[elpa] externals/undo-tree 21d3c89 004/195: Implemented redo command.

[Stefan Monnier]

branch: externals/undo-tree
commit 21d3c89f153fd371b886a904ec523d535cb3e21a
Author: tsc25 <tsc25@cantab.net>
Commit: tsc25 <tsc25@cantab.net>

    Implemented redo command.
---
 undo-tree.el | 37 +++++++++++++++++++++++++++++++++----
 1 file changed, 33 insertions(+), 4 deletions(-)

diff --git a/undo-tree.el b/undo-tree.el
index 251a720..54be572 100644
--- a/undo-tree.el
+++ b/undo-tree.el
@@ -86,11 +86,12 @@ to `buffer-undo-tree'."
     (setq buffer-undo-tree (make-undo-tree)))
   ;; transfer entries accumulated in `buffer-undo-list' to `buffer-undo-tree'
   (undo-list-to-tree)
+
   (dotimes (i arg)
-    ;; check if at top of tree
-    (if (null (undo-tree-node-undo (undo-tree-current buffer-undo-tree)))
+    ;; check if at top of undo tree
+    (if (null (undo-tree-node-previous (undo-tree-current buffer-undo-tree)))
        (error "No further undo information")
-      ;; undo one record from tree
+      ;; undo one record from undo tree
       (primitive-undo 1 (undo-copy-list
                         (undo-tree-node-undo
                          (undo-tree-current buffer-undo-tree))))
@@ -98,7 +99,35 @@ to `buffer-undo-tree'."
       ;; `buffer-undo-list' and record them in current node's redo record
       (setf (undo-tree-node-redo (undo-tree-current buffer-undo-tree))
            (undo-list-pop-changeset))
-      ;; rewind pointer to current node
+      ;; rewind current node
       (setf (undo-tree-current buffer-undo-tree)
            (undo-tree-node-previous (undo-tree-current buffer-undo-tree)))
       )))
+
+
+(defun undo-tree-redo (&optional arg)
+  "Redo changes. A numeric ARG serves as a repeat count."
+  (interactive "p")
+  ;; if `buffer-undo-tree' is empty, create initial undo-tree
+  (when (null buffer-undo-tree)
+    (setq buffer-undo-tree (make-undo-tree)))
+  ;; transfer entries accumulated in `buffer-undo-list' to `buffer-undo-tree'
+  (undo-list-to-tree)
+
+  (let ((current (undo-tree-current buffer-undo-tree)))
+    (dotimes (i arg)
+      ;; check if at bottom of undo tree
+      (if (null (undo-tree-node-next (undo-tree-current buffer-undo-tree)))
+         (error "No further redo information")
+       ;; advance current node
+       (setq current
+             (setf (undo-tree-current buffer-undo-tree)
+                   (nth (undo-tree-node-branch current)
+                        (undo-tree-node-next current))))
+       ;; redo one record from undo tree
+       (primitive-undo 1 (undo-copy-list (undo-tree-node-redo current)))
+       ;; discard undo entries that `primitive-undo' has added to
+       ;; `buffer-undo-list' since we already know how to undo from here
+       ;; (note: could overwrite old undo entry instead for safety's sake?)
+       (setq buffer-undo-list nil)
+       ))))