How do I display custom tooltips in a CTreeCtrl?

问题:

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?

回答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;
}

回答2:

I believe you still have to enable the tooltip, even though you are replacing the builtin.

EnableToolTips(TRUE);

Well, since that did not work for you and since no-one more expert has offered any help, here a few more suggestions from me. Although they are lame, they might get you moving again:

• Make sure your OnCreate() rotine is actually being executed.
• Enable the tool tip BEFORE you replace it.

• The code I use to do this looks like this. ( I confess I do not understand all the details, I copied it from some sample code, it worked and so I never looked at it any more. )

  // Enable the standard tooltip

  EnableToolTips(TRUE);

  // Disable the builtin tooltip

  CToolTipCtrl* pToolTipCtrl = (CToolTipCtrl*)CWnd::FromHandle((HWND)::SendMessage(m_hWnd, LVM_GETTOOLTIPS, 0, 0L));

回答3:

I haven't tried in a CTreeCtrl but I think you should call RelayEvent for the tooltip ctrl to know when the tooltip has to be displayed. Try this:

MyTreeCtrl.h:

virtual BOOL PreTranslateMessage(MSG* pMsg);

MyTreeCtrl.cpp:

BOOL CMyTreeCtrl::PreTranslateMessage(MSG* pMsg) 
{
    m_pToolTip.Activate(TRUE);
    m_pToolTip.RelayEvent(pMsg);

    return CTreeCtrl::PreTranslateMessage(pMsg);
}

I hope this help.

回答4:

Don't you have to override OnToolHitTest()?

(old) Resource 1

(old) Resource 2:

In addition to returning the hit code (nHit), you also have to fill out the TOOLINFO struct. Here's how VIRGIL does it in CMainFrame::OnToolHitTest:

 int nHit = MAKELONG(pt.x, pt.y);
 pTI->hwnd = m _ hWnd;
 pTI->uId  = nHit;
 pTI->rect = CRect(CPoint(pt.x-1,pt.y-1),CSize(2,2));
 pTI->uFlags |= TTF _ NOTBUTTON;
 pTI->lpszText = LPSTR _ TEXTCALLBACK;

Most of this is obvious—like setting hwnd and uId—but some of it is less so. I set the rect member to a 2-pixel-wide, 2-pixel-high rectangle centered around the mouse location. The tooltip control uses this rectangle as the bounding rectangle of the "tool," which I want to be tiny, so moving the mouse anywhere will constitute moving outside the tool. I set TTF _ NOTBUTTON in uFlags because the tooltip is not associated with a button. This is a special MFC flag defined in afxwin.h; MFC uses it to do help for tooltips. There's another MFC-extended flag for tooltips, TTF _ ALWAYSTIP. You can use it if you want MFC to display the tip even when your window is not active. You may have noticed that so far I haven't told MFC or the tooltip or the TOOLINFO what the actual text of the tip is. That's what LPSTR _ TEXTCALLBACK is for. This special value tells the tooltip control (the internal, thread-global one that MFC uses) to call my window back to get the text. It does this by sending my window a WM _ NOTIFY message with notification code TTN _ NEEDTEXT.

回答5:

Try to specifically handle all tooltip ids:

ON_NOTIFY_EX_RANGE(TTN_NEEDTEXT, 0, 0xFFFF, &CMyTreeCtrl::OnNeedTipText)

If that doesn't work, you may have to manually call RelayEvent() from PreTranslateMessage().