add back prefetching album cover callback to iterators

backend/servermanager.go

@@ -18,6 +18,7 @@ type ServerManager struct {
 	ServerID     uuid.UUID
 	Server       mediaprovider.MediaProvider
 
+	prefetchCoverCB   func(string)
 	appName           string
 	onServerConnected []func()
 	onLogout          []func()
@@ -29,12 +30,20 @@ func NewServerManager(appName string) *ServerManager {
 	return &ServerManager{appName: appName}
 }
 
+func (s *ServerManager) SetPrefetchAlbumCoverCallback(cb func(string)) {
+	s.prefetchCoverCB = cb
+	if s.Server != nil {
+		s.Server.SetPrefetchCoverCallback(cb)
+	}
+}
+
 func (s *ServerManager) ConnectToServer(conf *ServerConfig, password string) error {
 	cli, err := s.testConnectionAndCreateClient(conf.ServerConnection, password)
 	if err != nil {
 		return err
 	}
 	s.Server = subsonicMP.SubsonicMediaProvider(cli)
+	s.Server.SetPrefetchCoverCallback(s.prefetchCoverCB)
 	s.LoggedInUser = conf.Username
 	s.ServerID = conf.ID
 	for _, cb := range s.onServerConnected {