Thanks guys for your answer, I really appreciate.

@Spitfire: you are right, that's basically what I am trying to achieve. I have checked my code, I don't disable the indicator anywhere. Unfortunately it's not easy to make a compilable example, some work is involved, but I will do it if I can't find any solution soon.
I have overriden the paint event, however currently all it does is calling the base class (QtTreeWidget) paint method. So that's not the problem.

@ugluk: the flags seems to be fine, I added the piece of code below for each created item, the flag returned by flags() is 61 (decimal) and its value is not modified by the line just below:

Qt Code: 
  2. Qt::ItemFlags flag = pItem->flags();
  3. flag |= Qt::ItemIsDragEnabled | Qt::ItemIsDropEnabled;
  4. pItem->setFlags(flag);
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Below the full relevant code of my class:

Qt Code: 
  1. //////////////////////////////////////////////////////////////////////////
  2.  
  3. class imQMimeData : public QMimeData
  4. {
  5. public :
  6.  
  7. 	imQMimeData () : QMimeData () 
  8. 	{
  9. 		m_eDropAction = Qt::MoveAction;
  10. 	}
  11.  
  12. 	virtual ~imQMimeData () {}
  13.  
  14. 	imNode* GetNode(void) const { return m_pNode; }
  15. 	void SetNode(imNode* _pNode) { m_pNode = _pNode; }
  16.  
  17. 	QTreeWidgetItem* GetItem(void) const { return m_pItem; }
  18. 	void SetItem(QTreeWidgetItem* _pItem) { m_pItem = _pItem; }
  19.  
  20. 	imU32 GetOldIndex() const { return m_nOldIndex; }
  21. 	void SetOldIndex(imU32 _nIndex) { m_nOldIndex = _nIndex; }
  22.  
  23. public :
  24.  
  25. 	imNode* m_pNode;
  26. 	QTreeWidgetItem* m_pItem;
  27. 	imU32 m_nOldIndex;
  28. 	Qt::DropAction m_eDropAction;
  29. };
  30.  
  31. //////////////////////////////////////////////////////////////////////////
  32.  
  33. imGuiSceneExplorer::imGuiSceneExplorer(QWidget * parent) : QTreeWidget(parent), imIStreamingCallback()
  34. {
  35. 	m_pScene = imNULL;
  36. 	m_bBuildingTree = imFALSE;
  37. 	m_pUI = imNULL;
  38. }
  39.  
  40.  
  41. //////////////////////////////////////////////////////////////////////////
  42.  
  43. imGuiSceneExplorer::~imGuiSceneExplorer()
  44. {
  45. 	clear();
  46. }
  47.  
  48. //////////////////////////////////////////////////////////////////////////
  49.  
  50. void imGuiSceneExplorer::SetUI(Ui::imGuiMainWindowClass* _pUI)
  51. {
  52. 	m_pUI = _pUI;
  53.  
  54. 	setColumnCount(2);
  55.  
  56. 	headerItem()->setText(0, tr("Name"));
  57. 	headerItem()->setText(1, tr("Type"));
  58.  
  59. 	header()->setResizeMode(0, QHeaderView::ResizeToContents);
  60. 	header()->setResizeMode(1, QHeaderView::ResizeToContents);
  61.  
  62. 	// drag & drop
  63. 	setAcceptDrops(imTRUE);
  64. 	setDragEnabled(true);
  65. 	setDragDropMode(DragDrop);
  66. 	setDragDropOverwriteMode(imFALSE);
  67. 	setDropIndicatorShown(imTRUE);
  68.  
  69. 	setSelectionMode(QAbstractItemView::SingleSelection);
  70. 	setSelectionBehavior(QAbstractItemView::SelectRows);
  71.  
  72. 	// context menu
  73. 	setContextMenuPolicy(Qt::CustomContextMenu);
  74. 	connect(this, SIGNAL(customContextMenuRequested(const QPoint&)), this, SLOT(ShowTreeContextMenu(const QPoint&)));
  75. }
  76.  
