--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/common/undo.d	Wed Jul 15 23:49:02 2009 +0930
@@ -0,0 +1,15 @@
+module common.undo;
+
+abstract class Action {
+    void undo();
+    void redo();
+}
+
+interface IUndoObserver {
+    void canUndo(in bool value, in string description);
+    void canRedo(in bool value, in string description);
+}
+
+interface IUndoManager {
+    void addAction(Action action);
+}