drupal_add_css

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• Drupal 6
• Drupal 7

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Definition

drupal_add_css($path = NULL, $type = 'module', $media = 'all', $preprocess = TRUE)
includes/common.inc, line 1644

Description

Adds a CSS file to the stylesheet queue.

Modules should always prefix the names of their CSS files with the module name, for example: system-menus.css rather than simply menus.css. Themes can override module-supplied CSS files based on their filenames, and this prefixing helps prevent confusing name collisions for theme developers. See drupal_get_css where the overrides are performed.

If the direction of the current language is right-to-left (Hebrew, Arabic, etc.), the function will also look for an RTL CSS file and append it to the list. The name of this file should have an '-rtl.css' suffix. For example a CSS file called 'name.css' will have a 'name-rtl.css' file added to the list, if exists in the same directory. This CSS file should contain overrides for properties which should be reversed or otherwise different in a right-to-left display.

What does this actually mean? CSS preprocessing is the process of aggregating a bunch of separate CSS files into one file that is then compressed by removing all extraneous white space.

The reason for merging the CSS files is outlined quite thoroughly here: http://www.die.net/musings/page_load_time/ "Load fewer external objects. Due to request overhead, one bigger file just loads faster than two smaller ones half its size."

However, you should *not* preprocess every file as this can lead to redundant caches. You should set $preprocess = FALSE when:

• Your styles are only used rarely on the site. This could be a special admin page, the homepage, or a handful of pages that does not represent the majority of the pages on your site.

Typical candidates for caching are for example styles for nodes across the site, or used in the theme.

Parameters

$path (optional) The path to the CSS file relative to the base_path(), e.g., /modules/devel/devel.css.

$type (optional) The type of stylesheet that is being added. Types are: module or theme.

$media (optional) The media type for the stylesheet, e.g., all, print, screen.

$preprocess (optional) Should this CSS file be aggregated and compressed if this feature has been turned on under the performance section?

Return value

An array of CSS files.

Code

<?php
function drupal_add_css($path = NULL, $type = 'module', $media = 'all', $preprocess = TRUE) {
  static $css = array();
  global $language;

  // Create an array of CSS files for each media type first, since each type needs to be served
  // to the browser differently.
  if (isset($path)) {
    // This check is necessary to ensure proper cascading of styles and is faster than an asort().
    if (!isset($css[$media])) {
      $css[$media] = array('module' => array(), 'theme' => array());
    }
    $css[$media][$type][$path] = $preprocess;

    // If the current language is RTL, add the CSS file with RTL overrides.
    if (defined('LANGUAGE_RTL') && $language->direction == LANGUAGE_RTL) {
      $rtl_path = str_replace('.css', '-rtl.css', $path);
      if (file_exists($rtl_path)) {
        $css[$media][$type][$rtl_path] = $preprocess;
      }
    }
  }

  return $css;
}
?>