Getting IWebBrowser2 pointer from event DISPID_TITLECHANGE - c++

Question

Im working on a Browser Helper Object, and I am trying to access the IWebBrowser2 that fires an event. With NavigateComplete2 and other events I can easly do it because I get the pointer on the parameters of Invoke.
But I was reading this on msdn and it says the only parameter for TitleChange event is the title, so how do I get the pointer to the webbrowser interface from the event TitleChange?
Here's how I am getting it with other events:
HRESULT STDMETHODCALLTYPE CSiteEvents::Invoke( DISPID dispIdMember, REFIID riid, LCID lcid, WORD wFlags,
DISPPARAMS __RPC_FAR *Params, VARIANT __RPC_FAR *pVarResult,
EXCEPINFO __RPC_FAR *pExcepInfo, UINT __RPC_FAR *puArgErr )
{
switch ( dispIdMember )
{
case DISPID_DOCUMENTCOMPLETE:
{
IWebBrowser2 *pBrowser = GetBrowser(Params->rgvarg[1]);
// stuff
pBrowser->Release();
}
break;
}
}
IWebBrowser2* GetBrowser(const VARIANT &_Argument)
{
IWebBrowser2 *pBrowser = NULL;
if (_Argument.vt == VT_DISPATCH)
{
HRESULT hr;
IDispatch *pDisp = _Argument.pdispVal;
if (pDisp)
{
hr = pDisp->QueryInterface( IID_IWebBrowser2, reinterpret_cast<void **>(&pBrowser) );
if ( FAILED(hr) )
pBrowser = NULL;
}
}
return pBrowser;
}
I am using Visual Studio 2010.

Answer 1

Isn't the IDispatch context here implicit? With the other events, you have to distinguish whereabouts in the control the event happened, while for TitleChange it's at the top level - this means this is an IDispatch* that can be queried to get the interface you need.
DWebBrowserEvents2 inherits from IDispatch but also encapsulate another IDispatch for each component of the window.

Answer 2

Title can be changed only in main window, so you can use IWebBrowser2, retrieved from IUnknown passed to your SetSite implementation.
STDMETHODIMP CMyBHO::SetSite(IUnknown *punkSite)
{
if(punkSite != NULL)
{
// CComPtr<IWebBrowser2> m_pWebBrowser is member of CMyBHO class
CComQIPtr<IServiceProvider> pServiceProvider = punkSite;
if(pServiceProvider != NULL)
pServiceProvider->QueryService(SID_SWebBrowserApp, IID_IWebBrowser2, (void**)&m_pWebBrowser);
}
else
{
if(m_pWebBrowser != NULL)
{
m_pWebBrowser = NULL;
}
}
return IObjectWithSiteImpl<CMyBHO>::SetSite(punkSite);
}