--- /dev/null
+
+/*
+ * CINELERRA
+ * Copyright (C) 2008 Adam Williams <broadcast at earthling dot net>
+ *
+ * This program 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 2 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 this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ *
+ */
+
+#ifndef UNDOSTACKITEM_H
+#define UNDOSTACKITEM_H
+
+#include "linklist.h"
+
+
+class UndoStackItem : public ListItem<UndoStackItem>
+{
+public:
+ UndoStackItem();
+ virtual ~UndoStackItem();
+
+ void set_description(const char *description);
+ void set_creator(void *creator);
+
+// This function must be overridden in derived objects.
+// It is called both to undo and to redo an operation.
+// The override must do the following:
+// - change the EDL to undo an operation;
+// - change the internal information of the item so that the next invocation
+// of undo() does a redo (i.e. undoes the undone operation).
+ virtual void undo();
+
+// Return the amount of memory used for the data associated with this
+// object in order to enable limiting the amount of memory used by the
+// undo stack.
+// Ignore overhead and just report the specific data values that the
+// derived object adds.
+ virtual int get_size();
+
+
+// command description for the menu item
+ char *description;
+// who created this item
+ void* creator;
+};
+
+#endif