Use a creator with recycled items memory for the flowview

1 files changed, 37 insertions, 7 deletions

diff --git a/src/experimental/qgraphicsflowview.cpp b/src/experimental/qgraphicsflowview.cpp
index 56da1f8..928b3da 100644
--- a/src/experimental/qgraphicsflowview.cpp
+++ b/src/experimental/qgraphicsflowview.cpp
@@ -53,6 +53,15 @@ private:
     Q_DECLARE_PRIVATE(QtGraphicsListViewItem)
 };
 
+class QtGraphicsFlowViewItemCreator : public QtGraphicsListViewItemCreatorBase
+{
+public:
+    virtual QtGraphicsListViewItem *create(int index, QtGraphicsListView *view);
+    virtual void recycle(QtGraphicsListViewItem *item);
+
+private:
+    QList<QtGraphicsListViewItem*> m_recycledItems;
+};
 
 QtGraphicsFlowViewPrivate::QtGraphicsFlowViewPrivate()
     : itemSize(80, 60)
@@ -108,6 +117,23 @@ QtGraphicsFlowViewItem::QtGraphicsFlowViewItem(int index, QtGraphicsListView *la
     setCacheMode(DeviceCoordinateCache);
 }
 
+QtGraphicsListViewItem *QtGraphicsFlowViewItemCreator::create(int index, QtGraphicsListView *view)
+{
+    QtGraphicsListViewItem *item;
+    if (m_recycledItems.isEmpty()) {
+        item = new QtGraphicsFlowViewItem(index, view);
+    } else {
+        item = m_recycledItems.takeLast();
+        item->setIndex(index);
+    }
+    return item;
+}
+
+void QtGraphicsFlowViewItemCreator::recycle(QtGraphicsListViewItem *item)
+{
+    m_recycledItems.append(item);
+}
+
 
 /*!
   \class QtGraphicsFlowView
@@ -181,14 +207,16 @@ void QtGraphicsFlowView::doLayout()
     const int amountNeeded = qMin(d->model->count() - d->firstIndex, visibleRows * itemsPerRow);
 
     if (!d->items.isEmpty()) {
-        // reuse old items by moving them around. Starting from firstIndex, ending at firstIndex + amountNeeded
+        // reuse old items by moving them around. Working hard to make them keep their index.
+        // Starting from firstIndex, ending at firstIndex + amountNeeded
         const int index = d->firstIndex;
         while (d->items.first()->index() < index) { // scrolling down
             QtGraphicsListViewItem *item = d->items.takeFirst();
             item->setIndex(d->items.last()->index() + 1);
             d->items.append(item);
         }
-        while (d->items.last()->index() > index + d->items.count()) { // scrolling up
+        const int lastIndex = index + d->items.count();
+        while (d->items.last()->index() > lastIndex) { // scrolling up
             QtGraphicsListViewItem *item = d->items.takeLast();
             item->setIndex(d->items.first()->index() - 1);
             d->items.prepend(item);
@@ -196,17 +224,19 @@ void QtGraphicsFlowView::doLayout()
     }
 
     while (amountNeeded < d->items.count()) // remove old ones
-        delete d->items.takeLast();
+        d->creator->recycle(d->items.takeLast());
+    while (amountNeeded > d->items.count() && (d->items.isEmpty() || d->items.first()->index() > d->firstIndex))
+            d->items.prepend(d->creator->create(d->firstIndex, this));
     qreal x = 0;
     qreal y = 0;
     for (int index = d->firstIndex; index < d->firstIndex + amountNeeded; ++index) {
         QtGraphicsListViewItem *item = 0;
-        const int itemIndex = index - d->firstIndex;
-        if (itemIndex >= d->items.count()) {
-            item = new QtGraphicsFlowViewItem(index, this);
+        const int indexInItems = index - d->firstIndex;
+        if (indexInItems >= d->items.count()) {
+            item = d->creator->create(index, this);
             d->items.append(item);
         } else {
-            item = d->items.at(itemIndex);
+            item = d->items.at(indexInItems);
         }
         item->setGeometry(x, y, d->itemSize.width(), d->itemSize.height());
         x += d->itemSize.width();