private void Window_KeyDown(object sender, KeyEventArgs e)
{
// Key down get triggered only outside of a Text field
if (!Keyboard.FocusedElement.GetType().IsSubclassOf(typeof(TextBoxBase)))
{
// Will triggers lesson zoom, lesson translation or slide forward/backward
lessonPage.AppKeyDown(e);
layerStack.Viewport.AppKeyDown(e);
}
}