How To Display a Context Menu for CTreeCtrl (222905)

MORE INFORMATION

On Windows platforms, the windowing subsystem encourages the developer to handle context menu requests in top level windows. The traditional Windows programming paradigm therefore concentrates the code for handling all of the context menu requests in a few window and dialog procedures. However, with the advent of object oriented programming a different solution can be embraced; that is to handle the WM_CONTEXTMENU message within the control itself thereby creating self-contained entities and objects. This method allows reuse of the control in more than just one parent window and dialog.

In the case of a tree view control, the drag-and-drop functionality that it embeds requires that special steps be taken in order to obtain independence from the containing window. After the tree view control receives a WM_RBUTTONDOWN message, messages are not forwarded by the control until a WM_RBUTTONUP message is received. The control decides if a drag-and-drop operation was or was not initiated.

• If the user did initiate a drag-and-drop operation, then USER32 generates a WM_CONTEXTMENU message and sends it to the tree view control. If the tree view control does not handle this message then the default window procedure forwards it to the control's parent window.
• If the user did not initiate a drag-and-drop operation then the control's window procedure sends a WM_NOTIFY (code NM_RCLICK) message and then a WM_CONTEXTMENU message to the parent window.

Consequently, consider the following three cases:

• When SHIFT+F10 is pressed and the control has the focus, a WM_CONTEXTMENU message is sent to the tree view control.
• When the user performs a drag-and-drop operation a WM_CONTEXTMENU message is sent to the tree view control.
• When the user right-clicks, a WM_NOTIFY (code NM_RCLICK) message is sent by the tree control to the control's parent. If you handle the reflected notification as shown below, the control displays the context menu in all situations.

To implement a context menu for a tree view control it is recommended that message handlers for both the WM_CONTEXTMENU and reflected WM_NOTIFY (NM_RCLICK) messages be implemented by the control. For example:

BEGIN_MESSAGE_MAP(CMyTreeCtrl, CTreeCtrl)
	//{{AFX_MSG_MAP(CMyTreeCtrl)
	ON_NOTIFY_REFLECT(NM_RCLICK, OnRClick)
	ON_WM_CONTEXTMENU()
	//}}AFX_MSG_MAP
END_MESSAGE_MAP()

void CMyTreeCtrl::OnRClick(NMHDR* pNMHDR, LRESULT* pResult) 
{
	TRACE0("CMyTreeCtrl::OnRClick()\n");
	// Send WM_CONTEXTMENU to self
	SendMessage(WM_CONTEXTMENU, (WPARAM) m_hWnd, GetMessagePos());
	// Mark message as handled and suppress default handling
	*pResult = 1;
}

void CMyTreeCtrl::OnContextMenu(CWnd* pWnd, CPoint ptMousePos) 
{
	// if Shift-F10
	if (ptMousePos.x == -1 && ptMousePos.y == -1)
		ptMousePos = (CPoint) GetMessagePos();

	ScreenToClient(&ptMousePos);

	UINT uFlags;
	HTREEITEM htItem;
	
	htItem = HitTest( ptMousePos, &uFlags );

	if( htItem == NULL )
		return;
	
	m_hActiveItem = htItem;

	CMenu menu;
	CMenu* pPopup;

	// the font popup is stored in a resource
	menu.LoadMenu(IDR_TREEITEM_CONTEXTMENU);
	pPopup = menu.GetSubMenu(0);
	ClientToScreen(&ptMousePos);
	pPopup->TrackPopupMenu( TPM_LEFTALIGN, ptMousePos.x, ptMousePos.y, this );
}