QQuickListView: implement support for reusing items

This patch will implement delegate item recycling in
ListView. The API will be the same as used in TableView, except
that it will be off by default since the behavior of a delegate
that is reused is not compatible with legacy applications
which were not written with this in mind.

Most importantly:

- Component.onCompleted will only be called on a delegate the
first time it's created, and never when it's reused.

- Any user-declared properties in the delegate (that is, not
model roles, index, etc) will not be cleared or updated when an
item is reused. The application must do this manually upon
receiving the pooled or reused signal in the item.

[ChangeLog][ListView] ListView now has support for reusing delegate
items. This can be switched on by setting the reuseItems property of
ListView to true.

Task-number: QTBUG-80507
Change-Id: I68cc8300b050e4a1f89feebb1d31a2fd9189c793
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

1 files changed, 2 insertions, 2 deletions

diff --git a/src/quick/items/qquickgridview.cpp b/src/quick/items/qquickgridview.cpp
index e69e9cff46..5f6c194bcf 100644
--- a/src/quick/items/qquickgridview.cpp
+++ b/src/quick/items/qquickgridview.cpp
@@ -497,7 +497,7 @@ bool QQuickGridViewPrivate::addVisibleItems(qreal fillFrom, qreal fillTo, qreal
         // We've jumped more than a page.  Estimate which items are now
         // visible and fill from there.
         int count = (fillFrom - (rowPos + rowSize())) / (rowSize()) * columns;
-        releaseVisibleItems();
+        releaseVisibleItems(reusableFlag);
         modelIndex += count;
         if (modelIndex >= model->count())
             modelIndex = model->count() - 1;
@@ -576,7 +576,7 @@ void QQuickGridViewPrivate::removeItem(FxViewItem *item)
         item->releaseAfterTransition = true;
         releasePendingTransition.append(item);
     } else {
-        releaseItem(item);
+        releaseItem(item, QQmlDelegateModel::NotReusable);
     }
 }