)
-          (undo-tree-insert ?_ (- trunk-pos pos 2))
-          (goto-char pos)
-          (undo-tree-move-forward 1)
-          (undo-tree-move-down 1)
-          (undo-tree-insert ?/)
-          (undo-tree-move-backward 2)
-          (undo-tree-move-down 1)
-          ;; link node to its representation in visualizer
-          (unless (markerp (undo-tree-node-marker (car n)))
-            (setf (undo-tree-node-marker (car n)) (make-marker))
-            (set-marker-insertion-type (undo-tree-node-marker (car n)) nil))
-          (move-marker (undo-tree-node-marker (car n)) (point))
-          ;; add node to list of nodes to draw next
-          (push (car n) node-list))
-        (goto-char pos)
-        (undo-tree-move-forward
-         (+ (undo-tree-node-char-rwidth (car n))
-            (undo-tree-node-char-lwidth (cadr n))
-            undo-tree-visualizer-spacing 1))
-        (move-marker pos (point)))
-      ;; middle subtree (only when number of children is odd)
-      (when (= (mod num-children 2) 1)
-        (setq n (cdr n))
-        (when (or (null active-branch)
-                  (eq (car n)
-                      (nth (undo-tree-node-branch node)
-                           (undo-tree-node-next node))))
-          (undo-tree-move-down 1)
-          (undo-tree-insert ?|)
-          (undo-tree-move-backward 1)
-          (undo-tree-move-down 1)
-          ;; link node to its representation in visualizer
-          (unless (markerp (undo-tree-node-marker (car n)))
-            (setf (undo-tree-node-marker (car n)) (make-marker))
-            (set-marker-insertion-type (undo-tree-node-marker (car n)) nil))
-          (move-marker (undo-tree-node-marker (car n)) (point))
-          ;; add node to list of nodes to draw next
-          (push (car n) node-list))
-        (goto-char pos)
-        (undo-tree-move-forward
-         (+ (undo-tree-node-char-rwidth (car n))
-            (if (cadr n) (undo-tree-node-char-lwidth (cadr n)) 0)
-            undo-tree-visualizer-spacing 1))
-        (move-marker pos (point)))
-      ;; right subtrees
-      (move-marker trunk-pos (1+ trunk-pos))
-      (dotimes (i (/ num-children 2))
-        (setq n (cdr n))
-        (when (or (null active-branch)
-                  (eq (car n)
-                      (nth (undo-tree-node-branch node)
-                           (undo-tree-node-next node))))
-          (goto-char trunk-pos)
-          (undo-tree-insert ?_ (- pos trunk-pos 1))
-          (goto-char pos)
-          (undo-tree-move-backward 1)
-          (undo-tree-move-down 1)
-          (undo-tree-insert ?\\)
-          (undo-tree-move-down 1)
-          ;; link node to its representation in visualizer
-          (unless (markerp (undo-tree-node-marker (car n)))
-            (setf (undo-tree-node-marker (car n)) (make-marker))
-            (set-marker-insertion-type (undo-tree-node-marker (car n)) nil))
-          (move-marker (undo-tree-node-marker (car n)) (point))
-          ;; add node to list of nodes to draw next
-          (push (car n) node-list))
-        (when (cdr n)
-          (goto-char pos)
-          (undo-tree-move-forward
-           (+ (undo-tree-node-char-rwidth (car n))
-              (if (cadr n) (undo-tree-node-char-lwidth (cadr n)) 0)
-              undo-tree-visualizer-spacing 1))
-          (move-marker pos (point))))
-      ))
-    ;; return list of nodes to draw next
-    (nreverse node-list)))
-
-
-(defun undo-tree-node-char-lwidth (node)
-  ;; Return left-width of NODE measured in characters.
-  (if (= (length (undo-tree-node-next node)) 0) 0
-    (- (* (+ undo-tree-visualizer-spacing 1) (undo-tree-node-lwidth node))
-       (if (= (undo-tree-node-cwidth node) 0)
-           (1+ (/ undo-tree-visualizer-spacing 2)) 0))))
-
-
-(defun undo-tree-node-char-rwidth (node)
-  ;; Return right-width of NODE measured in characters.
-  (if (= (length (undo-tree-node-next node)) 0) 0
-    (- (* (+ undo-tree-visualizer-spacing 1) (undo-tree-node-rwidth node))
-       (if (= (undo-tree-node-cwidth node) 0)
-           (1+ (/ undo-tree-visualizer-spacing 2)) 0))))
-
-
-(defun undo-tree-insert (str &optional arg)
-  ;; Insert character or string STR ARG times, overwriting, and using
-  ;; `undo-tree-insert-face'.
