[jdev] invisibility on servers with no jabber:iq:privacy

[Robert McQueen]

I'm trying to implement invisibility on an XMPP server which doesn't
implement jabber:iq:privacy, namely Google Talk.

If disco shows jabber:iq:privacy isn't available, I've found that
jabberd2 and some other servers show up <feature
var='presence-invisible' /> which allows you to do <presence
type="invisible" /> for the Bad Old Way (tm) of invisibility. However,
on Google Talk this is rightly regarded as a syntax error worthy of
instant disconnection.

I've also found some clients implement invisibility by sending <presence
type="unavailable" /> to the server, which on Google Talk seems to be
interpreted just like invisible. The server still sends presence to you,
and other people's messages are returned with an offline error, but when
you send messages out to people they are able to reply (for how long? I
don't know...). This feels odd to me - is this behaviour peculiar to
Google's servers, or is it how a normal XMPP server whould behave too?

Regards,
Rob