Selecting ltmmCapture Object Sizes for C

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

// 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 
 
// 
// 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 
   IltmmCaptureSizes_get_Count(pSizes, &count);  
 
   for(i = 0; i < count; i++) 
   { 
      IltmmCaptureSize* pSize;  
      TCHAR sz[256];  
      int index;  
      VARIANT_BOOL f;  
      long width;  
      long height;  
 
      // retrieve collection item 
      IltmmCaptureSizes_Item(pSizes, i, &pSize);  
 
      // get displayable name 
      IltmmCaptureSize_get_Width(pSize, &width);  
      IltmmCaptureSize_get_Height(pSize, &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 
      IltmmCaptureSize_get_Selected(pSize, &f);  
      if(f)  
         selected = i;  
 
      // free the collection item 
      IUnknown_Release(pSize);  
   } 
 
   // 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;  
         IltmmCaptureSizes_Item(pSizes, item, &pSize);  
         hr = IltmmCaptureSize_put_Selected(pSize, VARIANT_TRUE);  
         IUnknown_Release(pSize); 
      } 
#else 
      hr = IltmmCaptureSizes_put_Selection(pSizes, item);  
#endif 
      // if new selection failed, we need to force the listbox to match the actual selection 
      if(FAILED(hr))  
      { 
         // get the real selection 
         IltmmCaptureSizes_get_Selection(pSizes, &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)  
{ 
   IltmmCaptureSizes* pSizes;  
   IltmmDevices* pDevices;  
   long index;  
 
 
   wParam = wParam ; 
   lParam = lParam ; 
 
   switch (msg)  
   { 
   case WM_INITDIALOG:  
      // select the first video capture device 
      IltmmCapture_get_VideoDevices(g_pCapture, &pDevices);  
      IltmmDevices_put_Selection(pDevices, 0);  
      IUnknown_Release(pDevices);  
 
      IltmmCapture_get_VideoCaptureSizes(g_pCapture, &pSizes);  
 
      // setup an initial size of 320 x 240 
      IltmmCaptureSizes_Find(pSizes, 320, 240, &index);  
      IltmmCaptureSizes_put_Selection(pSizes, index);  
 
      // initialize the video size listbox 
      BuildSizeList(pSizes, GetDlgItem(hwnd, IDC_CAPTURESIZES));  
      IUnknown_Release(pSizes);  
 
 
      return TRUE;  
      break;  
 
   case WM_COMMAND:  
      switch(LOWORD(wParam))  
      { 
      case IDC_CAPTURESIZES:  
         if(HIWORD(wParam) == LBN_SELCHANGE)  
         { 
            // select the video size 
            IltmmCapture_get_VideoCaptureSizes(g_pCapture, &pSizes);  
            SizeSelectionChanged(pSizes, GetDlgItem(hwnd, IDC_CAPTURESIZES));  
            IUnknown_Release(pSizes);  
         } 
         break;  
 
      case IDOK:  
         EndDialog(hwnd, IDOK);  
         return TRUE;  
         break;  
      } 
      break;  
   } 
   return FALSE;  
 
} 
 
void SelectingltmmCaptureObjectSizes_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_SIZEDLG, NULL, SizeDlgProc);  
 
 
error:  
   // cleanup 
 
   if(g_pCapture)  
      IUnknown_Release(g_pCapture);  
 
   CoUninitialize(); 
} 

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