Add cacheItemCount property to PathView

cacheItemCount specifies the number of items to cache off the path when
pathItemCount is specified.  This allows up to cacheItemCount items to be
kept alive when they move off the path, and also to asynchronously
create items off path in preparation for display when the path offset
changes.  This is the equivalent of cacheBuffer for other views.

Task-number: QTBUG-23931
Change-Id: I03497537d3f929e5e3579536850dd43eb2724c38
Reviewed-by: Bea Lam <bea.lam@nokia.com>

7 files changed, 216 insertions, 61 deletions

diff --git a/src/quick/items/qquickitem.cpp b/src/quick/items/qquickitem.cpp
index 2e9ee262d7..2e494c7533 100644
--- a/src/quick/items/qquickitem.cpp
+++ b/src/quick/items/qquickitem.cpp
@@ -5042,7 +5042,7 @@ void QQuickItemPrivate::setCulled(bool cull)
         return;
 
     culled = cull;
-    if ((cull && ++extra->hideRefCount == 1) || (!cull && --extra->hideRefCount == 0))
+    if ((cull && ++extra.value().hideRefCount == 1) || (!cull && --extra.value().hideRefCount == 0))
         dirty(HideReference);
 }
 
diff --git a/src/quick/items/qquickpathview.cpp b/src/quick/items/qquickpathview.cpp
index a30a292942..6ecad79f69 100644
--- a/src/quick/items/qquickpathview.cpp
+++ b/src/quick/items/qquickpathview.cpp
@@ -114,13 +114,13 @@ void QQuickPathViewAttached::setValue(const QByteArray &name, const QVariant &va
 
 QQuickPathViewPrivate::QQuickPathViewPrivate()
   : path(0), currentIndex(0), currentItemOffset(0.0), startPc(0)
-    , offset(0.0), offsetAdj(0.0), mappedRange(1.0)
+    , offset(0.0), offsetAdj(0.0), mappedRange(1.0), mappedCache(0.0)
     , stealMouse(false), ownModel(false), interactive(true), haveHighlightRange(true)
     , autoHighlight(true), highlightUp(false), layoutScheduled(false)
-    , moving(false), flicking(false), dragging(false), requestedOnPath(false), inRequest(false)
+    , moving(false), flicking(false), dragging(false), inRequest(false)
     , dragMargin(0), deceleration(100), maximumFlickVelocity(QML_FLICK_DEFAULTMAXVELOCITY)
     , moveOffset(this, &QQuickPathViewPrivate::setAdjustedOffset), flickDuration(0)
-    , firstIndex(-1), pathItems(-1), requestedIndex(-1), requestedZ(0)
+    , firstIndex(-1), pathItems(-1), requestedIndex(-1), cacheSize(0), requestedZ(0)
     , moveReason(Other), moveDirection(Shortest), attType(0), highlightComponent(0), highlightItem(0)
     , moveHighlight(this, &QQuickPathViewPrivate::setHighlightPosition)
     , highlightPosition(0)
@@ -144,22 +144,16 @@ void QQuickPathViewPrivate::init()
                       q, QQuickPathView, SLOT(movementEnding()))
 }
 
