Notifies the container that the object is about to be activated in place and that the object is going to replace the container's main menu with an in-place composite menu.
HRESULT IOleInPlaceSite::OnUIActivate();
This method supports the standard return value E_UNEXPECTED, as well as the following:
The in-place object calls IOleInPlaceSite::OnUIActivate just before activating its user interface.
The container should remove any user interface associated with its own activation. If the container is itself an embedded object, it should remove its document-level user interface.
If there is already an object active in place in the same document, the container should call IOleInPlaceObject::UIDeactivate before calling OnUIDeactivate.
Windows NT: Use version 3.1 or later.
Windows: Use Windows 95 or later.
Windows CE: Unsupported.
Header: Declared in oleidl.h.
IOleInPlaceObject::UIDeactivate