-  (unless arg (setq arg 1))
-  (when (characterp str)
-    (setq str (make-string arg str))
-    (setq arg 1))
-  (dotimes (i arg) (insert str))
-  (setq arg (* arg (length str)))
-  (undo-tree-move-forward arg)
-  ;; make sure mark isn't active, otherwise `backward-delete-char' might
-  ;; delete region instead of single char if transient-mark-mode is enabled
-  (setq mark-active nil)
-  (backward-delete-char arg)
-  (when undo-tree-insert-face
-    (put-text-property (- (point) arg) (point) 'face undo-tree-insert-face)))
-
-
-(defun undo-tree-move-down (&optional arg)
-  ;; Move down, extending buffer if necessary.
-  (let ((row (line-number-at-pos))
-        (col (current-column))
-        line)
-    (unless arg (setq arg 1))
-    (forward-line arg)
-    (setq line (line-number-at-pos))
-    ;; if buffer doesn't have enough lines, add some
-    (when (/= line (+ row arg))
-      (cond
-       ((< arg 0)
-	(insert (make-string (- line row arg) ?\n))
-	(forward-line (+ arg (- row line))))
-       (t (insert (make-string (- arg (- line row)) ?\n)))))
-    (undo-tree-move-forward col)))
-
-
-(defun undo-tree-move-up (&optional arg)
-  ;; Move up, extending buffer if necessary.
-  (unless arg (setq arg 1))
-  (undo-tree-move-down (- arg)))
-
-
-(defun undo-tree-move-forward (&optional arg)
-  ;; Move forward, extending buffer if necessary.
-  (unless arg (setq arg 1))
-  (let (n)
-    (cond
-     ((>= arg 0)
-      (setq n (- (line-end-position) (point)))
-      (if (> n arg)
-	  (forward-char arg)
-	(end-of-line)
-	(insert (make-string (- arg n) ? ))))
-     ((< arg 0)
-      (setq arg (- arg))
-      (setq n (- (point) (line-beginning-position)))
-      (when (< (- n 2) arg)  ; -2 to create left-margin
-	;; no space left - shift entire buffer contents right!
-	(let ((pos (move-marker (make-marker) (point))))
-	  (set-marker-insertion-type pos t)
-	  (goto-char (point-min))
-	  (while (not (eobp))
-	    (insert-before-markers (make-string (- arg -2 n) ? ))
-	    (forward-line 1))
-	  (goto-char pos)))
-      (backward-char arg)))))
-
-
-(defun undo-tree-move-backward (&optional arg)
-  ;; Move backward, extending buffer if necessary.
-  (unless arg (setq arg 1))
-  (undo-tree-move-forward (- arg)))
-
-
-(defun undo-tree-move-to-parent (node)
-  ;; Move to position of parent of NODE, extending buffer if necessary.
-  (let* ((parent (undo-tree-node-previous node))
-	 (n (undo-tree-node-next parent))
-	 (l (length n)) p)
-    (goto-char (undo-tree-node-marker node))
-    (unless (= l 1)
-      ;; move horizontally
-      (setq p (undo-tree-position node n))
-      (cond
-       ;; node in centre subtree: no horizontal movement
-       ((and (= (mod l 2) 1) (= p (/ l 2))))
-       ;; node in left subtree: move right
-       ((< p (/ l 2))
-	(setq n (nthcdr p n))
-	(undo-tree-move-forward
-	 (+ (undo-tree-node-char-rwidth (car n))
-	    (/ undo-tree-visualizer-spacing 2) 1))
-	(dotimes (i (- (/ l 2) p 1))
-	  (setq n (cdr n))
-	  (undo-tree-move-forward
-	   (+ (undo-tree-node-char-lwidth (car n))
-	      (undo-tree-node-char-rwidth (car n))
-	      undo-tree-visualizer-spacing 1)))
-	(when (= (mod l 2) 1)
-	  (setq n (cdr n))
-	  (undo-tree-move-forward
-	   (+ (undo-tree-node-char-lwidth (car n))
-	      (/ undo-tree-visualizer-spacing 2) 1))))
-       (t ;; node in right subtree: move left
-	(setq n (nthcdr (/ l 2) n))
-	(when (= (mod l 2) 1)
-	  (undo-tree-move-backward
-	   (+ (undo-tree-node-char-rwidth (car n))
-	      (/ undo-tree-visualizer-spacing 2) 1))
-	  (setq n (cdr n)))
-	(dotimes (i (- p (/ l 2) (mod l 2)))
-	  (undo-tree-move-backward
-	   (+ (undo-tree-node-char-lwidth (car n))
-	      (undo-tree-node-char-rwidth (car n))
-	      undo-tree-visualizer-spacing 1))
-	  (setq n (cdr n)))
-	(undo-tree-move-backward
-	 (+ (undo-tree-node-char-lwidth (car n))
-	    (/ undo-tree-visualizer-spacing 2) 1)))))
-    ;; move vertically
-    (undo-tree-move-up 3)))
-
-
-(defun undo-tree-timestamp-to-string
-  (timestamp &optional relative current register)
-  ;; Convert TIMESTAMP to string (either absolute or RELATVE time), indicating
-  ;; if it's the CURRENT node and/or has an associated REGISTER.
