Selecting ltmmCapture Object Sizes for C++

The following example shows how to enumerate and select ltmmCapture object sizes.

#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

//
// BuildSizeList
// fills a listbox to match the contents of the collection
//
// pSizes = size collection's interface pointer
// hwndListBox = listbox window handle
//
void BuildSizeList(IltmmCaptureSizes* pSizes, 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
   pSizes->get_Count(&count);

   for(i = 0; i < count; i++)
   {
      IltmmCaptureSize* pSize;
      TCHAR sz[256];
      int index;
      VARIANT_BOOL f;
      long width;
      long height;

      // retrieve collection item
      pSizes->Item(i, &pSize);
   
      // get displayable name
      pSize->get_Width(&width);
      pSize->get_Height(&height);
      _stprintf(sz, _T("%d x %d"), width, height);

      // 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
      pSize->get_Selected(&f);
      if(f)
         selected = i;
   
      // free the collection item
      pSize->Release();
   }

   // 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;
      }
   }

}

//
// SizeSelectionChanged
// called to reflect changes in the listbox selection
//
// pSizes = size collection's interface pointer
// hwndListBox = listbox window handle
//
void SizeSelectionChanged(IltmmCaptureSizes* pSizes, 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)
   {

      // get the collection item index
      item = (long) SendMessage(hwndListBox, LB_GETITEMDATA, index, 0);
   
      // select the item
#ifdef _DEBUG
      {
         IltmmCaptureSize* pSize;
         pSizes->Item(item, &pSize);
         hr = pSize->put_Selected(VARIANT_TRUE);
         pSize->Release();
      }
#else
      hr = pSizes->put_Selection(item);
#endif
      // if new selection failed, we need to force the listbox to match the actual selection
      if(FAILED(hr))
      {
         // get the real selection
         pSizes->get_Selection(&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;
            }
         }

      }
   
   }

}

//
// SizeDlgProc
// selects object sizes
//
BOOL CALLBACK SizeDlgProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
   IltmmDevices* pDevices;
   IltmmCaptureSizes* pSizes;
   long index;

   switch (msg) 
   {
   case WM_INITDIALOG:
      // select the first video capture device
      g_pCapture->get_VideoDevices( &pDevices);
      pDevices->put_Selection( 0);
      pDevices->Release();

      g_pCapture->get_VideoCaptureSizes(&pSizes);

      // setup an initial size of 320 x 240
      pSizes->Find( 320, 240, &index);
      pSizes->put_Selection(index);

      // initialize the video size listbox
      BuildSizeList(pSizes, GetDlgItem(hwnd, IDC_CAPTURESIZES));
      pSizes->Release();

      return TRUE;
      break;

   case WM_COMMAND:
      switch(LOWORD(wParam))
      {
      case IDC_CAPTURESIZES:
         if(HIWORD(wParam) == LBN_SELCHANGE)
         {
            // select the video size
            g_pCapture->get_VideoCaptureSizes(&pSizes);
            SizeSelectionChanged(pSizes, GetDlgItem(hwnd, IDC_CAPTURESIZES));
            pSizes->Release();
         }
         break;
         

      case IDOK:
         EndDialog(hwnd, IDOK);
         return TRUE;
         break;
      }
      break;
   }
   return FALSE;
   
}

   
int APIENTRY WinMain(HINSTANCE hInstance,
                     HINSTANCE hPrevInstance,
                     LPSTR     lpCmdLine,
                     int       nCmdShow)
{
   HRESULT hr;
   
   g_hInstance = hInstance;

   // initialize COM library
   hr = CoInitialize(NULL);
   if(FAILED(hr))
      goto error;
   
   // create the convert object
   hr = CoCreateInstance(CLSID_ltmmCapture, NULL, CLSCTX_INPROC_SERVER, IID_IltmmCapture, (void**) &g_pCapture);
   if(FAILED(hr))
      goto error;
   
   
   DialogBox(g_hInstance, (LPCTSTR)IDD_SIZEDLG, NULL, SizeDlgProc);


error:
   // cleanup

   if(g_pCapture)
      g_pCapture->Release();

   CoUninitialize();
   
   return 0;
}