TaskDialog with no buttons

Creating a TaskDialog without Buttons in C++

Explore how to leverage the Windows TaskDialog API to display informative messages without standard buttons, offering a cleaner, more controlled user experience for specific notifications.

The TaskDialog API in Windows provides a rich and flexible alternative to the traditional MessageBox for displaying information to users. While typically used with custom buttons or predefined sets like OK/Cancel, there are scenarios where you might want to display a TaskDialog purely for informational purposes, without any interactive buttons. This can be useful for transient notifications, progress indicators, or informational pop-ups that close programmatically or after a delay. This article delves into the specifics of achieving a button-less TaskDialog using C++.

Why a Button-less TaskDialog?

Standard MessageBox and even TaskDialog instances with buttons require user interaction to dismiss. In certain application flows, this can be undesirable. Consider a situation where your application is performing a background task and you want to inform the user about its status, but the dialog should not block further execution or wait for a click. Another use case might be a temporary notification that disappears after a few seconds, similar to a toast notification but with the richer content capabilities of TaskDialog. A button-less TaskDialog offers a non-intrusive way to convey information.

Conceptual flow for a button-less TaskDialog

Implementing a Button-less TaskDialog

To create a TaskDialog without buttons, the key is to omit the pButtons and cButtons fields in the TASKDIALOGCONFIG structure, or set cButtons to 0. While this prevents standard buttons from appearing, the dialog will still need a way to be dismissed. This usually involves either a programmatic close (e.g., using SendMessage with TDM_CLICK_BUTTON to simulate clicking a non-existent button, or DestroyWindow if you're managing the dialog window directly) or a timer-based auto-close mechanism. For simplicity and reliability, simulating a button click is often the most straightforward approach when working directly with the TaskDialogIndirect function.

#include <windows.h>
#include <commctrl.h>
#include <string>

#pragma comment(lib, "comctl32.lib")

// Forward declaration for the callback
HRESULT CALLBACK TaskDialogCallback(
    HWND hwnd, UINT uNotification, WPARAM wParam, LPARAM lParam, LONG_PTR dwRefData);

int APIENTRY wWinMain(_In_ HINSTANCE hInstance,
                      _In_opt_ HINSTANCE hPrevInstance,
                      _In_ LPWSTR    lpCmdLine,
                      _In_ int       nCmdShow)
{
    UNREFERENCED_PARAMETER(hPrevInstance);
    UNREFERENCED_PARAMETER(lpCmdLine);

    // Enable visual styles for common controls
    INITCOMMONCONTROLSEX icex;
    icex.dwSize = sizeof(INITCOMMONCONTROLSEX);
    icex.dwICC = ICC_TASKDLG_CLASSES;
    InitCommonControlsEx(&icex);

    TASKDIALOGCONFIG tdc = { sizeof(TASKDIALOGCONFIG) };
    tdc.hwndParent = NULL; // No parent window
    tdc.hInstance = hInstance;
    tdc.dwFlags = TDF_ALLOW_DIALOG_CANCELLATION | TDF_CAN_BE_CLOSED; // Allow closing with ESC/Alt+F4
    tdc.pszWindowTitle = L"Information";
    tdc.pszMainInstruction = L"Operation in Progress";
    tdc.pszContent = L"Please wait while the system completes the requested task.";
    // No buttons specified: tdc.pButtons = NULL; tdc.cButtons = 0;
    tdc.pfCallback = TaskDialogCallback;
    tdc.lpCallbackData = (LONG_PTR)NULL; // Example: Pass dialog handle or context

    int nButton = 0;
    HRESULT hr = TaskDialogIndirect(&tdc, &nButton, NULL, NULL);

    if (SUCCEEDED(hr))
    {
        // Dialog was closed (e.g., via ESC or programmatic close)
        OutputDebugStringW(L"TaskDialog closed.\n");
    }
    else
    {
        // Handle error
        std::wstring errorMsg = L"TaskDialogIndirect failed with HRESULT: " + std::to_wstring(hr) + L"\n";
        OutputDebugStringW(errorMsg.c_str());
    }

    return 0;
}

HRESULT CALLBACK TaskDialogCallback(
    HWND hwnd, UINT uNotification, WPARAM wParam, LPARAM lParam, LONG_PTR dwRefData)
{
    UNREFERENCED_PARAMETER(lParam);
    UNREFERENCED_PARAMETER(dwRefData);

    switch (uNotification)
    {
        case TDN_CREATED:
        {
            // Dialog has been created, can set a timer to close it after a delay
            SetTimer(hwnd, 1, 3000, NULL); // Close after 3 seconds
            break;
        }
        case TDN_TIMER:
        {
            // Timer elapsed, close the dialog
            KillTimer(hwnd, 1);
            // Simulate clicking a button with ID 0 to close the dialog.
            // Even if no buttons are visible, this works.
            SendMessage(hwnd, TDM_CLICK_BUTTON, IDCANCEL, 0); // IDCANCEL is a good default for programmatic close
            break;
        }
        case TDN_BUTTON_CLICKED:
        {
            // This case might be hit if TDM_CLICK_BUTTON is used.
            // wParam contains the button ID that was 'clicked'.
            break;
        }
    }
    return S_OK;
}

C++ code for a TaskDialog that displays no buttons and closes automatically after 3 seconds using a timer in its callback function.

Controlling the Dialog's Lifetime

The provided code uses the TDN_CREATED notification in the TaskDialogCallback to set a timer. When the timer elapses (TDN_TIMER), SendMessage(hwnd, TDM_CLICK_BUTTON, IDCANCEL, 0) is used to programmatically dismiss the dialog. IDCANCEL (or any other standard button ID like IDOK) works even if no such button is visible, effectively telling the TaskDialog to close. Alternatively, if you need to close the dialog based on an external event (e.g., a background thread completing its work), you would obtain the HWND of the TaskDialog (available in the TDN_CREATED notification) and then use PostMessage or SendMessage from your event handler to send TDM_CLICK_BUTTON to that HWND.

1. Step 1

Include necessary headers: <windows.h>, <commctrl.h>, and <string> for utility.

2. Step 2

Initialize common controls with InitCommonControlsEx to ensure TaskDialog styling is applied.

3. Step 3

Populate the TASKDIALOGCONFIG structure. Crucially, set pButtons to NULL and cButtons to 0 to prevent any buttons from appearing. Set dwFlags to TDF_ALLOW_DIALOG_CANCELLATION to allow the user to close it with ESC/Alt+F4 if needed.

4. Step 4

Implement a TaskDialogCallback function. Inside TDN_CREATED, set a timer using SetTimer. In TDN_TIMER, KillTimer and then use SendMessage(hwnd, TDM_CLICK_BUTTON, IDCANCEL, 0) to programmatically close the dialog.

5. Step 5

Call TaskDialogIndirect with your configured TASKDIALOGCONFIG structure. Handle the HRESULT return value to check for success or failure.