QListView: fix crash when hiding many of the lasts item in a QListView

Since 6c1388ee5a3c4796d hidden items are not taken in account when
counting the scrollbar position, and so the vector may be smaller.

Reviewed-by: Gabriel
Task-number: QTBUG-7929

2 files changed, 18 insertions, 1 deletions

diff --git a/src/gui/itemviews/qlistview.cpp b/src/gui/itemviews/qlistview.cpp
index 19b1e8c..b2def39 100644
--- a/src/gui/itemviews/qlistview.cpp
+++ b/src/gui/itemviews/qlistview.cpp
@@ -2160,7 +2160,7 @@ void QListModeViewBase::scrollContentsBy(int dx, int dy, bool scrollElasticBand)
     } else {
         if (flowPositions.isEmpty())
             return;
-        const int max = flowPositions.count() - 1;
+        const int max = scrollValueMap.count() - 1;
         if (vertical && flow() == QListView::TopToBottom && dy != 0) {
             int currentValue = qBound(0, verticalValue, max);
             int previousValue = qBound(0, currentValue + dy, max);
diff --git a/tests/auto/qlistview/tst_qlistview.cpp b/tests/auto/qlistview/tst_qlistview.cpp
index 7109213..1e6d36a 100644
--- a/tests/auto/qlistview/tst_qlistview.cpp
+++ b/tests/auto/qlistview/tst_qlistview.cpp
@@ -1834,6 +1834,23 @@ void tst_QListView::taskQTBUG_2233_scrollHiddenItems()
         QVERIFY(index.isValid());
         QCOMPARE(index.row(), 2 * i + 1);
     }
+
+    //QTBUG-7929  should not crash
+    view.show();
+    QTest::qWaitForWindowShown(&view);
+    QScrollBar *bar = view.flow() == QListView::TopToBottom
+            ? view.verticalScrollBar() : view.horizontalScrollBar();
+
+    int nbVisibleItem = rowCount / 2 - bar->maximum();
+
+    bar->setValue(bar->maximum());
+    QApplication::processEvents();
+    for (int i = rowCount; i > rowCount / 2; i--) {
+        view.setRowHidden(i, true);
+    }
+    QApplication::processEvents();
+    QCOMPARE(bar->value(), bar->maximum());
+    QCOMPARE(bar->maximum(), rowCount/4 - nbVisibleItem);
 }
 
 void tst_QListView::taskQTBUG_633_changeModelData()