nanogui: nano-X --> waiting_for_event
Subject:
Re: [nanogui] nano-X --> waiting_for_event
From:
"Greg Haerr" ####@####.####
Date:
14 Jan 2007 16:44:35 +0000
Message-Id: <1ab101c737fb$2b28c680$6401a8c0@winXP>
> I do not see the reason for some implementation specifics of the nano-X
client server protocol. I.e. what is the reason that the server only
sends events to the client on request and not as soon as there is an
event?
The reason for this is that in order for things to be kept
simple, there is no packet queuing mechanism in the client.
Thus when a client requires certain data, it can't handle
event data instead. Also, too much code is required
to stop the server from blocking should a client
not read its queue and the server write() blocks. The
list goes on.
For instance, when a client executes a GrGetXXX call,
it requires that return data synchronously.
> curclient->waiting_for_event = TRUE; /* was FALSE */
> That way, *no* GrPrepareSelect, i.e. AllocReq(GetNextEvent); GrFlush();
is required in the client. The client can simply do a select (on the
nanox fd) and call GetNextEvent. Events are queued in the client socket.
Now, the only thing that remains to be resolved is the select in
_GrGetNextEventTimeout (client.c)... Basically, a new GetNextEvent has
to be written that does not include a select statement (the select shall
be outside of the nano-X client).
The above code will work only when you KNOW that
the client is in fact waiting for an event. If it executes
a GrXXX call that requires other data, the system
may become unsynchronised.
Regards,
Greg