-QQuickItem *QQuickPathViewPrivate::getItem(int modelIndex, qreal z, bool onPath)
+QQuickItem *QQuickPathViewPrivate::getItem(int modelIndex, qreal z, bool async)
 {
     Q_Q(QQuickPathView);
     requestedIndex = modelIndex;
-    requestedOnPath = onPath;
     requestedZ = z;
     inRequest = true;
-    QQuickItem *item = model->item(modelIndex, false);
+    QQuickItem *item = model->item(modelIndex, async);
     if (item) {
         item->setParentItem(q);
         requestedIndex = -1;
-        qPathViewAttachedType = attType;
-        QQuickPathViewAttached *att = static_cast<QQuickPathViewAttached *>(qmlAttachedPropertiesObject<QQuickPathView>(item));
-        qPathViewAttachedType = 0;
-        if (att)
-            att->setOnPath(onPath);
         QQuickItemPrivate *itemPrivate = QQuickItemPrivate::get(item);
         itemPrivate->addItemChangeListener(this, QQuickItemPrivate::Geometry);
     }
@@ -179,7 +173,7 @@ void QQuickPathView::createdItem(int index, QQuickItem *item)
             att->setOnPath(false);
         }
         item->setParentItem(this);
-        d->updateItem(item, index < d->firstIndex ? 0.0 : 1.0);
+        d->updateItem(item, 1.0);
     } else {
         d->requestedIndex = -1;
         if (!d->inRequest)
@@ -191,6 +185,7 @@ void QQuickPathView::initItem(int index, QQuickItem *item)
 {
     Q_D(QQuickPathView);
     if (d->requestedIndex == index) {
+        QQuickItemPrivate::get(item)->setCulled(true);
         item->setParentItem(this);
         qPathViewAttachedType = d->attachedType();
         QQuickPathViewAttached *att = static_cast<QQuickPathViewAttached *>(qmlAttachedPropertiesObject<QQuickPathView>(item));
@@ -198,11 +193,12 @@ void QQuickPathView::initItem(int index, QQuickItem *item)
         if (att) {
             att->m_view = this;
             qreal percent = d->positionOfIndex(index);
-            foreach (const QString &attr, d->path->attributes())
-                att->setValue(attr.toUtf8(), d->path->attributeAt(attr, percent));
-            item->setZ(d->requestedZ);
-            if (att)
-                att->setOnPath(d->requestedOnPath);
+            if (percent < 1.0) {
+                foreach (const QString &attr, d->path->attributes())
+                    att->setValue(attr.toUtf8(), d->path->attributeAt(attr, percent));
+                item->setZ(d->requestedZ);
+            }
+            att->setOnPath(percent < 1.0);
         }
     }
 }
@@ -248,16 +244,25 @@ void QQuickPathViewPrivate::clear()
         QQuickItem *p = items[i];
         releaseItem(p);
     }
+    if (requestedIndex >= 0) {
+        if (model)
+            model->cancel(requestedIndex);
+        requestedIndex = -1;
+    }
+
     items.clear();
     tl.clear();
 }
 
 void QQuickPathViewPrivate::updateMappedRange()
 {
-    if (model && pathItems != -1 && pathItems < modelCount)
-        mappedRange = qreal(pathItems)/modelCount;
-    else
+    if (model && pathItems != -1 && pathItems < modelCount) {
+        mappedRange = qreal(modelCount)/pathItems;
+        mappedCache = qreal(cacheSize)/pathItems/2; // Half of cache at each end
+    } else {
         mappedRange = 1.0;
+        mappedCache = 0.0;
+    }
 }
 
 qreal QQuickPathViewPrivate::positionOfIndex(qreal index) const
@@ -272,10 +277,9 @@ qreal QQuickPathViewPrivate::positionOfIndex(qreal index) const
         qreal globalPos = index + offset;
         globalPos = qmlMod(globalPos, qreal(modelCount)) / modelCount;
         if (pathItems != -1 && pathItems < modelCount) {
-            globalPos += start * mappedRange;
+            globalPos += start / mappedRange;
             globalPos = qmlMod(globalPos, 1.0);
-            if (globalPos < mappedRange)
-                pos = globalPos / mappedRange;
+            pos = globalPos * mappedRange;
         } else {
             pos = qmlMod(globalPos + start, 1.0);
         }
@@ -284,6 +288,18 @@ qreal QQuickPathViewPrivate::positionOfIndex(qreal index) const
     return pos;
 }
 
+// returns true if position is between lower and upper, taking into
+// account the circular space.
+bool QQuickPathViewPrivate::isInBound(qreal position, qreal lower, qreal upper) const
+{
+    if (lower > upper) {
+        if (position > upper && position > lower)
+            position -= mappedRange;
+        lower -= mappedRange;
+    }
+    return position >= lower && position < upper;
+}
+
 void QQuickPathViewPrivate::createHighlight()
 {
     Q_Q(QQuickPathView);
@@ -376,11 +392,11 @@ void QQuickPathViewPrivate::setHighlightPosition(qreal pos)
         // calc normalized position of highlight relative to offset
         qreal relativeHighlight = qmlMod(pos + offset, range) / range;
 
-        if (!highlightUp && relativeHighlight > end * mappedRange) {
+        if (!highlightUp && relativeHighlight > end / mappedRange) {
             qreal diff = 1.0 - relativeHighlight;
             setOffset(offset + diff * range);
-        } else if (highlightUp && relativeHighlight >= (end - start) * mappedRange) {
-            qreal diff = relativeHighlight - (end - start) * mappedRange;
+        } else if (highlightUp && relativeHighlight >= (end - start) / mappedRange) {
+            qreal diff = relativeHighlight - (end - start) / mappedRange;
             setOffset(offset - diff * range - 0.00001);
         }
 
