The item delegate:
Qt Code: 
  1. class MyItemDelegate : public QItemDelegate
  2. {
  3.     Q_OBJECT
  4. public:
  5.     MyItemDelegate();
  6.     ~MyItemDelegate();
  7.     virtual QSize sizeHint ( const QStyleOptionViewItem & option, const QModelIndex & index ) const;    
  8.     virtual void paint ( QPainter * painter, const QStyleOptionViewItem & option, const QModelIndex & index ) const;
  9. private:
  10.     QSize mSize;
  11. };
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The item:
Qt Code: 
  1. class MyTreeWidgetItem : public QTreeWidgetItem
  2. {
  3. public:
  4.     enum DataRole 
  5.     {
  6.        TextRole = Qt::UserRole + 1,
  7.     //other roles
  8.     };
  9.     MyTreeWidgetItem(... );    
  10.      ~MyTreeWidgetItem();
  11.     QVariant data( int role )const;
  12. };
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The paint method should be something like:
Qt Code: 
  1. void MyItemDelegate::paint( QPainter * painter, const QStyleOptionViewItem & option, const QModelIndex & index ) const
  2. {
  3.     const QAbstractItemModel* model = index.model();
  4.     QString text = model->data(index, MyTreeWidgetItem::TextRole).toString();
  5.  
  6.     //here draw the item and the expand handle
  7.     //BTW  - you should keep a refernece to it's rect for when it is clicked
  8. }
  9.  
  10. This is a basic impl. You can add things to it according to your needs.
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