-(GNUNET_CADET_DisconnectEventHandler) (void *cls,
- const struct GNUNET_CADET_Channel *channel);
+(*GNUNET_CADET_DisconnectEventHandler) (void *cls,
+ const struct GNUNET_CADET_Channel *channel);
+
+
+/**
+ * Function called whenever an MQ-channel's transmission window size changes.
+ *
+ * The first callback in an outgoing channel will be with a non-zero value
+ * and will mean the channel is connected to the destination.
+ *
+ * For an incoming channel it will be called immediately after the
+ * #GNUNET_CADET_ConnectEventHandler, also with a non-zero value.
+ *
+ * @param cls Channel closure.
+ * @param channel Connection to the other end --- FIXME: drop?
+ * @param window_size New window size. If the is more messages than buffer size
+ * this value will be negative. -- FIXME: make unsigned, we never call negative?
+ */
+typedef void
+(*GNUNET_CADET_WindowSizeEventHandler) (void *cls,
+ const struct GNUNET_CADET_Channel *channel,
+ int window_size);