C / C++ / MFC

class CYourButton : public CButton
{
// Construction
public:
	CYourButton();

// Attributes
public:

// Operations
public:

// Overrides
	// ClassWizard generated virtual function overrides
	//{{AFX_VIRTUAL(CYourButton)
	//}}AFX_VIRTUAL

// Implementation
public:
	virtual ~CYourButton();

	// Generated message map functions
protected:
	//{{AFX_MSG(CYourButton)
	afx_msg void OnLButtonDown(UINT nFlags, CPoint point);
	//}}AFX_MSG

	DECLARE_MESSAGE_MAP()
};

/////////////////////////////////////////////////////////////////////////////
// CYourButton

CYourButton::CYourButton()
{
}

CYourButton::~CYourButton()
{
}

BEGIN_MESSAGE_MAP(CYourButton, CButton)
	//{{AFX_MSG_MAP(CYourButton)
	ON_WM_LBUTTONDOWN()
	//}}AFX_MSG_MAP
END_MESSAGE_MAP()

/////////////////////////////////////////////////////////////////////////////
// CYourButton message handlers

void CYourButton::OnLButtonDown(UINT nFlags, CPoint point) 
{
	// TODO: Add your message handler code here and/or call default

	TRACE("> Left mouse button down\n\r");	// This line has been manually added.

	CButton::OnLButtonDown(nFlags, point);
}

CComPtr<IPin> findPin(CComPtr<IBaseFilter>& pFilter, PIN_DIRECTION dir)
{
    PIN_DIRECTION pinDir;  // Direction of the current pin
    CComPtr<IEnumPins> pPinEnum;
    pFilter->EnumPins(&pPinEnum); // Get an enumeration of the filters pins
    while(1)
    {
        CComPtr<IPin> pPin; // Destroy at end of loop iteration
        if( pPinEnum->Next(1,&pPin,0) == S_OK )	// If enumeration works
        {
            pPin->QueryDirection(&pinDir);
            if(pinDir == dir) // If the pin direction matches
            {
                return pPin;
            }
        }
        else
        {
            return CComPtr<IPin>(); // Wraps a return of null (see default c'tor)
        }
    }
}
void setFormat(int width, int height, const GUID& subtype)
{
    int size;
    int count;
    VIDEO_STREAM_CONFIG_CAPS vscc;
    
    CComPtr<IPin> pPin = findPin(pSrc_,PINDIR_OUTPUT);
    CComQIPtr<IAMStreamConfig> pConfig(pPin);

    pConfig->GetNumberOfCapabilities(&count, &size);
    for(int i = 0; i < count; i++)
    {
        AM_MEDIA_TYPE *pMt;
        pConfig->GetStreamCaps(i, &pMt, (BYTE*)&vscc);
        if( (vscc.InputSize.cx == width) &&
            (vscc.InputSize.cy == height) &&
            (pMt->subtype == subtype) )
        {
            pConfig->SetFormat(pMt);
            DeleteMediaType(pMt);
            return;
        }
        DeleteMediaType(pMt);
    }
}