Index: modules/block/block.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/block/block.module,v
retrieving revision 1.321
diff -u -p -r1.321 block.module
--- modules/block/block.module	3 Feb 2009 12:30:14 -0000	1.321
+++ modules/block/block.module	6 Feb 2009 15:42:04 -0000
@@ -475,6 +475,22 @@ function _block_load_blocks() {
 
   $blocks = array();
   $rids = array_keys($user->roles);
+
+
+  $result = db_query("SELECT * FROM {block} WHERE theme = :theme AND status = 1, ORDER BY b.region, b.weight, b.module', array(':theme' => $theme_key));
+  foreach ($result as $record) {
+    $key = $record->module . $record->delta;
+    $blocks[$key] = $record;
+  }
+  foreach ($module_implements('block_visibility') as $module) {
+    $function = $module . 'block_visibility';
+    $function($blocks);
+  }
+
+  // TODO take the filtered array of blocks and have it keyed by region.
+  // and of course move everything else out of here into hook implementations.
+
+  $blocks = array();
   $result = db_query(db_rewrite_sql("SELECT DISTINCT b.* FROM {block} b LEFT JOIN {block_role} r ON b.module = r.module AND b.delta = r.delta WHERE b.theme = '%s' AND b.status = 1 AND (r.rid IN (" . db_placeholders($rids) . ") OR r.rid IS NULL) ORDER BY b.region, b.weight, b.module", 'b', 'bid'), array_merge(array($theme_key), $rids));
   while ($block = db_fetch_object($result)) {
     if (!isset($blocks[$block->region])) {
Index: modules/user/user.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/user/user.module,v
retrieving revision 1.962
diff -u -p -r1.962 user.module
--- modules/user/user.module	3 Feb 2009 18:55:32 -0000	1.962
+++ modules/user/user.module	6 Feb 2009 15:42:06 -0000
@@ -109,6 +109,29 @@ function user_field_build_modes($obj_typ
   return $modes;
 }
 
+/**
+ * Implementation of hook_block_visibility().
+ */
+function user_block_visibility(&$blocks) {
+  global $user;
+  $result = db_query('SELECT module, delta, rid FROM {block_role}')->fetchAll();
+
+  $blocks_roles = array();
+  foreach ($result as $record) {
+    $blocks_roles[$record->module . $record->delta][] = $record->rid;
+  }
+
+  $blocks_by_role = array_intersect_key($blocks, $blocks_roles);
+  foreach ($blocks_by_role as $block) {
+    if (!array_diff($blocks_roles[$block]), array_keys($user->roles)) {
+      unset $blocks[$block];
+    }
+  }
+}
+
+
+  
+
 function user_external_load($authname) {
   $result = db_query("SELECT uid FROM {authmap} WHERE authname = '%s'", $authname);