Add an extension to QPixmapCache to get rid of strings.

This commit add a new API to add/find/remove pixmaps into QPixmapCache.
This new extension is based on a key that the cache give you during
the insertion. This key is internally a int which makes all operations
in the cache much more faster that the string approach.
Auto-tests has been extended as well and a benchmark has been added to
compare both approach. I also depecrate the find method for the
string API to have a method pointer based and not reference based like
the Qt policy says.

Reviewed-by: bnilsen
Reviewed-by: andreas
Followed-deeply-by: trond

7 files changed, 455 insertions, 78 deletions

diff --git a/src/gui/graphicsview/qgraphicsitem.cpp b/src/gui/graphicsview/qgraphicsitem.cpp
index ec08aaf..72b832a 100644
--- a/src/gui/graphicsview/qgraphicsitem.cpp
+++ b/src/gui/graphicsview/qgraphicsitem.cpp
@@ -978,6 +978,7 @@ void QGraphicsItemPrivate::initStyleOption(QStyleOptionGraphicsItem *option, con
 void QGraphicsItemCache::purge()
 {
     QPixmapCache::remove(key);
+    key = QPixmapCache::Key();
     QMutableMapIterator<QPaintDevice *, DeviceData> it(deviceData);
     while (it.hasNext()) {
         DeviceData &data = it.next().value();
@@ -1426,12 +1427,6 @@ void QGraphicsItem::setCacheMode(CacheMode mode, const QSize &logicalCacheSize)
         cache->purge();
 
         if (mode == ItemCoordinateCache) {
-            if (cache->key.isEmpty()) {
-                // Generate new simple pixmap cache key.
-                QString tmp;
-                tmp.sprintf("qgv-%p", this);
-                cache->key = tmp;
-            }
             if (lastMode == mode && cache->fixedSize == logicalCacheSize)
                 noVisualChange = true;
             cache->fixedSize = logicalCacheSize;
@@ -4205,7 +4200,7 @@ void QGraphicsItem::scroll(qreal dx, qreal dy, const QRectF &rect)
                            && (d->cacheMode == ItemCoordinateCache && !c->fixedSize.isValid());
         if (scrollCache) {
             QPixmap pix;
-            if (QPixmapCache::find(c->key, pix)) {
+            if (QPixmapCache::find(c->key, &pix)) {
                 // Adjust with 2 pixel margin. Notice the loss of precision
                 // when converting to QRect.
                 int adjust = 2;
@@ -4214,7 +4209,7 @@ void QGraphicsItem::scroll(qreal dx, qreal dy, const QRectF &rect)
 
                 _q_scrollPixmap(&pix, irect, dx, dy);
 
-                QPixmapCache::insert(c->key, pix);
+                QPixmapCache::replace(c->key, pix);
 
                 // Translate the existing expose.
                 foreach (QRectF exposedRect, c->exposed)
diff --git a/src/gui/graphicsview/qgraphicsitem_p.h b/src/gui/graphicsview/qgraphicsitem_p.h
index 82a48fb..820ef04 100644
--- a/src/gui/graphicsview/qgraphicsitem_p.h
+++ b/src/gui/graphicsview/qgraphicsitem_p.h
@@ -54,6 +54,7 @@
 //
 
 #include "qgraphicsitem.h"
+#include "qpixmapcache.h"
 
 #if !defined(QT_NO_GRAPHICSVIEW) || (QT_EDITION & QT_MODULE_GRAPHICSVIEW) != QT_MODULE_GRAPHICSVIEW
 
@@ -69,13 +70,14 @@ public:
     // ItemCoordinateCache only
     QRect boundingRect;
     QSize fixedSize;
-    QString key;
+    QPixmapCache::Key key;
 
     // DeviceCoordinateCache only
     struct DeviceData {
+        DeviceData() {}
         QTransform lastTransform;
         QPoint cacheIndent;
-        QString key;
+        QPixmapCache::Key key;
     };
     QMap<QPaintDevice *, DeviceData> deviceData;
 
diff --git a/src/gui/graphicsview/qgraphicsscene.cpp b/src/gui/graphicsview/qgraphicsscene.cpp
index 7318fa5..1fbda85 100644
--- a/src/gui/graphicsview/qgraphicsscene.cpp
+++ b/src/gui/graphicsview/qgraphicsscene.cpp
@@ -4743,8 +4743,9 @@ void QGraphicsScenePrivate::drawItemHelper(QGraphicsItem *item, QPainter *painte
         return;
 
