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  1. 4th September 2013, 06:25 #1
    QtNewbieNeedsHelp
    QtNewbieNeedsHelp is offline Beginner
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    Aug 2013
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    Default Problem while deleting item in QTreeView

    Hello,

    I have a QTreeView with some simple custom items in it.
    I also have a simple CustomTreeModel derived from QAbstractItemModel.

    I have a QMenu setup so I can click on the items in the tree and press "Delete" which is supposed to delete the current selected item and all its children.

    this is the code that I use to delete the items, it works but only for the children, If I call deleteLater() on the current selected item the app crashes.

    Qt Code: 
    1. void MyCustomItem::OnDelete()
    2. {
    3.       const QObjectList& childrenList = children();
    4.       int numChildren = childrenList.size();
    5.       for(unsigned int i = 0; i < numChildren; ++i)
    6.       {
    7.                QObject* pChildObj = childrenList[0];
    8. 	 MyCustomItem* pChild = qobject_cast<MyCustomItem*>(pChildObj);
    9.                if(pChild)
    10. 	 {
    11. 	          pChild->OnDelete();
    12.                         delete pChild;
    13. 	  }
    14.        }
    15.  
    16.         QTreeView* pTV = mpAssociatedTreeView;  //for simplicity assume that every object knows the treeview it is in
    17.         pTV->clearSelection();
    18.         pTV->reset();
    19.  
    20.  
    21.         deleteLater();    <== if I comment out this line it doesn't crash and all the children objects in the tree are gone
    22. }
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    I have seen so many posts about using removeRows in the model rather than actually calling delete on the objects, but I fail to understand how these are exactly working.

    this is the crash callstack that I get when using deleteLater() on my currently selected item in the tree.

