Tracking tooltip in Win32 C++

Question

In a Win32 / C++ app, running under 64-bit Windows 7, using Visual Studio 16.7.7, I want to implement tracking tooltips in the main (and only) window. Following the examples in Microsoft SDK documentation, the tracking seems to work, but the tooltip window itself does not appear.

I have verified, using the debugger, that the tooltip is activated and deactivated, that the expected mouse tracking is occurring, that the screen coordinates in the TTM_TRACKPOSITION message are correct, and the text is OK. The app is Unicode, and I have checked that the structures are the Unicode versions, and common controls are initialized, and that the current version of the common controls library is linked. The tooltip window has the WS_EX_TOPMOST and WS_EX_TOOLWINDOW extended styles, per Spy++.

What changes are needed to make the tooltip show?

Here is the code I am using:

Global variables:

HINSTANCE hInst;
HWND hWnd;
HWND hwndTT;
WCHAR ttText[12];
TOOLINFO toolTipInfo;
BOOL trackingMouse;

Initialization:

BOOL InitInstance(HINSTANCE hInstance, int nCmdShow)
{
   hInst = hInstance; // Store instance handle in our global variable

   hWnd = CreateWindowW(szWindowClass, szTitle, WS_OVERLAPPEDWINDOW,
      CW_USEDEFAULT, 0, CW_USEDEFAULT, 0, nullptr, nullptr, hInstance, nullptr);

   if (!hWnd)
   {
      return FALSE;
   }

   // Set up for mouse tracking (tooltips)
   INITCOMMONCONTROLSEX icc;
   icc.dwSize = sizeof(INITCOMMONCONTROLSEX);
   icc.dwICC = ICC_BAR_CLASSES;
   BOOL ok=InitCommonControlsEx(&icc);
   trackingMouse = FALSE;//
   WCHAR nullString[15] = { L"After create" };
   hwndTT = CreateTrackingToolTip(0 /*toolID*/, hWnd, nullString);
   ...

HWND CreateTrackingToolTip(int toolID, HWND hWndParent, WCHAR* pText)
{
    // Create a tooltip.
    HWND h = CreateWindowEx(WS_EX_TOPMOST, TOOLTIPS_CLASS, NULL,
        WS_POPUP | TTS_NOPREFIX | TTS_ALWAYSTIP,
        CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT,
        hWndParent, NULL, hInst, NULL);

    if(!h)
    {
        return NULL;
    }

    // Set up the tool information. In this case, the "tool" is the entire parent window.
    memset(&toolTipInfo, 0, sizeof(TOOLINFO));
    toolTipInfo.cbSize = sizeof(TOOLINFO);
    toolTipInfo.uFlags = TTF_IDISHWND | TTF_TRACK | TTF_ABSOLUTE;
    toolTipInfo.hwnd = hWndParent;
    toolTipInfo.hinst = hInst;
    toolTipInfo.lpszText = pText;
    toolTipInfo.uId = (UINT_PTR)hWndParent;

    GetClientRect(hWndParent, &toolTipInfo.rect);

    // Associate the tooltip with the tool window.
    SendMessage(h, TTM_ADDTOOL, 0, (LPARAM)(LPTOOLINFO)&toolTipInfo);

    return h;
}

Window procedure:

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    switch (message)
    {
    case WM_MOUSELEAVE: // The mouse pointer has left our window. Deactivate the tooltip.

        SendMessage(hwndTT, TTM_TRACKACTIVATE, (WPARAM)FALSE, (LPARAM)&toolTipInfo);
        trackingMouse = FALSE;
        TRACE(L"\nDeactivate tooltip");
        return FALSE;

    case WM_MOUSEMOVE:
            static int oldX, oldY;
        int newX, newY;

        if(!trackingMouse)   // The mouse has just entered the window.
        {                    // Request notification when the mouse leaves.

            TRACKMOUSEEVENT tme = { sizeof(TRACKMOUSEEVENT) };
            tme.hwndTrack = hWnd;
            tme.dwFlags = TME_LEAVE;

            BOOL ok=TrackMouseEvent(&tme);

            // Activate the tooltip.
            SendMessage(hwndTT, TTM_TRACKACTIVATE, (WPARAM)TRUE, (LPARAM)&toolTipInfo);
            trackingMouse = TRUE;
            TRACE(L"\nActivate tooltip");
        }

        newX = GET_X_LPARAM(lParam); newY = GET_Y_LPARAM(lParam);

        // Make sure the mouse has actually moved. The presence of the tooltip 
        // causes Windows to send the message continuously.
        if((newX != oldX) || (newY != oldY))
        {
            oldX = newX; oldY = newY;

            // Update the text.
            swprintf_s(ttText, ARRAYSIZE(ttText), L"%d, %d", newX, newY);
            toolTipInfo.lpszText = ttText;
            SendMessage(hwndTT, TTM_SETTOOLINFO, 0, (LPARAM)&toolTipInfo);

            // Position the tooltip. The coordinates are adjusted so that the tooltip does not overlap the mouse pointer.
            POINT pt = { newX, newY };
            ClientToScreen(hWnd, &pt);
            SendMessage(hwndTT, TTM_TRACKPOSITION, 0, (LPARAM)MAKELONG(pt.x + 10, pt.y - 20));
        }
    return FALSE;
...

Answer 1

The following line is required:

#pragma comment(linker,"/manifestdependency:\"type='win32' name='Microsoft.Windows.Common-Controls' version='6.0.0.0' processorArchitecture='*' publicKeyToken='6595b64144ccf1df' language='*'\"")

Refer to "Using Manifests or Directives to Ensure That Visual Styles Can Be Applied to Applications" for more detailed information.