how implement a custom renderer ?

Ok i've read carrefully the doc. So my renderer works !
i've use the hook_forena_controls to refer my class file.
like this :

function mymodule_forena_controls() {

  $controls[] = array('file' => 'renderers/FrxTotal.inc',

                      'class' => 'FrxTotal',

                     );

  return $controls;

}

and i've writing this renderer
(i didn't fid the good way to replace the reportDocNode with an array of token->value... so i use the old way...)

/**
 * @file
 * Implements a total renderer
 * @author romain garçon
 *
 */
class FrxTotal extends FrxRenderer {
  public function render() {
    $xml = FrxData::instance()->currentContext();
    $html = $xml->asXML();
        $total=array_flip($this->teng->tokens($this->reportDocNode->asXML()));
        $total= array_pad($total, count($total), 0);
        foreach ($total as $key => &$row) {
          $data=$xml->xpath("//".$key."|".$key."/*[last()]");
          foreach ($data as $k => $cell) {
           $row+=(float)$cell[0];
          }
        }
        $tokens=array_map(function($token){return '{'.$token.'}';},array_keys($total));
        $output=str_replace($tokens, $total, $this->reportDocNode->asXML());
return $output;
}

(clear cache)
and in my layout :

<div class="FrxTable" frx:block="mymodule/report1" id="report1_block">
<table>
	<thead>
		<tr>
			<th>term</th>
			<th><strong>No. exp2</strong></th>
			<th><strong>No. of exp1<br />
			(on-time)</strong></th>
			<th><strong>The title</strong></th>
		</tr>
	</thead>
	<tbody>
		<tr frx:foreach="*" id="report1">
			<td>{taxonomy_term_data_name}</td>
			<td>{exp2} {total+1}</td>
			<td>{exp1}</td>
			<td class="forena-3">{percent}</td>
		</tr>
	</tbody>
	<tfoot frx:renderer="FrxTotal" id="forena-7">
		<tr>
			<td>Total</td>
			<td>{exp2}</td>
			<td>{exp1}</td>
			<td>{percent}</td>
		</tr>
	</tfoot>
</table>

et voilà.. maybe it could be usefull for someone...
thanks !