7 The OLE-Control-Framework Library

7.2 OLE Controls

Controls -- variously called OLE Controls, ActiveX Controls, and OCXs -- are applications that combine the features of an in-process OLE compound document server and an OLE Automation server. Thus much of the process of implementing a control has been described in Chapter 4, "OLE Automation" and Chapter 6, "The OLE-Server Library".

To implement an OLE control, use the OLE-Control-Framework library. The implementation process differs from using the OLE-Server library as follows:

You must build your OLE control application as a Dynamic Link Library, as you would for an in-process OLE server application. However, following convention, you can use the file extension .OCX instead of .DLL.
You must define a subclass of <OLE-control-framework>, page 337, instead of <ole-server-framework> or <ole-in-process-server>. (The class <OLE-control-framework> is a subclass of both <ole-in-process-server> and <simple-component-object>.)
Define coclass type information, as for an OLE Automation server.
Out-of-place activation will not be used.
Since there is no main program, self-registration and creation of a class factory are handled by code generated by the macro initialize-ole-control, page 338.

Overall, the code for an OLE control will look something like this:

define COM-interface <my-object-class> (<ole-control-framework>)
 ...
end;

define constant my-type-info = 
  make(<coclass-type-info>, class: <my-object-class>, ...);
...

initialize-ole-control(my-type-info, "my.prog.id");