Index: includes/common.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/common.inc,v
retrieving revision 1.809
diff -u -r1.809 common.inc
--- includes/common.inc	15 Oct 2008 16:05:51 -0000	1.809
+++ includes/common.inc	17 Oct 2008 02:36:27 -0000
@@ -1731,55 +1731,82 @@
  *   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.
- * @param $type
- *   (optional) The type of stylesheet that is being added. Types are: module
- *   or theme.
- * @param $media
- *   (optional) The media type for the stylesheet, e.g., all, print, screen.
- * @param $preprocess
- *   (optional) Should this CSS file be aggregated and compressed if this
- *   feature has been turned on under the performance section?
- *
- *   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.
+ * @param $options
+ *   (optional) A string defining the type of CSS that is being added in the
+ *   $path parameter ('module' or 'theme'), or an associative array of
+ *   additional options, with the following keys:
+ *     - 'type'
+ *       The type of stylesheet that is being added. Types are: module or
+ *       theme.
+ *     - 'media'
+ *       The media type for the stylesheet, e.g., all, print, screen.
+ *     - 'preprocess':
+ *       Should this CSS file be aggregated and compressed if this feature has
+ *       been turned on under the performance section?
+ *
+ *       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.
+ * @param $reset
+ *   (optional) Resets the currently loaded cascading stylesheets.
  * @return
  *   An array of CSS files.
  */
-function drupal_add_css($path = NULL, $type = 'module', $media = 'all', $preprocess = TRUE) {
+function drupal_add_css($path = NULL, $options = NULL, $reset = FALSE) {
   static $css = array();
   global $language;
 
+  // Request made to reset the CSS added so far.
+  if ($reset) {
+    $css = array();
+  }
+
   // Create an array of CSS files for each media type first, since each type needs to be served
   // to the browser differently.
   if (isset($path)) {
+    // Construct the options, taking the defaults into consideration.
+    if (isset($options)) {
+      if (!is_array($options)) {
+        $options = array('type' => $options);
+      }
+    }
+    else {
+      $options = array();
+    }
+    $options += array(
+      'type' => 'module',
+      'media' => 'all',
+      'preprocess' => TRUE
+    );  
+    $media = $options['media'];
+    $type = $options['type'];
+
     // This check is necessary to ensure proper cascading of styles and is faster than an asort().
     if (!isset($css[$media])) {
       $css[$media] = array('module' => array(), 'theme' => array());
     }
-    $css[$media][$type][$path] = $preprocess;
+    $css[$media][$type][$path] = $options['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;
+        $css[$media][$type][$rtl_path] = $options['preprocess'];
       }
     }
   }
Index: includes/locale.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/locale.inc,v
retrieving revision 1.189
diff -u -r1.189 locale.inc
--- includes/locale.inc	12 Oct 2008 04:30:05 -0000	1.189
+++ includes/locale.inc	17 Oct 2008 02:36:27 -0000
@@ -2215,7 +2215,7 @@
  */
 function _locale_translate_language_list($translation, $limit_language) {
   // Add CSS
-  drupal_add_css(drupal_get_path('module', 'locale') . '/locale.css', 'module', 'all', FALSE);
+  drupal_add_css(drupal_get_path('module', 'locale') . '/locale.css', array('preprocess' => FALSE));
 
   $languages = language_list();
   unset($languages['en']);
Index: includes/theme.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/theme.inc,v
retrieving revision 1.439
diff -u -r1.439 theme.inc
--- includes/theme.inc	16 Oct 2008 13:50:21 -0000	1.439
+++ includes/theme.inc	17 Oct 2008 02:36:28 -0000
@@ -133,7 +133,7 @@
   // And now add the stylesheets properly
   foreach ($final_stylesheets as $media => $stylesheets) {
     foreach ($stylesheets as $stylesheet) {
-      drupal_add_css($stylesheet, 'theme', $media);
+      drupal_add_css($stylesheet, array('type' => 'theme', 'media' => $media));
     }
   }
 
