Signature of a callback to be used to determine if a given presence
status can be set on the connection. Most users of this mixin do not need to
supply an implementation of this callback: the value of
#TpPresenceStatusSpec.self is enough to determine whether this is a
user-settable presence, so %NULL should be passed to
tp_presence_mixin_class_init() for this callback.
One place where this callback may be needed is on XMPP: not all server
implementation support the user becoming invisible. So an XMPP
implementation would implement this function, so that—once connected—the
hidden status is only available if the server supports it. Before the
connection is connected, this callback should return %TRUE for every status
that might possibly be supported: this allows the user to at least try to
sign in as invisible.
Signature of a callback to be used to determine if a given presence status can be set on the connection. Most users of this mixin do not need to supply an implementation of this callback: the value of #TpPresenceStatusSpec.self is enough to determine whether this is a user-settable presence, so %NULL should be passed to tp_presence_mixin_class_init() for this callback.
One place where this callback may be needed is on XMPP: not all server implementation support the user becoming invisible. So an XMPP implementation would implement this function, so that—once connected—the hidden status is only available if the server supports it. Before the connection is connected, this callback should return %TRUE for every status that might possibly be supported: this allows the user to at least try to sign in as invisible.