implement getDisplayNames in group manager

lib/private/group.php

@@ -263,17 +263,7 @@ class OC_Group {
 	 * @returns array with display names (value) and user ids(key)
 	 */
 	public static function displayNamesInGroup($gid, $search = '', $limit = -1, $offset = 0) {
-		$group = self::getManager()->get($gid);
-		if ($group) {
-			$users = $group->searchDisplayName($search, $limit, $offset);
-			$displayNames = array();
-			foreach ($users as $user) {
-				$displayNames[$user->getUID()] = $user->getDisplayName();
-			}
-			return $displayNames;
-		} else {
-			return array();
-		}
+		return self::getManager()->displayNamesInGroup($gid, $search, $limit, $offset);
 	}
 
 	/**

lib/private/group/manager.php

@@ -160,4 +160,37 @@ class Manager extends PublicEmitter {
 		}
 		return array_values($groups);
 	}
+
+	/**
+	 * @brief get a list of all display names in a group
+	 * @param string $gid
+	 * @param string $search
+	 * @param int $limit
+	 * @param int $offset
+	 * @return array with display names (value) and user ids (key)
+	 */
+	public function displayNamesInGroup($gid, $search = '', $limit = -1, $offset = 0) {
+		$group = $this->get($gid);
+		if(is_null($group)) {
+			return array();
+		}
+		// only user backends have the capability to do a complex search for users
+		$groupUsers  = $group->searchUsers('', $limit, $offset);
+		if(!empty(trim($search))) {
+			//TODO: for OC 7 earliest: user backend should get a method to check selected users against a pattern
+			$filteredUsers = $this->userManager->search($search);
+			$testUsers = true;
+		} else {
+			$filteredUsers = array();
+			$testUsers = false;
+		}
+
+		$matchingUsers = array();
+		foreach($groupUsers as $user) {
+			if(!$testUsers || isset($filteredUsers[$user->getUID()])) {
+				$matchingUsers[$user->getUID()] = $user->getDisplayName();
+			}
+		}
+		return $matchingUsers;
+	}
 }

lib/private/user/manager.php

@@ -174,12 +174,12 @@ class Manager extends PublicEmitter {
 			$backendUsers = $backend->getUsers($pattern, $limit, $offset);
 			if (is_array($backendUsers)) {
 				foreach ($backendUsers as $uid) {
-					$users[] = $this->getUserObject($uid, $backend);
+					$users[$uid] = $this->getUserObject($uid, $backend);
 				}
 			}
 		}
 
-		usort($users, function ($a, $b) {
+		uasort($users, function ($a, $b) {
 			/**
 			 * @var \OC\User\User $a
 			 * @var \OC\User\User $b