Index: modules/simpletest/simpletest.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/simpletest/simpletest.module,v
retrieving revision 1.21
diff -u -r1.21 simpletest.module
--- modules/simpletest/simpletest.module	15 Oct 2008 14:17:27 -0000	1.21
+++ modules/simpletest/simpletest.module	17 Oct 2008 02:36:28 -0000
@@ -199,7 +199,7 @@
 }
 
 function theme_simpletest_test_table($table) {
-  drupal_add_css(drupal_get_path('module', 'simpletest') . '/simpletest.css', 'module');
+  drupal_add_css(drupal_get_path('module', 'simpletest') . '/simpletest.css');
   drupal_add_js(drupal_get_path('module', 'simpletest') . '/simpletest.js', 'module');
 
   // Create header for test selection table.
Index: modules/openid/openid.pages.inc
===================================================================
RCS file: /cvs/drupal/drupal/modules/openid/openid.pages.inc,v
retrieving revision 1.10
diff -u -r1.10 openid.pages.inc
--- modules/openid/openid.pages.inc	13 Oct 2008 00:33:03 -0000	1.10
+++ modules/openid/openid.pages.inc	17 Oct 2008 02:36:28 -0000
@@ -29,7 +29,7 @@
  */
 function openid_user_identities($account) {
   drupal_set_title($account->name);
-  drupal_add_css(drupal_get_path('module', 'openid') . '/openid.css', 'module');
+  drupal_add_css(drupal_get_path('module', 'openid') . '/openid.css');
 
   // Check to see if we got a response
   $result = openid_complete();
Index: modules/openid/openid.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/openid/openid.module,v
retrieving revision 1.31
diff -u -r1.31 openid.module
--- modules/openid/openid.module	12 Oct 2008 04:30:06 -0000	1.31
+++ modules/openid/openid.module	17 Oct 2008 02:36:28 -0000
@@ -75,7 +75,7 @@
  */
 function openid_form_alter(&$form, $form_state, $form_id) {
   if ($form_id == 'user_login_block' || $form_id == 'user_login') {
-    drupal_add_css(drupal_get_path('module', 'openid') . '/openid.css', 'module');
+    drupal_add_css(drupal_get_path('module', 'openid') . '/openid.css');
     drupal_add_js(drupal_get_path('module', 'openid') . '/openid.js');
     if (!empty($form_state['post']['openid_identifier'])) {
       $form['name']['#required'] = FALSE;
Index: modules/help/help.admin.inc
===================================================================
RCS file: /cvs/drupal/drupal/modules/help/help.admin.inc,v
retrieving revision 1.6
diff -u -r1.6 help.admin.inc
--- modules/help/help.admin.inc	14 Apr 2008 17:48:37 -0000	1.6
+++ modules/help/help.admin.inc	17 Oct 2008 02:36:28 -0000
@@ -11,7 +11,7 @@
  */
 function help_main() {
   // Add CSS
-  drupal_add_css(drupal_get_path('module', 'help') . '/help.css', 'module', 'all', FALSE);
+  drupal_add_css(drupal_get_path('module', 'help') . '/help.css', array('preprocess' => FALSE));
   $output = '<h2>' . t('Help topics') . '</h2><p>' . t('Help is available on the following items:') . '</p>' . help_links_as_list();
   return $output;
 }
Index: modules/dblog/dblog.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/dblog/dblog.module,v
retrieving revision 1.28
diff -u -r1.28 dblog.module
--- modules/dblog/dblog.module	6 Oct 2008 11:30:11 -0000	1.28
+++ modules/dblog/dblog.module	17 Oct 2008 02:36:28 -0000
@@ -83,7 +83,7 @@
 function dblog_init() {
   if (arg(0) == 'admin' && arg(1) == 'reports') {
     // Add the CSS for this module
-    drupal_add_css(drupal_get_path('module', 'dblog') . '/dblog.css', 'module', 'all', FALSE);
+    drupal_add_css(drupal_get_path('module', 'dblog') . '/dblog.css', array('preprocess' => FALSE));
   }
 }
 
