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diff --git a/canvas/source/vcl/bitmapbackbuffer.hxx b/canvas/source/vcl/bitmapbackbuffer.hxx
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+++ b/canvas/source/vcl/bitmapbackbuffer.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 .
+ */
+
+#pragma once
+
+#include <vcl/virdev.hxx>
+#include <vcl/bitmapex.hxx>
+
+#include <vclwrapper.hxx>
+#include "outdevprovider.hxx"
+
+#include <memory>
+
+namespace vclcanvas
+{
+    /** Backbuffer implementation for canvas bitmap.
+
+        This class abstracts away the renderable bitmap for the bitmap
+        canvas. The actual VirtualDevice is only created when
+        necessary, which makes read-only bitmaps a lot smaller.
+    */
+    class BitmapBackBuffer : public OutDevProvider
+    {
+    public:
+        /** Create a backbuffer for given reference device
+         */
+        BitmapBackBuffer( const BitmapEx&       rBitmap,
+                          const OutputDevice&   rRefDevice );
+
+        virtual ~BitmapBackBuffer() override;
+
+        virtual OutputDevice&       getOutDev() override;
+        virtual const OutputDevice& getOutDev() const override;
+
+        /// Clear the underlying bitmap to white, all transparent
+        void clear();
+
+        /** Exposing our internal bitmap. Only to be used from
+            CanvasBitmapHelper
+
+            @internal
+        */
+        BitmapEx&                   getBitmapReference();
+        Size                        getBitmapSizePixel() const;
+
+    private:
+        void createVDev() const;
+        void updateVDev() const;
+
+        ::canvas::vcltools::VCLObject<BitmapEx> maBitmap;
+        mutable VclPtr<VirtualDevice>           mpVDev; // created only on demand
+
+        const OutputDevice&                     mrRefDevice;
+
+        /** When true, the bitmap contains the last valid
+            content. When false, and mbVDevContentIsCurrent is true,
+            the VDev contains the last valid content (which must be
+            copied back to the bitmap, when getBitmapReference() is
+            called). When both are false, this object is just
+            initialized.
+         */
+        mutable bool                            mbBitmapContentIsCurrent;
+
+        /** When true, and mpVDev is non-NULL, the VDev contains the
+            last valid content. When false, and
+            mbBitmapContentIsCurrent is true, the bitmap contains the
+            last valid content. When both are false, this object is
+            just initialized.
+         */
+        mutable bool                            mbVDevContentIsCurrent;
+    };
+
+    typedef std::shared_ptr< BitmapBackBuffer > BitmapBackBufferSharedPtr;
+
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */