PathView: fix infinite construction/destruction loop

... when all (or almost all) items are in the cache.

When all items are in cache, check lower bound is equal
to upper_bound.

In rare cases, especially when almost all items are in cache,
the inserting code was used (not only appending and prepending).
In this code there was not bound check before creation of item
and there was such situation:

1. Create item by inserting code (without bound check)
2. At the next call of refill() remove this item by life cycle
because this item does not meet the conditions. And go to step 1.

In other words at the first call we create some item, at the second
remove this item. And again.

So we had infinite construction/destruction loop. To break it we
should check position of new item before creation in inserting code
too (like we do in appending and prepending code).

Task-number: QTBUG-37815
Change-Id: I015cdeb67ca5fcd06c34b3145b49cbd3e38d4078
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

1 files changed, 26 insertions, 0 deletions

diff --git a/tests/auto/quick/qquickpathview/tst_qquickpathview.cpp b/tests/auto/quick/qquickpathview/tst_qquickpathview.cpp
index 2046391d02..493af97521 100644
--- a/tests/auto/quick/qquickpathview/tst_qquickpathview.cpp
+++ b/tests/auto/quick/qquickpathview/tst_qquickpathview.cpp
@@ -140,6 +140,7 @@ private slots:
     void nestedinFlickable();
     void flickableDelegate();
     void jsArrayChange();
+    void qtbug37815();
     void qtbug42716();
     void qtbug53464();
     void addCustomAttribute();
@@ -2334,6 +2335,31 @@ void tst_QQuickPathView::jsArrayChange()
     QCOMPARE(spy.count(), 1);
 }
 
+void tst_QQuickPathView::qtbug37815()
+{
+    QScopedPointer<QQuickView> window(createView());
+
+    window->setSource(testFileUrl("qtbug37815.qml"));
+    window->show();
+    window->requestActivate();
+    QVERIFY(QTest::qWaitForWindowActive(window.data()));
+
+    // cache items will be created async. Let's wait...
+    QTest::qWait(1000);
+
+    QQuickPathView *pathView = findItem<QQuickPathView>(window->rootObject(), "pathView");
+    QVERIFY(pathView != Q_NULLPTR);
+
+    const int pathItemCount = pathView->pathItemCount();
+    const int cacheItemCount = pathView->cacheItemCount();
+    int totalCount = 0;
+    foreach (QQuickItem *item, pathView->childItems()) {
+        if (item->objectName().startsWith(QLatin1String("delegate")))
+            ++totalCount;
+    }
+    QCOMPARE(pathItemCount + cacheItemCount, totalCount);
+}
+
 /* This bug was one where if you jump the list such that the sole missing item needed to be
  * added in the middle of the list, it would instead move an item somewhere else in the list
  * to the middle (messing it up very badly).