path: root/src/gui/image/qpixmapcache.cpp

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

QT_BEGIN_NAMESPACE

/*!
    \class QPixmapCache

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

    \ingroup painting

    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 user-provided string as a key,
    or with a QPixmapCache::Key that the cache generates.
    Using QPixmapCache::Key for keys is faster than using strings. The string API is
    very convenient for complex keys but the QPixmapCache::Key API will be very
    efficient and convenient for a one-to-one object-to-pixmap mapping \mdash in
    this case, you can store the keys as members of an object.

    If two pixmaps are inserted into the cache using equal keys then the
    last pixmap will replace the first pixmap in the cache. This follows the
    behavior of the QHash and QCache classes.

    The cache becomes full when the total size of all pixmaps in the
    cache exceeds cacheLimit(). The initial cache limit is
    2048 KB (2 MB) on embedded platforms, 10240 KB (10 MB) on desktop
    platforms; you can change this by calling setCacheLimit() with the
    required value.
    A pixmap takes roughly (\e{width} * \e{height} * \e{depth})/8 bytes of
    memory.

    The \e{Qt Quarterly} article
    \l{http://qt.nokia.com/doc/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_OS_SYMBIAN)
static int cache_limit = 1024; // 1048 KB cache limit for symbian
#elif defined(Q_WS_QWS) || defined(Q_WS_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

/*!
    \class QPixmapCache::Key
    \brief The QPixmapCache::Key class can be used for efficient access
    to the QPixmapCache.
    \since 4.6

    Use QPixmapCache::insert() to receive an instance of Key generated
    by the pixmap cache. You can store the key in your own objects for
    a very efficient one-to-one object-to-pixmap mapping.
*/

/*!
    Constructs an empty Key object.
*/
QPixmapCache::Key::Key() : d(0)
{
}

/*!
   \internal
    Constructs a copy of \a other.
*/
QPixmapCache::Key::Key(const Key &other)
{
    if (other.d)
        ++(other.d->ref);
    d = other.d;
}

/*!
    Destroys the key.
*/
QPixmapCache::Key::~Key()
{
    if (d && --(d->ref) == 0)
        delete d;
}

/*!
    \internal

    Returns true if this key is the same as the given \a key; otherwise returns
    false.
*/
bool QPixmapCache::Key::operator ==(const Key &key) const
{
    return (d == key.d);
}

/*!
    \fn bool QPixmapCache::Key::operator !=(const Key &key) const
    \internal
*/

/*!
    \internal
*/
QPixmapCache::Key &QPixmapCache::Key::operator =(const Key &other)
{
    if (d != other.d) {
        if (other.d)
            ++(other.d->ref);
        if (d && --(d->ref) == 0)
            delete d;
        d = other.d;
    }
    return *this;
}

class QPMCache : public QObject, public QCache<QPixmapCache::Key, QDetachedPixmap>
{
    Q_OBJECT
public:
    QPMCache();
    ~QPMCache();

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

    void resizeKeyArray(int size);
    QPixmapCache::Key createKey();
    void releaseKey(const QPixmapCache::Key &key);
    void clear();

    QPixmap *object(const QString &key) const;
    QPixmap *object(const QPixmapCache::Key &key) const;

    static inline QPixmapCache::KeyData *get(const QPixmapCache::Key &key)
    {return key.d;}

    static QPixmapCache::KeyData* getKeyData(QPixmapCache::Key *key);

private:
    int *keyArray;
    int theid;
    int ps;
    int keyArraySize;
    int freeKey;
    QHash<QString, QPixmapCache::Key> cacheKeys;
    bool t;
};

QT_BEGIN_INCLUDE_NAMESPACE
#include "qpixmapcache.moc"
QT_END_INCLUDE_NAMESPACE

uint qHash(const QPixmapCache::Key &k)
{
    return qHash(QPMCache::get(k)->key);
}

QPMCache::QPMCache()
    : QObject(0),
      QCache<QPixmapCache::Key, QDetachedPixmap>(cache_limit * 1024),
      keyArray(0), theid(0), ps(0), keyArraySize(0), freeKey(0), t(false)
{
}
QPMCache::~QPMCache()
{
    free(keyArray);
}

/*
  This is supposed to cut the cache size down by about 25% 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;
    QList<QPixmapCache::Key> keys = QCache<QPixmapCache::Key, QDetachedPixmap>::keys();
    setMaxCost(nt ? totalCost() * 3 / 4 : totalCost() -1);
    setMaxCost(mc);
    ps = totalCost();

    QHash<QString, QPixmapCache::Key>::iterator it = cacheKeys.begin();
    while (it != cacheKeys.end()) {
        if (!contains(it.value())) {
            releaseKey(it.value());
            it = cacheKeys.erase(it);
        } else {
            ++it;
        }
    }
    for (int i = 0; i < keys.size(); ++i) {
        if (!contains(keys.at(i)))
            releaseKey(keys.at(i));
    }

