title: UITableView check if the index is shown
body: <p>in order to get the necessary height of a cell, I implemented a function like</p>
  
  <pre><code>+(CGFloat)rowHeightForTableView:(UITableView*)tableView andObject:(NSObject*)theObject {...}
  </code></pre>
  
  <p>within the cells.</p>
  
  <p>Since the tableView is one of the parameters, I can check whether it's a plain or grouped style table and include the resulting width in my calculations. But how should I check if an index is being shown?</p>