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diff --git a/libs/canvas/canvas/lookup_table.h b/libs/canvas/canvas/lookup_table.h
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+++ b/libs/canvas/canvas/lookup_table.h
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+/*
+    Copyright (C) 2011-2013 Paul Davis
+    Author: Carl Hetherington <cth@carlh.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., 675 Mass Ave, Cambridge, MA 02139, USA.
+*/
+
+#ifndef __CANVAS_LOOKUP_TABLE_H__
+#define __CANVAS_LOOKUP_TABLE_H__
+
+#include <vector>
+#include <boost/multi_array.hpp>
+#include "canvas/types.h"
+
+class OptimizingLookupTableTest;
+
+namespace ArdourCanvas {
+
+class Item;
+class Group;
+
+class LookupTable
+{
+public:
+	LookupTable (Group const &);
+	virtual ~LookupTable ();
+
+	virtual std::vector<Item*> get (Rect const &) = 0;
+	virtual std::vector<Item*> items_at_point (Duple) const = 0;
+
+protected:
+	
+	Group const & _group;
+};
+
+class DumbLookupTable : public LookupTable
+{
+public:
+	DumbLookupTable (Group const &);
+
+	std::vector<Item*> get (Rect const &);
+	std::vector<Item*> items_at_point (Duple) const;
+};
+
+class OptimizingLookupTable : public LookupTable
+{
+public:
+	OptimizingLookupTable (Group const &, int);
+	~OptimizingLookupTable ();
+	std::vector<Item*> get (Rect const &);
+	std::vector<Item*> items_at_point (Duple) const;
+
+	static int default_items_per_cell;
+
+private:
+
+	void area_to_indices (Rect const &, int &, int &, int &, int &) const;
+	void point_to_indices (Duple, int &, int &) const;
+
+	friend class ::OptimizingLookupTableTest;
+
+	typedef std::vector<Item*> Cell;
+	int _items_per_cell;
+	int _dimension;
+	Duple _cell_size;
+	Duple _offset;
+	Cell** _cells;
+	bool _added;
+};
+
+}
+
+#endif