/**
  * Get a diff between the current contents of the edit box and the
  * version of the page we're editing from.
  *
  * If this is a section edit, we'll replace the section as for final
  * save and then make a comparison.
  */
 function showDiff()
 {
     $oldtext = $this->mArticle->fetchContent();
     $newtext = $this->mArticle->replaceSection($this->section, $this->textbox1, $this->summary, $this->edittime);
     wfRunHooks('EditPageGetDiffText', array($this, &$newtext));
     $newtext = $this->mArticle->preSaveTransform($newtext);
     $oldtitle = wfMsgExt('currentrev', array('parseinline'));
     $newtitle = wfMsgExt('yourtext', array('parseinline'));
     if ($oldtext !== false || $newtext != '') {
         $de = new DifferenceEngine($this->mTitle);
         $de->setText($oldtext, $newtext);
         $difftext = $de->getDiff($oldtitle, $newtitle);
         $de->showDiffStyle();
     } else {
         $difftext = '';
     }
     global $wgOut;
     $wgOut->addHTML('<div id="wikiDiff">' . $difftext . '</div>');
 }