WMP EventDispatcher: how to know who sent the event? - c++

Question

I am embedding Windows Media Player in a C program. I found the WMP Host example in C++ in the WMP SDK. It contains an even dispatcher. But when I receive an event, how do I know who sent the event and how do I access that class object's variables? For example, I want to set a class member (variable) or call a method.
The CWMPHost object creates the window containing the WMP object and creates the event object. The minimal code is:
LRESULT CWMPHost::OnCreate(UINT uMsg, WPARAM wParam, LPARAM lParam, BOOL& bHandled)
{
AtlAxWinInit();
CComPtr<IAxWinHostWindow> spHost;
CComPtr<IConnectionPointContainer> spConnectionContainer;
CComWMPEventDispatch *pEventListener = NULL;
CComPtr<IWMPEvents> spEventListener;
HRESULT hr;
RECT rcClient;
m_dwAdviseCookie = 0;
// create window
GetClientRect(&rcClient);
m_wndView.Create(m_hWnd, rcClient, NULL, WS_CHILD | WS_VISIBLE | WS_CLIPCHILDREN, 0);
// load OCX in window
hr = m_wndView.QueryHost(&spHost);
hr = spHost->CreateControl(CComBSTR(_T("{6BF52A52-394A-11d3-B153-00C04F79FAA6}")), m_wndView, 0);
hr = m_wndView.QueryControl(&m_spWMPPlayer);
// start listening to events
hr = CComWMPEventDispatch::CreateInstance(&pEventListener);
spEventListener = pEventListener;
hr = m_spWMPPlayer->QueryInterface(&spConnectionContainer);
// See if OCX supports the IWMPEvents interface
hr = spConnectionContainer->FindConnectionPoint(__uuidof(IWMPEvents), &m_spConnectionPoint);
if (FAILED(hr))
{
// If not, try the _WMPOCXEvents interface, which will use IDispatch
hr = spConnectionContainer->FindConnectionPoint(__uuidof(_WMPOCXEvents), &m_spConnectionPoint);
}
hr = m_spConnectionPoint->Advise(spEventListener, &m_dwAdviseCookie);
return 0;
}
The full sample code can be found at https://github.com/pauldotknopf/WindowsSDK7-Samples/tree/master/multimedia/WMP/cpp/WMPHost

Answer 1

EDIT: My improved solution that meets my needs:
First I untangled the include dependencies and applied include guards against circular includes. The CWMPHost class definition doesn't need to know about the CWMPEventDispatch class; however its implementation does, so the CWMPEventDispatch.h class definition is included in the CWMPHost.cpp file but not in the CWMPHost.h file.
This allows to define a member of CWMPEventDispatch to be a pointer to the owning CWMPHost object:
CWMPHost *pCWMPHost;
It is set in the CWMPHost::Create method:
hr = CComWMPEventDispatch::CreateInstance(&pEventListener);
pEventListener->pCWMPHost= this;
Now the event dispatcher can access the methods and members of the CWMPHost object that created the dispatcher.