-  (if relative
-      ;; relative time
-      (let ((time (floor (float-time
-			  (subtract-time (current-time) timestamp))))
-	    n)
-	(setq time
-	      ;; years
-	      (if (> (setq n (/ time 315360000)) 0)
-		  (if (> n 999) "-ages" (format "-%dy" n))
-		(setq time (% time 315360000))
-		;; days
-		(if (> (setq n (/ time 86400)) 0)
-		    (format "-%dd" n)
-		  (setq time (% time 86400))
-		  ;; hours
-		  (if (> (setq n (/ time 3600)) 0)
-		      (format "-%dh" n)
-		    (setq time (% time 3600))
-		    ;; mins
-		    (if (> (setq n (/ time 60)) 0)
-			(format "-%dm" n)
-		      ;; secs
-		      (format "-%ds" (% time 60)))))))
-	(setq time (concat
-		    (if current "*" " ")
-		    time
-		    (if register (concat "[" (char-to-string register) "]")
-		      "   ")))
-	(setq n (length time))
-	(if (< n 9)
-	    (concat (make-string (- 9 n) ? ) time)
-	  time))
-    ;; absolute time
-    (concat (if current " *" "  ")
-	    (format-time-string "%H:%M:%S" timestamp)
-	    (if register
-		(concat "[" (char-to-string register) "]")
-	      "   "))))
-
-
-
-
-;;; =====================================================================
-;;;                        Visualizer commands
-
-(define-derived-mode
-  undo-tree-visualizer-mode special-mode "undo-tree-visualizer"
-  "Major mode used in undo-tree visualizer.
-
-The undo-tree visualizer can only be invoked from a buffer in
-which `undo-tree-mode' is enabled. The visualizer displays the
-undo history tree graphically, and allows you to browse around
-the undo history, undoing or redoing the corresponding changes in
-the parent buffer.
-
-Within the undo-tree visualizer, the following keys are available:
-
-  \\{undo-tree-visualizer-mode-map}"
-  :syntax-table nil
-  :abbrev-table nil
-  (setq truncate-lines t)
-  (setq cursor-type nil)
-  (setq undo-tree-visualizer-selected-node nil))
-
-
-
-(defun undo-tree-visualize-undo (&optional arg)
-  "Undo changes. A numeric ARG serves as a repeat count."
-  (interactive "p")
-  (let ((old (undo-tree-current buffer-undo-tree))
-	current)
-    ;; unhighlight old current node
-    (let ((undo-tree-insert-face 'undo-tree-visualizer-active-branch-face)
-	  (inhibit-read-only t))
-      (undo-tree-draw-node old))
-    ;; undo in parent buffer
-    (switch-to-buffer-other-window undo-tree-visualizer-parent-buffer)
-    (deactivate-mark)
-    (unwind-protect
-	(let ((undo-tree-inhibit-kill-visualizer t)) (undo-tree-undo-1 arg))
-      (setq current (undo-tree-current buffer-undo-tree))
-      (switch-to-buffer-other-window undo-tree-visualizer-buffer-name)
-      ;; when using lazy drawing, extend tree upwards as required
-      (when undo-tree-visualizer-lazy-drawing
-	(undo-tree-expand-up old current))
-      ;; highlight new current node
-      (let ((inhibit-read-only t)) (undo-tree-draw-node current 'current))
-      ;; update diff display, if any
-      (when undo-tree-visualizer-diff (undo-tree-visualizer-update-diff)))))
-
-
-(defun undo-tree-visualize-redo (&optional arg)
-  "Redo changes. A numeric ARG serves as a repeat count."
-  (interactive "p")
-  (let ((old (undo-tree-current buffer-undo-tree))
-	current)
-    ;; unhighlight old current node
-    (let ((undo-tree-insert-face 'undo-tree-visualizer-active-branch-face)
-	  (inhibit-read-only t))
-      (undo-tree-draw-node (undo-tree-current buffer-undo-tree)))
-    ;; redo in parent buffer
-    (switch-to-buffer-other-window undo-tree-visualizer-parent-buffer)
-    (deactivate-mark)
-    (unwind-protect
-	(let ((undo-tree-inhibit-kill-visualizer t)) (undo-tree-redo-1 arg))
-      (setq current (undo-tree-current buffer-undo-tree))
-      (switch-to-buffer-other-window undo-tree-visualizer-buffer-name)
-      ;; when using lazy drawing, extend tree downwards as required
-      (when undo-tree-visualizer-lazy-drawing
-	(undo-tree-expand-down old current))
-      ;; highlight new current node
-      (let ((inhibit-read-only t)) (undo-tree-draw-node current 'current))
-      ;; update diff display, if any
-      (when undo-tree-visualizer-diff (undo-tree-visualizer-update-diff)))))
-
-
-(defun undo-tree-visualize-switch-branch-right (arg)
-  "Switch to next branch of the undo tree.
