Fix crash when all the items in a QListView are hidden

Calling QIconModeViewBase::initDynamicLayout() on the second and
successive segments would return QPoint(-1,-1), resulting in a
totally empty area rectangle for all the items while in
QIconModeViewBase::doDynamicLayout(). This rectangle is used to
initialize the BSP tree, and produces an arithmetic exception when
empty.

Furthermore, a rendering bug was also apparent when displaying the
first item of a segment while the last item of the previous segment
was hidden.

Auto-tests included.

Reviewed-by: Olivier
Task-number: QTBUG-12308
(cherry picked from commit 3c7e7992461b1fef37ada68244f1b5b891015bda)

Conflicts:

	src/gui/itemviews/qlistview.cpp
	tests/auto/qlistview/tst_qlistview.cpp

2 files changed, 58 insertions, 2 deletions

diff --git a/src/gui/itemviews/qlistview.cpp b/src/gui/itemviews/qlistview.cpp
index 1869093..76d7642 100644
--- a/src/gui/itemviews/qlistview.cpp
+++ b/src/gui/itemviews/qlistview.cpp
@@ -2782,7 +2782,10 @@ QPoint QIconModeViewBase::initDynamicLayout(const QListViewLayoutInfo &info)
         y = info.bounds.y() + info.spacing;
         items.reserve(rowCount() - hiddenCount());
     } else {
-        const QListViewItem item = items.at(info.first - 1);
+        int idx = info.first - 1;
+        while (idx > 0 && !items.at(idx).isValid())
+            --idx;
+        const QListViewItem &item = items.at(idx);
         x = item.x;
         y = item.y;
         if (info.flow == QListView::LeftToRight)
@@ -2913,6 +2916,8 @@ void QIconModeViewBase::doDynamicLayout(const QListViewLayoutInfo &info)
         else
             contentsSize.rwidth() += info.spacing;
     }
+    if (rect.size().isEmpty())
+        return;
     // resize tree
     int insertFrom = info.first;
     if (done || info.first == 0) {
diff --git a/tests/auto/qlistview/tst_qlistview.cpp b/tests/auto/qlistview/tst_qlistview.cpp
index 330f803..425ac89 100644
--- a/tests/auto/qlistview/tst_qlistview.cpp
+++ b/tests/auto/qlistview/tst_qlistview.cpp
@@ -45,6 +45,7 @@
 #include <qabstractitemmodel.h>
 #include <qapplication.h>
 #include <qlistview.h>
+#include <qlistwidget.h>
 #include <qitemdelegate.h>
 #include <qstandarditemmodel.h>
 #include <qstringlistmodel.h>
@@ -125,6 +126,8 @@ private slots:
     void taskQTBUG_5877_skippingItemInPageDownUp();
     void taskQTBUG_9455_wrongScrollbarRanges();
     void styleOptionViewItem();
+    void taskQTBUG_12308_artihmeticException();
+    void taskQTBUG_12308_wrongFlowLayout();
 };
 
 // Testing get/set functions
@@ -1653,8 +1656,8 @@ void tst_QListView::task254449_draggingItemToNegativeCoordinates()
     //we'll make sure the item is repainted
     delegate.numPaints = 0;
     QApplication::processEvents();
+    QTRY_COMPARE(delegate.numPaints, 1);
     QCOMPARE(list.visualRect(index).topLeft(), topLeft);
-    QCOMPARE(delegate.numPaints, 1);
 }
 
 
@@ -2002,5 +2005,53 @@ void tst_QListView::styleOptionViewItem()
     QApplication::processEvents();
 }
 
+void tst_QListView::taskQTBUG_12308_artihmeticException()
+{
+    QListWidget lw;
+    lw.setLayoutMode(QListView::Batched);
+    lw.setViewMode(QListView::IconMode);
+    for (int i = 0; i < lw.batchSize() + 1; i++) {
+        QListWidgetItem *item = new QListWidgetItem();
+        item->setText(QString("Item %L1").arg(i));
+        lw.addItem(item);
+        item->setHidden(true);
+    }
+    lw.show();
+    QTest::qWaitForWindowShown(&lw);
+    // No crash, it's all right.
+}
+
+class Delegate12308 : public QStyledItemDelegate
+{
+    Q_OBJECT
+public:
+    Delegate12308(QObject *parent = 0) : QStyledItemDelegate(parent)
+    { }
+
+    void paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const
+    {
+        QVERIFY(option.rect.topLeft() != QPoint(-1, -1));
+        QStyledItemDelegate::paint(painter, option, index);
+    }
+};
+
+void tst_QListView::taskQTBUG_12308_wrongFlowLayout()
+{
+    QListWidget lw;
+    Delegate12308 delegate;
+    lw.setLayoutMode(QListView::Batched);
+    lw.setViewMode(QListView::IconMode);
+    lw.setItemDelegate(&delegate);
+    for (int i = 0; i < lw.batchSize() + 1; i++) {
+        QListWidgetItem *item = new QListWidgetItem();
+        item->setText(QString("Item %L1").arg(i));
+        lw.addItem(item);
+        if (!item->text().contains(QString::fromAscii("1")))
+            item->setHidden(true);
+    }
+    lw.show();
+    QTest::qWaitForWindowShown(&lw);
+}
+
 QTEST_MAIN(tst_QListView)
 #include "tst_qlistview.moc"