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(); }