Is there a way to forward TTN_NEEDTEXT to CFrameWnd?

Question

I have an application that already deals with the generating of tooltips. I am modifying a CWnd derived class that has a parent frame. It doesn't implement tooltips.

From this, I can get tooltips to show up by adding the following code:

BEGIN_MESSAGE_MAP(CMyWindow, CWnd)
    ON_NOTIFY_EX_RANGE(TTN_NEEDTEXTW, 0, 0xFFFF, OnToolTipNotify)
    ON_NOTIFY_EX_RANGE(TTN_NEEDTEXTA, 0, 0xFFFF, OnToolTipNotify)
END_MESSAGE_MAP()

BOOL CMyWindow::OnToolTipNotify(UINT id, NMHDR* pNMHDR, LRESULT* pResult)
{
    UNREFERENCED_PARAMETER(id);
    UNREFERENCED_PARAMETER(pResult);

    // need to handle both ANSI and UNICODE versions of the message
    TOOLTIPTEXTA* pTTTA = (TOOLTIPTEXTA*)pNMHDR;
    TOOLTIPTEXTW* pTTTW = (TOOLTIPTEXTW*)pNMHDR;
    CStringA strTipText;
    UINT_PTR nID = pNMHDR->idFrom;
    if (pNMHDR->code == TTN_NEEDTEXTA && (pTTTA->uFlags & TTF_IDISHWND) ||
        pNMHDR->code == TTN_NEEDTEXTW && (pTTTW->uFlags & TTF_IDISHWND))
    {
        // idFrom is actually the HWND of the tool
        nID = ::GetDlgCtrlID((HWND)nID);
    }

    if (nID != 0) // will be zero on a separator
        strTipText.Format("Control ID = %d", nID);

    if (pNMHDR->code == TTN_NEEDTEXTA)
    {
        strncpy_s(pTTTA->szText, sizeof(pTTTA->szText), strTipText,
            strTipText.GetLength() + 1);
    }
    else
    {
        ::MultiByteToWideChar(CP_ACP, 0, strTipText, strTipText.GetLength() + 1,
            pTTTW->szText, sizeof(pTTTW->szText) / (sizeof pTTTW->szText[0]));
    }

    return TRUE;    // message was handled
}

I can use GetParentFrame() to get the frame window, so I'd like to leverage the tooltip code that is already in place so that I get a consistent look. Is there some way that I can forward the TTN_NEEDTEXT message so that it gets handled by the frame window?

Answer 1

In your message map, you use ON_NOTIFY_whatever, which should hint that the message that TTN_NEEDTEXT uses is WM_NOTIFY — and indeed this is the case. So you can just produce the WM_NOTIFY yourself and send it to the parent.

The documentation for WM_NOTIFY says wParam is the control's identifier and lParam is the NMHDR pointer. There's an example on the bottom of the page that shows wParam is just the idFrom member of the NMHDR, so you have everything you need to reconstruct the message:

LRESULT lr = this->GetParentFrame()->SendMessage(WM_NOTIFY, pNMHDR->idFrom, (LPARAM) pNMHDR);

When you should issue this call is up to what you need to do. In this case, you would probably want to make it the first call, override your string, and return TRUE. I'm not fully sure, though.

Note: if MFC provides a function to do this, I don't know it; I personally don't use MFC, but the concepts are the same.

So what about the return value from that SendMessage()? Well, you can return it via pResult (for instance, if you're just tweaking the parent's alterations slightly), or you can ignore it and return a custom value. But for TTN_NEEDTEXT, it won't matter; TTN_NEEDTEXT doesn't care what the LRESULT is.