@@ -388,7 +404,7 @@ void QQuickPathViewPrivate::setHighlightPosition(qreal pos)
         qreal pathPos = positionOfIndex(pos);
         updateItem(highlightItem, pathPos);
         if (QQuickPathViewAttached *att = attached(highlightItem))
-            att->setOnPath(pathPos != -1.0);
+            att->setOnPath(pathPos < 1.0);
     }
 }
 
@@ -413,8 +429,10 @@ void QQuickPathViewPrivate::updateItem(QQuickItem *item, qreal percent)
         att->m_percent = percent;
         foreach (const QString &attr, path->attributes())
             att->setValue(attr.toUtf8(), path->attributeAt(attr, percent));
+        att->setOnPath(percent < 1.0);
     }
-    QPointF pf = path->pointAt(percent);
+    QQuickItemPrivate::get(item)->setCulled(percent >= 1.0);
+    QPointF pf = path->pointAt(qMin(percent, qreal(1.0)));
     item->setX(pf.x() - item->width()/2);
     item->setY(pf.y() - item->height()/2);
 }
@@ -1255,6 +1273,43 @@ void QQuickPathView::resetPathItemCount()
 }
 
 /*!
+    \qmlproperty int QtQuick2::PathView::cacheItemCount
+    This property holds the maximum number of items to cache off the path.
+
+    For example, a PathView with a model containing 20 items, a pathItemCount
+    of 10, and an cacheItemCount of 4 will create up to 14 items, with 10 visible
+    on the path and 4 invisible cached items.
+
+    The cached delegates are created asynchronously,
+    allowing creation to occur across multiple frames and reducing the
+    likelihood of skipping frames.
+
+    Setting this value can improve the smoothness of scrolling behavior at the expense
+    of additional memory usage.  It is not a substitute for creating efficient
+    delegates; the fewer objects and bindings in a delegate, the faster a view can be
+    moved.
+
+    \sa pathItemCount
+*/
+int QQuickPathView::cacheItemCount() const
+{
+    Q_D(const QQuickPathView);
+    return d->cacheSize;
+}
+
+void QQuickPathView::setCacheItemCount(int i)
+{
+    Q_D(QQuickPathView);
+    if (i == d->cacheSize || i < 0)
+        return;
+
+    d->cacheSize = i;
+    d->updateMappedRange();
+    refill();
+    emit cacheItemCountChanged();
+}
+
+/*!
     \qmlproperty enumeration QtQuick2::PathView::snapMode
 
     This property determines how the items will settle following a drag or flick.
@@ -1567,7 +1622,8 @@ void QQuickPathViewPrivate::handleMouseMoveEvent(QMouseEvent *event)
         }
     } else {
         moveReason = QQuickPathViewPrivate::Mouse;
-        qreal diff = (newPc - startPc)*modelCount*mappedRange;
+        int count = pathItems == -1 ? modelCount : qMin(pathItems, modelCount);
+        qreal diff = (newPc - startPc)*count;
         if (diff) {
             q->setOffset(offset + diff);
 
@@ -1617,7 +1673,7 @@ void QQuickPathViewPrivate::handleMouseReleaseEvent(QMouseEvent *)
     }
 
     qreal velocity = calcVelocity();
-    qreal count = modelCount*mappedRange;
+    qreal count = pathItems == -1 ? modelCount : qMin(pathItems, modelCount);
     qreal pixelVelocity = (path->path().length()/count) * velocity;
     if (qAbs(pixelVelocity) > MinimumFlickVelocity) {
         if (qAbs(pixelVelocity) > maximumFlickVelocity || snapMode == QQuickPathView::SnapOneItem) {
@@ -1790,6 +1846,7 @@ void QQuickPathView::refill()
         return;
 
     bool currentVisible = false;
+    int count = d->pathItems == -1 ? d->modelCount : qMin(d->pathItems, d->modelCount);
 
