HOWTO: Packaging MFC Controls for Use Over the Internet

• Microsoft Visual C++, 32-bit Editions, versions 4.1, 4.2b, 5.0, 5.0sp1
• Microsoft Internet Explorer versions 3.0, 3.01, 3.02, 4.0, 4.01 for Windows 95
• Microsoft Internet Explorer versions 3.0, 3.01, 3.02, 4.0, 4.01 for Windows NT 4.0

SUMMARY

When you embed ActiveX Controls in a web page using the <OBJECT> tag, the CODEBASE attribute used to specify the download location can point to a .cab file. This is the recommended way to package MFC ActiveX Controls. Packaging an MFC ActiveX Control in a cabinet file allows an .inf file to be included to control installation of the ActiveX Control, allows for dependent DLLs to be named and a location for them provided, allows for code signing, and automatically compresses the code for quicker download.

MORE INFORMATION

ActiveX controls are embedded in web pages using the <OBJECT> tag. The CODEBASE attribute of the <OBJECT> tag specifies the location from which to download the control. CODEBASE can point to a number of different file types successfully.

For instance, CODEBASE can point directly to an .ocx file as follows:

CODEBASE="http://example.microsoft.com/somecontrol.ocx#version=4,70,0,1086"

Since this downloads and installs the .ocx file only, this solution relies on any necessary supporting DLLs already existing on the client machine. In most cases, it should not be assumed that these DLLs will exist on the client and be of the necessary version.

Another alternative is for CODEBASE to point to an .inf file, for example:

   CODEBASE="http://example.microsoft.com/doyoutrustme.inf"

The best solution is for CODEBASE to point to a cabinet file. With this method, supporting DLLs can be referenced and the cabinet file signed. Please note: if the below directions for referencing the MFC DLLs are followed, the MFC DLLs will not be downloaded if they already exist on the client. The CODEBASE line will look similar to the following:

   CODEBASE="http://example.microsoft.com/acontrol.cab#version=1,2,0,0"

Cab Packaging Overview

In the Cabinet Software Development Kit (also called Cabinet SDK, or CAB Development Kit) you will find the necessary tools to construct cabinet (.cab) files. The CAB SDK may be downloaded from http://www.microsoft.com/workshop/prog/cab/cabdl.htm.

The cabinet file that CODEBASE points to should contain the .ocx file and an .inf file which will control the installation of the ActiveX Control. Dependent DLLs that may already exist on the system, such as the MFC DLLs, should not be included in this cabinet file. Instead, the MFC DLLs, and other dependent DLLs, should be packaged in separate cabinet files and referenced by the control's .inf file. The following example illustrates how to package the MFC Spindial sample control.

The <OBJECT> tag to include the Spindial control in a web page will look similar to the following:

   <OBJECT ID="Spindial1" WIDTH=200 HEIGHT=200
   CLASSID="CLSID:06889605-B8D0-101A-91F1-00608CEAD5B3"
   CODEBASE="http://example.microsoft.com/spindial.cab#Version=1,0,0,001">
         <PARAM NAME="_Version" VALUE="65536">
         <PARAM NAME="_ExtentX" VALUE="2646">
         <PARAM NAME="_ExtentY" VALUE="1323">
         <PARAM NAME="_StockProps" VALUE="0">
         <PARAM NAME="NeedlePosition" VALUE="2">
   </OBJECT>

   C:\CabDevKit\cabarc.exe -s 6144 N spindial.cab spindial.ocx spindial.inf

   ; ========================= spindial.inf ========================

   ; This .inf file will control the installation of the MFC Spindial
   ; control. This control has been compiled with Visual C++ version 4.2.
   ; The FileVersion tags in the dependent DLLs section on this file
   ; reflect this requirement.

