--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Framework/Scene2DViewport/UndoStack.h	Mon Jun 24 10:31:04 2019 +0200
@@ -0,0 +1,77 @@
+/**
+ * Stone of Orthanc
+ * Copyright (C) 2012-2016 Sebastien Jodogne, Medical Physics
+ * Department, University Hospital of Liege, Belgium
+ * Copyright (C) 2017-2019 Osimis S.A., Belgium
+ *
+ * This program is free software: you can redistribute it and/or
+ * modify it under the terms of the GNU Affero 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
+ * Affero General Public License for more details.
+ * 
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ **/
+
+#pragma once
+
+#include <boost/shared_ptr.hpp>
+
+#include <vector>
+
+namespace OrthancStone
+{
+  class TrackerCommand;
+
+  class UndoStack
+  {
+  public:
+    UndoStack();
+
+    /**
+    Stores a command :
+    - this first trims the undo stack to keep the first numAppliedCommands_
+    - then it adds the supplied command at the top of the undo stack
+
+    In other words, when a new command is pushed, all the undone (and not
+    redone) commands are removed.
+    */
+    void PushCommand(boost::shared_ptr<TrackerCommand> command);
+
+    /**
+    Undoes the command at the top of the undo stack, or throws if there is no
+    command to undo.
+    You can check "CanUndo" first to protect against extraneous redo.
+    */
+    void Undo();
+
+    /**
+    Redoes the command that is just above the last applied command in the undo
+    stack or throws if there is no command to redo.
+    You can check "CanRedo" first to protect against extraneous redo.
+    */
+    void Redo();
+
+    /** selfexpl */
+    bool CanUndo() const;
+
+    /** selfexpl */
+    bool CanRedo() const;
+  
+  private:
+    std::vector<boost::shared_ptr<TrackerCommand> > commandStack_;
+
+    /**
+    This is always between >= 0 and <= undoStack_.size() and gives the
+    position where the controller is in the undo stack.
+    - If numAppliedCommands_ > 0, one can undo
+    - If numAppliedCommands_ < numAppliedCommands_.size(), one can redo
+    */
+    size_t                      numAppliedCommands_;
+  };
+}