Creating ActiveX Controls with C++Builder

INTRODUCTION

TOOLS

• MAKE.EXE
• BCC32.EXE
• BRCC32.EXE
• TLINK32.EXE
• TLIB.EXE
• MAKERSP.EXE
• REGSRVR.EXE
• The INCLUDE directory
• The LIB directory

• TD32.EXE
• IMPORT32.LIB - Use this one instead of the one in C++Builder. See below if you don't have BC++5.02
• GUIDGEN.EXE

• MIDL.EXE 3.0
• Win32SDK IDL files - Normally the interface descriptions you will write will need to include one or more of these files.
• RPCNDR.H - an updated version (defines __declspec(uuid))
• IMPORT32.LIB - from BC++ 5.02. Be sure to use this one instead of the one in C++Builder !
• CPP32.EXE - an updated version (Properly handles uuid's. See BCTOOLS.HLP)

CLASS LIBRARIES

• MFC
  
• ATL

  The newest MS class library, Active Template Library is now in version 2.1 available from MS website HTTP://www.microsoft.com/visualc/prodinfo/atlinst.htm. As the name suggests, these are template classes and this characteristic enables an ATL ActiveX to be smaller than controls built with MFC. ATL is shipped as source code which you include in your application. ATL also makes a DLL available (ATL.DLL) which contains code that may be shared across components. However, this DLL is not necessary.

• Control Frameworks

  This is found in the ActiveX SDK, which is available from MS website http://www.microsoft.com/msdownload/sbndownload/sbnaxsdk/sbnaxsdk.htm. All sample controls in this SDK link a static library CTLFW32.LIB the source for which is also provided. I have built this library and all ActiveX SDK sample controls with Borland C++Builder.

COMPILING TECHNIQUES

1. Microsoft code often uses anonymous structures and unions which are illegal in ANSI C++. tagVARIANT is one significant structure which uses anonymous structures and unions.

   Introduced in Borland C++5.0, BCC32.EXE has a -VF switch (called the MFC Compatability option) which forces the compiler to accept anonymous structures and unions. If you wanted to modify the code to be ANSI C++ compliant, you could define NONAMELESSUNION and change all instances of, for example,

     VARIANT v;
     v.vt = VT_EMPTY;
     v.lVal = 0;
   
   to,
   
     VARIANT v;
     v.n1.n2.vt = VT_EMPTY;
     v.n1.n2.n3.lVal = 0; 
   

   
   If you don't use this switch when building these samples, your output messages will be proliferated by error messages such as "vt is not a member of structure tagVARIANT".

2. For DLL's, which is what ActiveX controls are, MSVC++ uses the function name "DllMain" as the module's main entrypoint. Borland C++ uses the function name "DllEntryPoint". Be sure to change "DllMain" to "DllEntryPoint" when compiling a DLL written for MSVC++.

IMPORT AND STATIC LIBRARIES

• IMPORT32.LIB

  contains all OLE GUIDs

• INET.LIB

  contains all the import records of the internet API in HLINK.DLL, URLMON.DLL, MSCONF.DLL, WEBPOST.DLL and WININET.DLL.

• OLE2W32.LIB

  contains all the import records for OLE in OLE32.DLL, OLEAUT32.DLL, OLEPRO32.DLL and OLEDLG.DLL

• RPCEXTRA

  contains the import records from RPCDCE4.DLL

Just in case there is any doubt, .LIB and .OBJ files generated with MSVC++ can not be linked by Borland's linker at this time. Similarily, the MSVC++ linker can not link .LIB and .OBJ files generated by Borland's TLIB and BCC32.

BUILD PROCEDURE

1. Generate some GUIDs for your type library (LIBID), component class (CLSID), interfaces (IIDs and dispIDs)
2. Create the interface definition in the Object Description Language and save it to an .ODL file. Compile this with MKTYPLIB or MIDL. MIDL 3.0+ is best. No INITGUIDS macro since GUID instantiations are now split out to a .C file. Also if you are going to build a local or remote OLE server, you can specify your custom interfaces in .IDL and have the marshalling code generated.
3. Create a .REG file for your component.
4. Implement DllRegisterServer, DllCanUnloadNow, IClassFactory, IUnknown for your object.
5. Implement necessary OLE and custom interface methods.
6. Compile and link your source to a DLL renaming it with an OCX extension
7. Register your ActiveX control.
8. Test and debug.

