Installing and Registering COM Servers and Type Libraries

Windows uses various kinds of COM servers and type libraries. Tarma ExpertInstall has built-in support for all of them as far as installation and registration is concerned (this includes unregistration and safe removal). In particular, it knows about:

• In-process COM servers, essentially dynamic link libraries (DLLs) with .dll or .ocx file name extensions and special COM-defined entry points. (The actual file name extension is immaterial; Tarma ExpertInstall analyzes each installation file to determine its type and further characteristics.)
• Out-of-process COM servers, which are stand-alone executable programs that adhere to certain COM conventions.
• Type libraries, whether embedded in DLL or EXE files, or as stand-alone TLB files. (Again, Tarma ExpertInstall does not rely upon the file name extension, but inspects each installation file to see if it contains a type library.)

There are two ways of dealing with these types of files:

• Use the file's built-in self-registration, or
• Add explicit registration options for each file.

Using the built-in self-registration is the easiest from a development and maintenance point of view; it allows the file to control its own registration entries in the Windows registry. However, it does not allow the same amount of rollback protection as the explicit registration method.

Explicit registration requires you to specify, for each COM server or type library, exactly what needs to be registered for the file. This is more error prone, but it allows a degree of flexibility and control that is not available with self-registration.

Unless there is a good reason otherwise, we recommend that you use self-registration for the files.

Using the file's built-in self-registration

Here is how Tarma ExpertInstall deals with files that have built-in self-registration.

In-process COM servers

In-process COM servers have DllRegisterServer and DllUnregisterServer entry points that perform registration and unregistration upon request. Tarma ExpertInstall's Setup program calls these entry points as appropriate during installation and uninstallation of the server.

Out-of-process COM servers

Out-of-process COM servers adhere to the COM convention of using /RegServer and /UnregServer command line options to perform their registration and unregistration actions. When started with one of these options, the server is supposed to run invisibly and to terminate immediately after completing the (un-)registration. Tarma ExpertInstall's Setup program uses these command line options as appropriate during installation and uninstallation of the server. However, there are no hard and fast rules to recognize an out-of-process COM server, so you must judge for yourself whether or not registration is required.

Type libraries

Type libraries are sometimes contained in DLL files (often as part of an in-process COM server), sometimes in EXE files (presumably as part of an out-of-process COM server), and sometimes in a special type library file, usually with a .tlb file name extension. Tarma ExpertInstall's treatment of a type library depends on the situation, as follows:

• If the type library is contained in a DLL file and that DLL file is an in-process COM server (i.e., has a DllRegisterServer entry point), Tarma ExpertInstall assumes that the server will register the type library as part of its overall registration process (as it should).
• If the type library is contained in a DLL file and that DLL file is not an in-process COM server, Tarma ExpertInstall will register it with the Windows function RegisterTypeLib.
• If the type library is contained in an EXE file, Tarma ExpertInstall assumes that the file is an out-of-process COM server and will suggest that it be registered as such. However, there are no hard and fast rules to recognize an out-of-process COM server, so you must judge for yourself whether or not registration is required.
• If the type library is contained in a stand-alone TLB file, Tarma ExpertInstall will register it with the Windows function RegisterTypeLib.

Once again, the actual file name extensions are immaterial; Tarma ExpertInstall analyzes each installation file to determine its type and other characteristics.

COM servers and type libraries are typically installed as shared files in the Windows System folder. Within Tarma ExpertInstall, this folder is represented by the Windows Volume\Windows\System32 folder. Unless you know what you are doing and have a very good reason to do otherwise, we recommend that you follow this convention.

Using explicit COM server or Type Library registration

This method requires that you add the files to the project, but set their Registration attribute to No self-registration. You must then configure the required registration option on the following project pages, where applicable:

• File and MIME Types (for applications etc. that register their own file types);
• COM Classes and TypeLibs (for COM servers and type libraries).

How to add a COM server or Type Library to your project

To add a COM server or type library to your Tarma ExpertInstall project, act as follows.

1. Go to the Files and Folders project page.
2. Add the COM server or type library file to the Windows Volume\Windows\System32 folder. If necessary, refer to Installing Files for information about adding installation files to folders.

3. Select the newly added COM server or type library file in the file list to display its File attributes pane, then make sure that the following options are set:

   • Install action - Install if newer
   • Remove action - Remove if installed

   • Registration - Set to No self-registration if you want to use explicit COM server or Type Library registration (below), else choose one of the following (the option should be preset to the correct one):

     • For in-process COM servers, select Use DllRegisterServer
     • For out-of-process COM servers, select Run with /RegServer
     • For type libraries, select Use RegisterTypeLib
   • Shared file - checked

   If you followed the procedure above, Tarma ExpertInstall will have set these options for you and you don't have to change anything, with the exception of out-of-process COM servers (EXE files), which cannot be recognized automatically.

4. Repeat steps 2-3 for other COM servers or type libraries.
5. For any COM servers or type libraries that you want to register explicitly, make sure that their Registration attribute is set to No self-registration, then go to the File and MIME Types and COM Classes and TypeLibs project pages to add the desired registration information.

The net result is that the server or type library will be installed and registered when your application is installed, and unregistered and removed when your application is uninstalled. All this is subject to the usual rules for file installation; in particular, Tarma ExpertInstall will correctly handle updates of existing copies of the file (based on a version check) and will only remove the file if no other applications use it. This remains true even if the SharedDlls reference count of the file is unreliable (as is often the case with third-party servers).