The following example shows how to enumerate and select ltmmCapture object renderers.
#include "ltmm.h" #include "resource.h" #include "tchar.h" #include "stdio.h" HINSTANCE g_hInstance; // application instance handle IltmmCapture* g_pCapture; // convert object's interface pointer // // BuildRendererList // fills a listbox to match the contents of the collection // // pRenderers = renderer collection's interface pointer // hwndListBox = listbox window handle // void BuildRendererList(IltmmRenderers* pRenderers, 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 pRenderers->get_Count(&count); for(i = 0; i < count; i++) { IltmmRenderer* pRenderer; BSTR bstr; TCHAR sz[256]; int index; VARIANT_BOOL f; // retrieve collection item pRenderers->Item(i, &pRenderer); // get displayable name pRenderer->get_FriendlyName(&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 pRenderer->get_Selected(&f); if(f) selected = i; // free the collection item pRenderer->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; } } } // // RendererSelectionChanged // called to reflect changes in the listbox selection // // pRenderers = renderer collection's interface pointer // hwndListBox = listbox window handle // void RendererSelectionChanged(IltmmRenderers* pRenderers, 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 pRenderers->put_Selection(-1); } else { // get the collection item index item = (long) SendMessage(hwndListBox, LB_GETITEMDATA, index, 0); // select the item #ifdef _DEBUG { IltmmRenderer* pRenderer; pRenderers->Item(item, &pRenderer); hr = pRenderer->put_Selected(VARIANT_TRUE); pRenderer->Release(); } #else hr = pRenderers->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 pRenderers->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; } } } } } // // RefreshRendererList // called when to completely rebuild the collection // // pRenderers = renderer collection's interface pointer // hwndListBox = listbox window handle // void RefreshRendererList(IltmmRenderers* pRenderers, HWND hwndListBox) { IltmmRenderer* pRenderer; long item; BSTR bstr; // get the currently selected item pRenderers->get_Selection(&item); if(item >= 0) { // get it's unique name pRenderers->Item(item, &pRenderer); pRenderer->get_Name(&bstr); pRenderer->Release(); } else { bstr = NULL; } // rebuild the collection pRenderers->Refresh(); if(bstr) { // find the previously selected item pRenderers->Find(bstr, &item); // make it the current selection if(item >= 0) pRenderers->put_Selection(item); SysFreeString(bstr); } // rebuild the listbox BuildRendererList(pRenderers, hwndListBox); } // // RendererDlgProc // selects object renderers // BOOL CALLBACK RendererDlgProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam) { IltmmRenderers* pRenderers; switch (msg) { case WM_INITDIALOG: // initialize the audio renderer listbox g_pCapture->get_AudioRenderers(&pRenderers); BuildRendererList(pRenderers, GetDlgItem(hwnd, IDC_AUDIODEVICES)); pRenderers->Release(); return TRUE; break; case WM_COMMAND: switch(LOWORD(wParam)) { case IDC_REFRESHAUDIODEVICES: // refresh the audio renderer listbox g_pCapture->get_AudioRenderers(&pRenderers); RefreshRendererList(pRenderers, GetDlgItem(hwnd, IDC_AUDIODEVICES)); pRenderers->Release(); return TRUE; break; case IDC_AUDIODEVICES: if(HIWORD(wParam) == LBN_SELCHANGE) { // select the audio renderer g_pCapture->get_AudioRenderers(&pRenderers); RendererSelectionChanged(pRenderers, GetDlgItem(hwnd, IDC_AUDIODEVICES)); pRenderers->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_DEVICEDLG, NULL, RendererDlgProc); error: // cleanup if(g_pCapture) g_pCapture->Release(); CoUninitialize(); return 0; }