ThumbnailView/ThumbnailCache.h

   1 /* Copyright (C) 2008-2009 Henner Zeller <h.zeller@acm.org>
   2
   3    This program is free software; you can redistribute it and/or
   4    modify it under the terms of the GNU General Public
   5    License as published by the Free Software Foundation; either
   6    version 2 of the License, or (at your option) any later version.
   7
   8    This program is distributed in the hope that it will be useful,
   9    but WITHOUT ANY WARRANTY; without even the implied warranty of
  10    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11    General Public License for more details.
  12
  13    You should have received a copy of the GNU General Public License
  14    along with this program; see the file COPYING.  If not, write to
  15    the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  16    Boston, MA 02110-1301, USA.
  17 */
  18 #ifndef THUMBNAILVIEW_THUMBNAILCACHE_H
  19 #define THUMBNAILVIEW_THUMBNAILCACHE_H
  20
  21 #include <QHash>
  22 #include <QMutex>
  23 #include <QObject>
  24 #include <QSize>
  25 #include <QString>
  26
  27 #include "DB/Result.h"
  28 #include "ImageManager/ImageClient.h"
  29
  30 class QPixmap;
  31 class QTimer;
  32
  33 namespace DB {
  34     class ResultId;
  35 }
  36 namespace ThumbnailView {
  37
  38 /**
  39  * A cache for thumbnails that supports automatic pre-warming.
  40  *
  41  * This is a wrapper around QPixmapCache for the raw store/retrieve
  42  * functionality. In addition to that, given a current displayed page
  43  * out of a list of images, it attempts to pre-warm the cache with the
  44  * thumbnails of the surrounding pages if possible. The sequence of pre-loading
  45  * is scheduled according to the observed scroll direction.
  46  */
  47 class ThumbnailCache : public QObject, public ImageManager::ImageClient {
  48     Q_OBJECT
  49 public:
  50     ThumbnailCache();
  51
  52     /**
  53      * Find the pixmap for the given ResultId. If found, return 'true' and
  54      * insert found pixmap into result. Result must not be NULL.
  55      */
  56     bool find(const DB::ResultId& id, QPixmap *result) const;
  57
  58     /** insert the pixmap for the given Media ID */
  59     void insert(const DB::ResultId& id, const QPixmap& pix);
  60
  61     /** clear the cache */
  62     void clear();
  63
  64     /**
  65      * set the hot area of thumbnails currently displayed. The values
  66      * denote a range in the display list.
  67      * The Cache uses this to decide what images not to throw away and
  68      * what images to preload.
  69      */
  70     void setHotArea(int from, int to);
  71
  72     /** Set information about the thumbnails to be displayed.
  73      * TODO: view and cache should share a model */
  74     void setDisplayList(const DB::Result& displayList);
  75     void setThumbnailSize(const QSize& thumbSize);
  76
  77 public:
  78     bool thumbnailStillNeeded(const QString& fileName) const;
  79
  80 protected:
  81     // ImageManager interface. The callback just puts the resulting image
  82     // into the cache.
  83     virtual void pixmapLoaded( const QString& fileName,
  84                                const QSize& size, const QSize& fullSize,
  85                                int angle, const QImage& image,
  86                                const bool loadedOK);
  87
  88 protected slots:
  89     void slotAsyncCacheWarming();
  90
  91 private:
  92     static QString thumbnailPixmapCacheKey(const DB::ResultId& id);
  93
  94     /**
  95      * Warm the cache for the given range by requesting it.
  96      * Including 'from', exlcuding 'to'.
  97      */
  98     void requestRange(int from, int to);
  99
 100     DB::Result _displayList;
 101     QSize _thumbSize;
 102     int _hotFrom, _hotTo;
 103     int _lastHotFrom;
 104     QTimer* _asyncWarmingTimer;
 105
 106     mutable QMutex _requestedImagesLock;
 107     typedef QHash<QString, DB::ResultId> RequestedMap;
 108     RequestedMap _requestedImages;
 109 };
 110 }
 111
 112 #endif /* THUMBNAILVIEW_THUMBNAILCACHE_H */