-This will affect which branch to descend when *redoing* changes
-using `undo-tree-redo' or `undo-tree-visualizer-redo'."
-  (interactive "p")
-  ;; un-highlight old active branch below current node
-  (goto-char (undo-tree-node-marker (undo-tree-current buffer-undo-tree)))
-  (let ((undo-tree-insert-face 'undo-tree-visualizer-default-face)
-	(inhibit-read-only t))
-    (undo-tree-highlight-active-branch (undo-tree-current buffer-undo-tree)))
-  ;; increment branch
-  (let ((branch (undo-tree-node-branch (undo-tree-current buffer-undo-tree))))
-  (setf (undo-tree-node-branch (undo-tree-current buffer-undo-tree))
-        (cond
-         ((>= (+ branch arg) (undo-tree-num-branches))
-          (1- (undo-tree-num-branches)))
-         ((<= (+ branch arg) 0) 0)
-         (t (+ branch arg))))
-  (let ((inhibit-read-only t))
-    ;; highlight new active branch below current node
-    (goto-char (undo-tree-node-marker (undo-tree-current buffer-undo-tree)))
-    (let ((undo-tree-insert-face 'undo-tree-visualizer-active-branch-face))
-      (undo-tree-highlight-active-branch (undo-tree-current buffer-undo-tree)))
-    ;; re-highlight current node
-    (undo-tree-draw-node (undo-tree-current buffer-undo-tree) 'current))))
-
-
-(defun undo-tree-visualize-switch-branch-left (arg)
-  "Switch to previous branch of the undo tree.
-This will affect which branch to descend when *redoing* changes
-using `undo-tree-redo' or `undo-tree-visualizer-redo'."
-  (interactive "p")
-  (undo-tree-visualize-switch-branch-right (- arg)))
-
-
-(defun undo-tree-visualizer-quit ()
-  "Quit the undo-tree visualizer."
-  (interactive)
-  (undo-tree-clear-visualizer-data buffer-undo-tree)
-  ;; remove kill visualizer hook from parent buffer
-  (unwind-protect
-      (with-current-buffer undo-tree-visualizer-parent-buffer
-	(remove-hook 'before-change-functions 'undo-tree-kill-visualizer t))
-    ;; kill diff buffer, if any
-    (when undo-tree-visualizer-diff (undo-tree-visualizer-hide-diff))
-    (let ((parent undo-tree-visualizer-parent-buffer)
-	  window)
-      ;; kill visualizer buffer
-      (kill-buffer nil)
-      ;; switch back to parent buffer
-      (unwind-protect
-	  (if (setq window (get-buffer-window parent))
-	      (select-window window)
-	    (switch-to-buffer parent))))))
-
-
-(defun undo-tree-visualizer-abort ()
-  "Quit the undo-tree visualizer and return buffer to original state."
-  (interactive)
-  (let ((node undo-tree-visualizer-initial-node))
-    (undo-tree-visualizer-quit)
-    (undo-tree-set node)))
-
-
-(defun undo-tree-visualizer-set (&optional pos)
-  "Set buffer to state corresponding to undo tree node
-at POS, or point if POS is nil."
-  (interactive)
-  (unless pos (setq pos (point)))
-  (let ((node (get-text-property pos 'undo-tree-node)))
-    (when node
-      ;; set parent buffer to state corresponding to node at POS
-      (switch-to-buffer-other-window undo-tree-visualizer-parent-buffer)
-      (let ((undo-tree-inhibit-kill-visualizer t)) (undo-tree-set node))
-      (switch-to-buffer-other-window undo-tree-visualizer-buffer-name)
-      ;; re-draw undo tree
-      (let ((inhibit-read-only t)) (undo-tree-draw-tree buffer-undo-tree))
-      (when undo-tree-visualizer-diff (undo-tree-visualizer-update-diff)))))
-
-
-(defun undo-tree-visualizer-mouse-set (pos)
-  "Set buffer to state corresponding to undo tree node
-at mouse event POS."
-  (interactive "@e")
-  (undo-tree-visualizer-set (event-start (nth 1 pos))))
-
-
-(defun undo-tree-visualize-undo-to-x (&optional x)
-  "Undo to last branch point, register, or saved state.
-If X is the symbol `branch', undo to last branch point. If X is
-the symbol `register', undo to last register. If X is the sumbol
-`saved', undo to last saved state. If X is null, undo to first of
-these that's encountered.
