3 files changed, 48 insertions, 8 deletions
diff --git a/include/config_default.inc.php b/include/config_default.inc.php
index 838cc20b0..9956ba164 100644
--- a/include/config_default.inc.php
+++ b/include/config_default.inc.php
@@ -63,6 +63,16 @@
 //    the date_available
 $conf['order_by'] = ' ORDER BY date_available DESC, file ASC, id ASC';
 
+// order_by_inside_category : inside a category, images can also be ordered
+// by rank. A manually defined rank on each image for the category.
+//
+// In addition to fields of #images table, you can use the
+// #image_category.rank column
+//
+// $conf['order_by_inside_category'] = ' ORDER BY rank';
+// will sort images by the manually defined rank of images in this category.
+$conf['order_by_inside_category'] = $conf['order_by'];
+
 // file_ext : file extensions (case sensitive) authorized
 $conf['file_ext'] = array('jpg','JPG','jpeg','JPEG',
                           'png','PNG','gif','GIF','mpg','zip',
diff --git a/include/functions_category.inc.php b/include/functions_category.inc.php
index 0bca0897a..92e9cf229 100644
--- a/include/functions_category.inc.php
+++ b/include/functions_category.inc.php
@@ -257,15 +257,21 @@ SELECT galleries_url
 // returns an array of image orders available for users/visitors
 function get_category_preferred_image_orders()
 {
-  global $conf;
+  global $conf, $page;
+  
   return array(
     array(l10n('default_sort'), '', true),
     array(l10n('Average rate'), 'average_rate DESC', $conf['rate']),
     array(l10n('most_visited_cat'), 'hit DESC', true),
     array(l10n('Creation date'), 'date_creation DESC', true),
     array(l10n('Post date'), 'date_available DESC', true),
-    array(l10n('File name'), 'file ASC', true)
-  );
+    array(l10n('File name'), 'file ASC', true),
+    array(
+      l10n('Rank'),
+      'rank ASC',
+      ('categories' == $page['section'] and !isset($page['flat']))
+      )
+    );
 }
 
 function display_select_categories($categories,
diff --git a/include/section_init.inc.php b/include/section_init.inc.php
index 053607dfd..97f2f0a42 100644
--- a/include/section_init.inc.php
+++ b/include/section_init.inc.php
@@ -172,16 +172,40 @@ if ( script_basename()=='picture' and 'categories'==$page['section'] and
 // By default, it is the same as the $user['nb_image_page']
 $page['nb_image_page'] = $user['nb_image_page'];
 
+// if flat mode is active, we must consider the image set as a standard set
+// and not as a category set because we can't use the #image_category.rank :
+// displayed images are not directly linked to the displayed category
+if ('categories' == $page['section'] and !isset($page['flat']))
+{
+  $conf['order_by'] = $conf['order_by_inside_category'];
+}
+
 if (pwg_get_session_var('image_order',0) > 0)
 {
+  $image_order_id = pwg_get_session_var('image_order');
+  
   $orders = get_category_preferred_image_orders();
 
-  $conf['order_by'] = str_replace(
-    'ORDER BY ',
-    'ORDER BY '.$orders[ pwg_get_session_var('image_order',0) ][1].',',
-    $conf['order_by']
+  // the current session stored image_order might be not compatible with
+  // current image set, for example if the current image_order is the rank
+  // and that we are displaying images related to a tag.
+  //
+  // In case of incompatibility, the session stored image_order is removed.
+  if ($orders[$image_order_id][2])
+  {
+    $conf['order_by'] = str_replace(
+      'ORDER BY ',
+      'ORDER BY '.$orders[$image_order_id][1].',',
+      $conf['order_by']
     );
-  $page['super_order_by'] = true;
+    $page['super_order_by'] = true;
+
+  }
+  else
+  {
+    pwg_unset_session_var('image_order');
+    $page['super_order_by'] = false;
+  }
 }
 
 $forbidden = get_sql_condition_FandF(