GridView: Sanitize visible items after model insertion

This is basically the same patch as 35d8d060b8621cfd, but this
time for GridView instead of ListView.

The major difference is that GridView seems to do the right thing
when the model insertions happen after the visible index. That
explains the missing part of the patch in applyInsertionChange()
as compared to the same function in QQuickListView.

Also, QQuickGridView auto-tests are a bit more robust than their
ListView counterpart. So no changes were necessary to existing
test cases.

Task-number: QTBUG-48870
Change-Id: I19b24c4d84a1a4cef4fdb3ddd3381d0c6b93a76a
Reviewed-by: Robin Burchell <robin.burchell@viroteck.net>

2 files changed, 68 insertions, 0 deletions

diff --git a/tests/auto/quick/qquickgridview/data/qtbug48870.qml b/tests/auto/quick/qquickgridview/data/qtbug48870.qml
new file mode 100644
index 0000000000..7c0783fbb5
--- /dev/null
+++ b/tests/auto/quick/qquickgridview/data/qtbug48870.qml
@@ -0,0 +1,30 @@
+import QtQuick 2.6
+
+Rectangle {
+    width: 500
+    height: 500
+    color: "blue"
+
+    GridView {
+        id: view
+        objectName: "view"
+        anchors.fill: parent
+        model: testModel
+        cellWidth: 150
+        cellHeight: 150
+        readonly property int columns: Math.floor(width / cellWidth)
+
+        delegate: Rectangle {
+            width: GridView.view.cellWidth
+            height: GridView.view.cellHeight
+            color: (row & 1) != (col & 1) ? "green" : "red"
+            readonly property int row: index / view.columns
+            readonly property int col: index % view.columns
+
+            Text {
+                anchors.centerIn: parent
+                text: "Item " + index
+            }
+        }
+    }
+}
diff --git a/tests/auto/quick/qquickgridview/tst_qquickgridview.cpp b/tests/auto/quick/qquickgridview/tst_qquickgridview.cpp
index 3699bef56d..4edfb0ed3b 100644
--- a/tests/auto/quick/qquickgridview/tst_qquickgridview.cpp
+++ b/tests/auto/quick/qquickgridview/tst_qquickgridview.cpp
@@ -41,6 +41,7 @@
 #include <QtQml/qqmlincubator.h>
 #include <QtQml/qqmlcontext.h>
 #include <QtQuick/private/qquickitem_p.h>
+#include <QtQuick/private/qquickitemview_p_p.h>
 #include <QtQuick/private/qquickgridview_p.h>
 #include <QtQuick/private/qquicktext_p.h>
 #include <QtQml/private/qqmllistmodel_p.h>
@@ -210,6 +211,7 @@ private slots:
     void contentHeightWithDelayRemove();
 
     void QTBUG_45640();
+    void QTBUG_48870_fastModelUpdates();
 
 private:
     QList<int> toIntList(const QVariantList &list);
@@ -6566,6 +6568,42 @@ void tst_QQuickGridView::QTBUG_45640()
     delete window;
 }
 
+void tst_QQuickGridView::QTBUG_48870_fastModelUpdates()
+{
+    StressTestModel model;
+
+    QScopedPointer<QQuickView> window(createView());
+    QQmlContext *ctxt = window->rootContext();
+    ctxt->setContextProperty("testModel", &model);
+
+    window->setSource(testFileUrl("qtbug48870.qml"));
+    window->show();
+    QVERIFY(QTest::qWaitForWindowExposed(window.data()));
+
+    QQuickGridView *view = findItem<QQuickGridView>(window->rootObject(), "view");
+    QTRY_VERIFY(view != 0);
+
+    QQuickItemViewPrivate *priv = QQuickItemViewPrivate::get(view);
+    bool nonUnique;
+    FxViewItem *item = Q_NULLPTR;
+    int expectedIdx;
+    QVERIFY(testVisibleItems(priv, &nonUnique, &item, &expectedIdx));
+
+    for (int i = 0; i < 10; i++) {
+        QTest::qWait(100);
+        QVERIFY2(testVisibleItems(priv, &nonUnique, &item, &expectedIdx),
+                 qPrintable(!item ? QString("Unexpected null item")
+                            : nonUnique ? QString("Non-unique item at %1 and %2").arg(item->index).arg(expectedIdx)
+                                        : QString("Found index %1, expected index is %3").arg(item->index).arg(expectedIdx)));
+        if (i % 3 != 0) {
+            if (i & 1)
+                flick(window.data(), QPoint(100, 200), QPoint(100, 0), 100);
+            else
+                flick(window.data(), QPoint(100, 200), QPoint(100, 400), 100);
+        }
+    }
+}
+
 QTEST_MAIN(tst_QQuickGridView)
 
 #include "tst_qquickgridview.moc"