How do I display custom tooltips in a CTreeCtrl? - c++

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;
}

Answer 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));

Answer 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.

Answer 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.

Answer 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().