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

QPixmap *QPMCache::object(const QString &key) const
{
    QPixmapCache::Key cacheKey = cacheKeys.value(key);
    if (!cacheKey.d || !cacheKey.d->isValid) {
        const_cast<QPMCache *>(this)->cacheKeys.remove(key);
        return 0;
    }
    QPixmap *ptr = QCache<QPixmapCache::Key, QDetachedPixmap>::object(cacheKey);
     //We didn't find the pixmap in the cache, the key is not valid anymore
    if (!ptr) {
        const_cast<QPMCache *>(this)->cacheKeys.remove(key);
        const_cast<QPMCache *>(this)->releaseKey(cacheKey);
    }
    return ptr;
}

QPixmap *QPMCache::object(const QPixmapCache::Key &key) const
{
    Q_ASSERT(key.d->isValid);
    QPixmap *ptr = QCache<QPixmapCache::Key, QDetachedPixmap>::object(key);
    //We didn't find the pixmap in the cache, the key is not valid anymore
    if (!ptr)
        const_cast<QPMCache *>(this)->releaseKey(key);
    return ptr;
}

bool QPMCache::insert(const QString& key, const QPixmap &pixmap, int cost)
{
    QPixmapCache::Key cacheKey;
    QPixmapCache::Key oldCacheKey = cacheKeys.value(key);
    //If for the same key we add already a pixmap we should delete it
    if (oldCacheKey.d) {
        QCache<QPixmapCache::Key, QDetachedPixmap>::remove(oldCacheKey);
        cacheKey = oldCacheKey;
    } else {
         cacheKey = createKey();
     }

    bool success = QCache<QPixmapCache::Key, QDetachedPixmap>::insert(cacheKey, new QDetachedPixmap(pixmap), cost);
    if (success) {
        cacheKeys.insert(key, cacheKey);
        if (!theid) {
            theid = startTimer(30000);
            t = false;
        }
    } else {
        //Insertion failed we released the new allocated key
        releaseKey(cacheKey);
    }
    return success;
}

QPixmapCache::Key QPMCache::insert(const QPixmap &pixmap, int cost)
{
    QPixmapCache::Key cacheKey = createKey();
    bool success = QCache<QPixmapCache::Key, QDetachedPixmap>::insert(cacheKey, new QDetachedPixmap(pixmap), cost);
    if (success) {
        if (!theid) {
            theid = startTimer(30000);
            t = false;
        }
    } else {
        //Insertion failed we released the key and return an invalid one
        releaseKey(cacheKey);
    }
    return cacheKey;
}

bool QPMCache::replace(const QPixmapCache::Key &key, const QPixmap &pixmap, int cost)
{
    Q_ASSERT(key.d->isValid);
    //If for the same key we add already a pixmap we should delete it
    QCache<QPixmapCache::Key, QDetachedPixmap>::remove(key);

    bool success = QCache<QPixmapCache::Key, QDetachedPixmap>::insert(key, new QDetachedPixmap(pixmap), cost);
    if (success && !theid) {
        theid = startTimer(30000);
        t = false;
    }
    return success;
}

bool QPMCache::remove(const QString &key)
{
    QPixmapCache::Key cacheKey = cacheKeys.value(key);
    //The key was not in the cache
    if (!cacheKey.d)
        return false;
    cacheKeys.remove(key);
    releaseKey(cacheKey);
    return QCache<QPixmapCache::Key, QDetachedPixmap>::remove(cacheKey);
}

bool QPMCache::remove(const QPixmapCache::Key &key)
{
    bool result = QCache<QPixmapCache::Key, QDetachedPixmap>::remove(key);
    //We release the key after we removed it from the cache
    releaseKey(key);
    return result;
}

void QPMCache::resizeKeyArray(int size)
{
    if (size <= keyArraySize || size == 0)
        return;
    keyArray = q_check_ptr(reinterpret_cast<int *>(realloc(keyArray,
                    size * sizeof(int))));
    for (int i = keyArraySize; i != size; ++i)
        keyArray[i] = i + 1;
    keyArraySize = size;
}

QPixmapCache::Key QPMCache::createKey()
{
    if (freeKey == keyArraySize)
        resizeKeyArray(keyArraySize ? keyArraySize << 1 : 2);
    int id = freeKey;
    freeKey = keyArray[id];
    QPixmapCache::Key key;
    QPixmapCache::KeyData *d = QPMCache::getKeyData(&key);
    d->key = ++id;
    return key;
}

void QPMCache::releaseKey(const QPixmapCache::Key &key)
{
    if (key.d->key > keyArraySize || key.d->key <= 0)
        return;
    key.d->key--;
    keyArray[key.d->key] = freeKey;
    freeKey = key.d->key;
    key.d->isValid = false;
    key.d->key = 0;
}

void QPMCache::clear()
{
    free(keyArray);
    keyArray = 0;
    freeKey = 0;
    keyArraySize = 0;
    //Mark all keys as invalid
    QList<QPixmapCache::Key> keys = QCache<QPixmapCache::Key, QDetachedPixmap>::keys();
    for (int i = 0; i < keys.size(); ++i)
        keys.at(i).d->isValid = false;
    QCache<QPixmapCache::Key, QDetachedPixmap>::clear();
}

QPixmapCache::KeyData* QPMCache::getKeyData(QPixmapCache::Key *key)
{
    if (!key->d)
        key->d = new QPixmapCache::KeyData;
    return key->d;
}

Q_GLOBAL_STATIC(QPMCache, pm_cache)

/*!
    \obsolete
    \overload

    Returns the pixmap associated with the \a key in the cache, or
    null if there is no such pixmap.