     // Fetch the off-screen transparent buffer and exposed area info.
-    QString pixmapKey;
+    QPixmapCache::Key pixmapKey;
     QPixmap pix;
+    bool pixmapFound;
     QGraphicsItemCache *itemCache = itemd->extraItemCache();
     if (cacheMode == QGraphicsItem::ItemCoordinateCache) {
         if (itemCache->boundingRect != brect.toRect()) {
@@ -4754,17 +4755,14 @@ void QGraphicsScenePrivate::drawItemHelper(QGraphicsItem *item, QPainter *painte
         }
         pixmapKey = itemCache->key;
     } else {
-        if ((pixmapKey = itemCache->deviceData.value(widget).key).isEmpty()) {
-            pixmapKey.sprintf("qgv-%p-%p", item, widget);
-            QGraphicsItemCache::DeviceData data;
-            data.key = pixmapKey;
-            itemCache->deviceData.insert(widget, data);
-        }
+        pixmapKey = itemCache->deviceData.value(widget).key;
     }
 
     // Find pixmap in cache.
     if (!itemCache->allExposed)
-        QPixmapCache::find(pixmapKey, pix);
+       pixmapFound = QPixmapCache::find(pixmapKey, &pix);
+    else
+       pixmapFound = false;
 
     // Render using item coordinate cache mode.
     if (cacheMode == QGraphicsItem::ItemCoordinateCache) {
@@ -4817,8 +4815,12 @@ void QGraphicsScenePrivate::drawItemHelper(QGraphicsItem *item, QPainter *painte
             _q_paintIntoCache(&pix, item, pixmapExposed, itemToPixmap, painter->renderHints(),
                               &cacheOption, painterStateProtection);
 
-            // Reinsert this pixmap into the cache.
-            QPixmapCache::insert(pixmapKey, pix);
+            if (!pixmapFound) {
+                // insert this pixmap into the cache.
+                itemCache->key = QPixmapCache::insert(pix);
+            } else {
+                QPixmapCache::replace(pixmapKey, pix);
+            }
 
             // Reset expose data.
             itemCache->allExposed = false;
@@ -4985,8 +4987,13 @@ void QGraphicsScenePrivate::drawItemHelper(QGraphicsItem *item, QPainter *painte
         }
 
         if (pixModified) {
-            // Reinsert this pixmap into the cache
-            QPixmapCache::insert(pixmapKey, pix);
+            if (!pixmapFound) {
+                // Insert this pixmap into the cache.
+                deviceData->key = QPixmapCache::insert(pix);
+            } else {
+                //otherwise we replace the pixmap in the cache
+                QPixmapCache::replace(pixmapKey, pix);
+            }
         }
 
         // Redraw the exposed area using an untransformed painter. This
diff --git a/src/gui/image/image.pri b/src/gui/image/image.pri
index ca52974..bf348af 100644
--- a/src/gui/image/image.pri
+++ b/src/gui/image/image.pri
@@ -22,6 +22,7 @@ HEADERS += \
         image/qpixmap.h \
         image/qpixmap_raster_p.h \
         image/qpixmapcache.h \
+	image/qpixmapcache_p.h \
         image/qpixmapdata_p.h \
         image/qpixmapdatafactory_p.h \
         image/qpixmapfilter_p.h
diff --git a/src/gui/image/qpixmapcache.cpp b/src/gui/image/qpixmapcache.cpp
index 4916489..810ce65 100644
--- a/src/gui/image/qpixmapcache.cpp
+++ b/src/gui/image/qpixmapcache.cpp
@@ -40,13 +40,9 @@
 ****************************************************************************/
 
 #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>
+#include "qpixmapcache_p.h"
 
 QT_BEGIN_NAMESPACE
 
@@ -68,15 +64,17 @@ QT_BEGIN_NAMESPACE
     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
+    The cache associates a pixmap with a string as a key or with a QPixmapCache::Key.
+    The QPixmapCache::Key is faster than using strings as 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.
+    cache exceeds cacheLimit(). The initial cache limit is
+    2048 KB(2 MB) for Embedded, 10240 KB (10
+    MB) for Desktops; 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
@@ -92,52 +90,117 @@ static int cache_limit = 2048; // 2048 KB cache limit for embedded
 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
+/*!
+    Constructs an empty Key object.
+*/
+QPixmapCache::Key::Key() : d(0)
 {
-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;
-            }
-        }
+}
+
+/*!
+   \internal
+    Constructs a copy of \a other.
+*/
+QPixmapCache::Key::Key(const Key &other)
+{
+    if (other.d)
+        ++(other.d->ref);
+    d = other.d;
+}
+
+/*!
+    Destructor; called immediately before the object is deleted.
+*/
+QPixmapCache::Key::~Key()
+{
+    if (d && --(d->ref) == 0)
+        delete d;
+}
+
+/*!
+    \internal
+
+    Returns true if this key is the same as the given \a key.
+*/
+bool QPixmapCache::Key::operator ==(const Key &key) const
+{
+    return (d == key.d);
+}
+
+/*!
+    \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<qint64, QDetachedPixmap>
+class QPMCache : public QObject, public QCache<QPixmapCache::Key, QDetachedPixmap>
 {
     Q_OBJECT
 public:
-    QPMCache()
-        : QObject(0),
-          QCache<qint64, QDetachedPixmap>(cache_limit * 1024),
-          theid(0), ps(0), t(false) { }
-    ~QPMCache() { }
+    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:
-    QHash<QString, qint64> cacheKeys;
+    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
 
