[Interest] QGraphicsScene crash after removeItem() and delete item

[Pierre Fillard]

It's a sign that you probably forgot to call:

QGraphicsItem::prepareGeometryChange()

when changing the bounding rect of your item. Calling this function tells
the scene to update its indexing, and allows a proper cleanup of the item
when calling scene->removeItem() (AFAIK).

Check in your code if you do update your item's bounding rect, and make
sure to call this function before.

HTH,
Pierre.

On Thu, Nov 29, 2012 at 12:33 PM, Volker Poplawski <volker at openbios.org>wrote:

> Hi everybody,
>
> I'm facing segfault in succession of deleting a number of QGraphicsItems
> from a scene.
>
> The following code leads to the stack trace below on the next redraw of
> the scene.
>
>   while (not m_items.isEmpty())
>   {
>     QGraphicsItem *item = m_items.takeFirst();
>     m_scene->removeItem(item);  // qtdoc says it's faster to remove item
> first then delete
>     delete item;
>   }
>
>
> The interesting things is that without the removeItem() call, i.e. just
> calling delete on the items, my program does not crash.
>
>
>
>
>
>
> 0
> QGraphicsSceneFindItemBspTreeVisitor::visit(QList<QGraphicsItem*>*)
>             0x1075cff
> 1       QGraphicsSceneBspTree::climbTree(QGraphicsSceneBspTreeVisitor*,
> QRectF const&, int) const                       0x1074c40
> 2       QGraphicsSceneBspTree::climbTree(QGraphicsSceneBspTreeVisitor*,
> QRectF const&, int) const                       0x1074ce0
> 3       QGraphicsSceneBspTree::climbTree(QGraphicsSceneBspTreeVisitor*,
> QRectF const&, int) const                       0x1074c40
> 4       QGraphicsSceneBspTree::climbTree(QGraphicsSceneBspTreeVisitor*,
> QRectF const&, int) const                       0x1074c40
> 5       QGraphicsSceneBspTree::climbTree(QGraphicsSceneBspTreeVisitor*,
> QRectF const&, int) const                       0x1074c40
> 6       QGraphicsSceneBspTree::climbTree(QGraphicsSceneBspTreeVisitor*,
> QRectF const&, int) const                       0x1074c40
> 7       QGraphicsSceneBspTree::climbTree(QGraphicsSceneBspTreeVisitor*,
> QRectF const&, int) const                       0x1074c40
> 8       QGraphicsSceneBspTree::climbTree(QGraphicsSceneBspTreeVisitor*,
> QRectF const&, int) const                       0x1074c40
> 9       QGraphicsSceneBspTree::climbTree(QGraphicsSceneBspTreeVisitor*,
> QRectF const&, int) const                       0x1074ce0
> 10      QGraphicsSceneBspTree::items(QRectF const&, bool) const
>       0x107539e
> 11      QGraphicsSceneBspTreeIndexPrivate::estimateItems(QRectF const&,
> Qt::SortOrder, bool)                    0xf24058
> 12      QGraphicsSceneBspTreeIndex::estimateTopLevelItems(QRectF const&,
> Qt::SortOrder) const                   0xf24233
> 13      QGraphicsScenePrivate::drawItems(QPainter*, QTransform const*,
> QRegion*, QWidget*)                      0xf194ad
> 14      QGraphicsView::paintEvent(QPaintEvent*)                 0xf3505c
> 15      QWidget::event(QEvent*)                 0xa6941a
> 16      QFrame::event(QEvent*)                  0xd81236
> 17      QGraphicsView::viewportEvent(QEvent*)                   0xf362bb
> 18      QCoreApplicationPrivate::sendThroughObjectEventFilters(QObject*,
> QEvent*)                       0x11992b7
> 19      QApplicationPrivate::notify_helper(QObject*, QEvent*)
>       0xa240f1
> 20      QApplication::notify(QObject*, QEvent*)                 0xa2c63f
> ...     <More>
>
>
>
>
>
> ....Volker
> _______________________________________________
> Interest mailing list
> Interest at qt-project.org
> http://lists.qt-project.org/mailman/listinfo/interest
>



-- 
Pierre Fillard, Ph.D.,
Research Scientist
INRIA Saclay Ile-de-France
Bâtiment Alan Turing
1 rue Honoré d'Estienne d'Orves
Campus de l'École Polytechnique
91120 Palaiseau
tel: +33 1 72 92 59 62

INRIA Parietal - Neurospin
Bât 145, Point Courrier 156
91191 Gif/Yvette, France
tel: +33 1 69 08 79 92
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