Selecting ltmmCapture Object Target Devices 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;      // capture object's interface pointer 
// 
// BuildTargetDeviceList 
// fills a listbox to match the contents of the collection 
// 
// pTargetDevices = device collection's interface pointer 
// hwndListBox = listbox window handle 
// 
void BuildTargetDeviceList(IltmmTargetDevices* pTargetDevices, 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 
   IltmmTargetDevices_get_Count(pTargetDevices, &count); 
   for(i = 0; i < count; i++) 
   { 
      IltmmTargetDevice* pTargetDevice; 
      BSTR bstr; 
      TCHAR sz[256]; 
      int index; 
      VARIANT_BOOL f; 
      // retrieve collection item 
      IltmmTargetDevices_Item(pTargetDevices, i, &pTargetDevice); 
      // get displayable name 
      IltmmTargetDevice_get_FriendlyName(pTargetDevice, &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 
      IltmmTargetDevice_get_Selected(pTargetDevice, &f); 
      if(f) 
         selected = i; 
      // free the collection item 
      IUnknown_Release(pTargetDevice); 
   } 
   // 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; 
      } 
   } 
} 
// 
// TargetDeviceSelectionChanged 
// called to reflect changes in the listbox selection 
// 
// pTargetDevices = device collection's interface pointer 
// hwndListBox = listbox window handle 
// 
void TargetDeviceSelectionChanged(IltmmTargetDevices* pTargetDevices, 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 
      IltmmTargetDevices_put_Selection(pTargetDevices, -1); 
   } 
   else 
   { 
      // get the collection item index 
      item = (long) SendMessage(hwndListBox, LB_GETITEMDATA, index, 0); 
      // select the item 
#ifdef _DEBUG 
      { 
         IltmmTargetDevice* pTargetDevice; 
         IltmmTargetDevices_Item(pTargetDevices, item, &pTargetDevice); 
         hr = IltmmTargetDevice_put_Selected(pTargetDevice, VARIANT_TRUE); 
         IUnknown_Release(pTargetDevice); 
      } 
#else 
      hr = IltmmTargetDevices_put_Selection(pTargetDevices, item); 
#endif 
      // if new selection failed, we need to force the listbox to match the actual selection 
      if(FAILED(hr)) 
      { 
         // get the real selection 
         IltmmTargetDevices_get_Selection(pTargetDevices, &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; 
            } 
         } 
      } 
   } 
} 
// 
// RefreshTargetDeviceList 
// called when to completely rebuild the collection 
// 
// pTargetDevices = device collection's interface pointer 
// hwndListBox = listbox window handle 
// 
void RefreshTargetDeviceList(IltmmTargetDevices* pTargetDevices, HWND hwndListBox) 
{ 
   IltmmTargetDevice* pTargetDevice; 
   long item; 
   BSTR bstr; 
   // get the currently selected item 
   IltmmTargetDevices_get_Selection(pTargetDevices, &item); 
   if(item >= 0) 
   { 
      // get it's unique name 
      IltmmTargetDevices_Item(pTargetDevices, item, &pTargetDevice); 
      IltmmTargetDevice_get_Name(pTargetDevice, &bstr); 
      IUnknown_Release(pTargetDevice); 
   } 
   else 
   { 
      bstr = NULL; 
   } 
   // rebuild the collection 
   IltmmTargetDevices_Refresh(pTargetDevices); 
   if(bstr) 
   { 
      // find the previously selected item 
      IltmmTargetDevices_Find(pTargetDevices, bstr, &item); 
      // make it the current selection 
      if(item >= 0) 
         IltmmTargetDevices_put_Selection (pTargetDevices, item); 
      SysFreeString(bstr); 
   } 
   // rebuild the listbox 
   BuildTargetDeviceList(pTargetDevices, hwndListBox); 
} 
// 
// TargetDeviceDlgProc 
// selects object devices 
// 
BOOL CALLBACK TargetDeviceDlgProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam) 
{ 
   IltmmTargetDevices* pTargetDevices; 
   lParam = lParam ; 
   switch (msg) 
   { 
   case WM_INITDIALOG: 
      // initialize the target device listbox 
      IltmmCapture_get_TargetDevices(g_pCapture, &pTargetDevices); 
      BuildTargetDeviceList(pTargetDevices, GetDlgItem(hwnd, IDC_TARGETDEVICES)); 
      IUnknown_Release(pTargetDevices); 
      return TRUE; 
      break; 
   case WM_COMMAND: 
      switch(LOWORD(wParam)) 
      { 
   case IDC_REFRESHTARGETDEVICES: 
         // initialize the target device listbox 
         IltmmCapture_get_TargetDevices(g_pCapture, &pTargetDevices); 
         RefreshTargetDeviceList(pTargetDevices, GetDlgItem(hwnd, IDC_TARGETDEVICES)); 
         IUnknown_Release(pTargetDevices); 
         return TRUE; 
         break; 
   case IDC_TARGETDEVICES: 
         if(HIWORD(wParam) == LBN_SELCHANGE) 
         { 
            // select the target device 
            IltmmCapture_get_TargetDevices(g_pCapture, &pTargetDevices); 
            TargetDeviceSelectionChanged(pTargetDevices, GetDlgItem(hwnd, IDC_TARGETDEVICES)); 
            IUnknown_Release(pTargetDevices); 
         } 
         break; 
   case IDOK: 
         EndDialog(hwnd, IDOK); 
         return TRUE; 
         break; 
      } 
      break; 
   } 
   return FALSE; 
} 
void SelectingltmmCaptureObjectTargetDevices_Example ( HINSTANCE hInstance /*application instance handle*/ ) 
{ 
   HRESULT hr; 
   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; 
   DialogBox(g_hInstance, (LPCTSTR)IDD_TARGETDEVICEDLG, NULL, TargetDeviceDlgProc); 
error: 
   // cleanup 
   if(g_pCapture) 
      IUnknown_Release(g_pCapture); 
   CoUninitialize(); 
}