title: How to get the id of a window in qml?
body: <p>I want to get the id of a specific qml window in a cpp class, but I don't know how.</p>
  <p>something like:</p>
  <blockquote>
  <p>int id = testWindow.id()</p>
  </blockquote>
  <p>The id that I'm talking about is the id of the window in the system.</p>
  <p>How can I do this without change the main.cpp?</p>