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diff --git a/sd/source/ui/slidesorter/inc/cache/SlsPageCache.hxx b/sd/source/ui/slidesorter/inc/cache/SlsPageCache.hxx
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+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*************************************************************************
+ *
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * Copyright 2000, 2010 Oracle and/or its affiliates.
+ *
+ * OpenOffice.org - a multi-platform office productivity suite
+ *
+ * This file is part of OpenOffice.org.
+ *
+ * OpenOffice.org is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License version 3
+ * only, as published by the Free Software Foundation.
+ *
+ * OpenOffice.org 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 Lesser General Public License version 3 for more details
+ * (a copy is included in the LICENSE file that accompanied this code).
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * version 3 along with OpenOffice.org.  If not, see
+ * <http://www.openoffice.org/license.html>
+ * for a copy of the LGPLv3 License.
+ *
+ ************************************************************************/
+
+#ifndef SD_SLIDESORTER_PAGE_CACHE_HXX
+#define SD_SLIDESORTER_PAGE_CACHE_HXX
+
+#include "cache/SlsCacheContext.hxx"
+#include <sal/types.h>
+#include <vcl/bitmapex.hxx>
+#include <boost/function.hpp>
+#include <boost/scoped_ptr.hpp>
+#include <boost/shared_ptr.hpp>
+
+namespace sd { namespace slidesorter { namespace view {
+class PageObjectViewObjectContact;
+} } }
+
+namespace sd { namespace slidesorter { namespace cache {
+
+class GenericPageCache;
+class RequestData;
+
+/** The page cache is responsible for the creation and storage of preview
+    bitmaps of pages that are shown by the slide sorter.
+
+    <p>Bitmaps for previews and a cache are used to speed up the display
+    (painting) of the slide sorter.  But, of course, we have to limit this
+    time-space-tradeoff by limiting the amount of space that can be use to
+    store bitmaps.</p>
+
+    <p>There are several strategies employed by this class to shorten the
+    perceived time that is used to paint the slide sorter:
+    <ul>
+    <li>Rendering pages ahead of time.  Additionally to rendering the
+    visible slides we try to render part or all of the slides that are not
+    (yet) visible.  This, of course, makes sense only when the computer is
+    ohterwise idle while doing that.</li>
+    <li>When the size of the slides on the screen changes we mark the
+    bitmaps as needing an update but use them while the new bitmap in the
+    correct size is not available.</li>
+    <li>Give the UI the chance to handle user events between the rendering
+    of differe slides.</li>
+    <li>Limit the amount of space that may be used for storing preview
+    bitmaps and throw.</li>
+    </p>
+
+    <p>There is another somewhat similar methods for requesting new previews:
+    GetPreviewBitmap() schedules a re-rendering (when necessary) and
+    returns the preview what is currently available, either as a preview of
+    the preview or, when nothing has changed since the last call, as the
+    final thing.
+    </p>
+*/
+class PageCache
+{
+public:
+    /** The page chache is created with a reference to the slide sorter so
+        that it has access to both the view and the model and so can fill
+        itself with requests for all or just the visible pages.
+
+        It is the task of the PageCacheManager to create new objects of this
+        class.
+    */
+    PageCache (
+        const Size& rPreviewSize,
+        const SharedCacheContext& rpCacheContext);
+
+    ~PageCache (void);
+
+    void ChangeSize(const Size& rPreviewSize);
+
+    /** Request a preview bitmap for the specified page object in the
+        specified size.  The returned bitmap may be a preview of the
+        preview, i.e. either a scaled (up or down) version of a previous
+        preview (of the wrong size) or an empty bitmap.  In this case a
+        request for the generation of a new preview is created and inserted
+        into the request queue.  When the preview is available the page
+        shape will be told to paint itself again.  When it then calls this
+        method again if receives the correctly sized preview bitmap.
+        @param rRequestData
+            This data is used to determine the preview.
+        @param rSize
+            The size of the requested preview bitmap.
+        @return
+            Returns a bitmap that is either empty, contains a scaled (up or
+            down) version or is the requested bitmap.
+    */
+    BitmapEx GetPreviewBitmap (
+        CacheKey aKey,
+        const Size& rSize);
+
+    /** Call this method when a view-object-contact object is being deleted
+        and does not need (a) its current bitmap in the cache and (b) a
+        requested new bitmap.
+    */
+    void ReleasePreviewBitmap (CacheKey aKey);
+
+    /** Call this method when all preview bitmaps have to be generated anew.
+        This is the case when the size of the page objects on the screen has
+        changed or when the model has changed.
+        @param bUpdateCache
+            When this flags is <TRUE/> then requests for updated previews
+            are created.  When it is <FALSE/> the existing previews are only
+            marked as not being up-to-date anymore.
+    */
+    void InvalidateCache (bool bUpdateCache = true);
+
+    /** With the precious flag you can control whether a bitmap can be
+        removed or reduced in size to make room for other bitmaps or is so
+        precious that it will not touched.  A typical use is to set the
+        precious flag for exactly the visible pages.
+    */
+    void SetPreciousFlag (CacheKey aKey, bool bIsPrecious);
+
+    void Pause (void);
+    void Resume (void);
+
+private:
+    ::boost::scoped_ptr<GenericPageCache> mpImplementation;
+};
+
+} } } // end of namespace ::sd::slidesorter::cache
+
+#endif
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */