Retrieve WTL object from handle

Question

I had to rewrite a custom file dialog (derived from MFC's CFileDialog) to WTL's CFileDialog. I have a bit of a problem to retrieve data when I don't have access to the dialog object itself. Imagine the following.

I have a member in the class

static WNDPROC m_wndProc;

I initialize it in the following static member fnct.

void CMyFileDialog::OnInitDone(LPOFNOTIFY lpon)
{
  m_wndProc = (WNDPROC)::SetWindowLong(thisHWND, GWL_WNDPROC, reinterpret_cast<long>
                                       (&CMyFileDialog::WndProcSelect));
}

The handle comes into the callback method with no problem and I can "connect" to it with CWindow

LRESULT CALLBACK CMyFileDialog::WndProcSelect(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
  // ...
  CWindow callerWnd(hwnd);
}

And here, I don't know the real methodology to convert the CWindow to my CMyFileDialog. As I think, this CWindow class is just connected somehow to the handle itself, but does not the same object as it was created before. So for example, if I have a CString or other members in my CMyFileDialog, it won't access its state, because it was created in another object.

Answer 1

You could always use SetWindowLongPtr with your "this" pointer, then it would be fairly easy to extract the pointer to your CMyFileDialog.