Create a nicer output for summary or trimmed text fields

I've been trying to makeup a little bit the output for text that are trimmed and/or summary to have a look similar to the one get from the views module, but I haven't had to much luck.

I read issue #841188: About the teaser size but this is for Drupal 6 so I tried to find a way around and this is what I came with:

<?php
function mytheme_preprocess_field(&$variables) {
  if (isset($variables['element']['#field_name'])) {
    switch ($variables['element']['#field_name']) {
      case 'body':
        if ($variables['element']['#formatter'] = 'text_summary_or_trimmed') {
          $item = $variables['element']['#items'][0];          
          if (!empty($item['safe_summary'])) {
            $text = $item['safe_summary'];
          }
          else {
            $text = $item['safe_value'];
          }
          
          $trimmed = views_trim_text(
            array(
            'max_length' => 100, /* we need the lenght set by UI */
            'word_boundary' => TRUE,
            'ellipsis' => TRUE,
            'html' => TRUE,
            ),
            $text
          );
          
          $variables['items'][0]['#markup'] = $trimmed;
        }
        break;
    }
  }
}
?>

As you can see I'm using the function views_trim_text($alter, $value) that does what I need, but I haven't been able to find the actual length value for this trim.

I feel that I'm really close to the solution but my search in the multiple dpm() that I have placed around are not helping me.

Any ideas of how to get this value? By the way, how can I do it with a display suit hook alter? I read the API but I didn't have much luck either.

I wish this was already part of Display Suite.