title: How to load combo options on a control click (not initially)?
body: <p>I am seeking a way to implement the scenario where ui.combo (Webix control) options can be loaded/reloaded from the server only when the user clicks it. Basically, I'm able only to load them initially as follows:</p>
  
  <pre><code>{
     view: "combo",
     options: "myurl.php"
  }
  </code></pre>
  
  <p>But is there a way to detect the click on a control and load/reload the options?</p>