-
-Interactively, a single \\[universal-argument] specifies
-`branch', a double \\[universal-argument] \\[universal-argument]
-specifies `saved', and a negative prefix argument specifies
-`register'."
-  (interactive "P")
-  (when (and (called-interactively-p 'any) x)
-    (setq x (prefix-numeric-value x)
-	  x (cond
-	     ((< x 0)  'register)
-	     ((<= x 4) 'branch)
-	     (t        'saved))))
-  (let ((current (if undo-tree-visualizer-selection-mode
-		     undo-tree-visualizer-selected-node
-		   (undo-tree-current buffer-undo-tree)))
-	(diff undo-tree-visualizer-diff)
-	r)
-    (undo-tree-visualizer-hide-diff)
-    (while (and (undo-tree-node-previous current)
-		(or (if undo-tree-visualizer-selection-mode
-			(progn
-			  (undo-tree-visualizer-select-previous)
-			  (setq current undo-tree-visualizer-selected-node))
-		      (undo-tree-visualize-undo)
-		      (setq current (undo-tree-current buffer-undo-tree)))
-		    t)
-		         ;; branch point
-		(not (or (and (or (null x) (eq x 'branch))
-			      (> (undo-tree-num-branches) 1))
-			 ;; register
-			 (and (or (null x) (eq x 'register))
-			      (setq r (undo-tree-node-register current))
-			      (undo-tree-register-data-p
-			       (setq r (registerv-data (get-register r))))
-			      (eq current (undo-tree-register-data-node r)))
-			 ;; saved state
-			 (and (or (null x) (eq x 'saved))
-			      (undo-tree-node-unmodified-p current))
-			 ))))
-    ;; update diff display, if any
-    (when diff
-      (undo-tree-visualizer-show-diff
-       (when undo-tree-visualizer-selection-mode
-	 undo-tree-visualizer-selected-node)))))
-
-
-(defun undo-tree-visualize-redo-to-x (&optional x)
-  "Redo to last branch point, register, or saved state.
-If X is the symbol `branch', redo to last branch point. If X is
-the symbol `register', redo to last register. If X is the sumbol
-`saved', redo to last saved state. If X is null, redo to first of
-these that's encountered.
-
-Interactively, a single \\[universal-argument] specifies
-`branch', a double \\[universal-argument] \\[universal-argument]
-specifies `saved', and a negative prefix argument specifies
-`register'."
-  (interactive "P")
-  (when (and (called-interactively-p 'any) x)
-    (setq x (prefix-numeric-value x)
-	  x (cond
-	     ((< x 0)  'register)
-	     ((<= x 4) 'branch)
-	     (t        'saved))))
-  (let ((current (if undo-tree-visualizer-selection-mode
-		     undo-tree-visualizer-selected-node
-		   (undo-tree-current buffer-undo-tree)))
-	(diff undo-tree-visualizer-diff)
-	r)
-    (undo-tree-visualizer-hide-diff)
-    (while (and (undo-tree-node-next current)
-		(or (if undo-tree-visualizer-selection-mode
-			(progn
-			  (undo-tree-visualizer-select-next)
-			  (setq current undo-tree-visualizer-selected-node))
-		      (undo-tree-visualize-redo)
-		      (setq current (undo-tree-current buffer-undo-tree)))
-		    t)
-		         ;; branch point
-		(not (or (and (or (null x) (eq x 'branch))
-			      (> (undo-tree-num-branches) 1))
-			 ;; register
-			 (and (or (null x) (eq x 'register))
-			      (setq r (undo-tree-node-register current))
-			      (undo-tree-register-data-p
-			       (setq r (registerv-data (get-register r))))
-			      (eq current (undo-tree-register-data-node r)))
-			 ;; saved state
-			 (and (or (null x) (eq x 'saved))
-			      (undo-tree-node-unmodified-p current))
-			 ))))
-    ;; update diff display, if any
-    (when diff
-      (undo-tree-visualizer-show-diff
-       (when undo-tree-visualizer-selection-mode
-	 undo-tree-visualizer-selected-node)))))
-
-
-(defun undo-tree-visualizer-toggle-timestamps ()
-  "Toggle display of time-stamps."
