ListView: don't stop moving the highlight because of model updates

In QQuickItemViewPrivate::applyModelChanges(), if
moveReason = QQuickItemViewPrivate::Other,
then QQuickItemView::trackedPositionChanged() will fail to call
d->setPosition(pos), which is normally what keeps the Flickable
moving for a while.  Leave the reason as-is (it will be SetIndex in
this case), so as not to forget that we were actually trying to move
down.  Updating the model was just a side-effect of that: either
because some QML code was trying to append to the model or because
fetchMore() was called.

Task-number: QTBUG-61269
Task-number: QTBUG-62864
Change-Id: I3fd402469950d6c12e6a8d6e42be83ea4f54776a
Reviewed-by: J-P Nurmi <jpnurmi@qt.io>

3 files changed, 60 insertions, 1 deletions

diff --git a/src/quick/items/qquickitemview.cpp b/src/quick/items/qquickitemview.cpp
index 9038f7cde4..8f3fe9f0f2 100644
--- a/src/quick/items/qquickitemview.cpp
+++ b/src/quick/items/qquickitemview.cpp
@@ -1979,7 +1979,6 @@ bool QQuickItemViewPrivate::applyModelChanges(ChangeResult *totalInsertionResult
     }
 
     updateUnrequestedIndexes();
-    moveReason = QQuickItemViewPrivate::Other;
 
     FxViewItem *prevVisibleItemsFirst = visibleItems.count() ? *visibleItems.constBegin() : 0;
     int prevItemCount = itemCount;
diff --git a/tests/auto/quick/qquicklistview/data/appendDuringScrollDown.qml b/tests/auto/quick/qquicklistview/data/appendDuringScrollDown.qml
new file mode 100644
index 0000000000..af35c29143
--- /dev/null
+++ b/tests/auto/quick/qquicklistview/data/appendDuringScrollDown.qml
@@ -0,0 +1,28 @@
+import QtQuick 2.6
+
+ListView {
+    width: 320; height: 240
+    focus: true
+    delegate: Text {
+        height: 40; width: parent.width
+        text: model.text
+        verticalAlignment: Text.AlignVCenter
+        horizontalAlignment: Text.AlignHCenter
+    }
+    highlight: Rectangle { color: "red" }
+    model: ListModel {
+        ListElement { text: "0" }
+        ListElement { text: "1" }
+        ListElement { text: "2" }
+        ListElement { text: "3" }
+        ListElement { text: "4" }
+        ListElement { text: "5" }
+        ListElement { text: "6" }
+        ListElement { text: "7" }
+        ListElement { text: "8" }
+        ListElement { text: "9" }
+    }
+
+    readonly property Item topItem: itemAt(0, contentY)
+    onTopItemChanged: model.append({ "text": "new" })
+}
diff --git a/tests/auto/quick/qquicklistview/tst_qquicklistview.cpp b/tests/auto/quick/qquicklistview/tst_qquicklistview.cpp
index 0d0f234d33..2e9c54c5a3 100644
--- a/tests/auto/quick/qquicklistview/tst_qquicklistview.cpp
+++ b/tests/auto/quick/qquicklistview/tst_qquicklistview.cpp
@@ -254,6 +254,7 @@ private slots:
 
     void QTBUG_50105();
     void keyNavigationEnabled();
+    void QTBUG_61269_appendDuringScrollDown();
     void QTBUG_50097_stickyHeader_positionViewAtIndex();
     void itemFiltered();
     void releaseItems();
@@ -8468,6 +8469,37 @@ void tst_QQuickListView::keyNavigationEnabled()
     QCOMPARE(listView->currentIndex(), 1);
 }
 
+void tst_QQuickListView::QTBUG_61269_appendDuringScrollDown()
+{
+    QScopedPointer<QQuickView> window(createView());
+    window->setSource(testFileUrl("appendDuringScrollDown.qml"));
+    window->show();
+    window->requestActivate();
+    QVERIFY(QTest::qWaitForWindowActive(window.data()));
+
+    QQuickListView *listView = qobject_cast<QQuickListView *>(window->rootObject());
+    QQuickItem *highlightItem = listView->highlightItem();
+    QVERIFY(listView);
+    QCOMPARE(listView->isKeyNavigationEnabled(), true);
+    listView->setHighlightMoveVelocity(400);
+    listView->setHighlightMoveDuration(-1); // let it animate
+    listView->setFocus(true);
+    QVERIFY(listView->hasActiveFocus());
+    qreal highlightYLimit = listView->height() - highlightItem->height(); // should be 200
+
+    for (int i = 1; i < 15; ++i) {
+        QTest::keyClick(window.data(), Qt::Key_Down);
+
+        // Wait for the highlight movement animation to finish.
+        QTRY_COMPARE(highlightItem->y(), 40.0 * i);
+
+        // As we scroll down, the QML will append rows to its own model.
+        // Make sure the highlighted row and highlight item stay within the view.
+        // In QTBUG-62864 and QTBUG-61269, it would go off the bottom.
+        QVERIFY(highlightItem->y() - listView->contentY() <= highlightYLimit);
+    }
+}
+
 void tst_QQuickListView::QTBUG_48870_fastModelUpdates()
 {
     StressTestModel model;