Receiving parent's window handle on IShellFolder/IShellFolder2 EnumObjects implementations while searching? - c++

Question

I'm scratching my head in receiving the parent window handle in a namespace extension project i'm working on.
The use case is as follows:
User browses to a virtual folder through windows explorer
User performs search (search box above)
I need to retrieve the search box's text before the search starts.
I've managed to do that on a test console app with ISearchBoxInfo interface (https://msdn.microsoft.com/en-us/library/windows/desktop/dd562062%28v=vs.85%29.aspx?f=255&MSPPError=-2147217396)
There are 2 ways i can receive a pointer to this interface:
Using IObjectWithSite::SetSite call - which is not relevant as the search is conducted in a different thread, and i cannot share the COM object between those threads
Identifying the window handle and retrieve the ISearchBox through IWebBrowser2 interface.
Both methods don't work as when i perform the search, the EnumObjects is called via a different thread, and i cannot find a way to identify who is te parent explorer window.
When doing search, the hwnd that comes is always null as follows:
This is the EnumObjects code:
// Allows a client to determine the contents of a folder by
// creating an item identifier enumeration object and returning
// its IEnumIDList interface. The methods supported by that
// interface can then be used to enumerate the folder's contents.
HRESULT CFolderViewImplFolder::EnumObjects(HWND hwnd, DWORD grfFlags, IEnumIDList **ppenumIDList)
{
HRESULT hr;
_fd = hwnd;
if (hwnd != NULL) // NULL when performing a search
{
const int n = GetWindowTextLength(hwnd);
wstring text(n + 1, L'#');
if (n > 0)
{
GetWindowText(hwnd, &text[0], text.length());
}
}
if (m_nLevel >= g_nMaxLevel)
{
*ppenumIDList = NULL;
hr = S_FALSE; // S_FALSE is allowed with NULL out param to indicate no contents.
}
else
{
CFolderViewImplEnumIDList *penum = new (std::nothrow) CFolderViewImplEnumIDList(grfFlags, m_nLevel + 1, this);
hr = penum ? S_OK : E_OUTOFMEMORY;
if (SUCCEEDED(hr))
{
hr = penum->Initialize();
if (SUCCEEDED(hr))
{
hr = penum->QueryInterface(IID_PPV_ARGS(ppenumIDList));
}
penum->Release();
}
}
return hr;
}
In addition to my tests, as i have also implementation of IShellFolderViewCB.MessageSFVCB, which runs on the correct thread where i can retrieve the IShellBrowser and thus the handle - when i conduct the search i encounter the following messages:
103, 103, 67, UnmergeMenu, WindowClosing, 106, ViewRelease, ViewRelease
Afterward, no more messages are posted (no matter if i re-search) - the first breakpoint is always at EnumObjects method which i have no context about the parent window.
Any light shedding would be nice.
== EDIT ==
I've came up with some workaround - this is not perfect for all cases but works for most of them - other options will still be nice.
Whenever EnumObjects is called with hwnd = NULL, i'm doing the following: (it's in C# - but it can be easily in C++ also)
static public string PrepareSearch(string currentFolderName, IntPtr hwnd)
{
SHDocVw.ShellWindows shellWindows = new ShellWindows();
SHDocVw.IWebBrowser2 foundBrowser = null;
bool wasFound = false;
string foundTxt = null;
foreach (SHDocVw.IWebBrowser2 eie in shellWindows)
{
// as the search is conducted in another thread, while the main window is "free" and in a search mode, it should be first busy.
string locName = eie.LocationName;
string exeName = eie.FullName;
if (!string.IsNullOrEmpty(exeName) && exeName.IndexOf("explorer.exe", StringComparison.OrdinalIgnoreCase) >= 0 &&
!string.IsNullOrEmpty(locName) &&
eie.Busy && eie.ReadyState == tagREADYSTATE.READYSTATE_LOADING)
{
// in here we're ok, we would also want to get the window title to make sure we're searching correctly.
string title = NSEFolder.WindowText((IntPtr)eie.HWND);
if (!string.IsNullOrEmpty(title) &&
title.IndexOf(currentFolderName) >= 0)
{
// one or more windows were found, ignore the quick search.
if (wasFound)
{
return null;
}
wasFound = true;
foundTxt = locName;
}
}
}
if (wasFound && !string.IsNullOrEmpty(foundTxt))
{
return foundTxt;
}
return null;
}
Basically i'm going over all explorer windows, trying to find one that is indeed "explorer.exe" + not empty search string (LocationName) + busy... + title contains name of the current folder name.
it will fail when 2 windows are busy and have the same folder name in the title - but this might be good enough... Not sure here.

Answer 1

So, after a talk with microsoft - it's not possible to do so.
the workaround i've added is a valid one (thoguh not perfect).