How to get HWND of a windowless ATL control? - com

Question

I created a ATL windows less control and the class definition is like this:
class ATL_NO_VTABLE CRSPClient :
public IObjectSafetyImpl<CRSPClient, INTERFACESAFE_FOR_UNTRUSTED_CALLER|INTERFACESAFE_FOR_UNTRUSTED_DATA>,
public CComObjectRootEx<CComSingleThreadModel>,
public IDispatchImpl<IRSPClient, &IID_IRSPClient, &LIBID_axBanckleRSPClientLib, /*wMajor =*/ 1, /*wMinor =*/ 0>,
public IPersistStreamInitImpl<CRSPClient>,
public IOleControlImpl<CRSPClient>,
public IOleObjectImpl<CRSPClient>,
public IOleInPlaceActiveObjectImpl<CRSPClient>,
public IQuickActivateImpl<CRSPClient>,
public IViewObjectExImpl<CRSPClient>,
public IOleInPlaceObjectWindowlessImpl<CRSPClient>,
#ifdef _WIN32_WCE // IObjectSafety is required on Windows CE for the control to be loaded correctly
public IObjectSafetyImpl<CRSPClient, INTERFACESAFE_FOR_UNTRUSTED_CALLER>,
#endif
public CComCoClass<CRSPClient, &CLSID_RSPClient>,
public CComControl<CRSPClient>
Then for some purpose I need to post message to the window. I tried to get the handle of the window in quite many ways and ALL of them failed:
HWND CRSPClient::GetHwnd()
{
HWND hwndRet = NULL;
// hwndRet = m_hWnd;
//IOleInPlaceActiveObjectImpl<CRSPClient>::GetWindow(&hwndRet);
//IOleWindow<CRSPClient>::GetWindow(&hwndRet);
//this->m_spInPlaceSite->GetWindow(&hwndRet);
//CComQIPtr<IOleInPlaceSite> spSite = this->m_spClientSite;
//spSite->GetWindow(&hwndRet);
//hwndRet = ::WindowFromDC(GetDC());
return hwndRet;
}
Anybody know be there any way to get the HWND?
OMG I'm totally frustrated by microsoft's great ATL framework!

Answer 1

The whole point of the windowless control is that it works without a window handle. If you wanted to use window handle in case it, by any chance, exists and the control falled back into windowed mode, then it's easy: m_hWndCD.
If otherwise you have to have a window, then you have m_bWindowOnly to flag in constructor and indicate that you will need a HWND:
Flag indicating the control should be windowed, even if the container supports windowless controls.
If you still want it windowless and need a window just sometimes, under certain condition that come up on runtime, you always have an option to create a private message only window and dispatch messages through it.

Answer 2

Here is some code taken from Microsoft's Direct3D ATL sample. I haven't tested it yet.
// Get the window we need to use. This will either be the window that has already
// been created if we are window. If we are windowless the HWND of the client
// will be retrieved from the HDC.
void GetOurWindow()
{
// If we're windowless we still need an HWND for Direct3d
if (m_bWndLess)
{
HDC hDC;
// Get the HDC from the client
m_spInPlaceSite->GetDC(NULL, OLEDC_NODRAW, &hDC);
m_hOurWnd = WindowFromDC(hDC);
#if 1
// Code to make VB5 paint properly now it has clipped it's own hDC
RECT rect;
::GetClientRect(m_hOurWnd,&rect);
HRGN hRegion = CreateRectRgn(rect.left,rect.top,rect.right,rect.bottom);
SelectClipRgn(hDC,hRegion);
#endif
m_spInPlaceSite->ReleaseDC(hDC);
}
else
m_hOurWnd = m_hWnd;
}