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From: tbecker@sirius.informatik.uni-kl.de (Thomas Becker)
Newsgroups: comp.windows.x
Subject: Re: Receiving XEvents asynchronously
Message-ID: <tbecker.664209752@sirius>
Date: 18 Jan 91 14:42:32 GMT
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In comp.windows.x you write:

>I am trying to write a program, using Xlib right now, which receives
>input from several sockets and displays them on the screen.

I have had the same problem some time ago (using Xlib only).
In fact X events are nothing else but messages coming in through a socket.
By the macro
        socket = ConnectionNumber(display)
you get the socket connection id to the X server, which you can use as any
other socket for setting up masks required in select().
However, I had some slight trouble with this: calling select() for the FIRST
time, select() told me that an X event is ready to be received, but
XNextEvent() couldn't find any.
I have solved the problem by looking for the first X event with XPpending()
or some other non-blocking function, and then using select() only. So your
program should roughly look like that:

        x_socket = (1 << ConnectionNumber(display));
        sockwet_mask |= x_socket;

        if (XPending(display)) {
                /* handle event */
        }

        do {
                i = select(..., &socket_mask, ...);
                if (socket_mask & x_socket) {
                        XNextEvent(display, &event);
                        /* handle event */
                }
                else {
                        /* ... */
                }
        }


Hope that helps.

Thomas Becker
-- 
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