unsigned m_bAutoSize:1;
Remarks
Flag indicating the control cannot be any other size. This flag is checked by IOleObjectImpl::SetExtent and, if TRUE, causes the function to return E_FAIL.
If you choose the AUTOSIZE option from the Stock Properties tab in the ATL Object Wizard, the wizard automatically creates this data member in your control class, creates put and get methods for the property, and supports IPropertyNotifySink to automatically notify the container when the property changes.
CComControl Overview | Class Members
See Also IOleObjectImpl::SetExtent