+static 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 80-90% in a
+  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
@@ -146,23 +209,28 @@ QT_END_INCLUDE_NAMESPACE
   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, qint64>::iterator it = cacheKeys.begin();
+    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);
@@ -176,38 +244,154 @@ void QPMCache::timerEvent(QTimerEvent *)
 
 QPixmap *QPMCache::object(const QString &key) const
 {
-    return QCache<qint64, QDetachedPixmap>::object(cacheKeys.value(key, -1));
+    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)
 {
-    qint64 cacheKey = pixmap.cacheKey();
-    if (QCache<qint64, QDetachedPixmap>::object(cacheKey)) {
+    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);
-        return true;
+        if (!theid) {
+            theid = startTimer(30000);
+            t = false;
+        }
+    } else {
+        //Insertion failed we released the new allocated key
+        releaseKey(cacheKey);
     }
-    qint64 oldCacheKey = cacheKeys.value(key, -1);
-    //If for the same key we add already a pixmap we should delete it
-    if (oldCacheKey != -1)
-        QCache<qint64, QDetachedPixmap>::remove(oldCacheKey);
+    return success;
+}
 
-    bool success = QCache<qint64, QDetachedPixmap>::insert(cacheKey, new QDetachedPixmap(pixmap), cost);
+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) {
-        cacheKeys.insert(key, cacheKey);
         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)
 {
-    qint64 cacheKey = cacheKeys.value(key, -1);
+    QPixmapCache::Key cacheKey = cacheKeys.value(key);
+    //The key was not in the cache
+    if (!cacheKey.d)
+        return false;
     cacheKeys.remove(key);
-    return QCache<qint64, QDetachedPixmap>::remove(cacheKey);
+    releaseKey(cacheKey);
+    return QCache<QPixmapCache::Key, QDetachedPixmap>::remove(cacheKey);
+}
+
+bool QPMCache::remove(const QPixmapCache::Key &key)
+{
+    releaseKey(key);
+    return QCache<QPixmapCache::Key, QDetachedPixmap>::remove(key);
+}
+
+void QPMCache::resizeKeyArray(int size)
+{
+    if (size <= keyArraySize || size == 0)
+        return;
+    keyArray = 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)
@@ -222,7 +406,7 @@ Q_GLOBAL_STATIC(QPMCache, pm_cache)
     \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
-    find(const QString&, QPixmap&) instead.
+    bool find(const QString&, QPixmap*) instead.
 
     Example:
     \snippet doc/src/snippets/code/src_gui_image_qpixmapcache.cpp 0
@@ -235,6 +419,17 @@ QPixmap *QPixmapCache::find(const QString &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 \a key in the cache.
     If the pixmap is found, the function sets \a pm to that pixmap and
     returns true; otherwise it leaves \a pm alone and returns false.
@@ -243,14 +438,31 @@ QPixmap *QPixmapCache::find(const QString &key)
     \snippet doc/src/snippets/code/src_gui_image_qpixmapcache.cpp 1
 */
 
-bool QPixmapCache::find(const QString &key, QPixmap& pm)
+bool QPixmapCache::find(const QString &key, QPixmap* pixmap)
 {
     QPixmap *ptr = pm_cache()->object(key);
-    if (ptr)
-        pm = *ptr;
+    if (ptr && pixmap)
+        *pixmap = *ptr;
     return ptr != 0;
 }
 
+/*!
+    Looks for a cached pixmap associated with the \a key in the cache.
+    If the pixmap is found, the function sets \a pm to that pixmap and
+    returns true; otherwise it leaves \a pm alone and returns false. If
+    the pixmap is not found, it means that the \a key is not valid anymore,
+    so it will be released for the next insertion.
+*/
+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 pm associated with the \a key into
@@ -272,9 +484,43 @@ bool QPixmapCache::find(const QString &key, QPixmap& pm)
     \sa setCacheLimit()
 */
 