-  (interactive)
-  (setq undo-tree-visualizer-timestamps (not undo-tree-visualizer-timestamps))
-  (setq undo-tree-visualizer-spacing (undo-tree-visualizer-calculate-spacing))
-  ;; redraw tree
-  (let ((inhibit-read-only t)) (undo-tree-draw-tree buffer-undo-tree)))
-
-
-(defun undo-tree-visualizer-scroll-left (&optional arg)
-  (interactive "p")
-  (scroll-left (or arg 1) t))
-
-
-(defun undo-tree-visualizer-scroll-right (&optional arg)
-  (interactive "p")
-  (scroll-right (or arg 1) t))
-
-
-(defun undo-tree-visualizer-scroll-up (&optional arg)
-  (interactive "P")
-  (if (or (and (numberp arg) (< arg 0)) (eq arg '-))
-      (undo-tree-visualizer-scroll-down arg)
-    ;; scroll up and expand newly-visible portion of tree
-    (unwind-protect
-	(scroll-up-command arg)
-      (undo-tree-expand-down
-       (nth (undo-tree-node-branch (undo-tree-current buffer-undo-tree))
-	    (undo-tree-node-next (undo-tree-current buffer-undo-tree)))))
-    ;; signal error if at eob
-    (when (and (not undo-tree-visualizer-needs-extending-down) (eobp))
-      (scroll-up))))
-
-
-(defun undo-tree-visualizer-scroll-down (&optional arg)
-  (interactive "P")
-  (if (or (and (numberp arg) (< arg 0)) (eq arg '-))
-      (undo-tree-visualizer-scroll-up arg)
-    ;; ensure there's enough room at top of buffer to scroll
-    (let ((scroll-lines
-	   (or arg (- (window-height) next-screen-context-lines)))
-	  (window-line (1- (line-number-at-pos (window-start)))))
-      (when (and undo-tree-visualizer-needs-extending-up
-		 (< window-line scroll-lines))
-	(let ((inhibit-read-only t))
-	  (goto-char (point-min))
-	  (undo-tree-move-up (- scroll-lines window-line)))))
-    ;; scroll down and expand newly-visible portion of tree
-    (unwind-protect
-	(scroll-down-command arg)
-      (undo-tree-expand-up
-       (undo-tree-node-previous (undo-tree-current buffer-undo-tree))))
-    ;; signal error if at bob
-    (when (and (not undo-tree-visualizer-needs-extending-down) (bobp))
-      (scroll-down))))
-
-
-
-
-;;; =====================================================================
-;;;                    Visualizer selection mode
-
-(define-minor-mode undo-tree-visualizer-selection-mode
-  "Toggle mode to select nodes in undo-tree visualizer."
-  :lighter "Select"
-  :keymap undo-tree-visualizer-selection-mode-map
-  :group undo-tree
-  (cond
-   ;; enable selection mode
-   (undo-tree-visualizer-selection-mode
-    (setq cursor-type 'box)
-    (setq undo-tree-visualizer-selected-node
-	  (undo-tree-current buffer-undo-tree))
-    ;; erase diff (if any), as initially selected node is identical to current
-    (when undo-tree-visualizer-diff
-      (let ((buff (get-buffer undo-tree-diff-buffer-name))
-	    (inhibit-read-only t))
-	(when buff (with-current-buffer buff (erase-buffer))))))
-   (t ;; disable selection mode
-    (setq cursor-type nil)
-    (setq undo-tree-visualizer-selected-node nil)
-    (goto-char (undo-tree-node-marker (undo-tree-current buffer-undo-tree)))
-    (when undo-tree-visualizer-diff (undo-tree-visualizer-update-diff)))
-   ))
-
-
-(defun undo-tree-visualizer-select-previous (&optional arg)
-  "Move to previous node."
-  (interactive "p")
-  (let ((node undo-tree-visualizer-selected-node))
-    (catch 'top
-      (dotimes (i (or arg 1))
-	(unless (undo-tree-node-previous node) (throw 'top t))
-	(setq node (undo-tree-node-previous node))))
-    ;; when using lazy drawing, extend tree upwards as required
-    (when undo-tree-visualizer-lazy-drawing
-      (undo-tree-expand-up undo-tree-visualizer-selected-node node))
-    ;; update diff display, if any
-    (when (and undo-tree-visualizer-diff
-	       (not (eq node undo-tree-visualizer-selected-node)))
-      (undo-tree-visualizer-update-diff node))
-    ;; move to selected node
-    (goto-char (undo-tree-node-marker node))
-    (setq undo-tree-visualizer-selected-node node)))
-
-
-(defun undo-tree-visualizer-select-next (&optional arg)
-  "Move to next node."
-  (interactive "p")
-  (let ((node undo-tree-visualizer-selected-node))
-    (catch 'bottom
-      (dotimes (i (or arg 1))
-	(unless (nth (undo-tree-node-branch node) (undo-tree-node-next node))
-	  (throw 'bottom t))
-	(setq node
-	      (nth (undo-tree-node-branch node) (undo-tree-node-next node)))))
-    ;; when using lazy drawing, extend tree downwards as required
-    (when undo-tree-visualizer-lazy-drawing
-      (undo-tree-expand-down undo-tree-visualizer-selected-node node))
-    ;; update diff display, if any
-    (when (and undo-tree-visualizer-diff
-	       (not (eq node undo-tree-visualizer-selected-node)))
-      (undo-tree-visualizer-update-diff node))
-    ;; move to selected node
-    (goto-char (undo-tree-node-marker node))
-    (setq undo-tree-visualizer-selected-node node)))
-
-
-(defun undo-tree-visualizer-select-right (&optional arg)
-  "Move right to a sibling node."