In the least, you will likely have IDataObject for Uniform Data Transfer, IViewObject2, IOleCache, IOleCacheControl to display your data, IPersist* for Structured Storage, IOleObject for OLE Document Embedding, and IDispatch for Automation. Other basic interfaces you might want are IConnectionPointContainer, IConnectionPoint for outgoing interfaces and events, and IOleControl for keyboard and mouse handling withing the container, IOleInplaceObject, IOleInplaceActiveObject for In-place Activation, ISpecifyPropertyPages for those property pages you see controls have. IPerProperyBrowsing would be nice to have if you want a control's stock properties to be displayed in a container-supplied property sheet, likely along with ambient and extended properties as in the BCB IDE.

WHAT IS AN ACTIVEX CONTROL ?

Make no mistake about it. ActiveX requires on OLE. OLE requires COM.

THE MISSION

Borland C++, in any current flavor, can build OCX's from any of Microsoft's class libraries: MFC, Control Frameworks, or ATL. For examples of MFC, see BC502. For examples of Control Frameworks see my website. For examples of ATL, wait for the BCB3 beta. But we've been building Microsoft code for sometime now. Just no wizards.

I have not finished the control I set out to build - I've only got as far as data transfer and persistence. My control is called "George's Bitmap Control". It simply . . .

Please come and visit http://apsoft.com/~gcross/homebrew.html to see a number of the ActiveX SDK Samples, Brockschmidt Samples built with C++Builder 1.0.

References

1. "Inside OLE", Kraig Brockschmidt, MS Press 1995, Second Edition
2. Ole Programmer's Reference, MS Help file in Borland C++Builder, chapter titled "ActiveX Controls"

// from OAIDL.H
#if (__STDC__ && !defined(_FORCENAMELESSUNION)) || defined(NONAMELESSUNION)
#define __VARIANT_NAME_1 n1
#define __VARIANT_NAME_2 n2
#define __VARIANT_NAME_3 n3
#else
#define __tagVARIANT
#define __VARIANT_NAME_1
#define __VARIANT_NAME_2
#define __VARIANT_NAME_3
#endif
typedef /* [wire_marshal] */ struct tagVARIANT VARIANT;

struct  tagVARIANT
    {
    union 
        {
        struct  __tagVARIANT
            {
            VARTYPE vt;
            WORD wReserved1;
            WORD wReserved2;
            WORD wReserved3;
            union
                {
                LONG lVal;
                BYTE bVal;
                SHORT iVal;
                FLOAT fltVal;
                DOUBLE dblVal;
                VARIANT_BOOL boolVal;
#if !defined (__BORLANDC__)
                _VARIANT_BOOL bool;
#endif
                SCODE scode;
                CY cyVal;
                DATE date;
                BSTR bstrVal;
                IUnknown __RPC_FAR *punkVal;
                IDispatch __RPC_FAR *pdispVal;
                SAFEARRAY __RPC_FAR *parray;
                BYTE __RPC_FAR *pbVal;
                SHORT __RPC_FAR *piVal;
                LONG __RPC_FAR *plVal;
                FLOAT __RPC_FAR *pfltVal;
                DOUBLE __RPC_FAR *pdblVal;
                VARIANT_BOOL __RPC_FAR *pboolVal;
                _VARIANT_BOOL __RPC_FAR *pbool;
                SCODE __RPC_FAR *pscode;
                CY __RPC_FAR *pcyVal;
                DATE __RPC_FAR *pdate;
                BSTR __RPC_FAR *pbstrVal;
                IUnknown __RPC_FAR *__RPC_FAR *ppunkVal;
                IDispatch __RPC_FAR *__RPC_FAR *ppdispVal;
                SAFEARRAY __RPC_FAR *__RPC_FAR *pparray;
                VARIANT __RPC_FAR *pvarVal;
                PVOID byref;
                CHAR cVal;
                USHORT uiVal;
                ULONG ulVal;
                INT intVal;
                UINT uintVal;
                DECIMAL __RPC_FAR *pdecVal;
                CHAR __RPC_FAR *pcVal;
                USHORT __RPC_FAR *puiVal;
                ULONG __RPC_FAR *pulVal;
                INT __RPC_FAR *pintVal;
                UINT __RPC_FAR *puintVal;
                }	__VARIANT_NAME_3;
            }	__VARIANT_NAME_2;
        DECIMAL decVal;
        }	__VARIANT_NAME_1;
    };