    \warning If valid, you should copy the pixmap immediately (this is
    fast). Subsequent insertions into the cache could cause the
    pointer to become invalid. For this reason, we recommend you use
    bool find(const QString&, QPixmap*) instead.

    Example:
    \snippet doc/src/snippets/code/src_gui_image_qpixmapcache.cpp 0
*/

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


/*!
    \obsolete

    Use bool find(const QString&, QPixmap*) instead.
*/

bool QPixmapCache::find(const QString &key, QPixmap& pixmap)
{
    return find(key, &pixmap);
}

/*!
    Looks for a cached pixmap associated with the given \a key in the cache.
    If the pixmap is found, the function sets \a pixmap to that pixmap and
    returns true; otherwise it leaves \a pixmap alone and returns false.

    \since 4.6

    Example:
    \snippet doc/src/snippets/code/src_gui_image_qpixmapcache.cpp 1
*/

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

/*!
    Looks for a cached pixmap associated with the given \a key in the cache.
    If the pixmap is found, the function sets \a pixmap to that pixmap and
    returns true; otherwise it leaves \a pixmap alone and returns false. If
    the pixmap is not found, it means that the \a key is no longer valid,
    so it will be released for the next insertion.

    \since 4.6
*/
bool QPixmapCache::find(const Key &key, QPixmap* pixmap)
{
    //The key is not valid anymore, a flush happened before probably
    if (!key.d || !key.d->isValid)
        return false;
    QPixmap *ptr = pm_cache()->object(key);
    if (ptr && pixmap)
        *pixmap = *ptr;
    return ptr != 0;
}

/*!
    Inserts a copy of the pixmap \a pixmap associated with the \a key into
    the cache.

    All pixmaps inserted by the Qt library have a key starting with
    "$qt", so your own pixmap keys should never begin "$qt".

    When a pixmap is inserted and the cache is about to exceed its
    limit, it removes pixmaps until there is enough room for the
    pixmap to be inserted.

    The oldest pixmaps (least recently accessed in the cache) are
    deleted when more space is needed.

    The function returns true if the object was inserted into the
    cache; otherwise it returns false.

    \sa setCacheLimit()
*/

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

/*!
    Inserts a copy of the given \a pixmap into the cache and returns a key
    that can be used to retrieve it.

    When a pixmap is inserted and the cache is about to exceed its
    limit, it removes pixmaps until there is enough room for the
    pixmap to be inserted.

    The oldest pixmaps (least recently accessed in the cache) are
    deleted when more space is needed.

    \sa setCacheLimit(), replace()

    \since 4.6
*/
QPixmapCache::Key QPixmapCache::insert(const QPixmap &pixmap)
{
    return pm_cache()->insert(pixmap, pixmap.width() * pixmap.height() * pixmap.depth() / 8);
}

/*!
    Replaces the pixmap associated with the given \a key with the \a pixmap
    specified. Returns true if the \a pixmap has been correctly inserted into
    the cache; otherwise returns false.

    \sa setCacheLimit(), insert()

    \since 4.6
*/
bool QPixmapCache::replace(const Key &key, const QPixmap &pixmap)
{
    //The key is not valid anymore, a flush happened before probably
    if (!key.d || !key.d->isValid)
        return false;
    return pm_cache()->replace(key, pixmap, pixmap.width() * pixmap.height() * pixmap.depth() / 8);
}

/*!
    Returns the cache limit (in kilobytes).

    The default cache limit is 2048 KB on embedded platforms, 10240 KB on
    desktop platforms.

    \sa setCacheLimit()
*/

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

/*!
    Sets the cache limit to \a n kilobytes.

    The default setting is 2048 KB on embedded platforms, 10240 KB on
    desktop platforms.

    \sa cacheLimit()
*/

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

/*!
  Removes the pixmap associated with \a key from the cache.
*/
void QPixmapCache::remove(const QString &key)
{
    pm_cache()->remove(key);
}

/*!
  Removes the pixmap associated with \a key from the cache and releases
  the key for a future insertion.

  \since 4.6
*/
void QPixmapCache::remove(const Key &key)
{
    //The key is not valid anymore, a flush happened before probably
    if (!key.d || !key.d->isValid)
        return;
    pm_cache()->remove(key);
}

/*!
    Removes all pixmaps from the cache.
*/

void QPixmapCache::clear()
{
    QT_TRY {
        pm_cache()->clear();
    } QT_CATCH(const std::bad_alloc &) {
        // if we ran out of memory during pm_cache(), it's no leak,
        // so just ignore it.
    }
}

QT_END_NAMESPACE