+  else
+    {
+      DEBUG ("We no longer care about unread mail");
+    }

You already trace when interest goes to FALSE, why tracing again ?

+  if (!(conn->features & GABBLE_CONNECTION_FEATURES_GOOGLE_MAIL_NOTIFY))
+    {
+      DEBUG ("Not a Google server - no MailNotification here");
+      return;
+    }

This trace does not give information, please remove.

-  return TRUE;
+#define MY_INTERFACE GABBLE_IFACE_CONNECTION_INTERFACE_MAIL_NOTIFICATION
+  g_signal_connect (conn, "clients-interested::" MY_INTERFACE,

Please undef MY_INTERFACE at the end, or don't use it. I'm not a big fan of using defines for such trivial constructions. Maybe you should use "const gchar *self_interface = GABBLE_IFACE_CONNECTION_INTERFACE_MAIL_NOTIFICATION" or similar instead ?

(In reply to comment #1)
> You already trace when interest goes to FALSE, why tracing again ?

No good reason, really; I was using the vague rule of thumb that if one code path logs, all of them should log. fb61a6c6bc97c79

> This trace does not give information, please remove.

Same commit as above.

> Please undef MY_INTERFACE at the end, or don't use it. I'm not a big fan of
> using defines for such trivial constructions. Maybe you should use "const gchar
> *self_interface = GABBLE_IFACE_CONNECTION_INTERFACE_MAIL_NOTIFICATION" or
> similar instead ?

I'm relying on cpp string concatenation and I don't really want to g_strdup_printf the constant signal names, so, no. d8794e70cee1de4 drops the use of MY_INTERFACE in favour of concatenating the full-length name, at the cost that the lines are a bit over-long.

All good.

Fixed in git, will be in 0.11.0 soon. Thanks!