  77. //////////////////////////////////////////////////////////////////////////
  78.  
  79. QSize imGuiSceneExplorer::sizeHint() const
  80. {
  81. 	QSize theSize(256, 768);
  82. 	return theSize;
  83. }
  84.  
  85. //////////////////////////////////////////////////////////////////////////
  86.  
  87. void imGuiSceneExplorer::SelectNode(imNode* _pNode)
  88. {
  90. 	while (*it)
  91. 	{
  92. 		imNode* pNode = GetNodeFromItem(*it);
  93. 		if (pNode == _pNode)
  94. 		{
  95. 			setCurrentItem(*it);
  96.  
  97. 			if (m_pScene)
  98. 				m_pScene->SetSelectedNode(_pNode);
  99.  
  100. 			return;
  101. 		}
  102. 		++it;
  103. 	}
  104. }
  105.  
  106. //////////////////////////////////////////////////////////////////////////
  107.  
  108. imNode* imGuiSceneExplorer::GetNodeFromItem(QTreeWidgetItem* _pItem)
  109. {
  110. 	if (!_pItem)
  111. 		return imNULL;
  112. 	return *(imNode**)_pItem->data(0, Qt::UserRole).toByteArray().constData();
  113. }
  114.  
  115. //////////////////////////////////////////////////////////////////////////
  116.  
  117. void imGuiSceneExplorer::BuildContent( imScene* _pScene )
  118. {
  119. 	clear();
  120.  
  121. 	m_pScene = _pScene;
  122. 	if (!_pScene)
  123. 		return;
  124.  
  125. 	// create top level item
  126. 	m_bBuildingTree = imTRUE;
  127. 	imNode* pRoot = _pScene->GetRootNode();
  128. 	AddNodeItem(pRoot, imNULL, -1);
  129. 	m_bBuildingTree = imFALSE;
  130. }
  131.  
  132. //////////////////////////////////////////////////////////////////////////
  133.  
  134. QTreeWidgetItem* imGuiSceneExplorer::CreateItemFromNode(imNode* _pNode)
  135. {
  136. 	imAssert(_pNode);
  137. 	if (_pNode)
  138. 	{
  139. 		QTreeWidgetItem* pItem = imNew QTreeWidgetItem();
  140. 		Qt::ItemFlags flag = pItem->flags();
  141. 		flag |= Qt::ItemIsDragEnabled | Qt::ItemIsDropEnabled;
  142. 		pItem->setFlags(flag);
  143.  
  144. 		// node name
  145. 		imStringBase sName(_pNode->GetName().GetLength() ? _pNode->GetName() : _pNode->RTTIGetClass()->getName());
  146. 		QString sQName = QString::fromWCharArray((const wchar_t*)sName);
  147. 		pItem->setText(0, sQName);
  148.  
  149. 		// node type
  150. 		imStringBase sType(_pNode->RTTIGetClass()->getName());
  151. 		QString sQType = QString::fromWCharArray((const wchar_t*)sType);
  152. 		pItem->setText(1, sQType);
  153.  
  154. 		// set data
  155. 		QByteArray data((const char *)&_pNode, sizeof(_pNode));
  156. 		QVariant oVariant(data);
  157. 		pItem->setData( 0, Qt::UserRole, oVariant);
  158.  
  159. 		return pItem;
  160. 	}
  161. 	return imNULL;
  162. }
  163.  
  164. //////////////////////////////////////////////////////////////////////////
  165.  
  166. void imGuiSceneExplorer::rowsInserted ( const QModelIndex & parent, int start, int end )
  167. {
  168. 	if (!m_bBuildingTree)
  169. 	{
  170. 		QTreeWidgetItem* pItemParent = itemFromIndex(parent);
  171. 		if (pItemParent)
  172. 		{
  173. 			imNode* pParent = GetNodeFromItem(pItemParent);
  174. 			if (pParent)
  175. 			{
  176. 				for (imInt i = start; i <= end; ++i)
  177. 				{
  178. 					QTreeWidgetItem* pItemChild = pItemParent->child(i);
  179. 					imNode* pChild = GetNodeFromItem(pItemChild);
  180. 					pParent->InsertChild(pChild, i);
  181. 				}
  182. 			}
  183. 		}
  184. 	}
  185.  
