Question

I have a class derived from CTreeCtrl. In OnCreate() I replace the default CToolTipCtrl object with a custom one:

int CMyTreeCtrl::OnCreate(LPCREATESTRUCT lpCreateStruct)
{
    if (CTreeCtrl::OnCreate(lpCreateStruct) == -1)
        return -1;

    // Replace tool tip with our own which will
    // ask us for the text to display with a TTN_NEEDTEXT message
    CTooltipManager::CreateToolTip(m_pToolTip, this, AFX_TOOLTIP_TYPE_DEFAULT);
    m_pToolTip->AddTool(this, LPSTR_TEXTCALLBACK);
    SetToolTips(m_pToolTip);

    // Update: Added these two lines, which don't help either
    m_pToolTip->Activate(TRUE);
    EnableToolTips(TRUE);
    
    return 0;
}

My message handler looks like this:

ON_NOTIFY_EX(TTN_NEEDTEXT, 0, &CMyTreeCtrl::OnTtnNeedText)

However I never receive a TTN_NEEDTEXT message. I had a look with Spy++ and it also looks like this message never gets sent.

What could be the problem here?

Update

I’m not sure whether this is relevant: The CTreeCtrl‘s parent window is of type CDockablePane. Could there be some extra work needed for this to work?

Answer 1

Finally! I (partially) solved it:

It looks like the CDockablePane parent window indeed caused this problem…

First I removed all the tooltip-specific code from the CTreeCtrl-derived class. Everything is done in the parent pane window.

Then I edited the parent window’s OnCreate() method:

int CMyPane::OnCreate(LPCREATESTRUCT lpCreateStruct)
{
    if (CDockablePane::OnCreate(lpCreateStruct) == -1)
        return -1;

const DWORD dwStyle = WS_CHILD | WS_VISIBLE | WS_CLIPSIBLINGS | WS_CLIPCHILDREN |
    TVS_CHECKBOXES | TVS_DISABLEDRAGDROP | TVS_HASBUTTONS | TVS_HASLINES | TVS_LINESATROOT |
    TVS_INFOTIP | TVS_NOHSCROLL | TVS_SHOWSELALWAYS;

// TREECTRL_ID is a custom member constant, set to 1
if(!m_tree.Create(dwStyle, m_treeRect, this, TREECTRL_ID ) )
{
    TRACE0("Failed to create trace tree list control.\n");
    return -1;
}

// m_pToolTip is a protected member of CDockablePane
m_pToolTip->AddTool(&m_tree, LPSTR_TEXTCALLBACK, &m_treeRect, TREECTRL_ID);
m_tree.SetToolTips(m_pToolTip);


return 0;

}

Unforunately we cannot simply call AddTool() with less parameters because the base class will complain in the form of an ASSERT about a uFlag member if there is no tool ID set.
And since we need to set the ID, we also need to set a rectangle. I created a CRect member and set it to (0, 0, 10000, 10000) in the CTor. I have not yet found a working way to change the tool’s rect size so this is my very ugly workaround. This is also why I call this solution partial. Update: I asked a question regarding this.

Finally there is the handler to get the tooltip info:

// Message map entry
ON_NOTIFY(TVN_GETINFOTIP, TREECTRL_ID, &CMobileCatalogPane::OnTvnGetInfoTip)


// Handler
void CMyPane::OnTvnGetInfoTip(NMHDR *pNMHDR, LRESULT *pResult)
{
    LPNMTVGETINFOTIP pGetInfoTip = reinterpret_cast<LPNMTVGETINFOTIP>(pNMHDR);

    // This is a CString member
    m_toolTipText.ReleaseBuffer();
    m_toolTipText.Empty();

    // Set your text here...

    pGetInfoTip->pszText = m_toolTipText.GetBuffer();

    *pResult = 0;
}