   [version]
   ; version signature (same for both NT and Win95) do not remove
   signature="$CHICAGO$"
   AdvancedINF=2.0

   [Add.Code]
   spindial.ocx=spindial.ocx
   ; These are the necessary supporting DLLs for MFC 4.2 ActiveX Controls
   msvcrt.dll=msvcrt.dll
   mfc42.dll=mfc42.dll
   olepro32.dll=olepro32.dll
   ; thiscab is a keyword which, in this case, means that Spindial.ocx
   ; can be found in the same .cab file as this .inf file
   ; file-win32-x86 is an x86 platform specific identifier
   ; See the ActiveX SDK - ActiveX Controls - Internet Component Download -
   ; Packaging component code for automatic download

   [spindial.ocx]
   file-win32-x86=thiscab
   ; *** add your controls CLSID here ***
   clsid={06889605-B8D0-101A-91F1-00608CEAD5B3}
   ; Add your ocx's file version here.
   FileVersion=1,0,0,001
   RegisterServer=yes

   ; dependent DLLs
   [msvcrt.dll]
   ; This is an example of conditional hook. The hook only gets processed
   ; if msvcrt.dll of the specified version is absent on client machine.
   FileVersion=4,20,0,6164
   hook=mfc42installer

   [mfc42.dll]
   FileVersion=4,2,0,6256
   hook=mfc42installer

   [olepro32.dll]
   FileVersion=4,2,0,6068
   hook=mfc42installer

   [mfc42installer]
   file-win32-x86=http://activex.microsoft.com/controls/vc/mfc42.cab
   ; If dependent DLLs are packaged directly into the above cabinet file
   ; along with an .inf file, specify that .inf file to run as follows:
   ;InfFile=mfc42.inf
   ; The mfc42.cab file actually contains a self extracting executable.
   ; In this case we specify a run= command.
   run=%EXTRACT_DIR%\mfc42.exe

   ; ====================== end of spindial.inf =====================

Any reference to spindial should be changed to the name or your control. This includes comments and the following:

   spindial.ocx=spindial.ocx
   [spindial.ocx]

   clsid={06889605-B8D0-101A-91F1-00608CEAD5B3}
   FileVersion=1,0,0,001

   [ uuid(06889605-B8D0-101A-91F1-00608CEAD5B3),
     helpstring("Spindial Control"), control ]
     coclass Spindial

The last change that you will need to make is to enter the correct FileVersion for each of the MFC DLLs, [mfc42.dll], [olepro32.dll], and [mscvrt.dll]. Note that if you are using VC 4.1 or earlier, you will need to change any reference to mfc42.dll to mfc40.dll and any reference to msvcrt.dll to msvcrt40.dll.

The following FileVersions should be used:

VC 4.1 and earlier, use http://activex.microsoft.com/controls/vc/mfc40.cab

   Olepro32.dll   4,1,0,6038
   Mfc40.dll      4,1,0,6139
   Msvcrt40.dll  4,10,0,6038

   Olepro32.dll   4,2,0,6068
   Mfc42.dll      4,2,0,6256
   Msvcrt.dll    4,20,0,6164

   Olepro32.dll   5,0,4055,1
   Mfc42.dll     4,21,0,7022
   Msvcrt.dll     5,0,0,7022

   Olepro32.dll   5,0,4055,1
   Mfc42.dll     4,21,0,7160
   Msvcrt.dll     5,0,0,7128

   Olepro32.dll   5,0,4055,1
   Mfc42.dll     4,21,0,7160
   Msvcrt.dll     5,0,0,7128

   Olepro32.dll   5,0,4230,1
   Mfc42.dll     4,21,0,7303
   Msvcrt.dll     5,0,0,7303

REFERENCES

• ActiveX SDK - Packaging component code for automatic download
• ActiveX SDK - Safety API Reference
• ActiveX SDK - Signing with Microsoft Authenticode Technology
• ActiveX SDK - Cabinet (.cab) File Technology: Data Compression and Disk Layout
• Internet Client SDK – Component Development, ActiveX Controls