private void OnActivated(object sender, EventArgs e)
        {
            var windows = SystemWindow.FilterToplevelWindows(new Predicate <SystemWindow>(IsAppWindow));

            Array.Sort(windows, (wnd1, wnd2) => wnd1.Title.CompareTo(wnd2.Title));

            //
            // If an item was already selected in the list, try to find it in the new list and
            // select it.
            //

            var selectedWindow = WindowList.SelectedItem as SystemWindow;

            m_Windows.Clear();
            m_Windows.AddRange(windows);

            WindowList.Items.Refresh();
            CollectionViewSource.GetDefaultView(WindowList.ItemsSource).Refresh();

            //
            // If the previously selected window is not found in the new list, simply select
            // the first element.
            //

            int selectIndex = 0;

            if (selectedWindow != null)
            {
                for (int i = 0; i < WindowList.Items.Count; ++i)
                {
                    SystemWindow wnd = WindowList.Items[i] as SystemWindow;
                    if (wnd.HWnd == selectedWindow.HWnd)
                    {
                        selectIndex = i;
                        break;
                    }
                }
            }

            if (!WindowList.Items.IsEmpty)
            {
                WindowList.SelectedIndex = selectIndex;
                WindowList.UpdateLayout();
                (WindowList.ItemContainerGenerator.ContainerFromIndex(selectIndex) as ListViewItem).Focus();
            }

            FuzzySearchTitle.Focus();
        }