The invalid region as a set of envelopes. Use after StartDrawing and before FinishDrawing.
[Visual Basic 6.0] Property ClipEnvelopes As ISet
[Visual Basic .NET] Public ReadOnly Property ClipEnvelopes As ISet
[C#] public ISet ClipEnvelopes {get;}
[Java] public ISet getClipEnvelopes() throws IOException, AutomationException
[C++] HRESULT get_ClipEnvelopes( ISet** envelopes );