Tells the container that the object no longer has any undo state and that the container should not call IOleInPlaceObject::ReActivateAndUndo.
HRESULT IOleInPlaceSite::DiscardUndoState();
This method supports the standard return value E_UNEXPECTED, as well as the following:
If an object is activated in place and the object's associated object application maintains only one level of undo, there is no need to have more than one entry on the undo stack. That is, once a change has been made to the active object that invalidates its undo state saved by the container, there is no need to maintain this undo state in the container.
IOleInPlaceSite::DiscardUndoState is called by the active object while performing some action that would discard the undo state of the object. The in-place object calls this method to notify the container to discard the object's last saved undo state.
Windows NT: Use version 3.1 or later.
Windows: Use Windows 95 or later.
Windows CE: Unsupported.
Header: Declared in oleidl.h.
IOleInPlaceSite::DeactivateAndUndo