Currently, add-ons are disconnected when ChatProtocol::Shutdown() is
called, which the add-on can do by itself― but there is no standard way
for add-ons to notify the app about their Shutdown. Because of this,
they tend to not call Shutdown()― instead (as in the case of the Jabber
add-on), they display a BAlert (IM_ERROR) notifying the user of the
connection error, but the account is considered active by Cardie (and
its threads are still existant, including its ProtocolLooper).
Zombies are bad, so this is redesigned somewhat with this commit:
Protocols should no longer call ChatProtocol::Shutdown() themselves,
they must send an IM_MESSAGE of IM_PROTOCOL_DISABLE to the app.
This will delete its ProtocolLooper, which in turn will send a
notification to the user and delete the ChatProtocol, and so
calling ChatProtocol::Shutdown().
In the included protocols, an IM_ERROR is sent right before
IM_PROTOCOL_DISABLE is sent if due to a connection error. This is not
required, but it is courteous to inform your user about the "why." :)
4905dbbe6c