Insertions were calculating wrong insertion pos

After removes, and after each insertion, the view must adjust the
visibleItems.first() position and call layoutVisibleItems() to ensure
that the correct insertion position is calculated for insertions that
follow.

When applyInsertionChange() in GridView and ListView calculates the
position for item insertion, it looks at the current positions of the
items in visibleItems, so these positions must be updated prior to
this calculation. Otherwise, insertions that follow a remove may not
calculate this position correctly and will neglect to add some items,
and multiple insertions may unnecessarily create items at positions that
are not actually visible.

resetFirstItemPosition() is changed to take a set position and it
replaces resetItemPosition() since it can do the same thing.

Task-number: QTBUG-23610 QTBUG-23609

Change-Id: I8839ee7d15853301435e80c0dc563f93fc3605cf
Reviewed-by: Martin Jones <martin.jones@nokia.com>

1 files changed, 13 insertions, 19 deletions

diff --git a/src/quick/items/qquicklistview.cpp b/src/quick/items/qquicklistview.cpp
index e2c428838b..f0ced5fc71 100644
--- a/src/quick/items/qquicklistview.cpp
+++ b/src/quick/items/qquicklistview.cpp
@@ -93,8 +93,7 @@ public:
     virtual void initializeViewItem(FxViewItem *item);
     virtual void releaseItem(FxViewItem *item);
     virtual void repositionPackageItemAt(QQuickItem *item, int index);
-    virtual void resetItemPosition(FxViewItem *item, FxViewItem *toItem);
-    virtual void resetFirstItemPosition();
+    virtual void resetFirstItemPosition(qreal pos = 0.0);
     virtual void adjustFirstItem(qreal forwards, qreal backwards);
 
     virtual void createHighlight();
@@ -102,8 +101,8 @@ public:
     virtual void resetHighlightPosition();
 
     virtual void setPosition(qreal pos);
-    virtual void layoutVisibleItems();
-    virtual bool applyInsertionChange(const QDeclarativeChangeSet::Insert &insert, ChangeResult *changeResult, bool *newVisibleItemsFirst, QList<FxViewItem *> *addedItems);
+    virtual void layoutVisibleItems(int fromModelIndex = 0);
+    virtual bool applyInsertionChange(const QDeclarativeChangeSet::Insert &insert, ChangeResult *changeResult, QList<FxViewItem *> *addedItems);
 
     virtual void updateSections();
     QQuickItem *getSectionItem(const QString &section);
@@ -689,7 +688,7 @@ void QQuickListViewPrivate::visibleItemsChanged()
     updateUnrequestedPositions();
 }
 
-void QQuickListViewPrivate::layoutVisibleItems()
+void QQuickListViewPrivate::layoutVisibleItems(int fromModelIndex)
 {
     if (!visibleItems.isEmpty()) {
         const qreal from = isContentFlowReversed() ? -position() - size() : position();
@@ -702,8 +701,10 @@ void QQuickListViewPrivate::layoutVisibleItems()
         firstItem->item->setVisible(firstItem->endPosition() >= from && firstItem->position() <= to);
         for (int i=1; i < visibleItems.count(); ++i) {
             FxListItemSG *item = static_cast<FxListItemSG*>(visibleItems.at(i));
-            item->setPosition(pos);
-            item->item->setVisible(item->endPosition() >= from && item->position() <= to);
+            if (item->index >= fromModelIndex) {
+                item->setPosition(pos);
+                item->item->setVisible(item->endPosition() >= from && item->position() <= to);
+            }
             pos += item->size() + spacing;
             sum += item->size();
             fixedCurrent = fixedCurrent || (currentItem && item->item == currentItem->item);
@@ -734,17 +735,10 @@ void QQuickListViewPrivate::repositionPackageItemAt(QQuickItem *item, int index)
     }
 }
 
-void QQuickListViewPrivate::resetItemPosition(FxViewItem *item, FxViewItem *toItem)
-{
-    if (item == toItem)
-        return;
-    static_cast<FxListItemSG*>(item)->setPosition(toItem->position());
-}
-
-void QQuickListViewPrivate::resetFirstItemPosition()
+void QQuickListViewPrivate::resetFirstItemPosition(qreal pos)
 {
     FxListItemSG *item = static_cast<FxListItemSG*>(visibleItems.first());
-    item->setPosition(0);
+    item->setPosition(pos);
 }
 
 void QQuickListViewPrivate::adjustFirstItem(qreal forwards, qreal backwards)
@@ -2376,7 +2370,7 @@ void QQuickListView::updateSections()
     }
 }
 
-bool QQuickListViewPrivate::applyInsertionChange(const QDeclarativeChangeSet::Insert &change, ChangeResult *insertResult, bool *newVisibleItemsFirst, QList<FxViewItem *> *addedItems)
+bool QQuickListViewPrivate::applyInsertionChange(const QDeclarativeChangeSet::Insert &change, ChangeResult *insertResult, QList<FxViewItem *> *addedItems)
 {
     int modelIndex = change.index;
     int count = change.count;
@@ -2440,7 +2434,7 @@ bool QQuickListViewPrivate::applyInsertionChange(const QDeclarativeChangeSet::In
 
                 visibleItems.insert(insertionIdx, item);
                 if (insertionIdx == 0)
-                    *newVisibleItemsFirst = true;
+                    insertResult->changedFirstItem = true;
                 if (!change.isMove())
                     addedItems->append(item);
                 insertResult->sizeChangesBeforeVisiblePos += item->size() + spacing;
@@ -2462,7 +2456,7 @@ bool QQuickListViewPrivate::applyInsertionChange(const QDeclarativeChangeSet::In
 
             visibleItems.insert(index, item);
             if (index == 0)
-                *newVisibleItemsFirst = true;
+                insertResult->changedFirstItem = true;
             if (!change.isMove())
                 addedItems->append(item);
             insertResult->sizeChangesAfterVisiblePos += item->size() + spacing;