title: Safari iPad : prevent zoom on double-tap
body: <p>I'm creating a site on Safari for iPad. I need to prevent the zoom on double-tapping event but I have two problems:</p>
  
  <ul>
  <li>a double tap doesn’t generate any events, so I can't use "event.preventDefault();"</li>
  <li>I need to do this only when some conditions are fulfilled, so I can't use the tag "<code>&lt;meta name = "viewport" content = "user-scalable = no"&gt;</code>"... If I did that, users could never zoom on my page.</li>
  </ul>
  
  <p>How can I fix these problems?</p>