Selecting ltmmCapture Object Inputs for C

// define helper macros for using interfaces under C 
#ifndef COBJMACROS 
#define COBJMACROS 
#endif 
#include "ltmm.h" 
#include "resource.h" 
#include "tchar.h" 
#include "stdio.h" 
HINSTANCE g_hInstance; // application instance handle 
IltmmCapture* g_pCapture; // convert object's interface pointer 
// 
// BuildCaptureInputList 
// fills a listbox to match the contents of the collection 
// 
// pCaptureInputs = input collection's interface pointer 
// hwndListBox = listbox window handle 
// 
void BuildCaptureInputList(IltmmCaptureInputs* pCaptureInputs, HWND hwndListBox) 
{ 
   long i; 
   long count; 
   int selected = -1; 
   // reset the listbox contents 
   SendMessage(hwndListBox, LB_RESETCONTENT, 0, 0); 
   // get the collection's item count 
   IltmmCaptureInputs_get_Count (pCaptureInputs, &count); 
   for(i = 0; i < count; i++) 
   { 
      IltmmCaptureInput* pCaptureInput; 
      BSTR bstr; 
      TCHAR sz[256]; 
      int index; 
      VARIANT_BOOL f; 
      // retrieve collection item 
      IltmmCaptureInputs_Item (pCaptureInputs, i, &pCaptureInput); 
      // get displayable name 
      IltmmCaptureInput_get_Name (pCaptureInput, &bstr); 
      // convert from unicode 
      _stprintf(sz, _T("%ls"), bstr); 
      // free name 
      SysFreeString(bstr); 
      // add the name to the listbox 
      index = SendMessage(hwndListBox, LB_ADDSTRING, 0, (LPARAM) (LPCTSTR) sz); 
      // associate the listbox item with the collection item index 
      SendMessage(hwndListBox, LB_SETITEMDATA, index, i); 
      // remember this listbox item, if it is selected in the collection 
      IltmmCaptureInput_get_Selected (pCaptureInput, &f); 
      if(f) 
         selected = i; 
      // free the collection item 
      IUnknown_Release(pCaptureInput); 
   } 
   // select the appropriate listbox item 
   for(i = 0; i < count; i++) 
   { 
      if(selected == (long) SendMessage(hwndListBox, LB_GETITEMDATA, i, 0)) 
      { 
         SendMessage(hwndListBox, LB_SETCURSEL, i, 0); 
         break; 
      } 
   } 
} 
// 
// CaptureInputSelectionChanged 
// called to reflect changes in the listbox selection 
// 
// pCaptureInputs = input collection's interface pointer 
// hwndListBox = listbox window handle 
// 
void CaptureInputSelectionChanged(IltmmCaptureInputs* pCaptureInputs, HWND hwndListBox) 
{ 
   int index; 
   long item; 
   int i; 
   int count; 
   HRESULT hr; 
   // get the index of current listbox selection 
   index = (int) SendMessage(hwndListBox, LB_GETCURSEL, 0, 0); 
   if(index < 0) 
   { 
      // clear selection 
      IltmmCaptureInputs_put_Selection (pCaptureInputs, -1); 
   } 
   else 
   { 
      // get the collection item index 
      item = (long) SendMessage(hwndListBox, LB_GETITEMDATA, index, 0); 
      // select the item 
#ifdef _DEBUG 
      { 
         IltmmCaptureInput* pCaptureInput; 
         IltmmCaptureInputs_Item (pCaptureInputs, item, &pCaptureInput); 
         hr = IltmmCaptureInput_put_Selected (pCaptureInput, VARIANT_TRUE); 
         IUnknown_Release(pCaptureInput); 
      } 
#else 
      hr = IltmmCaptureInputs_put_Selection (pCaptureInputs, item); 
#endif 
      // if new selection failed, we need to force the listbox to match the actual selection 
      if(FAILED(hr)) 
      { 
         // get the real selection 
         IltmmCaptureInputs_get_Selection (pCaptureInputs, &item); 
         // find the matching listbox item 
         count = (int) SendMessage(hwndListBox, LB_GETCOUNT, 0, 0); 
         for(i = 0; i < count; i++) 
         { 
