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diff --git a/slideshow/source/engine/transitions/parametricpolypolygon.hxx b/slideshow/source/engine/transitions/parametricpolypolygon.hxx
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+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ *
+ * This file incorporates work covered by the following license notice:
+ *
+ *   Licensed to the Apache Software Foundation (ASF) under one or more
+ *   contributor license agreements. See the NOTICE file distributed
+ *   with this work for additional information regarding copyright
+ *   ownership. The ASF licenses this file to you under the Apache
+ *   License, Version 2.0 (the "License"); you may not use this file
+ *   except in compliance with the License. You may obtain a copy of
+ *   the License at http://www.apache.org/licenses/LICENSE-2.0 .
+ */
+
+#ifndef INCLUDED_SLIDESHOW_SOURCE_ENGINE_TRANSITIONS_PARAMETRICPOLYPOLYGON_HXX
+#define INCLUDED_SLIDESHOW_SOURCE_ENGINE_TRANSITIONS_PARAMETRICPOLYPOLYGON_HXX
+
+#include <basegfx/polygon/b2dpolypolygon.hxx>
+#include <memory>
+
+
+/* Definition of ParametricPolyPolygon interface */
+
+namespace slideshow
+{
+    namespace internal
+    {
+        /** Interface defining a parametric poly-polygon.
+
+            This interface defines a poly-polygon, whose actual shape
+            is parameterized by a floating point value. This is
+            e.g. used to generically access the various clip polygon
+            generators for transition effects.
+
+            Since for every parametric poly-polygon, there is a set of
+            variations, which can easily be generated by simple
+            transformations or change in parameter range sweep
+            direction, objects implementing this interface only
+            generate <em>one</em> prototypical instance of the
+            parametric poly-polygon. Generally speaking, the main
+            effect direction should be horizontal, it should make
+            increasingly more area visible (transition 'in'), and when
+            there is a designated direction given, that should be
+            left-to-right.
+         */
+        class ParametricPolyPolygon
+        {
+        public:
+            virtual ~ParametricPolyPolygon() {}
+
+            /** Retrieve the poly-polygon for value t.
+
+                @param t
+                Current parameter value to retrieve the corresponding
+                poly-polygon for. Permissible values for t must be in
+                the range [0,1].
+
+                @return a poly-polygon corresponding to the given
+                parameter value. The poly-polygon is interpreted as
+                living in the unit rectangle (i.e. [0,1]x[0,1]), but
+                is not necessarily constrained to completely lie in
+                this area (this very much depends on the actual effect
+                to be generated). Although, from a performance
+                perspective, it currently <em>is</em> advantageous to
+                try to keep the poly-polygon within these bounds (at
+                least if there are no hard reasons not to do so),
+                because then reversion or out transformations are
+                potentially faster to compute (see the
+                TransitionInfo::meReverseMethod member in
+                transitionfactory.cxx). Furthermore, if one of the
+                polygon modifications involve subtraction (also see
+                TransitionInfo::meReverseMethod), all generated
+                polygons should be oriented clock-wise
+                (i.e. traversing the polygon vertices with increasing
+                vertex index should generate a clock-wise movement).
+             */
+            virtual ::basegfx::B2DPolyPolygon operator()( double t ) = 0;
+        };
+
+        typedef ::std::shared_ptr< ParametricPolyPolygon > ParametricPolyPolygonSharedPtr;
+
+    }
+}
+
+#endif // INCLUDED_SLIDESHOW_SOURCE_ENGINE_TRANSITIONS_PARAMETRICPOLYPOLYGON_HXX
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */