Fix section delegates not updating when changed.

Delete all allocated section items before doing an update when the
section delegate is changed.

Task-number: QTBUG-24899
Change-Id: I09dc7a1c602a49ad7bb37512a7e5116392259457
Reviewed-by: Martin Jones <martin.jones@nokia.com>

2 files changed, 102 insertions, 0 deletions

diff --git a/tests/auto/quick/qquicklistview/data/sectiondelegatechange.qml b/tests/auto/quick/qquicklistview/data/sectiondelegatechange.qml
new file mode 100644
index 0000000000..eee15ed2e0
--- /dev/null
+++ b/tests/auto/quick/qquicklistview/data/sectiondelegatechange.qml
@@ -0,0 +1,61 @@
+import QtQuick 2.0
+
+ListView {
+    width: 240
+    height: 320
+
+    function switchDelegates() {
+        section.delegate = section.delegate === delegate1
+                ? delegate2
+                : delegate1
+    }
+
+    Component {
+        id: delegate1
+
+        Rectangle {
+            objectName: "section1"
+            color: "lightsteelblue"
+            border.width: 1;
+            width: 240
+            height: 25
+
+            Text {
+                anchors.centerIn: parent
+                text: section
+            }
+        }
+    }
+    Component {
+        id: delegate2
+
+        Rectangle {
+            objectName: "section2"
+            color: "yellow"
+            border.width: 1;
+            width: 240
+            height: 50
+
+            Text {
+                anchors.centerIn: parent
+                text: section
+            }
+        }
+    }
+
+    section.property: "modelData"
+    section.delegate: delegate1
+
+    model: 20
+    delegate: Rectangle {
+        objectName: "item"
+        border.width: 1
+        width: 240
+        height: 25
+
+        Text {
+            anchors.centerIn: parent
+            text: modelData
+        }
+    }
+}
diff --git a/tests/auto/quick/qquicklistview/tst_qquicklistview.cpp b/tests/auto/quick/qquicklistview/tst_qquicklistview.cpp
index c6a72306f9..848ffb10ff 100644
--- a/tests/auto/quick/qquicklistview/tst_qquicklistview.cpp
+++ b/tests/auto/quick/qquicklistview/tst_qquicklistview.cpp
@@ -146,6 +146,7 @@ private slots:
     void sectionsDragOutsideBounds();
     void sectionsDelegate_headerVisibility();
     void sectionPropertyChange();
+    void sectionDelegateChange();
     void cacheBuffer();
     void positionViewAtIndex();
     void resetModel();
@@ -2431,6 +2432,46 @@ void tst_QQuickListView::sectionPropertyChange()
     delete canvas;
 }
 
+void tst_QQuickListView::sectionDelegateChange()
+{
+    QQuickView *canvas = createView();
+
+    canvas->setSource(testFileUrl("sectiondelegatechange.qml"));
+    canvas->show();
+    qApp->processEvents();
+
+    QQuickListView *listview = qobject_cast<QQuickListView *>(canvas->rootObject());
+    QVERIFY(listview != 0);
+
+    QQuickItem *contentItem = listview->contentItem();
+    QVERIFY(contentItem != 0);
+
+    QQUICK_VERIFY_POLISH(listview);
+
+    QVERIFY(findItems<QQuickItem>(contentItem, "section1").count() > 0);
+    QCOMPARE(findItems<QQuickItem>(contentItem, "section2").count(), 0);
+
+    for (int i = 0; i < 3; ++i) {
+        QQuickItem *item = findItem<QQuickItem>(contentItem, "item", i);
+        QTRY_VERIFY(item);
+        QTRY_COMPARE(item->y(), qreal(25. + i*50.));
+    }
+
+    QMetaObject::invokeMethod(canvas->rootObject(), "switchDelegates");
+    QQUICK_VERIFY_POLISH(listview);
+
+    QCOMPARE(findItems<QQuickItem>(contentItem, "section1").count(), 0);
+    QVERIFY(findItems<QQuickItem>(contentItem, "section2").count() > 0);
+
+    for (int i = 0; i < 3; ++i) {
+        QQuickItem *item = findItem<QQuickItem>(contentItem, "item", i);
+        QVERIFY(item);
+        QTRY_COMPARE(item->y(), qreal(50. + i*75.));
+    }
+
+    delete canvas;
+}
+
 void tst_QQuickListView::currentIndex_delayedItemCreation()
 {
     QFETCH(bool, setCurrentToZero);