The following example shows how to enumerate and select ltmmConvert object compressors.
// 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 IltmmConvert* g_pConvert; // capture object's interface pointer // // BuildCompressorList // fills a listbox to match the contents of the collection // // pCompressors = compressor collection's interface pointer // hwndListBox = listbox window handle // void BuildCompressorList(IltmmCompressors* pCompressors, 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 IltmmCompressors_get_Count(pCompressors, &count); for(i = 0; i < count; i++) { IltmmCompressor* pCompressor; BSTR bstr; TCHAR sz[256]; int index; VARIANT_BOOL f; // retrieve collection item IltmmCompressors_Item (pCompressors, i, &pCompressor); // get displayable name IltmmCompressor_get_FriendlyName (pCompressor, &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 IltmmCompressor_get_Selected (pCompressor, &f); if(f) selected = i; // free the collection item IUnknown_Release(pCompressor); } // 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; } } } // // CompressorSelectionChanged // called to reflect changes in the listbox selection // // pCompressors = compressor collection's interface pointer // hwndListBox = listbox window handle // void CompressorSelectionChanged(IltmmCompressors* pCompressors, 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 IltmmCompressors_put_Selection (pCompressors, -1); } else { // get the collection item index item = (long) SendMessage(hwndListBox, LB_GETITEMDATA, index, 0); // select the item #ifdef _DEBUG { IltmmCompressor* pCompressor; IltmmCompressors_Item (pCompressors, item, &pCompressor); hr = IltmmCompressor_put_Selected (pCompressor, VARIANT_TRUE); IUnknown_Release(pCompressor); } #else hr = IltmmCompressors_put_Selection (pCompressors, item); #endif // if new selection failed, we need to force the listbox to match the actual selection if(FAILED(hr)) { // get the real selection IltmmCompressors_get_Selection (pCompressors, &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; } } } } } // // RefreshCompressorList // called when to completely rebuild the collection // // pCompressors = compressor collection's interface pointer // hwndListBox = listbox window handle // void RefreshCompressorList(IltmmCompressors* pCompressors, HWND hwndListBox) { IltmmCompressor* pCompressor; long item; BSTR bstr; // get the currently selected item IltmmCompressors_get_Selection (pCompressors, &item); if(item >= 0) { // get it's unique name IltmmCompressors_Item (pCompressors, item, &pCompressor); IltmmCompressor_get_Name (pCompressor, &bstr); IUnknown_Release(pCompressor); } else { bstr = NULL; } // rebuild the collection IltmmCompressors_Refresh (pCompressors); if(bstr) { // find the previously selected item IltmmCompressors_Find(pCompressors, bstr, &item); // make it the current selection if(item >= 0) IltmmCompressors_put_Selection (pCompressors, item); SysFreeString(bstr); } // rebuild the listbox BuildCompressorList(pCompressors, hwndListBox); } // // CompressorDlgProc // selects object compressors // BOOL CALLBACK CompressorDlgProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam) { IltmmCompressors* pCompressors; lParam = lParam ; switch (msg) { case WM_INITDIALOG: // initialize the audio compressor listbox IltmmConvert_get_AudioCompressors (g_pConvert, &pCompressors); BuildCompressorList(pCompressors, GetDlgItem(hwnd, IDC_AUDIOCOMPRESSORS)); IUnknown_Release(pCompressors); // initialize the video compressor listbox IltmmConvert_get_VideoCompressors (g_pConvert, &pCompressors); BuildCompressorList(pCompressors, GetDlgItem(hwnd, IDC_VIDEOCOMPRESSORS)); IUnknown_Release(pCompressors); return TRUE; break; case WM_COMMAND: switch(LOWORD(wParam)) { case IDC_REFRESHAUDIOCOMPRESSORS: // refresh the audio compressor listbox IltmmConvert_get_AudioCompressors (g_pConvert, &pCompressors); RefreshCompressorList(pCompressors, GetDlgItem(hwnd, IDC_AUDIOCOMPRESSORS)); IUnknown_Release(pCompressors); return TRUE; break; case IDC_AUDIOCOMPRESSORS: if(HIWORD(wParam) == LBN_SELCHANGE) { // select the audio compressor IltmmConvert_get_AudioCompressors (g_pConvert, &pCompressors); CompressorSelectionChanged(pCompressors, GetDlgItem(hwnd, IDC_AUDIOCOMPRESSORS)); IUnknown_Release(pCompressors); } break; case IDC_REFRESHVIDEOCOMPRESSORS: // initialize the video compressor listbox IltmmConvert_get_VideoCompressors (g_pConvert, &pCompressors); RefreshCompressorList(pCompressors, GetDlgItem(hwnd, IDC_VIDEOCOMPRESSORS)); IUnknown_Release(pCompressors); return TRUE; break; case IDC_VIDEOCOMPRESSORS: if(HIWORD(wParam) == LBN_SELCHANGE) { // select the video compressor IltmmConvert_get_VideoCompressors (g_pConvert, &pCompressors); CompressorSelectionChanged(pCompressors, GetDlgItem(hwnd, IDC_VIDEOCOMPRESSORS)); IUnknown_Release(pCompressors); } break; case IDOK: EndDialog(hwnd, IDOK); return TRUE; break; } break; } return FALSE; } void SelectingltmmConvertObjectCompressors_Example ( HINSTANCE hInstance /*application instance handle*/ ) { HRESULT hr; g_hInstance = hInstance; // initialize COM library hr = CoInitialize(NULL); if(FAILED(hr)) goto error; // create the convert object hr = CoCreateInstance(&CLSID_ltmmConvert, NULL, CLSCTX_INPROC_SERVER, &IID_IltmmConvert, (void**) &g_pConvert); if(FAILED(hr)) goto error; DialogBox(g_hInstance, (LPCTSTR)IDD_COMPRESSORDLG, NULL, CompressorDlgProc); error: // cleanup if(g_pConvert) IUnknown_Release(g_pConvert); CoUninitialize(); }