[qtquick] Correctly initialize ListView section attached properties. …

…Fixes JB#29647

During item insertion, indexes of items in the visibleItems list were
not adjusted before new items were created. Section initialization was
broken during insertion because section calculation relies on the
indexes of the items in the visibleItems list. The incorrect section
properties caused spurious section header creation, and layout issues.

Apply the index offset before creating the new items. This mirrors what
GridView already does.

src/quick/items/qquicklistview.cpp

@@ -1163,9 +1163,11 @@ void QQuickListViewPrivate::updateSections()
         if (visibleIndex > 0)
             prevSection = sectionAt(visibleIndex-1);
         QQuickListViewAttached *prevAtt = 0;
+        int prevIdx = -1;
         int idx = -1;
         for (int i = 0; i < visibleItems.count(); ++i) {
-            QQuickListViewAttached *attached = static_cast<QQuickListViewAttached*>(visibleItems.at(i)->attached);
+            FxViewItem *item = visibleItems.at(i);
+            QQuickListViewAttached *attached = static_cast<QQuickListViewAttached*>(item->attached);
             attached->setPrevSection(prevSection);
             if (visibleItems.at(i)->index != -1) {
                 QString propValue = model->stringValue(visibleItems.at(i)->index, sectionCriteria->property());
@@ -1174,9 +1176,10 @@ void QQuickListViewPrivate::updateSections()
             }
             updateInlineSection(static_cast<FxListItemSG*>(visibleItems.at(i)));
             if (prevAtt)
-                prevAtt->setNextSection(attached->section());
+                prevAtt->setNextSection(sectionAt(prevIdx+1));
             prevSection = attached->section();
             prevAtt = attached;
+            prevIdx = item->index;
         }
         if (prevAtt) {
             if (idx > 0 && idx < model->count()-1)
@@ -2969,6 +2972,18 @@ bool QQuickListViewPrivate::applyInsertionChange(const QQmlChangeSet::Insert &ch
                                                 : visibleItems.last()->endPosition()+spacing;
     }
 
+    // Update the indexes of the following visible items.
+    for (int i = 0; i < visibleItems.count(); ++i) {
+        FxViewItem *item = visibleItems.at(i);
+        if (item->index != -1 && item->index >= modelIndex) {
+            item->index += count;
+            if (change.isMove())
+                item->transitionNextReposition(transitioner, QQuickItemViewTransitioner::MoveTransition, false);
+            else
+                item->transitionNextReposition(transitioner, QQuickItemViewTransitioner::AddTransition, false);
+        }
+    }
+
     int prevVisibleCount = visibleItems.count();
     if (insertResult->visiblePos.isValid() && pos < insertResult->visiblePos) {
         // Insert items before the visible item.
@@ -3034,17 +3049,6 @@ bool QQuickListViewPrivate::applyInsertionChange(const QQmlChangeSet::Insert &ch
         }
     }
 
-    for (; index < visibleItems.count(); ++index) {
-        FxViewItem *item = visibleItems.at(index);
-        if (item->index != -1) {
-            item->index += count;
-            if (change.isMove())
-                item->transitionNextReposition(transitioner, QQuickItemViewTransitioner::MoveTransition, false);
-            else
-                item->transitionNextReposition(transitioner, QQuickItemViewTransitioner::AddTransition, false);
-        }
-    }
-
     updateVisibleIndex();
 
     return visibleItems.count() > prevVisibleCount;

tests/auto/quick/qquicklistview/data/listview-sections_delegate.qml

@@ -12,6 +12,9 @@ Rectangle {
             Item {
                 id: wrapper
                 objectName: "wrapper"
+                property string section: ListView.section
+                property string nextSection: ListView.nextSection
+                property string prevSection: ListView.previousSection
                 height: 20;
                 width: 240
                 Rectangle {

tests/auto/quick/qquicklistview/tst_qquicklistview.cpp

@@ -142,6 +142,7 @@ private slots:
     void sectionsDelegate_headerVisibility();
     void sectionPropertyChange();
     void sectionDelegateChange();
+    void sectionsItemInsertion();
     void cacheBuffer();
     void positionViewAtBeginningEnd();
     void positionViewAtIndex();
@@ -2533,6 +2534,67 @@ void tst_QQuickListView::sectionDelegateChange()
     delete window;
 }
 
+// QTBUG-43873
+void tst_QQuickListView::sectionsItemInsertion()
+{
+    QQuickView *window = createView();
+
+    QaimModel model;
+    for (int i = 0; i < 30; i++)
+        model.addItem("Item" + QString::number(i), QString::number(i/5));
+
+    QQmlContext *ctxt = window->rootContext();
+    ctxt->setContextProperty("testModel", &model);
+
+    window->setSource(testFileUrl("listview-sections_delegate.qml"));
+    window->show();
+    QVERIFY(QTest::qWaitForWindowExposed(window));
+
+    QQuickListView *listview = findItem<QQuickListView>(window->rootObject(), "list");
+    QTRY_VERIFY(listview != 0);
+    QQuickItem *contentItem = listview->contentItem();
+    QTRY_VERIFY(contentItem != 0);
+    QTRY_COMPARE(QQuickItemPrivate::get(listview)->polishScheduled, false);
+
+    for (int i = 0; i < 3; ++i) {
+        QQuickItem *item = findItem<QQuickItem>(contentItem, "sect_" + QString::number(i));
+        QVERIFY(item);
+        QTRY_COMPARE(item->y(), qreal(i*20*6));
+    }
+
+    QQuickItem *topItem = findVisibleChild(contentItem, "sect_0"); // section header
+    QVERIFY(topItem);
+    QCOMPARE(topItem->y(), 0.);
+
+    // Insert a full screen of items at the beginning.
+    for (int i = 0; i < 10; i++)
+        model.insertItem(i, "Item" + QString::number(i), QLatin1String("A"));
+
+    QTRY_COMPARE(QQuickItemPrivate::get(listview)->polishScheduled, false);
+
+    int itemCount = findItems<QQuickItem>(contentItem, "wrapper").count();
+    QVERIFY(itemCount > 10);
+
+    // Verify that the new items are postioned correctly, and have the correct attached section properties
+    for (int i = 0; i < 10 && i < itemCount; ++i) {
+        QQuickItem *item = findItem<QQuickItem>(contentItem, "wrapper", i);
+        QVERIFY(item);
+        QTRY_COMPARE(item->y(), 20+i*20.0);
+        QCOMPARE(item->property("section").toString(), QLatin1String("A"));
+        QCOMPARE(item->property("nextSection").toString(), i < 9 ? QLatin1String("A") : QLatin1String("0"));
+        QCOMPARE(item->property("prevSection").toString(), i > 0 ? QLatin1String("A") : QLatin1String(""));
+    }
+    // Verify that the exiting items are postioned correctly, and have the correct attached section properties
+    for (int i = 10; i < 15 && i < itemCount; ++i) {
+        QQuickItem *item = findItem<QQuickItem>(contentItem, "wrapper", i);
+        QVERIFY(item);
+        QTRY_COMPARE(item->y(), 40+i*20.0);
+        QCOMPARE(item->property("section").toString(), QLatin1String("0"));
+        QCOMPARE(item->property("nextSection").toString(), i < 14 ? QLatin1String("0") : QLatin1String("1"));
+        QCOMPARE(item->property("prevSection").toString(), i > 10 ? QLatin1String("0") : QLatin1String("A"));
+    }
+}
+
 void tst_QQuickListView::currentIndex_delayedItemCreation()
 {
     QFETCH(bool, setCurrentToZero);