DAX FAQs 1.0
  by Conrad Herrmann
24 June 97
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Q: I want to use my favorite ActiveX control, but it seems not to work 
   in Delphi 3.   What interfaces are required for my control to work?

A: Here are the required and optional interfaces.

Required
  IPersistStreamInit - some older controls use IPersistStorage instead, 
    especially if they double as document object servers.
  IOleControl - *must* support GetWindow. Some newer controls are 
    "lightweight, windowless" controls designed for downloading off 
    the Internet.  These controls sacrifice backward compatibility for
    smaller code size.
  IDispatch - this is the automation interface

Optional
  IPerPropertyBrowsing - without it, will not use display strings/value menus
      in property editor
  IConnectionPointContainer - without it, will not use property notify sinks
  IPropertyNotifySink connection point
  IOleInPlaceObject - without it, will not activate in place (i.e. not create HWND)
  IOleInPlaceActiveObject - without it, will not have keystrokes

Most controls obtain interfaces from their container.  Newer controls may
attempt to obtain interfaces that Delphi does not provide.  These controls
ought to behave properly when the attempt to retrieve these interfaces fails,
however they might not.  Here is a list of interfaces that Delphi's container
can provide to controls it hosts:
  
Interfaces published by site object:
    IUnknown, IOleClientSite,
    IOleControlSite, IOleInPlaceSite, IOleInPlaceFrame, IDispatch,
    IPropertyNotifySink, ISimpleFrameSite