- Patch #38981 by Robert: add permission to enable/disbale theme switching by users.

modules/system.module

@@ -47,7 +47,7 @@ function system_help($section) {
  * Implementation of hook_perm().
  */
 function system_perm() {
-  return array('administer site configuration', 'access administration pages');
+  return array('administer site configuration', 'access administration pages', 'select different theme');
 }
 
 /**
@@ -159,7 +159,10 @@ function system_test() {
  */
 function system_user($type, $edit, &$user, $category = NULL) {
   if ($type == 'form' && $category == 'account') {
+    if (user_access('select different theme')) {
       $themes = list_themes();
+
+      if (count($themes) > 1) {
         ksort($themes);
 
         // Reset to follow site default theme if user selects the site default
@@ -183,6 +186,8 @@ function system_user($type, $edit, &$user, $category = NULL) {
         }
 
         $form['themes']['theme'] = array('#type' => 'radios', '#options' => $options, '#default_value' => $edit['theme'] ? $edit['theme'] : variable_get('theme_default', 'bluemarine'));
+      }
+    }
 
     if (variable_get('configurable_timezones', 1)) {
       $zones = _system_zonelist();

modules/system/system.module

@@ -47,7 +47,7 @@ function system_help($section) {
  * Implementation of hook_perm().
  */
 function system_perm() {
-  return array('administer site configuration', 'access administration pages');
+  return array('administer site configuration', 'access administration pages', 'select different theme');
 }
 
 /**
@@ -159,7 +159,10 @@ function system_test() {
  */
 function system_user($type, $edit, &$user, $category = NULL) {
   if ($type == 'form' && $category == 'account') {
+    if (user_access('select different theme')) {
       $themes = list_themes();
+
+      if (count($themes) > 1) {
         ksort($themes);
 
         // Reset to follow site default theme if user selects the site default
@@ -183,6 +186,8 @@ function system_user($type, $edit, &$user, $category = NULL) {
         }
 
         $form['themes']['theme'] = array('#type' => 'radios', '#options' => $options, '#default_value' => $edit['theme'] ? $edit['theme'] : variable_get('theme_default', 'bluemarine'));
+      }
+    }
 
     if (variable_get('configurable_timezones', 1)) {
       $zones = _system_zonelist();

modules/user.module

@@ -1820,7 +1820,7 @@ function user_help($section) {
 <ul>
 <li>view your <a href="%user">user page</a>.</li>
 <li>administer user at <a href="%admin-user">administer &gt;&gt; user</a>.</li>
-<li>allow users to select themes from their user account by enabling themes in <a href="%admin-themes">administer &gt;&gt; themes</a>.</li>
+<li>allow users who have the "select different theme" permission to select themes from their user account by enabling themes in <a href="%admin-themes">administer &gt;&gt; themes</a>.</li>
 <li>read user profile help at <a href="%admin-help-profile">administer &gt;&gt; help &gt;&gt; profile</a>.</li>
 <li>read about distributed authentication in the system module help at <a href="%admin-help-system">administer &gt;&gt; help &gt;&gt; system</a>.</li>
 </ul>

modules/user/user.module

@@ -1820,7 +1820,7 @@ function user_help($section) {
 <ul>
 <li>view your <a href="%user">user page</a>.</li>
 <li>administer user at <a href="%admin-user">administer &gt;&gt; user</a>.</li>
-<li>allow users to select themes from their user account by enabling themes in <a href="%admin-themes">administer &gt;&gt; themes</a>.</li>
+<li>allow users who have the "select different theme" permission to select themes from their user account by enabling themes in <a href="%admin-themes">administer &gt;&gt; themes</a>.</li>
 <li>read user profile help at <a href="%admin-help-profile">administer &gt;&gt; help &gt;&gt; profile</a>.</li>
 <li>read about distributed authentication in the system module help at <a href="%admin-help-system">administer &gt;&gt; help &gt;&gt; system</a>.</li>
 </ul>