The following example shows how to enumerate and select ltmmConvert object compressors.
#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
pCompressors->get_Count(&count);
for(i = 0; i < count; i++)
{
IltmmCompressor* pCompressor;
BSTR bstr;
TCHAR sz[256];
int index;
VARIANT_BOOL f;
// retrieve collection item
pCompressors->Item(i, &pCompressor);
// get displayable name
pCompressor->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
pCompressor->get_Selected(&f);
if(f)
selected = i;
// free the collection item
pCompressor->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;
}
}
}
//
// 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
pCompressors->put_Selection(-1);
} else
{
// get the collection item index
item = (long) SendMessage(hwndListBox, LB_GETITEMDATA, index, 0);
// select the item
#ifdef _DEBUG
{
IltmmCompressor* pCompressor;
pCompressors->Item(item, &pCompressor);
hr = pCompressor->put_Selected(VARIANT_TRUE);
pCompressor->Release();
}
#else
hr = pCompressors->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
pCompressors->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;
}
}
}
}
}
//
// 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
pCompressors->get_Selection(&item);
if(item >= 0)
{
// get it's unique name
pCompressors->Item(item, &pCompressor);
pCompressor->get_Name(&bstr);
pCompressor->Release();
}
else
{
bstr = NULL;
}
// rebuild the collection
pCompressors->Refresh();
if(bstr)
{
// find the previously selected item
pCompressors->Find(bstr, &item);
// make it the current selection
if(item >= 0)
pCompressors->put_Selection(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;
switch (msg)
{
case WM_INITDIALOG:
// initialize the audio compressor listbox
g_pConvert->get_AudioCompressors(&pCompressors);
BuildCompressorList(pCompressors, GetDlgItem(hwnd, IDC_AUDIOCOMPRESSORS));
pCompressors->Release();
// initialize the video compressor listbox
g_pConvert->get_VideoCompressors(&pCompressors);
BuildCompressorList(pCompressors, GetDlgItem(hwnd, IDC_VIDEOCOMPRESSORS));
pCompressors->Release();
return TRUE;
break;
case WM_COMMAND:
switch(LOWORD(wParam))
{
case IDC_REFRESHAUDIOCOMPRESSORS:
// refresh the audio compressor listbox
g_pConvert->get_AudioCompressors(&pCompressors);
RefreshCompressorList(pCompressors, GetDlgItem(hwnd, IDC_AUDIOCOMPRESSORS));
pCompressors->Release();
return TRUE;
break;
case IDC_AUDIOCOMPRESSORS:
if(HIWORD(wParam) == LBN_SELCHANGE)
{
// select the audio compressor
g_pConvert->get_AudioCompressors(&pCompressors);
CompressorSelectionChanged(pCompressors, GetDlgItem(hwnd, IDC_AUDIOCOMPRESSORS));
pCompressors->Release();
}
break;
case IDC_REFRESHVIDEOCOMPRESSORS:
// initialize the video compressor listbox
g_pConvert->get_VideoCompressors(&pCompressors);
RefreshCompressorList(pCompressors, GetDlgItem(hwnd, IDC_VIDEOCOMPRESSORS));
pCompressors->Release();
return TRUE;
break;
case IDC_VIDEOCOMPRESSORS:
if(HIWORD(wParam) == LBN_SELCHANGE)
{
// select the video compressor
g_pConvert->get_VideoCompressors(&pCompressors);
CompressorSelectionChanged(pCompressors, GetDlgItem(hwnd, IDC_VIDEOCOMPRESSORS));
pCompressors->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 capture 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)
g_pConvert->Release();
CoUninitialize();
return 0;
}