Index: modules/system/system.js
===================================================================
RCS file: modules/system/system.js
diff -N modules/system/system.js
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ modules/system/system.js	11 Feb 2007 03:28:28 -0000
@@ -0,0 +1,39 @@
+/**
+ * Internal function to check using Ajax if clean URLs can potentially be
+ * enabled.
+ * 
+ * This function is not used to verify whether or not clean URLs
+ * are currently enabled.
+ *
+ * @param checkType
+ *   The type of check to the done; defaults to "settings". This allows clean
+ *   URLs to be tested on both the settings page and the installation page.
+ *
+ * @param url
+ *   The url used to test clean URLs; defaults to admin/settings/clean-urls.
+ *   If this parameter is specified it should generally include base_path().
+ */
+Drupal.cleanURLsCheck = function(checkType, url) {
+  // Default to the settings page for clean URLs.
+  var checkType = checkType || "settings";
+  var url = url || location.pathname +"admin/settings/clean-urls";
+  if (checkType == "settings") {
+    $("#clean-url .description span").hide();
+    $("#clean-url p").hide();
+  }
+  $.ajax({url: location.protocol +"//"+ location.hostname + url, type: "GET", data: " ", complete: function(response) {
+    if (response.status == 200) {
+      // Check was successful.
+      if (checkType == "settings") {
+        $("#clean-url input.form-radio").attr("disabled", "");
+        $("<span> "+ Drupal.settings.cleanURL.success +"</span>").insertBefore("#clean-url .description span");
+      }
+    }
+    else {
+      // Check failed.
+      if (checkType == "settings") {
+        $("<span>"+ Drupal.settings.cleanURL.failure +"</span>").insertBefore("#clean-url .description span");
+      }
+    }
+  }});
+}
Index: modules/system/system.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/system/system.module,v
retrieving revision 1.448
diff -u -p -r1.448 system.module
--- modules/system/system.module	4 Feb 2007 21:20:50 -0000	1.448
+++ modules/system/system.module	11 Feb 2007 03:28:29 -0000
@@ -572,23 +572,35 @@ function system_site_information_setting
 }
 
 function system_clean_url_settings() {
-  // We check for clean URL support using an image on the client side.
   $form['clean_url'] = array(
     '#type' => 'radios',
     '#title' => t('Clean URLs'),
     '#default_value' => variable_get('clean_url', 0),
     '#options' => array(t('Disabled'), t('Enabled')),
-    '#description' => t('This option makes Drupal emit "clean" URLs (i.e. without <code>?q=</code> in the URL.)'),
+    '#description' => t('This option makes Drupal emit "clean" URLs (i.e. without <code>?q=</code> in the URL).'),
   );
 
   if (!variable_get('clean_url', 0)) {
+    $clean_url_success = t('Your server has been successfully tested to support this feature.');
     if (strpos(request_uri(), '?q=') !== FALSE) {
-      $form['clean_url']['#description'] .= t(' Before enabling clean URLs, you must perform a test to determine if your server is properly configured. If you are able to see this page again after clicking the "Run the clean URL test" link, the test has succeeded and the radio buttons above will be available. If instead you are directed to a "Page not found" error, you will need to change the configuration of your server. The <a href="@handbook">handbook page on Clean URLs</a> has additional troubleshooting information. !run-test', array('@handbook' => 'http://drupal.org/node/15365', '!run-test' => '<a href ="'. base_path() .'admin/settings/clean-urls">'. t('Run the clean URL test') .'</a>'));
+      drupal_add_js(array('cleanURL' => array('success' => $clean_url_success, 'failure' => t('Your system does not currently support this feature.'))), 'setting');
+      drupal_add_js(drupal_get_path('module', 'system') .'/system.js', 'module');
+      drupal_add_js('
+// Global Killswitch
+if (Drupal.jsEnabled) {
+  $(document).ready(function() {
+    Drupal.cleanURLsCheck("settings");
+  });
+}', 'inline');
+
+      $form['clean_url']['#description'] .= ' <span>'. t('Before enabling clean URLs, you must perform a test to determine if your server is properly configured. If you are able to see this page again after clicking the "Run the clean URL test" link, the test has succeeded and the radio buttons above will be available. If instead you are directed to a "Page not found" error, you will need to change the configuration of your server. The <a href="@handbook">handbook page on Clean URLs</a> has additional troubleshooting information.', array('@handbook' => 'http://drupal.org/node/15365')) .'</span>';
+
       $form['clean_url']['#disabled'] = TRUE;
+      $form['clean_url']['#prefix'] = '<div id="clean-url">';
+      $form['clean_url']['#suffix'] = '<p>'. t('<a href="@clean_url">Run the clean url test</a>.', array('@clean_url' => base_path() .'admin/settings/clean-urls')) .'</p></div>';
     }
     else {
-      $form['clean_url']['#description'] .= t(' You have successfully demonstrated that clean URLs work on your server. You may enable/disable them as you wish.');
-      $form['#collapsed'] = FALSE;
+      $form['clean_url']['#description'] .= ' '. $clean_url_success;
     }
   }