     // first move existing items and remove items off path
     int idx = d->firstIndex;
@@ -1797,7 +1854,7 @@ void QQuickPathView::refill()
     while (it != d->items.end()) {
         qreal pos = d->positionOfIndex(idx);
         QQuickItem *item = *it;
-        if (pos >= 0.0) {
+        if (pos < 1.0) {
             d->updateItem(item, pos);
             if (idx == d->currentIndex) {
                 currentVisible = true;
@@ -1805,27 +1862,34 @@ void QQuickPathView::refill()
             }
             ++it;
         } else {
-            // qDebug() << "release";
-            d->updateItem(item, 1.0);
-            d->releaseItem(item);
-            if (it == d->items.begin()) {
-                if (++d->firstIndex >= d->modelCount)
-                    d->firstIndex = 0;
+            d->updateItem(item, pos);
+            if (QQuickPathViewAttached *att = d->attached(item))
+                att->setOnPath(pos < 1.0);
+            if (!d->isInBound(pos, d->mappedRange - d->mappedCache, 1.0 + d->mappedCache)) {
+//                qDebug() << "release";
+                d->releaseItem(item);
+                if (it == d->items.begin()) {
+                    if (++d->firstIndex >= d->modelCount) {
+                        d->firstIndex = 0;
+                    }
+                }
+                it = d->items.erase(it);
+            } else {
+                ++it;
             }
-            it = d->items.erase(it);
         }
         ++idx;
         if (idx >= d->modelCount)
             idx = 0;
     }
+
     if (!d->items.count())
         d->firstIndex = -1;
 
     bool waiting = false;
     if (d->modelCount) {
         // add items to beginning and end
-        int count = d->pathItems == -1 ? d->modelCount : qMin(d->pathItems, d->modelCount);
-        if (d->items.count() < count) {
+        if (d->items.count() < count+d->cacheSize) {
             int idx = qRound(d->modelCount - d->offset) % d->modelCount;
             qreal startPos = 0.0;
             if (d->haveHighlightRange && (d->highlightRangeMode != QQuickPathView::NoHighlightRange
@@ -1836,9 +1900,9 @@ void QQuickPathView::refill()
                 idx = (d->firstIndex + d->items.count()) % d->modelCount;
             }
             qreal pos = d->positionOfIndex(idx);
-            while ((pos > startPos || !d->items.count()) && d->items.count() < count) {
+            while ((d->isInBound(pos, startPos, 1.0 + d->mappedCache) || !d->items.count()) && d->items.count() < count+d->cacheSize) {
 //                qDebug() << "append" << idx;
-                QQuickItem *item = d->getItem(idx, idx+1);
+                QQuickItem *item = d->getItem(idx, idx+1, pos >= 1.0);
                 if (!item) {
                     waiting = true;
                     break;
@@ -1861,9 +1925,9 @@ void QQuickPathView::refill()
             if (idx < 0)
                 idx = d->modelCount - 1;
             pos = d->positionOfIndex(idx);
-            while (!waiting && (pos >= 0.0 && pos < startPos) && d->items.count() < count) {
+            while (!waiting && d->isInBound(pos, d->mappedRange - d->mappedCache, startPos) && d->items.count() < count+d->cacheSize) {
 //                 qDebug() << "prepend" << idx;
-                QQuickItem *item = d->getItem(idx, idx+1);
+                QQuickItem *item = d->getItem(idx, idx+1, pos >= 1.0);
                 if (!item) {
                     waiting = true;
                     break;
@@ -1886,17 +1950,16 @@ void QQuickPathView::refill()
     if (!currentVisible) {
         d->currentItemOffset = 1.0;
         if (d->currentItem) {
-            if (QQuickPathViewAttached *att = d->attached(d->currentItem))
-                att->setOnPath(false);
+            d->updateItem(d->currentItem, 1.0);
         } else if (!waiting && d->currentIndex >= 0 && d->currentIndex < d->modelCount) {
-            if ((d->currentItem = d->getItem(d->currentIndex, d->currentIndex, false))) {
-                d->updateItem(d->currentItem, d->currentIndex < d->firstIndex ? 0.0 : 1.0);
+            if ((d->currentItem = d->getItem(d->currentIndex, d->currentIndex))) {
+                d->updateItem(d->currentItem, 1.0);
                 if (QQuickPathViewAttached *att = d->attached(d->currentItem))
                     att->setIsCurrentItem(true);
             }
         }
     } else if (!waiting && !d->currentItem) {
-        if ((d->currentItem = d->getItem(d->currentIndex, d->currentIndex, true))) {
+        if ((d->currentItem = d->getItem(d->currentIndex, d->currentIndex))) {
             d->currentItem->setFocus(true);
             if (QQuickPathViewAttached *att = d->attached(d->currentItem))
                 att->setIsCurrentItem(true);
@@ -2062,14 +2125,14 @@ void QQuickPathViewPrivate::createCurrentItem()
         return;
     int itemIndex = (currentIndex - firstIndex + modelCount) % modelCount;
     if (itemIndex < items.count()) {
-        if ((currentItem = getItem(currentIndex, currentIndex, true))) {
+        if ((currentItem = getItem(currentIndex, currentIndex))) {
             currentItem->setFocus(true);
             if (QQuickPathViewAttached *att = attached(currentItem))
                 att->setIsCurrentItem(true);
         }
     } else if (currentIndex >= 0 && currentIndex < modelCount) {
-        if ((currentItem = getItem(currentIndex, currentIndex, false))) {
-            updateItem(currentItem, currentIndex < firstIndex ? 0.0 : 1.0);
+        if ((currentItem = getItem(currentIndex, currentIndex))) {
+            updateItem(currentItem, 1.0);
             if (QQuickPathViewAttached *att = attached(currentItem))
                 att->setIsCurrentItem(true);
         }
diff --git a/src/quick/items/qquickpathview_p.h b/src/quick/items/qquickpathview_p.h
index 7f7f344205..ce5d395ec7 100644
--- a/src/quick/items/qquickpathview_p.h
+++ b/src/quick/items/qquickpathview_p.h
@@ -86,6 +86,8 @@ class Q_AUTOTEST_EXPORT QQuickPathView : public QQuickItem
     Q_PROPERTY(int pathItemCount READ pathItemCount WRITE setPathItemCount RESET resetPathItemCount NOTIFY pathItemCountChanged)
     Q_PROPERTY(SnapMode snapMode READ snapMode WRITE setSnapMode NOTIFY snapModeChanged)
 
