How to handle events for ActiveX controls in a CWnd dialog template in Visual C++

ActiveX controls are most often used in MFC CDialog or CFormView derived classes. There are occasions that call for an ActiveX control to be a child of a window that is not associated with a dialog template, such as a CWnd. Adding event handlers for a control created as a child of a CWnd requires a slightly different approach than adding the same handlers for the control when placed on a dialog box. This article provides step-by-step instructions for adding event handlers to the CWnd derived class that parents the control.

Step-by-step example

Use the following steps to create an ActiveX control dynamically in a CWnd derived window. The control used here is the Circ3 control from the Circle Tutorial, but the approach is valid for any OLE control. After creating the control, handlers are created for the ClickIn and ClickOut events of Circ3.

1. Create the MFC application that is to contain the ActiveX control. This application must include support for ActiveX controls. The default MFC Application Template project is sufficient for this article.
2. Insert a new class that wraps the ActiveX control that you want to use:
   1. On the Project menu, click Add Class.
   2. In the Add Class dialog box, select the MFC subcategory in the left view pane and then select the MFC Class From ActiveX Control template in the right view pane. Click Open.
   3. In the Add Class From ActiveX Control Wizard that appears next, click to select the Circ3 control from the Available ActiveX controls drop-down list. Alternatively, you can click to select File and then search for the Circ3 .ocx file if you know its location in the file system.
   4. After you have found and selected the Circ3 control, select all available interfaces and then click Finish to generate the MFC ActiveX wrapper classes.
3. Add a new dialog resource to your project:
   1. On the Project menu, click Add Resource.
   2. In the Add Resource dialog box, click to select Dialog Resource, and then click New.
   3. In the dialog box designer editor window that appears with your new dialog resource, right-click the new dialog, and then click Insert ActiveX Control.
   4. In the Insert ActiveX Control dialog box that appears, select the Circ3 control, and then click OK.
4. With the dialog box open in the editor, right-click the Circ3 control that was just added, and then click Add Class. In the MFC Class Wizard, type a class name for your new class, and then click to select CDialog in the Base class drop-down box. Click Finish.
5. Go back to the dialog editor, right-click the Circ3 class that was inserted earlier, and then click Add Event Handler. In the Event Handler Wizard, you see the ClickIn and ClickOut message types. Click to select the ClickIn message type. In the Class list, click to select the class in which you want the message handler to be generated. Use the CWnd or CWnd derived class that you identified earlier. After you have selected the message type and class, click Add and Edit to generate the message handling code. Repeat this step for each event or message you are interested in handling for this control.
6. Add a CCirc3 member variable named m_circ to the CWnd derived class declaration, as follows. You must include the header file of the CCirc3 wrapper class for this declaration:

   CCirc3 m_circ;
   					

   To do this in the Class View window, right-click the CWnd derived class in the Class View, point to Add, and then click Add Variable. In the Add Variable Wizard, type CCirc3 (or whatever class name was generated in step 2 by the Add ActiveX Control Wizard) as the Variable type and m_circ as the Variable name. Type a comment if you want to, and then click Finish to add the member variable to your class.
7. Override the Create() virtual function for the CWnd derived class. To do this, click to select the CWnd derived class in the Class View window. With the class selected in the Class View, click Overrides in the Properties window to display the overrideable base class methods. Find the Create override and then select the right-most column in the Properties window to the right of and in the same row as the Create override. Click the drop-down button in the rightmost column, and you have an option to add a Create handler, or to jump to the Create method in the code editor if your class already contains a Create override. In the handler, call the Create() method of your ActiveX control wrapper class to create the Circ3 child control, as follows:
   
   Note If you are creating the ActiveX control in a view, you may override OnInitialUpdate() instead of Create().

         BOOL MyCWnd::Create(LPCTSTR lpszClassName, LPCTSTR lpszWindowName,
           DWORD dwStyle, const RECT& rect, CWnd* pParentWnd, UINT nID,
           CCreateContext* pContext)
         {
         BOOL result = CWnd::Create(lpszClassName, lpszWindowName, dwStyle,
           rect, pParentWnd, nID, pContext);
   
         if(result != 0)   //Create the Circ3 ActiveX control.
           result = m_circ.Create("Test", WS_VISIBLE, CRect(1,1,130, 120),
              this, IDC_CIRC3CTRL1);
   
         return result;
         }
   					

   Important Parameter 5 is the ID for the control. This ID must match the ID that is used in the ON_EVENT macro that is created in step 5. This is the ID of the Circ3 control that is created in step 3.
8. After you add the necessary event handlers, you may delete the temporary dialog resource from the project. After you delete the dialog resource, you must add the m_circ member variable and a #define for IDC_CIRC3CTRL1, the ID of the Circ3 control. You may also delete the class that you created in step 4, unless you used this class as the class to which you added event method handlers in step 5.

Optional Another approach that is often used to add event handlers to CWnd derived classes is to add controls and event handlers to a dialog class, and then cut and paste the appropriate code into the View.h and View.cpp files, making modifications as necessary. Note, however, that the previous method is less prone to errors.

"MFC 4.0 Helps You Contain Your OLE Controls," MSDN Nov/Dec 1995.

OLE Control Containers: Using AppWizard to Create a Container Application

OLE Control Containers: Programming OLE Controls in an OLE Control Container - Visual C++ Books Online, MFC Encyclopedia