private void EditorControl_KeyDown(object sender, KeyEventArgs e)
        {
            bool handled = false;

            if (e.Key == Key.Tab)
            {
                equationRoot.ConsumeText("    ");
                handled = true;
            }
            else if (equationRoot.ConsumeKey(e.Key))
            {
                handled = true;
            }
            if (handled)
            {
                e.Handled = true;
                AdjustView();
                Dirty = true;
            }
        }