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; }