Moving a Video Window (Video Renderer Filter) by Using the Mouse

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Environment: VC++, MFC, DirectX

Introduction

If you are creating your own video player and you are using a Video Renderer Filter, I guess you’ll have a problem getting the HWND of the Video Window because the IVideoWindow interface of DirectShow doesn’t provide you with a GetVideoWindowHandler method. To get the HWND of the Video Window and drag it with the mouse, please complete the following steps:

Step 1

The main problem of the IVideoWindow interface is that a method such as “GetVideoWindowHandler” doesn’t exist. Really, I don’t understand why Microsoft didn’t create such a method. So, you can find the GetWindowHandle method in the IOverlay interface on the input pin (!) of the Video Renderer Filter. First, let’s get the IOverlay interface:

IGraphBuilder m_pFilterGraph;
IOverlay m_pOverlay;
// here you should create a filter graph and render your video file
...
hr = m_pFilterGraph->Render(...);
...
// getting IOverlay interface.
IBaseFilter *pFilter= NULL;
IPin *pin = NULL;
if (SUCCEEDED(m_pFilterGraph->FindFilterByName(L"Video Renderer",
    &pFilter))) {
  if (SUCCEEDED(pFilter->FindPin(L"VMR Input0", &pin))) {
    if (SUCCEEDED(pin->QueryInterface(IID_IOverlay,
        (void **)&m_pOverlay))){
      pin->Release();
      pFilter->Release();
    }
  } else {
    pFilter->Release();
  }
}

Step 2

Create a window class to receive the ON_WM_LBUTTONDOWN message from your Video Window. It can be a main application window, or some hidden child window.

CVideoWindowListner : public CWnd
{
...
};
...
void CVideoWindowListner::OnLButtonDown(UINT nFlags, CPoint point)
{
  if(m_pOverlay == NULL) return;
  HWND hWnd;
  // getting HWND of Video Window
  HRESULT hr = m_pOverlay->GetWindowHandle(&hWnd);
  // move it!
  ::SendMessage(hWnd,WM_SYSCOMMAND, SC_MOVE | HTCAPTION, 0);

  CWnd::OnLButtonDown(nFlags, point);
}

Step 3

Your Video Window should send an ON_WM_LBUTTONDOWN message to the window defined in the previous step.

// this is your target window for the Video Window messages
CVideoWindowListner m_VideoWindowListner;
m_VideoWindowListner.Create(...);
...
// getting IVideoWindow interface
IVideoWindow  *pVW ;
hr = m_pFilterGraph->QueryInterface(IID_IVideoWindow,
                                       (void **)&pVW);

// specifying m_VideoWindowListner like receiver all Video Window
// messages
pVW->put_MessageDrain((OAHWND)m_VideoWindowListner.m_hWnd);

Step 4

If you want to put a Video Window to the main application window:

pVW->put_Owner((OAHWND)AfxGetApp()->m_pMainWnd->m_hWnd);
CRect rect;
rect.left = ... ;
rect.top  = ... ;
...
pVW->SetWindowPosition(rect.left, rect.top, rect.right,
                       rect.bottom);

If you want to detach the Video Window from the main window and show it separately:

pVW->put_Owner(NULL);

In both cases, m_VideoWindowListner will receive all Video Window messages!

Tip

If you have some problems with the video (blinking, or not properly repainting) in the child window: “MFC applications which place the video window in a child window must define an empty WM_ERASEBKGND message handler, or the video display area will not repaint correctly.”© Microsoft: IVideoWindow Interface.