marquee.module

<?php
/**
 * @file
 * Provide a marquee element.
 */

/**
 * Implements hook_page_alter().
 */
function marquee_page_alter(&$page) {
  //dsm($page);
  
  /*
  if (drupal_is_front_page()) {
    $first_node = array_shift($page['content']['system_main']['nodes']);
    $ad = array(
      'my_add' => array(
        '#markup' => '<div style="padding: 20px; text-align: center; border: 1px solid #000"><img src="http://2011.tcdrupal.org/sites/2011.tcdrupal.org/themes/tcdrupal3/images/logo.png" /></div>',
      ),
    );
    array_unshift($page['content']['system_main']['nodes'], $first_node,  $ad);
  }
  */

  $page = _marquee_page_alter($page);  
}

/**
 * Implements hook_element_info().
 */
function marquee_element_info() {
  $types = array();
  // The key of the array will become the element #type. For example,
  // #type => 'marquee'.
  $types['marquee'] = array(
    '#theme' => 'marquee_marquee',
  );
  return $types;
}

/**
 * Implements hook_theme().
 */
function marquee_theme() {
  return array(
    'marquee_marquee' => array(
      'render element' => 'element',
    ),
    'marquee_wrapper' => array(
      'render element' => 'element',
    ),
  );
}

/**
 * Returns HTML for a marquee element.
 *
 * @param $variables
 *   An associative array containing:
 *   - element: A render element representing the marquee.
 *
 * @ingroup themeable
 */
function theme_marquee_marquee($variables) {
  $element = $variables['element'];
  $attributes = isset($element['#attributes']) ? $element['#attributes'] : array();
  $output = '<marquee' . drupal_attributes($attributes) . '>';
  $output .= $element['#value'];
  $output .= '</marquee>';
  return $output;
}

/**
 * Wrap a div around the already-rendered #children.
 */
function theme_marquee_wrapper($variables) {
  $amount = abs(rand(1, 50));
  $direction = (abs(rand(0, 1)) == 1) ? 'left' : 'right';
  $element = $variables['element'];
  $output = '<marquee scrollamount="' . $amount . '" direction="'. $direction . '">';
  $output .= $element['#children'];
  $output .= '</div>';
  return $output;
}

function _marquee_page_alter($element) {
  $element['#theme_wrappers'][] = 'marquee_wrapper';
  foreach (element_children($element) as $key) {
    $element[$key] = _marquee_page_alter($element[$key]);
  }
  return $element;
}