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