SAMPLE: Using VBX Controls in a "Non-MFC" Application

The information in this article applies to:

   The Microsoft Foundation Classes (MFC) included with:
    - Microsoft Visual C++ for Windows, versions 1.0 and 1.5

SUMMARY

Occasionally, you may want to have the capability of using VBX controls in an application that has been written in straight C instead of C++ or that was not written to use the entire Microsoft Foundation Classes framework. Although the support for VBX controls is available only to a Microsoft Foundation Classes application, it is possible to create a minimal Foundation Classes application which provides the ability to use VBX controls.

The following sample, VBXC, demonstrates a technique for creating a minimal MFC application which enables VBX support. The "minimal MFC application" here is a C++ based module that uses the MFC CWinApp class and that can be linked with a C based application to provide support for VBX controls.

Download VBXC.EXE, a self-extracting file, from the Microsoft Software Library (MSL) on the following services:

• Microsoft Download Service (MSDL)

        Dial (206) 936-6735 to connect to MSDL
        Download VBXC.EXE (size: 41629 bytes) 
  

• Internet (anonymous FTP)

        ftp ftp.microsoft.com
        Change to the \softlib\mslfiles directory
        Get VBXC.EXE (size: 41629 bytes) 
  

MORE INFORMATION

Any application which uses VBX controls will have to be a Microsoft Foundation Classes application. This simply means that it must have a CWinApp object. This article shows you how to create this CWinApp object, and provides the code necessary to support use of VBX controls. One of the consequences of including a CWinApp object is that you are automatically using the Foundation-provided WinMain function and the message loop contained within the CWinApp::Run() function. However, you must have a CWinApp object to use VBX controls in your application.

NOTE: Be aware that this is not intended as a replacement for knowledge of the Microsoft Foundation Classes. You will be linking with and calling into the MFC library functions, and you should be aware of how this will affect your program.

The idea is to create a CWinApp object which initializes the VBX support and then calls the underlying code in your application (i.e. it uses your application's WinMain). After creating a module which contains such an object, you can link with this module to obtain rudimentary support for VBX controls. You can then enhance the module as necessary to obtain further VBX capabilities. This article outlines the header and implementation files for a module which will give you this capability.

Following is the general implementation of the module which is referred to in this article as USEVBX:

//////////////////////////////////////////////////
//   FILE USEVBX.H
//
#ifdef __cplusplus      // two underscores

void InitializeVBX(HWND hDlg,LPCSTR lpszResourceName);

//
//  EOF - USEVBX.H
///////////////////////////////////////////////////

//////////////////////////////////////////////////
// FILE USEVBX.CPP
//
#include <afxwin.h>
#include <afxext.h>
#include "usevbx.h"

// Prototype the application's _WinMain

int PASCAL _WinMain(HINSTANCE hInstance,
                    HINSTANCE hPrevInstance,
                     LPSTR lpCmdLine,
                     int nCmdShow);

  virtual BOOL InitInstance();
  virtual int Run();

BOOL CVBXApp::InitInstance() {

  EnableVBX();
  return CWinApp::InitInstance();

int CVBXApp::Run()

  // Call the main application's WinMain.
  return _WinMain(m_hInstance,m_hPrevInstance,
                  m_lpCmdLine,m_nCmdShow);
}

void InitializeVBX(HWND hDlg,LPCSTR lpszResourceName)

  CWnd wndDlg;
  wndDlg.Attach(hDlg);
  wndDlg.ExecuteDlgInit(lpszResourceName);
  wndDlg.Detach();

CVBXApp theVBXApp;

//
// EOF - USEVBX.CPP
////////////////////////////////////////////////////////

1. Select Project/Edit and add the file USEVBX.CPP to your project.

2. Link in the appropriate MFC libraries. (e.g. MAFXCWD, LAFXCWD). You can do this by just selecting Options/Project, and checking the "Use Microsoft Foundation Classes" option, or you can explicitly put the library file name in your link options under Options/Project/ Linker/Libraries. For more information on library naming conventions, see Appendix B of the "Class Library User's Guide".

3. Rename your current application's WinMain function to _WinMain.

4. For any dialog box which contains VBX controls, add a handler for WM_INITDIALOG which first calls InitializeVBX(hDlg,lpszResourceName). This will initialize the VBX controls with the properties you specify in App Studio. You should also include the USEVBX.H header file in any module which calls this function.

This will enable VBX support in your application. You will probably want to be able to use App Studio to put VBXs on your dialog templates. You can't do this with a non-Microsoft Foundation Classes resource file so you must convert your current RC file. There is an article which discusses how to perform this conversion. The article is available in the Microsoft Knowledge Base and can be found by querying on the following words:

  converting rc file symbol directives

Once you have a resource script which is compatible with the Microsoft Foundation Classes you can use App Studio to put VBX controls on your dialog templates. You can also use App Studio to set initial properties for the controls, but for the initialization to be performed you must make the call to InitializeVBX in the WM_INITDIALOG processing of your dialog box.

To access the properties of the VBX you will have to create a C interface which implements the functionality contained in the CVBControl class. This can be done as needed. NOTE: The example VBXC implements most of these functions but the sample is for demonstration purposes only, and does not include instructions on how to re-implement the entire CVBControl class. For example, here is how you might add the capability to use the SetNumProperty and GetNumProperty functions:

1. Insert these prototypes directly after the InitializeVBX function in the header file USEVBX.H:

   // The last parameter in CVBControl::GetNumProperty has a
   // default of 0 in C++ but the default of 0 must be supplied
   // by the caller in C because default parameters are not
   // allowed.
   
   
   

                    LONG lValue,int index);