IOleInPlaceObjectWindowlessImpl::GetWindow
The container calls this function to get the window handle of the control.
HRESULT GetWindow(
HWND* phwnd
);
Remarks
Some containers will not work with a control that has been windowless, even if it is currently windowed. In ATL's implementation, if the control class's data member m_bWasOnceWindowless is TRUE, the function returns E_FAIL. Otherwise, if phwnd is not NULL, GetWindow sets *phwnd to the control class's data member m_hWnd and returns S_OK.
See IOleWindow::GetWindow in the Windows SDK.
Requirements
Header: atlctl.h