title: How to make gtk_window_set_position of gtk work?
body: <p>I want to set the position of the window using  <code>gtk_window_set_position</code></p>
  
  <p>but it seems that after the window is created, the <code>gtk_window_set_position</code> will not take               effect.<br>
  I'm wondering how to call <code>gtk_window_set_position</code> after the window shows up, i.e. a button event?</p>