Index: modules/search/search.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/search/search.module,v
retrieving revision 1.270
diff -u -r1.270 search.module
--- modules/search/search.module	12 Oct 2008 19:00:56 -0000	1.270
+++ modules/search/search.module	17 Oct 2008 02:36:28 -0000
@@ -1031,7 +1031,7 @@
 function search_form(&$form_state, $action = '', $keys = '', $type = NULL, $prompt = NULL) {
 
   // Add CSS
-  drupal_add_css(drupal_get_path('module', 'search') . '/search.css', 'module', 'all', FALSE);
+  drupal_add_css(drupal_get_path('module', 'search') . '/search.css', array('preprocess' => FALSE));
 
   if (!$action) {
     $action = url('search/' . $type);
Index: modules/tracker/tracker.pages.inc
===================================================================
RCS file: /cvs/drupal/drupal/modules/tracker/tracker.pages.inc,v
retrieving revision 1.11
diff -u -r1.11 tracker.pages.inc
--- modules/tracker/tracker.pages.inc	13 Oct 2008 00:33:05 -0000	1.11
+++ modules/tracker/tracker.pages.inc	17 Oct 2008 02:36:28 -0000
@@ -12,7 +12,7 @@
  */
 function tracker_page($account = NULL, $set_title = FALSE) {
   // Add CSS
-  drupal_add_css(drupal_get_path('module', 'tracker') . '/tracker.css', 'module', 'all', FALSE);
+  drupal_add_css(drupal_get_path('module', 'tracker') . '/tracker.css', array('preprocess' => FALSE));
 
   if ($account) {
     if ($set_title) {
Index: modules/simpletest/tests/common.test
===================================================================
RCS file: /cvs/drupal/drupal/modules/simpletest/tests/common.test,v
retrieving revision 1.8
diff -u -r1.8 common.test
--- modules/simpletest/tests/common.test	15 Oct 2008 16:05:51 -0000	1.8
+++ modules/simpletest/tests/common.test	17 Oct 2008 02:36:28 -0000
@@ -115,6 +115,56 @@
 }
 
 /**
+ * Test the Drupal CSS system.
+ */
+class CascadingStylesheetsTestCase extends DrupalWebTestCase {
+  /**
+   * Implementation of getInfo().
+   */
+  function getInfo() {
+    return array(
+      'name' => t('Cascading Stylesheets'),
+      'description' => t("Tests adding various cascading stylesheets to the page."),
+      'group' => t('System')
+    );
+  }
+
+  /**
+   * Implementation of setUp().
+   */
+  function setUp() {
+    parent::setUp();
+    // Reset drupal_add_css() before each test.
+    drupal_add_css(NULL, NULL, TRUE);
+  }
+
+  /**
+   * Check default stylesheets as empty.
+   */
+  function testDefault() {
+    $this->assertEqual(array(), drupal_add_css(), t('Default CSS is empty.'));
+  }
+
+  /**
+   * Tests adding a file stylesheet.
+   */
+  function testAddFile() {
+    $simpletestcss = drupal_get_path('module', 'simpletest') . '/simpletest.css';
+    $css = drupal_add_css($simpletestcss);
+    $this->assertEqual($css['all']['module'][$simpletestcss], TRUE, t('Adding a CSS file caches it properly.'));
+  }
+
+  /**
+   * Tests rendering the stylesheets.
+   */
+  function testRenderFile() {
+    $simpletestcss = drupal_get_path('module', 'simpletest') . '/simpletest.css';
+    drupal_add_css($simpletestcss);
+    $this->assertTrue(strpos(drupal_get_css(), $simpletestcss) > 0, t('Rendered CSS includes the added stylesheet.'));
+  }
+}
+
+/**
  * Test drupal_http_request().
  */
 class DrupalHTTPRequestTestCase extends DrupalWebTestCase {
Index: modules/color/color.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/color/color.module,v
retrieving revision 1.48
diff -u -r1.48 color.module
--- modules/color/color.module	9 Oct 2008 00:02:28 -0000	1.48
+++ modules/color/color.module	17 Oct 2008 02:36:28 -0000
@@ -153,11 +153,11 @@
   $info = color_get_info($theme);
 