+    Q_PROPERTY(int cacheItemCount READ cacheItemCount WRITE setCacheItemCount NOTIFY cacheItemCountChanged)
+
     Q_ENUMS(HighlightRangeMode)
     Q_ENUMS(SnapMode)
     Q_ENUMS(PositionMode)
@@ -150,6 +152,9 @@ public:
     void setPathItemCount(int);
     void resetPathItemCount();
 
+    int cacheItemCount() const;
+    void setCacheItemCount(int);
+
     enum SnapMode { NoSnap, SnapToItem, SnapOneItem };
     SnapMode snapMode() const;
     void setSnapMode(SnapMode mode);
@@ -195,6 +200,7 @@ Q_SIGNALS:
     void dragStarted();
     void dragEnded();
     void snapModeChanged();
+    void cacheItemCountChanged();
 
 protected:
     virtual void updatePolish();
diff --git a/src/quick/items/qquickpathview_p_p.h b/src/quick/items/qquickpathview_p_p.h
index 2a547d9b47..46ad22f3f8 100644
--- a/src/quick/items/qquickpathview_p_p.h
+++ b/src/quick/items/qquickpathview_p_p.h
@@ -95,13 +95,14 @@ public:
         }
     }
 
-    QQuickItem *getItem(int modelIndex, qreal z = 0, bool onPath=true);
+    QQuickItem *getItem(int modelIndex, qreal z = 0, bool async=false);
     void releaseItem(QQuickItem *item);
     QQuickPathViewAttached *attached(QQuickItem *item);
     QQmlOpenMetaObjectType *attachedType();
     void clear();
     void updateMappedRange();
     qreal positionOfIndex(qreal index) const;
+    bool isInBound(qreal position, qreal lower, qreal upper) const;
     void createHighlight();
     void updateHighlight();
     void setHighlightPosition(qreal pos);
@@ -138,6 +139,7 @@ public:
     qreal offset;
     qreal offsetAdj;
     qreal mappedRange;
+    qreal mappedCache;
     bool stealMouse : 1;
     bool ownModel : 1;
     bool interactive : 1;
@@ -162,6 +164,7 @@ public:
     int firstIndex;
     int pathItems;
     int requestedIndex;
+    int cacheSize;
     qreal requestedZ;
     QList<QQuickItem *> items;
     QList<QQuickItem *> itemCache;
diff --git a/src/quick/items/qquickwindow.cpp b/src/quick/items/qquickwindow.cpp
index ca94570a3c..c95a28dac5 100644
--- a/src/quick/items/qquickwindow.cpp
+++ b/src/quick/items/qquickwindow.cpp
@@ -1167,7 +1167,7 @@ bool QQuickWindowPrivate::deliverInitialMousePressEvent(QQuickItem *item, QMouse
     QList<QQuickItem *> children = itemPrivate->paintOrderChildItems();
     for (int ii = children.count() - 1; ii >= 0; --ii) {
         QQuickItem *child = children.at(ii);
-        if (!child->isVisible() || !child->isEnabled())
+        if (!child->isVisible() || !child->isEnabled() || QQuickItemPrivate::get(child)->culled)
             continue;
         if (deliverInitialMousePressEvent(child, event))
             return true;
@@ -1329,7 +1329,7 @@ bool QQuickWindowPrivate::deliverHoverEvent(QQuickItem *item, const QPointF &sce
     QList<QQuickItem *> children = itemPrivate->paintOrderChildItems();
     for (int ii = children.count() - 1; ii >= 0; --ii) {
         QQuickItem *child = children.at(ii);
