The MFC CDHtmlDialog class

• Download source and statically linked demo app (beta 1) - 181 Kb
• Download source and statically linked demo app (beta 2) - 274 Kb

Introduction

This sample demonstrates using the new MFC7 CDHtmlDialog class. A dialog with a simple HTML page is created and displayed, and events from objects within that page are handled, and the HTML within the page modified dynamically to respond to these events.

Please note that you need the new MFC libraries to compile this application. I have statically linked the demo application so you can at least see the new class in action.

Creating the Application

The sample application is based on the MFC AppWizard. To create the project, use the wizard to create a standard MFC dialog and in the Application Type property page ensure that you choose dialog based, and check the Use HTML dialog. An application will be created with the main dialog derived from CDHtmlDialog. A resource containing a HTML page will also be created, and it's this page that will be displayed in the dialog at execution.

The HTML designer in Visual Studio allows you to edit the HTML. Each element on the HTML should be given an ID so that it can be accessed from within your CDHtmlDialog derived class.

HTML Element events

To catch events fired by HTML elements (such as mouse clicks on buttons) you must add an entry to the dialog's DHTML event map. This is analogous to adding message handlers for normal windows controls:

BEGIN_DHTML_EVENT_MAP(CDHTMLDialogDlg)
    DHTML_EVENT_ONCLICK(_T("ButtonOK"), OnButtonOK)
    DHTML_EVENT_ONCLICK(_T("ButtonCancel"), OnButtonCancel)
    DHTML_EVENT_ONCLICK(_T("CheckLink"), OnCheckClick)
END_DHTML_EVENT_MAP()

Our HTML page contains 2 buttons (OK, with ID ButtonOK and Cancel, with ID ButtonCancel) and a checkbox (ID CheckLink). We will use the checkbox to enable/disable a hyperlink element (ID LinkCP) on the same page.

The DHTML event map shown above associates click events for the buttons and check boxes with member functions of the dialog. The OK and Cancel button handlers simply call base class members that close the dialog. The OnCheckClick handler is called when the checkbox in the HTML page is clicked.

To make the check box determine the state of the hyperlink we catch the click event for the checkbox and replace the outer HTML of the hyperlink (the outer HTML is the HTML within the hyperlink plus the open and closing tags). For a non-active state we replace the out HTML with plain text, and for an active state we insert the <a href=...> tag.

Our click event handler function looks like the following. We use a member variable m_LinkActive to keep track of the state of the link.

<a>HRESULT CDHTMLDialogDlg::OnCheckClick(IHTMLElement* pElement)
{
    // toggle the link's active state
    m_LinkActive = !m_LinkActive;

    // we need to get an interface pointer to the link element
    IHTMLElement* pLinkElement = NULL;

    if (GetElement(_T("LinkCP"), &pLinkElement) == S_OK && 
          pLinkElement != NULL)
    {
        // For an active link, set the outerHTML as the appropriate <a ...> tag
        if (m_LinkActive)
        {
            pLinkElement->put_outerHTML(_bstr_t("<a ID=LinkCP target=_blank href='http://www.codeproject.com'>here</a>"));
        }
        // For an inactive link, replace the outerHTML with grey text
        else
        {
            pLinkElement->put_outerHTML(_bstr_t("<font ID=LinkCP color='#COCOCO'>here</font>"));
        }

        pLinkElement->Release();  // Thanks Heath
    }

    return S_OK;
}
</a>