   // Add Farbtastic color picker.
-  drupal_add_css('misc/farbtastic/farbtastic.css', 'module', 'all', FALSE);
+  drupal_add_css('misc/farbtastic/farbtastic.css', array('preprocess' => FALSE));
   drupal_add_js('misc/farbtastic/farbtastic.js');
 
   // Add custom CSS and JS.
-  drupal_add_css($base . '/color.css', 'module', 'all', FALSE);
+  drupal_add_css($base . '/color.css', array('preprocess' => FALSE));
   drupal_add_js($base . '/color.js');
   drupal_add_js(array('color' => array(
     'reference' => color_get_palette($theme, TRUE)
Index: modules/system/system.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/system/system.module,v
retrieving revision 1.632
diff -u -r1.632 system.module
--- modules/system/system.module	14 Oct 2008 20:44:57 -0000	1.632
+++ modules/system/system.module	17 Oct 2008 02:36:28 -0000
@@ -706,13 +706,13 @@
   if (arg(0) == 'admin' || (variable_get('node_admin_theme', '0') && arg(0) == 'node' && (arg(1) == 'add' || arg(2) == 'edit'))) {
     global $custom_theme;
     $custom_theme = variable_get('admin_theme', '0');
-    drupal_add_css(drupal_get_path('module', 'system') . '/admin.css', 'module');
+    drupal_add_css(drupal_get_path('module', 'system') . '/admin.css');
   }
 
   // Add the CSS for this module.
-  drupal_add_css(drupal_get_path('module', 'system') . '/defaults.css', 'module');
-  drupal_add_css(drupal_get_path('module', 'system') . '/system.css', 'module');
-  drupal_add_css(drupal_get_path('module', 'system') . '/system-menus.css', 'module');
+  drupal_add_css(drupal_get_path('module', 'system') . '/defaults.css');
+  drupal_add_css(drupal_get_path('module', 'system') . '/system.css');
+  drupal_add_css(drupal_get_path('module', 'system') . '/system-menus.css');
 }
 
 /**
Index: modules/user/user.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/user/user.module,v
retrieving revision 1.928
diff -u -r1.928 user.module
--- modules/user/user.module	12 Oct 2008 04:30:09 -0000	1.928
+++ modules/user/user.module	17 Oct 2008 02:36:28 -0000
@@ -1120,7 +1120,7 @@
 }
 
 function user_init() {
-  drupal_add_css(drupal_get_path('module', 'user') . '/user.css', 'module');
+  drupal_add_css(drupal_get_path('module', 'user') . '/user.css');
 }
 
 function user_uid_optional_load($arg) {
Index: modules/block/block.admin.inc
===================================================================
RCS file: /cvs/drupal/drupal/modules/block/block.admin.inc,v
retrieving revision 1.22
diff -u -r1.22 block.admin.inc
--- modules/block/block.admin.inc	13 Oct 2008 00:33:01 -0000	1.22
+++ modules/block/block.admin.inc	17 Oct 2008 02:36:28 -0000
@@ -28,7 +28,7 @@
 function block_admin_display_form(&$form_state, $blocks, $theme = NULL) {
   global $theme_key, $custom_theme;
 
-  drupal_add_css(drupal_get_path('module', 'block') . '/block.css', 'module', 'all', FALSE);
+  drupal_add_css(drupal_get_path('module', 'block') . '/block.css', array('preprocess' => FALSE));
 
   // If non-default theme configuration has been selected, set the custom theme.
   $custom_theme = isset($theme) ? $theme : variable_get('theme_default', 'garland');