            if(item == (long) SendMessage(hwndListBox, LB_GETITEMDATA, i, 0)) 
            { 
               SendMessage(hwndListBox, LB_SETCURSEL, i, 0); 
               break; 
            } 
         } 
      } 
   } 
} 
// 
// SelectCompositeVideo 
// selects composite video, if available 
// 
// pCaptureInputs = input collection's interface pointer 
// hwndListBox = listbox window handle 
// 
void SelectCompositeVideo(IltmmCaptureInputs* pCaptureInputs, HWND hwndListBox) 
{ 
   long item; 
   BSTR bstr; 
   long i; 
   long count; 
   // Find the composite video input 
   bstr = SysAllocString(L"Video Composite"); 
   IltmmCaptureInputs_Find(pCaptureInputs, bstr, &item); 
   SysFreeString(bstr); 
   // make it the current selection 
   if(item >= 0) 
   { 
      IltmmCaptureInputs_put_Selection (pCaptureInputs, item); 
      IltmmCaptureInputs_get_Count (pCaptureInputs, &count); 
      // select the appropriate listbox item 
      for(i = 0; i < count; i++) 
      { 
         if(item == (long) SendMessage(hwndListBox, LB_GETITEMDATA, i, 0)) 
         { 
            SendMessage(hwndListBox, LB_SETCURSEL, i, 0); 
            break; 
         } 
      } 
   } 
} 
// 
// CaptureInputDlgProc 
// selects object inputs 
// 
BOOL CALLBACK CaptureInputDlgProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam) 
{ 
   IltmmCaptureInputs* pCaptureInputs; 
   wParam = wParam ; 
   lParam = lParam ; 
   switch (msg) 
   { 
   case WM_INITDIALOG: 
      // initialize the video input listbox 
      IltmmCapture_get_VideoInputs (g_pCapture, &pCaptureInputs); 
      BuildCaptureInputList(pCaptureInputs, GetDlgItem(hwnd, IDC_VIDEOINPUTS)); 
      IUnknown_Release(pCaptureInputs); 
      return TRUE; 
      break; 
   case WM_COMMAND: 
      switch(LOWORD(wParam)) 
      { 
   case IDC_SELECTCOMPOSITEVIDEO: 
         // select composite video 
         IltmmCapture_get_VideoInputs (g_pCapture, &pCaptureInputs); 
         SelectCompositeVideo(pCaptureInputs, GetDlgItem(hwnd, IDC_VIDEOINPUTS)); 
         IUnknown_Release(pCaptureInputs); 
         return TRUE; 
         break; 
   case IDC_VIDEOINPUTS: 
         if(HIWORD(wParam) == LBN_SELCHANGE) 
         { 
            // select the video input 
            IltmmCapture_get_VideoInputs (g_pCapture, &pCaptureInputs); 
            CaptureInputSelectionChanged(pCaptureInputs, GetDlgItem(hwnd, IDC_VIDEOINPUTS)); 
            IUnknown_Release(pCaptureInputs); 
         } 
         break; 
   case IDOK: 
         EndDialog(hwnd, IDOK); 
         return TRUE; 
         break; 
      } 
      break; 
   } 
   return FALSE; 
} 
void SelectingltmmCaptureObjectInputs_Example ( HINSTANCE hInstance /*application instance handle*/ ) 
{ 
   HRESULT hr; 
   IltmmDevices* pDevices; 
   g_hInstance = hInstance; 
   // initialize COM library 
   hr = CoInitialize(NULL); 
   if(FAILED(hr)) 
      goto error; 
   // create the capture object 
   hr = CoCreateInstance(&CLSID_ltmmCapture, NULL, CLSCTX_INPROC_SERVER, &IID_IltmmCapture, (void**) &g_pCapture); 
   if(FAILED(hr)) 
      goto error; 
   // select the first audio device available 
   IltmmCapture_get_AudioDevices (g_pCapture, &pDevices); 
   IltmmDevices_put_Selection (pDevices, 0); 
   IUnknown_Release(pDevices); 
   // select the first video device available 
   IltmmCapture_get_VideoDevices (g_pCapture, &pDevices); 
   IltmmDevices_put_Selection (pDevices, 0); 
   IUnknown_Release(pDevices); 
   DialogBox(g_hInstance, (LPCTSTR)IDD_INPUTDLG, NULL, CaptureInputDlgProc); 
error: 
   // cleanup 
   if(g_pCapture) 
      IUnknown_Release(g_pCapture); 
   CoUninitialize(); 
}