Make the login form autofocus if an error occurs while logging in.

A bit of a hack - see the comment in the diff.

htdocs/auth/lib.php

@@ -992,6 +992,15 @@ function auth_get_login_form() {
  * @private
  */
 function get_login_form_js($form) {
+    // Add the autofocus class to the username input. This is because Mahara 
+    // doesn't always render the login form when it is built. Sometimes, the 
+    // form is built to process a login attempt, and then built again when that 
+    // attempt fails. This makes sure that every time the login form is 
+    // actually displayed it has the autofocus class.
+    $form = str_replace(
+        'class="required text" id="login_login_username"',
+        'class="required text autofocus" id="login_login_username"',
+        $form);
     $form = str_replace('/', '\/', str_replace("'", "\'", (str_replace(array("\n", "\t"), '', $form))));
     $strcookiesnotenabled    = json_encode(get_string('cookiesnotenabled'));
     $cookiename = get_config('cookieprefix') . 'ctest';