-  (interactive "p")
-  (let ((node undo-tree-visualizer-selected-node)
-	end)
-    (goto-char (undo-tree-node-marker undo-tree-visualizer-selected-node))
-    (setq end (line-end-position))
-    (catch 'end
-      (dotimes (i arg)
-	(while (or (null node) (eq node undo-tree-visualizer-selected-node))
-	  (forward-char)
-	  (setq node (get-text-property (point) 'undo-tree-node))
-	  (when (= (point) end) (throw 'end t)))))
-    (goto-char (undo-tree-node-marker
-		(or node undo-tree-visualizer-selected-node)))
-    (when (and undo-tree-visualizer-diff node
-	       (not (eq node undo-tree-visualizer-selected-node)))
-      (undo-tree-visualizer-update-diff node))
-    (when node (setq undo-tree-visualizer-selected-node node))))
-
-
-(defun undo-tree-visualizer-select-left (&optional arg)
-  "Move left to a sibling node."
-  (interactive "p")
-  (let ((node (get-text-property (point) 'undo-tree-node))
-	beg)
-    (goto-char (undo-tree-node-marker undo-tree-visualizer-selected-node))
-    (setq beg (line-beginning-position))
-    (catch 'beg
-      (dotimes (i arg)
-	(while (or (null node) (eq node undo-tree-visualizer-selected-node))
-	  (backward-char)
-	  (setq node (get-text-property (point) 'undo-tree-node))
-	  (when (= (point) beg) (throw 'beg t)))))
-    (goto-char (undo-tree-node-marker
-		(or node undo-tree-visualizer-selected-node)))
-    (when (and undo-tree-visualizer-diff node
-	       (not (eq node undo-tree-visualizer-selected-node)))
-      (undo-tree-visualizer-update-diff node))
-    (when node (setq undo-tree-visualizer-selected-node node))))
-
-
-(defun undo-tree-visualizer-select (pos)
-  (let ((node (get-text-property pos 'undo-tree-node)))
-    (when node
-      ;; select node at POS
-      (goto-char (undo-tree-node-marker node))
-      ;; when using lazy drawing, extend tree up and down as required
-      (when undo-tree-visualizer-lazy-drawing
-	(undo-tree-expand-up undo-tree-visualizer-selected-node node)
-	(undo-tree-expand-down undo-tree-visualizer-selected-node node))
-      ;; update diff display, if any
-      (when (and undo-tree-visualizer-diff
-		 (not (eq node undo-tree-visualizer-selected-node)))
-	(undo-tree-visualizer-update-diff node))
-      ;; update selected node
-      (setq undo-tree-visualizer-selected-node node)
-      )))
-
-
-(defun undo-tree-visualizer-mouse-select (pos)
-  "Select undo tree node at mouse event POS."
-  (interactive "@e")
-  (undo-tree-visualizer-select (event-start (nth 1 pos))))
-
-
-
-
-;;; =====================================================================
-;;;                      Visualizer diff display
-
-(defun undo-tree-visualizer-toggle-diff ()
-  "Toggle diff display in undo-tree visualizer."
-  (interactive)
-  (if undo-tree-visualizer-diff
-      (undo-tree-visualizer-hide-diff)
-    (undo-tree-visualizer-show-diff)))
-
-
-(defun undo-tree-visualizer-selection-toggle-diff ()
-  "Toggle diff display in undo-tree visualizer selection mode."
-  (interactive)
-  (if undo-tree-visualizer-diff
-      (undo-tree-visualizer-hide-diff)
-    (let ((node (get-text-property (point) 'undo-tree-node)))
-      (when node (undo-tree-visualizer-show-diff node)))))
-
-
-(defun undo-tree-visualizer-show-diff (&optional node)
-  ;; show visualizer diff display
-  (setq undo-tree-visualizer-diff t)
-  (let ((buff (with-current-buffer undo-tree-visualizer-parent-buffer
-		(undo-tree-diff node)))
-	(display-buffer-mark-dedicated 'soft)
-	win)
-    (setq win (split-window))
-    (set-window-buffer win buff)
-    (shrink-window-if-larger-than-buffer win)))
-
-
-(defun undo-tree-visualizer-hide-diff ()
-  ;; hide visualizer diff display
-  (setq undo-tree-visualizer-diff nil)
-  (let ((win (get-buffer-window undo-tree-diff-buffer-name)))
-    (when win (with-selected-window win (kill-buffer-and-window)))))
-
-
-(defun undo-tree-diff (&optional node)
-  ;; Create diff between NODE and current state (or previous state and current
-  ;; state, if NODE is null). Returns buffer containing diff.
