source: trunk/src/gui/image/qpixmapcache.cpp@ 147

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#include "qpixmapcache.h"
#include "qcache.h"
#include "qobject.h"
#include "qdebug.h"

#include "qpaintengine.h"
#include <private/qimage_p.h>
#include <private/qpixmap_raster_p.h>

QT_BEGIN_NAMESPACE

/*!
    \class QPixmapCache

    \brief The QPixmapCache class provides an application-wide cache for pixmaps.

    \ingroup environment
    \ingroup multimedia

    This class is a tool for optimized drawing with QPixmap. You can
    use it to store temporary pixmaps that are expensive to generate
    without using more storage space than cacheLimit(). Use insert()
    to insert pixmaps, find() to find them, and clear() to empty the
    cache.

    QPixmapCache contains no member data, only static functions to
    access the global pixmap cache. It creates an internal QCache
    object for caching the pixmaps.

    The cache associates a pixmap with a string (key). If two pixmaps
    are inserted into the cache using equal keys, then the last pixmap
    will hide the first pixmap. The QHash and QCache classes do
    exactly the same.

    The cache becomes full when the total size of all pixmaps in the
    cache exceeds cacheLimit(). The initial cache limit is 1024 KB (1
    MB); it is changed with setCacheLimit(). A pixmap takes roughly
    (\e{width} * \e{height} * \e{depth})/8 bytes of memory.

    The \e{Qt Quarterly} article
    \l{http://doc.trolltech.com/qq/qq12-qpixmapcache.html}{Optimizing
    with QPixmapCache} explains how to use QPixmapCache to speed up
    applications by caching the results of painting.

    \sa QCache, QPixmap
*/

#if defined(Q_WS_QWS) || defined(Q_OS_WINCE)
static int cache_limit = 2048; // 2048 KB cache limit for embedded
#else
static int cache_limit = 10240; // 10 MB cache limit for desktop
#endif

// XXX: hw: is this a general concept we need to abstract?
class QDetachedPixmap : public QPixmap
{
public:
    QDetachedPixmap(const QPixmap &pix) : QPixmap(pix)
    {
        if (data && data->classId() == QPixmapData::RasterClass) {
            QRasterPixmapData *d = static_cast<QRasterPixmapData*>(data);
            if (!d->image.isNull() && d->image.d->paintEngine
                && !d->image.d->paintEngine->isActive())
            {
                delete d->image.d->paintEngine;
                d->image.d->paintEngine = 0;
            }
        }
    }
};

class QPMCache : public QObject, public QCache<qint64, QDetachedPixmap>
{
    Q_OBJECT
public:
    QPMCache()
        : QObject(0),
          QCache<qint64, QDetachedPixmap>(cache_limit * 1024),
          theid(0), ps(0), t(false) { }
    ~QPMCache() { }

    void timerEvent(QTimerEvent *);
    bool insert(const QString& key, const QPixmap &pixmap, int cost);
    bool remove(const QString &key);

    QPixmap *object(const QString &key) const;