ActiveX designers can rely on the host to implement some of the interfaces required for OLE embedding. The list includes IAdviseSink, IOleClientSite, IOleInPlaceFrame, IOleInPlaceSite, IOleInPlaceUIWindow, and IOleWindow.
The host also implements the IActiveDesignerRuntimeSite interface, which allows a designer to delay connecting event sources and sinks; see "Handling Events" in Chapter 3 for details.
The host provides additional useful interfaces through the service mechanism, described in Chapter 6, "Services."