-  (let (tmpfile buff)
-    ;; generate diff
-    (let ((undo-tree-inhibit-kill-visualizer t)
-	  (current (undo-tree-current buffer-undo-tree)))
-      (undo-tree-set (or node (undo-tree-node-previous current) current)
-		     'preserve-timestamps)
-      (setq tmpfile (diff-file-local-copy (current-buffer)))
-      (undo-tree-set current 'preserve-timestamps))
-    (setq buff (diff-no-select
-		tmpfile (current-buffer) nil 'noasync
-		(get-buffer-create undo-tree-diff-buffer-name)))
-    ;; delete process messages and useless headers from diff buffer
-    (let ((inhibit-read-only t))
-      (with-current-buffer buff
-	(goto-char (point-min))
-	(delete-region (point) (1+ (line-end-position 3)))
-	(goto-char (point-max))
-	(forward-line -2)
-	(delete-region (point) (point-max))
-	(setq cursor-type nil)
-	(setq buffer-read-only t)))
-    buff))
-
-
-(defun undo-tree-visualizer-update-diff (&optional node)
-  ;; update visualizer diff display to show diff between current state and
-  ;; NODE (or previous state, if NODE is null)
-  (with-current-buffer undo-tree-visualizer-parent-buffer
-    (undo-tree-diff node))
-  (let ((win (get-buffer-window undo-tree-diff-buffer-name)))
-    (when win
-      (balance-windows)
-      (shrink-window-if-larger-than-buffer win))))
-
-;;;; ChangeLog:
-
-;; 2013-12-28  Toby S. Cubitt  <tsc25@cantab.net>
-;; 
-;; 	* undo-tree: Update to version 0.6.5.
-;; 
-;; 2012-12-05  Toby S. Cubitt  <tsc25@cantab.net>
-;; 
-;; 	Update undo-tree to version 0.6.3
-;; 
-;; 	* undo-tree.el: Implement lazy tree drawing to significantly speed up 
-;; 	visualization of large trees + various more minor improvements.
-;; 
-;; 2012-09-25  Toby S. Cubitt  <tsc25@cantab.net>
-;; 
-;; 	Updated undo-tree package to version 0.5.5.
-;; 
-;; 	Small bug-fix to avoid hooks triggering an error when trying to save
-;; 	undo history in a buffer where undo is disabled.
-;; 
-;; 2012-09-11  Toby S. Cubitt  <tsc25@cantab.net>
-;; 
-;; 	Updated undo-tree package to version 0.5.4
-;; 
-;; 	Bug-fixes and improvements to persistent history storage.
-;; 
-;; 2012-07-18  Toby S. Cubitt  <tsc25@cantab.net>
-;; 
-;; 	Update undo-tree to version 0.5.3
-;; 
-;; 	* undo-tree.el: Cope gracefully with undo boundaries being deleted
-;; 	 (cf. bug#11774). Allow customization of directory to which undo
-;; 	history is
-;; 	 saved.
-;; 
-;; 2012-05-24  Toby S. Cubitt  <tsc25@cantab.net>
-;; 
-;; 	updated undo-tree package to version 0.5.2
-;; 
-;; 	* undo-tree.el: add diff view feature in undo-tree visualizer.
-;; 
-;; 2012-05-02  Toby S. Cubitt  <tsc25@cantab.net>
-;; 
-;; 	undo-tree.el: Update package to version 0.4
-;; 
-;; 2012-04-20  Toby S. Cubitt  <tsc25@cantab.net>
-;; 
-;; 	undo-tree.el: Update package to version 0.3.4
-;; 
-;; 	* undo-tree.el (undo-list-pop-changeset): fix pernicious bug causing
-;; 	undo history to be lost.
-;; 	(buffer-undo-tree): set permanent-local property.
-;; 	(undo-tree-enable-undo-in-region): add new customization option
-;; 	allowing undo-in-region to be disabled.
-;; 
-;; 2012-01-26  Toby S. Cubitt  <tsc25@cantab.net>
-;; 
-;; 	undo-tree.el: Fixed copyright attribution and Emacs status.
-;; 
-;; 2012-01-26  Toby S. Cubitt  <tsc25@cantab.net>
-;; 
-;; 	undo-tree.el: Update package to version 0.3.3
-;; 
-;; 2011-09-17  Stefan Monnier  <monnier@iro.umontreal.ca>
-;; 
-;; 	Add undo-tree.el
-;; 
-
-
-
-
-(provide 'undo-tree)
-
-;;; undo-tree.el ends here