    Qt Code: 
    1. >	Qt5Cored.dll!QObject::parent() Line 386	C++
    2.  	MyApp.exe!CustomTreeModel::parent(const QModelIndex & index={...}) Line 109	C++
    3.  	Qt5Cored.dll!QModelIndex::parent() Line 462	C++
    4.  	Qt5Widgetsd.dll!QTreeView::drawRow(QPainter * painter=0x000000000018a9a8, const QStyleOptionViewItem & option={...}, const QModelIndex & index={...}) Line 1545	C++
    5.  	Qt5Widgetsd.dll!QTreeView::drawTree(QPainter * painter=0x000000000018a9a8, const QRegion & region={...}) Line 1456	C++
    6.  	Qt5Widgetsd.dll!QTreeView::paintEvent(QPaintEvent * event=0x000000000018bca0) Line 1282	C++
    7.  	Qt5Widgetsd.dll!QWidget::event(QEvent * event=0x000000000018bca0) Line 8030	C++
    8.  	Qt5Widgetsd.dll!QFrame::event(QEvent * e=0x000000000018bca0) Line 534	C++
    9.  	Qt5Widgetsd.dll!QAbstractScrollArea::viewportEvent(QEvent * e=0x000000000018bca0) Line 1163	C++
    10.  	Qt5Widgetsd.dll!QAbstractItemView::viewportEvent(QEvent * event=0x000000000018bca0) Line 1680	C++
    11.  	Qt5Widgetsd.dll!QTreeView::viewportEvent(QEvent * event=0x000000000018bca0) Line 1263	C++
    12.  	Qt5Widgetsd.dll!QAbstractScrollAreaPrivate::viewportEvent(QEvent * event=0x000000000018bca0) Line 105	C++
    13.  	Qt5Widgetsd.dll!QAbstractScrollAreaFilter::eventFilter(QObject * o=0x0000000008993450, QEvent * e=0x000000000018bca0) Line 121	C++
    14.  	Qt5Cored.dll!QCoreApplicationPrivate::sendThroughObjectEventFilters(QObject * receiver=0x0000000008993450, QEvent * event=0x000000000018bca0) Line 967	C++
    15.  	Qt5Widgetsd.dll!QApplicationPrivate::notify_helper(QObject * receiver=0x0000000008993450, QEvent * e=0x000000000018bca0) Line 3451	C++
    16.  	Qt5Widgetsd.dll!QApplication::notify(QObject * receiver=0x0000000008993450, QEvent * e=0x000000000018bca0) Line 3420	C++
    17.  	Qt5Cored.dll!QCoreApplication::notifyInternal(QObject * receiver=0x0000000008993450, QEvent * event=0x000000000018bca0) Line 871	C++
    18.  	Qt5Cored.dll!QCoreApplication::sendSpontaneousEvent(QObject * receiver=0x0000000008993450, QEvent * event=0x000000000018bca0) Line 235	C++
    19.  	Qt5Widgetsd.dll!QWidgetPrivate::drawWidget(QPaintDevice * pdev=0x0000000008949888, const QRegion & rgn={...}, const QPoint & offset={...}, int flags=4, QPainter * sharedPainter=0x0000000000000000, QWidgetBackingStore * backingStore=0x0000000008b1f1c0) Line 5133	C++
    20.  	Qt5Widgetsd.dll!QWidgetPrivate::paintSiblingsRecursive(QPaintDevice * pdev=0x0000000008949888, const QList<QObject *> & siblings={...}, int index=0, const QRegion & rgn={...}, const QPoint & offset={...}, int flags=4, QPainter * sharedPainter=0x0000000000000000, QWidgetBackingStore * backingStore=0x0000000008b1f1c0) Line 5325	C++
    21.  	Qt5Widgetsd.dll!QWidgetPrivate::paintSiblingsRecursive(QPaintDevice * pdev=0x0000000008949888, const QList<QObject *> & siblings={...}, int index=2, const QRegion & rgn={...}, const QPoint & offset={...}, int flags=4, QPainter * sharedPainter=0x0000000000000000, QWidgetBackingStore * backingStore=0x0000000008b1f1c0) Line 5312	C++
    22.  	Qt5Widgetsd.dll!QWidgetPrivate::drawWidget(QPaintDevice * pdev=0x0000000008949888, const QRegion & rgn={...}, const QPoint & offset={...}, int flags=4, QPainter * sharedPainter=0x0000000000000000, QWidgetBackingStore * backingStore=0x0000000008b1f1c0) Line 5183	C++
    23.  	Qt5Widgetsd.dll!QWidgetPrivate::paintSiblingsRecursive(QPaintDevice * pdev=0x0000000008949888, const QList<QObject *> & siblings={...}, int index=0, const QRegion & rgn={...}, const QPoint & offset={...}, int flags=4, QPainter * sharedPainter=0x0000000000000000, QWidgetBackingStore * backingStore=0x0000000008b1f1c0) Line 5325	C++
    24.  	Qt5Widgetsd.dll!QWidgetPrivate::drawWidget(QPaintDevice * pdev=0x0000000008949888, const QRegion & rgn={...}, const QPoint & offset={...}, int flags=4, QPainter * sharedPainter=0x0000000000000000, QWidgetBackingStore * backingStore=0x0000000008b1f1c0) Line 5183	C++
    25.  	Qt5Widgetsd.dll!QWidgetPrivate::paintSiblingsRecursive(QPaintDevice * pdev=0x0000000008949888, const QList<QObject *> & siblings={...}, int index=4, const QRegion & rgn={...}, const QPoint & offset={...}, int flags=4, QPainter * sharedPainter=0x0000000000000000, QWidgetBackingStore * backingStore=0x0000000008b1f1c0) Line 5325	C++
