src/gui/image/qpixmapcache.cpp

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/****************************************************************************
**
** Copyright (C) 1992-2006 Trolltech ASA. All rights reserved.
**
** This file is part of the QtGui module of the Qt Toolkit.
**
** This file may be used under the terms of the GNU General Public
** License version 2.0 as published by the Free Software Foundation
** and appearing in the file LICENSE.GPL included in the packaging of
** this file.  Please review the following information to ensure GNU
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**
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** review the following information:
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** This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
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****************************************************************************/

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

static int cache_limit = 1024;                        // 1024 KB cache limit

class QPMCache : public QObject, public QCache<int, QPixmap>
{
    Q_OBJECT
public:
    QPMCache()
        : QObject(0),
          QCache<int, QPixmap>(cache_limit * 1024),
          id(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;

private:
    QHash<QString, int> serialNumbers;
    int id;
    int ps;
    bool t;
};
#include "qpixmapcache.moc"

/*
  This is supposed to cut the cache size down by about 80-90% in a
  minute once the application becomes idle, to let any inserted pixmap
  remain in the cache for some time before it becomes a candidate for
  cleaning-up, and to not cut down the size of the cache while the
  cache is in active use.

  When the last pixmap has been deleted from the cache, kill the
  timer so Qt won't keep the CPU from going into sleep mode.
*/

void QPMCache::timerEvent(QTimerEvent *)
{
    int mc = maxCost();
    bool nt = totalCost() == ps;
    setMaxCost(nt ? totalCost() * 3 / 4 : totalCost() -1);
    setMaxCost(mc);
    ps = totalCost();

    QHash<QString,int>::iterator it = serialNumbers.begin();
    while (it != serialNumbers.end()) {
        if (!contains(it.value())) {
            it = serialNumbers.erase(it);
        }
        else
            ++it;
    }


    if (!size()) {
        killTimer(id);
        id = 0;
    } else if (nt != t) {
        killTimer(id);
        id = startTimer(nt ? 10000 : 30000);
        t = nt;
    }
}

QPixmap *QPMCache::object(const QString &key) const
{
    return QCache<int,QPixmap>::object(serialNumbers.value(key, -1));
}


bool QPMCache::insert(const QString& key, const QPixmap &pixmap, int cost)
{
    int serialNumber = pixmap.serialNumber();
    if (contains(serialNumber)) {
        serialNumbers.insert(key, serialNumber);
        return true;
    }
    bool success = QCache<int, QPixmap>::insert(serialNumber, new QPixmap(pixmap), cost);
    if (success) {
        serialNumbers.insert(key, serialNumber);
        if (!id) {
            id = startTimer(30000);
            t = false;
        }
    }
    return success;
}

bool QPMCache::remove(const QString &key)
{
    int serialNumber = serialNumbers.value(key, -1);
    serialNumbers.remove(key);
    return QCache<int, QPixmap>::remove(serialNumber);
}

Q_GLOBAL_STATIC(QPMCache, pm_cache)


QPixmap *QPixmapCache::find(const QString &key)
{
    return pm_cache()->object(key);
}


bool QPixmapCache::find(const QString &key, QPixmap& pm)
{
    QPixmap *ptr = pm_cache()->object(key);
    if (ptr)
        pm = *ptr;
    return ptr != 0;
}


bool QPixmapCache::insert(const QString &key, const QPixmap &pm)
{
    return pm_cache()->insert(key, pm, pm.width() * pm.height() * pm.depth() / 8);
}

int QPixmapCache::cacheLimit()
{
    return cache_limit;
}

void QPixmapCache::setCacheLimit(int n)
{
    cache_limit = n;
    pm_cache()->setMaxCost(1024 * cache_limit);
}

void QPixmapCache::remove(const QString &key)
{
    pm_cache()->remove(key);
}


void QPixmapCache::clear()
{
    pm_cache()->clear();
}

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