[RFC] : coherent message add/delete notification

[Emmanuel <e allaud wanadoo fr>]

	Hi all,
Tim and I was discussing about filters being run upon reception that will 
let deleted messages even if you had checked "hide deleted" or "delete 
irremediably...".
Finally I think this is an issue rooted deeper than filters. For me it is 
the add/delete messages scheme that lacks a coherent notification. We 
should emit the mailbox notification messages (either "MESSAGE[S]_DELETE" 
for deletion or "MESSAGES_NEW" for adding) within the functions that are 
used to add/delete messages (libbalsa_message[s]_delete/copy, this is 
sufficient because libbalsa_message[s]_move rely on 
libbalsa_message[s]_delete). That is the backend should send notification 
of what it is doing to let the frontend refresh or take actions depending 
of user pref (esp. the index displaying the mailbox will use this 
notification to know if it removes the messages being deleted depending on 
"hide deleted" pref and friends).
The way I would do it :

	* all backend messages moving/copying messages and involving a 
mailbox should send the notification themselves : in fact there is now 
only libbalsa_message[s]_copy(dest_mailbox,messages) in that case, and it 
should tell the dest_mailbox that it has new messages (sending it the 
"MESSAGES_NEW" message).
	* all backend messages moving/copying messages not involving a 
mailbox should not notify themselves; indeed for example think of 
libbalsa_messages_delete(messages), their is no garantee that the list of 
messages to delete all come from the same mailbox, so there, this should 
be the responsability of the caller (which knows about the mailbox[es] 
being altered) to send the notification (ie send "MESSAGES_DELETE" to the 
mailbox[es]).

Is this OK for everyone, comments?

Anyway if you propose something else we should really clean this issue to 
have a coherent messaging scheme to be more efficient that now (there is a 
lot of wasted time to sync things in the balsa index code because of lack 
of reliable notfication).
Bye
Manu