CssCollectionGrouper::group

public CssCollectionGrouper::group(array $css_assets)

public function group(array $css_assets) {
  $groups = array();
  // If a group can contain multiple items, we track the information that must
  // be the same for each item in the group, so that when we iterate the next
  // item, we can determine if it can be put into the current group, or if a
  // new group needs to be made for it.
  $current_group_keys = NULL;
  // When creating a new group, we pre-increment $i, so by initializing it to
  // -1, the first group will have index 0.
  $i = -1;
  foreach ($css_assets as $item) {
    // The browsers for which the CSS item needs to be loaded is part of the
    // information that determines when a new group is needed, but the order
    // of keys in the array doesn't matter, and we don't want a new group if
    // all that's different is that order.
    ksort($item['browsers']);

    // If the item can be grouped with other items, set $group_keys to an
    // array of information that must be the same for all items in its group.
    // If the item can't be grouped with other items, set $group_keys to
    // FALSE. We put items into a group that can be aggregated together:
    // whether they will be aggregated is up to the _drupal_css_aggregate()
    // function or an
    // override of that function specified in hook_css_alter(), but regardless
    // of the details of that function, a group represents items that can be
    // aggregated. Since a group may be rendered with a single HTML tag, all
    // items in the group must share the same information that would need to
    // be part of that HTML tag.
    switch ($item['type']) {
      case 'file':
        // Group file items if their 'preprocess' flag is TRUE.
        // Help ensure maximum reuse of aggregate files by only grouping
        // together items that share the same 'group' value.
        $group_keys = $item['preprocess'] ? array($item['type'], $item['group'], $item['media'], $item['browsers']) : FALSE;
        break;

      case 'external':
        // Do not group external items.
        $group_keys = FALSE;
        break;
    }

    // If the group keys don't match the most recent group we're working with,
    // then a new group must be made.
    if ($group_keys !== $current_group_keys) {
      $i++;
      // Initialize the new group with the same properties as the first item
      // being placed into it. The item's 'data', 'weight' and 'basename'
      // properties are unique to the item and should not be carried over to
      // the group.
      $groups[$i] = $item;
      unset($groups[$i]['data'], $groups[$i]['weight'], $groups[$i]['basename']);
      $groups[$i]['items'] = array();
      $current_group_keys = $group_keys ? $group_keys : NULL;
    }

    // Add the item to the current group.
    $groups[$i]['items'][] = $item;
  }

  return $groups;
}