server: Clarify signal emission

diff --git a/src/librygel-server/rygel-data-source.vala b/src/librygel-server/rygel-data-source.vala
index 8eebcf6..437f550 100644 (file)
--- a/src/librygel-server/rygel-data-source.vala
+++ b/src/librygel-server/rygel-data-source.vala
@@ -93,16 +93,22 @@ public interface Rygel.DataSource : GLib.Object {
 
     /**
      * Emitted when the source has produced some data.
+     *
+     * This signal has to be emitted in the main thread.
      */
     public signal void data_available (uint8[] data);
 
     /**
      * Emitted when the source does not have data anymore.
+     *
+     * This signal has to be emitted in the main thread.
      */
     public signal void done ();
 
     /**
      * Emitted when the source encounters a problem during data generation.
+     *
+     * This signal has to be emitted in the main thread.
      */
     public signal void error (Error error);
 }