-        if (!child->isVisible() || !child->isEnabled())
+        if (!child->isVisible() || !child->isEnabled() || QQuickItemPrivate::get(child)->culled)
             continue;
         if (deliverHoverEvent(child, scenePos, lastScenePos, modifiers, accepted))
             return true;
@@ -1395,7 +1395,7 @@ bool QQuickWindowPrivate::deliverWheelEvent(QQuickItem *item, QWheelEvent *event
     QList<QQuickItem *> children = itemPrivate->paintOrderChildItems();
     for (int ii = children.count() - 1; ii >= 0; --ii) {
         QQuickItem *child = children.at(ii);
-        if (!child->isVisible() || !child->isEnabled())
+        if (!child->isVisible() || !child->isEnabled() || QQuickItemPrivate::get(child)->culled)
             continue;
         if (deliverWheelEvent(child, event))
             return true;
@@ -1542,7 +1542,7 @@ bool QQuickWindowPrivate::deliverTouchPoints(QQuickItem *item, QTouchEvent *even
     QList<QQuickItem *> children = itemPrivate->paintOrderChildItems();
     for (int ii = children.count() - 1; ii >= 0; --ii) {
         QQuickItem *child = children.at(ii);
-        if (!child->isEnabled() || !child->isVisible())
+        if (!child->isEnabled() || !child->isVisible() || QQuickItemPrivate::get(child)->culled)
             continue;
         if (deliverTouchPoints(child, event, newPoints, acceptedNewPoints, updatedPoints))
             return true;
@@ -1782,7 +1782,7 @@ bool QQuickWindowPrivate::deliverDragEvent(QQuickDragGrabber *grabber, QQuickIte
     Q_Q(QQuickWindow);
     bool accepted = false;
     QQuickItemPrivate *itemPrivate = QQuickItemPrivate::get(item);
-    if (!item->isVisible() || !item->isEnabled())
+    if (!item->isVisible() || !item->isEnabled() || QQuickItemPrivate::get(item)->culled)
         return false;
 
     QPointF p = item->mapFromScene(event->pos());
@@ -1855,7 +1855,7 @@ QQuickItem *QQuickWindowPrivate::findCursorItem(QQuickItem *item, const QPointF
     QList<QQuickItem *> children = itemPrivate->paintOrderChildItems();
     for (int ii = children.count() - 1; ii >= 0; --ii) {
         QQuickItem *child = children.at(ii);
-        if (!child->isVisible() || !child->isEnabled())
+        if (!child->isVisible() || !child->isEnabled() || QQuickItemPrivate::get(child)->culled)
             continue;
         if (QQuickItem *cursorItem = findCursorItem(child, scenePos))
             return cursorItem;
diff --git a/tests/auto/quick/qquickpathview/data/pathview3.qml b/tests/auto/quick/qquickpathview/data/pathview3.qml
index 53b4df1d15..4687776e0b 100644
--- a/tests/auto/quick/qquickpathview/data/pathview3.qml
+++ b/tests/auto/quick/qquickpathview/data/pathview3.qml
@@ -9,6 +9,10 @@ PathView {
     preferredHighlightBegin: 0.50
     preferredHighlightEnd: 0.50
 
+    function addColor(color) {
+        model.append({"lColor":color})
+    }
+
     path: Path {
         startX: -50; startY: 40;
 
