Selecting ltmmCapture Object Sizes for C
The following example shows how to enumerate and select ltmmCapture object sizes.
// define helper macros for using interfaces under C
#define COBJMACROS
#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
//
// BuildSizeList
// fills a listbox to match the contents of the collection
//
// pSizes = size collection's interface pointer
// hwndListBox = listbox window handle
//
void BuildSizeList(IltmmCaptureSizes* pSizes, 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
IltmmCaptureSizes_get_Count(pSizes, &count);
for(i = 0; i < count; i++)
{
IltmmCaptureSize* pSize;
TCHAR sz[256];
int index;
VARIANT_BOOL f;
long width;
long height;
// retrieve collection item
IltmmCaptureSizes_Item(pSizes, i, &pSize);
// get displayable name
IltmmCaptureSize_get_Width(pSize, &width);
IltmmCaptureSize_get_Height(pSize, &height);
_stprintf(sz, _T("%d x %d"), width, height);
// 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
IltmmCaptureSize_get_Selected(pSize, &f);
if(f)
selected = i;
// free the collection item
IUnknown_Release(pSize);
}
// 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;
}
}
}
//
// SizeSelectionChanged
// called to reflect changes in the listbox selection
//
// pSizes = size collection's interface pointer
// hwndListBox = listbox window handle
//
void SizeSelectionChanged(IltmmCaptureSizes* pSizes, 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)
{
// get the collection item index
item = (long) SendMessage(hwndListBox, LB__getITEMDATA, index, 0);
// select the item
#ifdef _DEBUG
{
IltmmCaptureSize* pSize;
IltmmCaptureSizes_Item(pSizes, item, &pSize);
hr = IltmmCaptureSize_put_Selected(pSize, VARIANT_TRUE);
IUnknown_Release(pSize);
}
#else
hr = IltmmCaptureSizes_put_Selection(pSizes, item);
#endif
// if new selection failed, we need to force the listbox to match the actual selection
if(FAILED(hr))
{
// get the real selection
IltmmCaptureSizes_get_Selection(pSizes, &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;
}
}
}
}
}
//
// SizeDlgProc
// selects object sizes
//
BOOL CALLBACK SizeDlgProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
IltmmCaptureSizes* pSizes;
IltmmDevices* pDevices;
long index;
switch (msg)
{
case WM_INITDIALOG:
// select the first video capture device
IltmmCapture_get_VideoDevices(g_pCapture, &pDevices);
IltmmDevices__put_Selection(pDevices, 0);
IUnknown_Release(pDevices);
IltmmCapture_get_VideoCaptureSizes(g_pCapture, &pSizes);
// setup an initial size of 320 x 240
IltmmCaptureSizes_Find(pSizes, 320, 240, &index);
IltmmCaptureSizes_put_Selection(pSizes, index);
// initialize the video size listbox
BuildSizeList(pSizes, GetDlgItem(hwnd, IDC_CAPTURESIZES));
IUnknown_Release(pSizes);
return TRUE;
break;
case WM_COMMAND:
switch(LOWORD(wParam))
{
case IDC_CAPTURESIZES:
if(HIWORD(wParam) == LBN_SELCHANGE)
{
// select the video size
IltmmCapture_get_VideoCaptureSizes(g_pCapture, &pSizes);
SizeSelectionChanged(pSizes, GetDlgItem(hwnd, IDC_CAPTURESIZES));
IUnknown_Release(pSizes);
}
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_ltmmCapture, NULL, CLSCTX_INPROC_SERVER, &IID_IltmmCapture, (void**) &g_pCapture);
if(FAILED(hr))
goto error;
DialogBox(g_hInstance, (LPCTSTR)IDD_SIZEDLG, NULL, SizeDlgProc);
error:
// cleanup
if(g_pCapture)
IUnknown_Release(g_pCapture);
CoUninitialize();
return 0;
}