Tool tips for custom made control using CToolTipCtrl ? (MFC)

Question

I made a custom control derived from CWnd (a line chart) and I'm wondering if I can use CToolTipCtrl for displaying tool tips for points on the graph. If yes, how could I do that?

Btw, when I move my mouse over the point, the rectangle containg string with information about values of the point, should pop up.

Answer 1

Yes, this works, actually I do this exact same thing, also in a line graph chart, however there are a few drawbacks/remarks. The message handling is a bit wonky, with some messages not being send according to the documentation, and some workarounds being necessary to keep the control self-contained (not requiring help from the parent to reflect notifications).

What you do is declare a variable in your CWnd-derived class

CToolTipCtrl m_ToolTipCtrl;
CString m_ToolTipContent;

Then do this on OnCreate:

m_ToolTipCtrl.Create(this, TTS_ALWAYSTIP);
m_ToolTipCtrl.Activate(TRUE);

Optionally, you can also set the delay time:

m_ToolTipCtrl.SetDelayTime(TTDT_AUTOPOP, -1);
m_ToolTipCtrl.SetDelayTime(TTDT_INITIAL, 0);
m_ToolTipCtrl.SetDelayTime(TTDT_RESHOW, 0);

When you want to show your tooltip (presumably in OnMouseMove()), use

m_ToolTipCtrl.Pop();

BUT this only works in UNICODE builds. So if you're still on MBCS (like I am), you can only show the tooltip after a certain delay. Use this to set your tooltip text (also in OnMouseMove):

// Not using CToolTipCtrl::AddTool() because
// it redirects the messages to the parent
TOOLINFO ti = {0};
ti.cbSize = sizeof(TOOLINFO);
ti.uFlags = TTF_IDISHWND;    // Indicate that uId is handle to a control
ti.uId = (UINT_PTR)m_hWnd;   // Handle to the control
ti.hwnd = m_hWnd;            // Handle to window
// to receive the tooltip-messages
ti.hinst = ::AfxGetInstanceHandle();
ti.lpszText = LPSTR_TEXTCALLBACK;
ti.rect = <rectangle where, when the mouse is over it, the tooltip should be shown>;
m_ToolTipCtrl.SendMessage(TTM_ADDTOOL, 0, (LPARAM) (LPTOOLINFO) &ti);
m_ToolTipCtrl.Activate(TRUE);

m_ToolTipContent = "my tooltip content";

Furthermore, you need to handle TTNNeedText:

// The build-agnostic one doesn't work for some reason.
ON_NOTIFY_EX(TTN_NEEDTEXTA, 0, OnTTNNeedText)
ON_NOTIFY_EX(TTN_NEEDTEXTW, 0, OnTTNNeedText)

BOOL GraphCtrlOnTTNNeedText(UINT id, NMHDR* pTTTStruct,  LRESULT* pResult)
{
    TOOLTIPTEXT* pTTT = (TOOLTIPTEXT*)pTTTStruct;
    //pTTT->lpszText = "some test text";
    //pTTT->lpszText = m_ToolTipContent;
    strncpy_s(pTTT->lpszText, 80, m_ToolTipContent, _TRUNCATE);

    return TRUE;
}

You'll have to modify this a bit, and read the documentation of the functions and messages, to get this to work in your project but yes it can be done.

Answer 2

For those that may still be looking for an answer to this as I was. (I couldn't get the one above to work - Things in MFC may have changed.)

All code is contained within the custom control class.

In your class definition add:

CToolTipCtrl ToolTip;

In PreSubclassWindow() add:

#define TOOLTIP_ID 1
ToolTip.Create(this, TTS_ALWAYSTIP );

CRect rc;
GetClientRect(rc);
ToolTip.AddTool(this, "Tool tip text", rc, TOOLTIP_ID);

In PreTranslateMessage() add:

ToolTip.RelayEvent(msg);

Whenever your tool tip text changes add:

ToolTip.UpdateTipText("New Tip Text", this, TOOLTIP_ID);