Strange EnumChildWindows issue

[Maxwell Chen]

When I declare a LVFINDINFO object in the function body, EnumChildWindows fails to locate the control of SysListView32 type (a Windows class type). When I remove the LVFINDINFO object from the body, it works well. The code snippet is as the below.

void CMainDlg::OnBnClickedGetDolby()
{
// Kill any running window if any.
KillRunningApplet(_T("Sound"));

// Launch it.
if(!LaunchCplApplet(\_T("mmsys.cpl"), 0, 0)) {
	OutputDebugString(\_T("LaunchCplApplet fails. \\n"));
	return;
}

// Make sure the applet pops up.
CWnd\* pWnd = NULL;
int i = 0;
while(!pWnd) {
	pWnd = FindWindow(NULL, \_T("Sound"));
	if(pWnd) {
		OutputDebugString(\_T("Found Sound window. \\n"));
		break;
	}
	Sleep(10);
	i++;
	if(i > 1000) {
		OutputDebugString(\_T("Sound window is not found. \\n"));
		return;
	}
}

// ---
m\_pListView = NULL;
EnumChildWindows(pWnd->m\_hWnd, DoSomethingHelper, (LPARAM)this);

if(m\_pListView) {
	OutputDebugString(\_T("Got SysListView32"));
}
else {
	OutputDebugString(\_T("SysListView32 is not found."));
	return;
}
m\_pListView->SendMessage(WM\_KEYDOWN, VK\_DOWN, 0);

CListView\* pView = (CListView\*)m\_pListView;
CListCtrl& Ctrl = pView->GetListCtrl();

LVFINDINFO info;  // <--- This line fails SysListView32.
int iIndex = 0;

info.flags = LVFI\_PARTIAL | LVFI\_STRING;
info.psz = \_T("Speaker");

/*

while ((iIndex = Ctrl.FindItem(&info)) != -1) {
	OutputDebugString(\_T("Speaker-like entry is found."));
	CString s = Ctrl.GetItemText(iIndex, 0);
	OutputDebugString(s);
}

*/

}

BOOL CALLBACK DoSomethingHelper(HWND hwnd, LPARAM lParam)
{
TCHAR sClassName[MAX_PATH] = {0};
GetClassName(hwnd, sClassName, MAX_PATH);
if(wcscmp(sClassName, _T("SysListView32")) == 0) {
CMainDlg* pMain = (CMainDlg*)lParam;
pMain->m_pListView = CWnd::FromHandle(hwnd);
}
OutputDebugString(sClassName);
return TRUE;
}

Maxwell Chen

[Maxwell Chen]

Okay, never mind. Constructing the LVFINDINFO object takes some time so EnumChildWindows takes longer time to complete. So I added a Sleep(10) after EnumChildWindows call to make it happy.

Maxwell Chen

[CPallini]

Maxwell Chen wrote:

pMain->m_pListView = CWnd::FromHandle(hwnd);

Since CWnd::FromHandle documentation [^] states:

The pointer may be temporary and should not be stored for later use.

I would use instead something like

pMain->m_hListView = hwnd;

and then obtain the CWnd pointer inside the CMainDlg::OnBnClickedGetDolby body. Anyway I really don't know if it would help. :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.
This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong. -- Iain Clarke
[My articles]

[Maxwell Chen]

CPallini wrote:

pMain->m_hListView = hwnd;

Thanks! It resolved the timing problem. :-D

Maxwell Chen