Where does theme($row) get evaluated? I am baffled by this line of code:

$work[$id] = $view-&gt;field[$id]-&gt;theme($row);


Does anyone know where theme($row) gets evaluated?  

$word[$id] gets set to this emfield's url, "http://mysite.com/myvideo.flv", which is the value of both:

$view-&gt;field[$id]-&gt;last_render
$view-&gt;field[$id]-&gt;original_value


So I am guessing that theme($row) gets evaluated to either 'last_render' or 'original_value'.
But when I add debug code to print theme($row), nothing gets printed.  

Any ideas?

Here is the context in which this line of code appears, from views-view-swftools.tpl.php:

   foreach ($rows as $key =&gt; $row) {

          // Reset the work array
          $work = array();

          // Render each field in this row using the assigned handler
          foreach ($keys as $id) {
            $work[$id] = $view-&gt;field[$id]-&gt;theme($row);
          }
          ...
    }
This is a method call, the theme method is invoked on the $view-&gt;field[$id] object. The method is likely views_handler_field::theme but it may have been overrided by the  views_handler_field subclass used for a particular field handler. Usually, the method will eventually ends up calling the theme() function to use a defined theme function or template for the field (if this is a CCK field, a formatter will likely be used).