-bool QPixmapCache::insert(const QString &key, const QPixmap &pm)
+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 pixmap \a pm into
+    the cache and return you the key. The key is always greater than 0.
+    If the key is equals 0 then the insertion failed.
+
+    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()
+*/
+QPixmapCache::Key QPixmapCache::insert(const QPixmap &pixmap)
+{
+    return pm_cache()->insert(pixmap, pixmap.width() * pixmap.height() * pixmap.depth() / 8);
+}
+
+/*!
+    Replace the pixmap associated to the \a key into
+    the cache. It return true if the pixmap \a pm has been correctly
+    inserted into the cache false otherwise.
+
+    \sa setCacheLimit(), insert()
+*/
+bool QPixmapCache::replace(const Key &key, const QPixmap &pixmap)
 {
-    return pm_cache()->insert(key, pm, pm.width() * pm.height() * pm.depth() / 8);
+    //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);
 }
 
 /*!
@@ -314,6 +560,17 @@ void QPixmapCache::remove(const QString &key)
     pm_cache()->remove(key);
 }
 
+/*!
+  Removes the pixmap associated with \a key from the cache and release
+  the key for a future insertion.
+*/
+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.
diff --git a/src/gui/image/qpixmapcache.h b/src/gui/image/qpixmapcache.h
index 2750a88..ae64310 100644
--- a/src/gui/image/qpixmapcache.h
+++ b/src/gui/image/qpixmapcache.h
@@ -53,12 +53,35 @@ QT_MODULE(Gui)
 class Q_GUI_EXPORT QPixmapCache
 {
 public:
+    class KeyData;
+    class Key
+    {
+    public:
+        Key();
+        Key(const Key &other);
+        ~Key();
+        bool operator ==(const Key &key) const;
+        inline bool operator !=(const Key &key) const
+        { return !operator==(key); }
+        Key &operator =(const Key &other);
+
+    private:
+        KeyData *d;
+        friend class QPMCache;
+        friend class QPixmapCache;
+    };
+
     static int cacheLimit();
     static void setCacheLimit(int);
     static QPixmap *find(const QString &key);
-    static bool find(const QString &key, QPixmap&);
-    static bool insert(const QString &key, const QPixmap&);
+    static bool find(const QString &key, QPixmap &pixmap);
+    static bool find(const QString &key, QPixmap *pixmap);
+    static bool find(const Key &key, QPixmap *pixmap);
+    static bool insert(const QString &key, const QPixmap &pixmap);
+    static Key insert(const QPixmap &pixmap);
+    static bool replace(const Key &key, const QPixmap &pixmap);
     static void remove(const QString &key);
+    static void remove(const Key &key);
     static void clear();
 };
 
diff --git a/src/gui/image/qpixmapcache_p.h b/src/gui/image/qpixmapcache_p.h
new file mode 100644
index 0000000..66b30d2
--- /dev/null
+++ b/src/gui/image/qpixmapcache_p.h
@@ -0,0 +1,92 @@
+/****************************************************************************
+**
+** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
+** Contact: Qt Software Information (qt-info@nokia.com)
+**
+** This file is part of the QtGui module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** No Commercial Usage
+** This file contains pre-release code and may not be distributed.
+** You may use this file in accordance with the terms and conditions
+** contained in the either Technology Preview License Agreement or the
+** Beta Release License Agreement.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Nokia gives you certain
+** additional rights. These rights are described in the Nokia Qt LGPL
+** Exception version 1.0, included in the file LGPL_EXCEPTION.txt in this
+** package.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3.0 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 the GNU General Public License version 3.0 requirements will be
+** met: http://www.gnu.org/copyleft/gpl.html.
+**
+** If you are unsure which license is appropriate for your use, please
+** contact the sales department at qt-sales@nokia.com.
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QPIXMAPCACHE_P_H
+#define QPIXMAPCACHE_P_H
+
+//
+//  W A R N I N G
+//  -------------
+//
+// This file is not part of the Qt API. This header
+// file may change from version to version without notice, or even be removed.
+//
+// We mean it.
+//
+
+#include "qpixmapcache.h"
+#include "qpaintengine.h"
+#include <private/qimage_p.h>
+#include <private/qpixmap_raster_p.h>
+#include "qcache.h"
+
+class QPixmapCache::KeyData
+{
+public:
+    KeyData() : isValid(true), key(0), ref(1) {}
+    KeyData(const KeyData &other)
+     : isValid(other.isValid), key(other.key), ref(1) {}
+    ~KeyData() {}
+
+    bool isValid;
+    int key;
+    int ref;
+};
+
+// 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;
+            }
+        }
+    }
+};
+
+#endif // QPIXMAPCACHE_P_H