title: how to center ui icon in jquery ui button
body: <p>I'm looking for a way to create toolbar buttons uisng jquery ui.</p>
  
  <p>I tried to create button using</p>
  
  <pre><code>&lt;div id='menubar_home' style='vertical-align: middle;width: 20px; height: 20px;'&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>and using</p>
  
  <pre><code>$('#menubar_home').button({
      icons: { primary: "ui-icon-home" }
  });
  </code></pre>
  
  <p>But image in button is not centered:</p>
  
  <p><img src="https://i.stack.imgur.com/TBO1q.png" alt="not centered"></p>
  
  <p>How to center image in button ?</p>