QQmlDelegateModel: Use cache item's index for resolving delegates

The raw index doesn't take the filter group into account.

Fixes: QTBUG-78297
Change-Id: Ie6514c8acdc380fe3f8f267d02335afc357abd17
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>
Reviewed-by: Joshua GPBeta <studiocghibli@gmail.com>

3 files changed, 92 insertions, 1 deletions

diff --git a/src/qmlmodels/qqmldelegatemodel.cpp b/src/qmlmodels/qqmldelegatemodel.cpp
index 24632fe16b..d5b30df45b 100644
--- a/src/qmlmodels/qqmldelegatemodel.cpp
+++ b/src/qmlmodels/qqmldelegatemodel.cpp
@@ -1038,7 +1038,7 @@ QObject *QQmlDelegateModelPrivate::object(Compositor::Group group, int index, QQ
         if (m_delegateChooser) {
             QQmlAbstractDelegateComponent *chooser = m_delegateChooser;
             do {
-                delegate = chooser->delegate(&m_adaptorModel, index);
+                delegate = chooser->delegate(&m_adaptorModel, cacheItem->index);
                 chooser = qobject_cast<QQmlAbstractDelegateComponent *>(delegate);
             } while (chooser);
             if (!delegate)
diff --git a/tests/auto/quick/qquickvisualdatamodel/data/filterGroupForDelegate.qml b/tests/auto/quick/qquickvisualdatamodel/data/filterGroupForDelegate.qml
new file mode 100644
index 0000000000..d72ca51d7f
--- /dev/null
+++ b/tests/auto/quick/qquickvisualdatamodel/data/filterGroupForDelegate.qml
@@ -0,0 +1,77 @@
+import QtQml.Models 2.12
+import Qt.labs.qmlmodels 1.0
+import QtQuick 2.12
+
+Item {
+    id: root
+    width: 200
+    height: 320
+
+    property int numChanges: 0
+    property bool ok: true
+
+    DelegateModel {
+        id: theModel
+
+        model: ListModel {
+            ListElement { role: "section" }
+            ListElement { role: "item" }
+            ListElement { role: "section" }
+            ListElement { role: "item" }
+            ListElement { role: "section" }
+            ListElement { role: "item" }
+            ListElement { role: "item" }
+            ListElement { role: "item" }
+        }
+
+        filterOnGroup: "expanded"
+        groups: DelegateModelGroup {
+            name: "expanded"
+        }
+
+        delegate: DelegateChooser {
+            role: "role"
+
+            DelegateChoice {
+                roleValue: "section"
+                Text {
+                    text: "+ Section " + index
+
+                    Timer {
+                        interval: (index + 10)
+                        repeat: true
+                        running: true
+                        onTriggered: {
+                            ++ root.numChanges;
+                            if (model.role !== "section") {
+                                root.ok = false;
+                                console.warn("wrong!", root.numChanges);
+                            }
+                            let i = parent.DelegateModel.itemsIndex + 1;
+                            for (; i < theModel.items.count; ++i) {
+                                let item = theModel.items.get(i);
+                                if (item.model.role === "section")
+                                    break;
+                                item.inExpanded = !item.inExpanded;
+                            }
+                        }
+                    }
+                }
+            }
+
+            DelegateChoice {
+                roleValue: "item"
+                Text {
+                    text: "Item " + index
+                }
+            }
+        }
+
+        Component.onCompleted: items.addGroups(0, items.count, ["expanded"])
+    }
+
+    ListView {
+        anchors.fill: parent
+        model: theModel
+    }
+}
diff --git a/tests/auto/quick/qquickvisualdatamodel/tst_qquickvisualdatamodel.cpp b/tests/auto/quick/qquickvisualdatamodel/tst_qquickvisualdatamodel.cpp
index fe56cad018..c5a3bceee0 100644
--- a/tests/auto/quick/qquickvisualdatamodel/tst_qquickvisualdatamodel.cpp
+++ b/tests/auto/quick/qquickvisualdatamodel/tst_qquickvisualdatamodel.cpp
@@ -433,6 +433,7 @@ private slots:
     void invalidContext();
     void externalManagedModel();
     void delegateModelChangeDelegate();
+    void checkFilterGroupForDelegate();
 
 private:
     template <int N> void groups_verify(
@@ -4342,6 +4343,19 @@ void tst_qquickvisualdatamodel::delegateModelChangeDelegate()
     QCOMPARE(visualModel->count(), 3);
 }
 
+void tst_qquickvisualdatamodel::checkFilterGroupForDelegate()
+{
+    QQuickView view;
+    view.setSource(testFileUrl("filterGroupForDelegate.qml"));
+    view.show();
+
+    QQuickItem *obj = view.rootObject();
+    QVERIFY(obj);
+
+    QTRY_VERIFY(obj->property("numChanges").toInt() > 100);
+    QVERIFY(obj->property("ok").toBool());
+}
+
 QTEST_MAIN(tst_qquickvisualdatamodel)
 
 #include "tst_qquickvisualdatamodel.moc"