    26.  	Qt5Widgetsd.dll!QWidgetPrivate::drawWidget(QPaintDevice * pdev=0x0000000008949888, const QRegion & rgn={...}, const QPoint & offset={...}, int flags=4, QPainter * sharedPainter=0x0000000000000000, QWidgetBackingStore * backingStore=0x0000000008b1f1c0) Line 5183	C++
    27.  	Qt5Widgetsd.dll!QWidgetPrivate::paintSiblingsRecursive(QPaintDevice * pdev=0x0000000008949888, const QList<QObject *> & siblings={...}, int index=1, const QRegion & rgn={...}, const QPoint & offset={...}, int flags=4, QPainter * sharedPainter=0x0000000000000000, QWidgetBackingStore * backingStore=0x0000000008b1f1c0) Line 5325	C++
    28.  	Qt5Widgetsd.dll!QWidgetPrivate::drawWidget(QPaintDevice * pdev=0x0000000008949888, const QRegion & rgn={...}, const QPoint & offset={...}, int flags=4, QPainter * sharedPainter=0x0000000000000000, QWidgetBackingStore * backingStore=0x0000000008b1f1c0) Line 5183	C++
    29.  	Qt5Widgetsd.dll!QWidgetPrivate::paintSiblingsRecursive(QPaintDevice * pdev=0x0000000008949888, const QList<QObject *> & siblings={...}, int index=0, const QRegion & rgn={...}, const QPoint & offset={...}, int flags=4, QPainter * sharedPainter=0x0000000000000000, QWidgetBackingStore * backingStore=0x0000000008b1f1c0) Line 5325	C++
    30.  	Qt5Widgetsd.dll!QWidgetPrivate::drawWidget(QPaintDevice * pdev=0x0000000008949888, const QRegion & rgn={...}, const QPoint & offset={...}, int flags=4, QPainter * sharedPainter=0x0000000000000000, QWidgetBackingStore * backingStore=0x0000000008b1f1c0) Line 5183	C++
    31.  	Qt5Widgetsd.dll!QWidgetPrivate::paintSiblingsRecursive(QPaintDevice * pdev=0x0000000008949888, const QList<QObject *> & siblings={...}, int index=0, const QRegion & rgn={...}, const QPoint & offset={...}, int flags=4, QPainter * sharedPainter=0x0000000000000000, QWidgetBackingStore * backingStore=0x0000000008b1f1c0) Line 5325	C++
    32.  	Qt5Widgetsd.dll!QWidgetPrivate::drawWidget(QPaintDevice * pdev=0x0000000008949888, const QRegion & rgn={...}, const QPoint & offset={...}, int flags=4, QPainter * sharedPainter=0x0000000000000000, QWidgetBackingStore * backingStore=0x0000000008b1f1c0) Line 5183	C++
    33.  	Qt5Widgetsd.dll!QWidgetPrivate::paintSiblingsRecursive(QPaintDevice * pdev=0x0000000008949888, const QList<QObject *> & siblings={...}, int index=9, const QRegion & rgn={...}, const QPoint & offset={...}, int flags=4, QPainter * sharedPainter=0x0000000000000000, QWidgetBackingStore * backingStore=0x0000000008b1f1c0) Line 5325	C++
    34.  	Qt5Widgetsd.dll!QWidgetPrivate::drawWidget(QPaintDevice * pdev=0x0000000008949888, const QRegion & rgn={...}, const QPoint & offset={...}, int flags=5, QPainter * sharedPainter=0x0000000000000000, QWidgetBackingStore * backingStore=0x0000000008b1f1c0) Line 5183	C++
    35.  	Qt5Widgetsd.dll!QWidgetBackingStore::sync() Line 1093	C++
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    it looks to me as if the qtreeview is still drawing the items but I have just deleted one. In fact

    Qt Code: 
    1. QModelIndex CustomTreeModel::parent(const QModelIndex &index) const
    2. {
    3. 	if( !index.isValid() )
    4. 		return QModelIndex();
    5.  
    6. 	QObject *indexObject = static_cast<QObject*>( index.internalPointer() );
    7. 	QObject *parentObject = indexObject->parent();          //the indexObject  is garbage at this point
    8.  
    9. 	if( parentObject == m_root )
    10. 		return QModelIndex();
    11.  
    12. 	QObject *grandParentObject = parentObject->parent();
    13.  
    14. 	return createIndex( grandParentObject->children().indexOf( parentObject ), 0, parentObject );
    15. }
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    one more thing I can say is that from looking at my CustomTreeModel (where I store the root of my tree) I can tell that the root is the only object left after I delete its only child (with 1 subchild).

    this is the tree before calling pItemA->OnDelete()

    root (invisible)
    +--- ItemA
    +-------- ItemA0



    anyone has some suggestions ? I tried look at the Qt examples as well to understand how to create a clean QTreeView but its not very clear to me.

    any help is appreciated.
    Last edited by QtNewbieNeedsHelp; 4th September 2013 at 06:35.
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