The following example shows how to enumerate and select ltmmCapture target devices.
#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 // // BuildTargetDeviceList // fills a listbox to match the contents of the collection // // pTargetDevices = device collection's interface pointer // hwndListBox = listbox window handle // void BuildTargetDeviceList(IltmmTargetDevices* pTargetDevices, 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 pTargetDevices->get_Count(&count); for(i = 0; i < count; i++) { IltmmTargetDevice* pTargetDevice; BSTR bstr; TCHAR sz[256]; int index; VARIANT_BOOL f; // retrieve collection item pTargetDevices->Item(i, &pTargetDevice); // get displayable name pTargetDevice->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 pTargetDevice->get_Selected(&f); if(f) selected = i; // free the collection item pTargetDevice->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; } } } // // TargetDeviceSelectionChanged // called to reflect changes in the listbox selection // // pTargetDevices = device collection's interface pointer // hwndListBox = listbox window handle // void TargetDeviceSelectionChanged(IltmmTargetDevices* pTargetDevices, 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 pTargetDevices->put_Selection(-1); } else { // get the collection item index item = (long) SendMessage(hwndListBox, LB_GETITEMDATA, index, 0); // select the item #ifdef _DEBUG { IltmmTargetDevice* pTargetDevice; pTargetDevices->Item(item, &pTargetDevice); hr = pTargetDevice->put_Selected(VARIANT_TRUE); pTargetDevice->Release(); } #else hr = pTargetDevices->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 pTargetDevices->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; } } } } } // // RefreshTargetDeviceList // called when to completely rebuild the collection // // pTargetDevices = device collection's interface pointer // hwndListBox = listbox window handle // void RefreshTargetDeviceList(IltmmTargetDevices* pTargetDevices, HWND hwndListBox) { IltmmTargetDevice* pTargetDevice; long item; BSTR bstr; // get the currently selected item pTargetDevices->get_Selection(&item); if(item >= 0) { // get it's unique name pTargetDevices->Item(item, &pTargetDevice); pTargetDevice->get_Name(&bstr); pTargetDevice->Release(); } else { bstr = NULL; } // rebuild the collection pTargetDevices->Refresh(); if(bstr) { // find the previously selected item pTargetDevices->Find(bstr, &item); // make it the current selection if(item >= 0) pTargetDevices->put_Selection(item); SysFreeString(bstr); } // rebuild the listbox BuildTargetDeviceList(pTargetDevices, hwndListBox); } // // TargetDeviceDlgProc // selects object devices // BOOL CALLBACK TargetDeviceDlgProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam) { IltmmTargetDevices* pTargetDevices; switch (msg) { case WM_INITDIALOG: // initialize the target device listbox g_pCapture->get_TargetDevices(&pTargetDevices); BuildTargetDeviceList(pTargetDevices, GetDlgItem(hwnd, IDC_TARGETDEVICES)); pTargetDevices->Release(); return TRUE; break; case WM_COMMAND: switch(LOWORD(wParam)) { case IDC_REFRESHTARGETDEVICES: // initialize the target device listbox g_pCapture->get_TargetDevices(&pTargetDevices); RefreshTargetDeviceList(pTargetDevices, GetDlgItem(hwnd, IDC_TARGETDEVICES)); pTargetDevices->Release(); return TRUE; break; case IDC_TARGETDEVICES: if(HIWORD(wParam) == LBN_SELCHANGE) { // select the target device g_pCapture->get_TargetDevices(&pTargetDevices); TargetDeviceSelectionChanged(pTargetDevices, GetDlgItem(hwnd, IDC_TARGETDEVICES)); pTargetDevices->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_TARGETDEVICEDLG, NULL, TargetDeviceDlgProc); error: // cleanup if(g_pCapture) g_pCapture->Release(); CoUninitialize(); return 0; }