  186. 	QTreeWidget::rowsInserted(parent,start,end);
  187. }
  188.  
  189. //////////////////////////////////////////////////////////////////////////
  190.  
  191. void imGuiSceneExplorer::rowsAboutToBeRemoved ( const QModelIndex & parent, int start, int end )
  192. {
  193. 	if (!m_bBuildingTree)
  194. 	{
  195. 		QTreeWidgetItem* pItemParent = itemFromIndex(parent);
  196. 		imNode* pParent = GetNodeFromItem(pItemParent);
  197.  
  198. 		for (imInt i = start; i <= end; ++i)
  199. 		{
  200. 			QTreeWidgetItem* pItemChild = pItemParent->child(i);
  201. 			imNode* pChild = GetNodeFromItem(pItemChild);
  202. 			pParent->RemoveChild(i, imFALSE);
  203. 		}		
  204. 	}
  205.  
  206. 	QTreeWidget::rowsAboutToBeRemoved(parent,start,end);
  207. }
  208.  
  209. //////////////////////////////////////////////////////////////////////////
  210.  
  211. QMimeData *imGuiSceneExplorer::mimeData(const QList<QTreeWidgetItem *> items) const
  212. {
  213. 	imAssert(items.size());
  214. 	if (items.size())
  215. 	{
  216. 		imQMimeData *mimeData = imNew imQMimeData();
  217. 		imNode* pNode = *(imNode**)items[0]->data(0, Qt::UserRole).toByteArray().constData();
  218. 		mimeData->SetNode(pNode);
  219. 		mimeData->SetItem(items[0]);
  220. 		mimeData->SetOldIndex(items[0]->parent() ? items[0]->parent()->indexOfChild(items[0]) : 0);
  221.  
  222. 		return mimeData;
  223. 	}
  224. 	return imNULL;
  225. }
  226.  
  227. //////////////////////////////////////////////////////////////////////////
  228.  
  229. bool imGuiSceneExplorer::dropMimeData(QTreeWidgetItem *parent, int index, const QMimeData *data, Qt::DropAction action)
  230. {
  231. 	if (action == Qt::IgnoreAction)
  232. 		return true;
  233.  
  234. 	if (parent) 
  235. 	{	
  236. 		const imQMimeData* myData = static_cast<const imQMimeData *>(data);
  237. 		if (myData && parent != myData->GetItem())  
  238. 		{
  239. 			imNode* pNode = myData->GetNode();
  240. 			AddNodeItem(pNode, parent, index);
  241. 		}
  242. 	}
  243. 	return true;
  244. }
  245.  
  246. //////////////////////////////////////////////////////////////////////////
  247.  
  248. void imGuiSceneExplorer::dragEnterEvent ( QDragEnterEvent * event )
  249. {
  250. 	QTreeWidget::dragEnterEvent(event);
  251.  
  252. 	event->accept();
  253. }
  254.  
  255. //////////////////////////////////////////////////////////////////////////
  256.  
  257. void imGuiSceneExplorer::dragMoveEvent ( QDragMoveEvent * event )
  258. {
  259. 	QTreeWidget::dragMoveEvent(event);
  260.  
  261. 	event->accept();
  262. }
  263.  
  264. //////////////////////////////////////////////////////////////////////////
  265.  
  266. void imGuiSceneExplorer::paintEvent( QPaintEvent* event )
  267. {  
  268. 	QTreeWidget::paintEvent (event);
  269. }
  270.  
  271. //////////////////////////////////////////////////////////////////////////
  272.  
  273. void imGuiSceneExplorer::OnItemSelected()
  274. {
  275. 	// do something
  276. }
  277.  
  278. //////////////////////////////////////////////////////////////////////////
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