@@ -35,7 +39,6 @@ PathView {
     }
 
     model: ListModel {
-        id: rssModel
         ListElement { lColor: "red" }
         ListElement { lColor: "green" }
         ListElement { lColor: "yellow" }
diff --git a/tests/auto/quick/qquickpathview/tst_qquickpathview.cpp b/tests/auto/quick/qquickpathview/tst_qquickpathview.cpp
index 16545fe815..748df947e9 100644
--- a/tests/auto/quick/qquickpathview/tst_qquickpathview.cpp
+++ b/tests/auto/quick/qquickpathview/tst_qquickpathview.cpp
@@ -139,6 +139,7 @@ private slots:
     void positionViewAtIndex_data();
     void indexAt_itemAt();
     void indexAt_itemAt_data();
+    void cacheItemCount();
 };
 
 class TestObject : public QObject
@@ -2021,6 +2022,85 @@ void tst_QQuickPathView::indexAt_itemAt_data()
     QTest::newRow("Item 7 - 360, 200") << 360. << 200. << 7;
 }
 
+void tst_QQuickPathView::cacheItemCount()
+{
+    QQuickView *window = createView();
+
+    window->setSource(testFileUrl("pathview3.qml"));
+    window->show();
+    qApp->processEvents();
+
+    QQuickPathView *pathview = qobject_cast<QQuickPathView*>(window->rootObject());
+    QVERIFY(pathview != 0);
+
+    QMetaObject::invokeMethod(pathview, "addColor", Q_ARG(QVariant, QString("orange")));
+    QMetaObject::invokeMethod(pathview, "addColor", Q_ARG(QVariant, QString("lightsteelblue")));
+    QMetaObject::invokeMethod(pathview, "addColor", Q_ARG(QVariant, QString("teal")));
+    QMetaObject::invokeMethod(pathview, "addColor", Q_ARG(QVariant, QString("aqua")));
+
+    pathview->setOffset(0);
+
+    pathview->setCacheItemCount(3);
+    QVERIFY(pathview->cacheItemCount() == 3);
+
+    QQmlIncubationController controller;
+    window->engine()->setIncubationController(&controller);
+
+    // Items on the path are created immediately
+    QVERIFY(findItem<QQuickItem>(pathview, "wrapper", 0));
+    QVERIFY(findItem<QQuickItem>(pathview, "wrapper", 1));
+    QVERIFY(findItem<QQuickItem>(pathview, "wrapper", 11));
+    QVERIFY(findItem<QQuickItem>(pathview, "wrapper", 10));
+
+    const int cached[] = { 2, 3, 9, -1 }; // two appended, one prepended
+
+    int i = 0;
+    while (cached[i] >= 0) {
+        // items will be created one at a time
+        QVERIFY(findItem<QQuickItem>(pathview, "wrapper", cached[i]) == 0);
+        QQuickItem *item = 0;
+        while (!item) {
+            bool b = false;
+            controller.incubateWhile(&b);
+            item = findItem<QQuickItem>(pathview, "wrapper", cached[i]);
+        }
+        ++i;
+    }
+
+    {
+        bool b = true;
+        controller.incubateWhile(&b);
+    }
+
+    // move view and confirm items in view are visible immediately and outside are created async
+    pathview->setOffset(4);
+
+    // Items on the path are created immediately
+    QVERIFY(findItem<QQuickItem>(pathview, "wrapper", 6));
+    QVERIFY(findItem<QQuickItem>(pathview, "wrapper", 7));
+    QVERIFY(findItem<QQuickItem>(pathview, "wrapper", 8));
+    QVERIFY(findItem<QQuickItem>(pathview, "wrapper", 9));
+    // already created items within cache stay created
+    QVERIFY(findItem<QQuickItem>(pathview, "wrapper", 10));
+    QVERIFY(findItem<QQuickItem>(pathview, "wrapper", 11));
+
+    // one item prepended async.
+    QVERIFY(findItem<QQuickItem>(pathview, "wrapper", 5) == 0);
+    QQuickItem *item = 0;
+    while (!item) {
+        bool b = false;
+        controller.incubateWhile(&b);
+        item = findItem<QQuickItem>(pathview, "wrapper", 5);
+    }
+
+    {
+        bool b = true;
+        controller.incubateWhile(&b);
+    }
+
+    delete window;
+}
+
 QTEST_MAIN(tst_QQuickPathView)
 
 #include "tst_qquickpathview.moc"